Chapter 1 Homework
1. Drag the appropriate labels to their respective targets
(From Top to Bottom)
Chemical level, cellular level, Tissue level, Organ level, Organ System level
2. Which of the following is true of negative feedback mechanisms?
The output shuts off the original stimulus or reduces its intensity
3. Drag the appropriate labels to their respective targets.
(starting with top half to bottom half)
(from left to right)
Stimulus, Receptors, control centers, effectors, balance
(from right to left)
receptors, control center, effectors
4. Which of the following best demonstrates the principle of complementarity of structure and function?
Bones can support and protect body organs because they contain hard mineral deposits.
5. Drag each image to the appropriate location in the sequence.
High Blood glucose levels
Blood glucose becomes high --> Pancreas releases insulin -->Insulin binds to receptors on target cells --> cells take in glucose --> Blood glucose returns to normal
6. Drag the appropriate labels to their respective targets.
(from left to right)
Stimulus, receptor, input, control center, output, response, balance (middle)
7. What does the principle of complementarity of structure and function mean?
Function reflects structure and structure determines function.
8. Which level of structural organization is considered to be the highest level?
Organismal
9. Which of the following is the simplest level of structural organization in the human body?
Chemical
10. In a homeostatic control mechanism, which component monitors the environment?
Receptor
11. Which life process in the body sustains all others?
Metabolism
12. Which of the following is not an example of maintaining boundaries?
When your hand is exposed to extreme heat, you involuntarily pull your hand away from the painful stimulus.
13. Which represents the correct order in which the elements interact in a homeostatic control system?
The receptor, the control center and the effector.
14. Drag the appropriate labels to their respective targets.
(from left to bottom right)
Digestive system, respiratory system, integumentary system, urinary system, Cardiovascular system (middle)
15. The regulation of body temperature is an example of which type of homeostatic control?
negative feedback
16. Which body systems are absolutely essential for homeostasis?
nervous and endocrine systems
Chapter 3 (Cells) Homework
1. Which of the following is characteristic of cilia?
They are whiplike, motile cellular extensions that occur in large numbers on the exposed surfaces of certain cells.
2. Which of the following is not a concept of the cell theory?
Cells are given life through a process known as spontaneous generation.
3. DNA replication is performed by:
DNA polymerase.
4. The plasma membrane is made primarily of_________.
Phospholipids
5. Some types of cells move freely through the body, while others are bound into tightly knit communities.
True
6. Which of the following is not a primary function of peroxisomes?
They contain powerful enzymes called free radicals.
7. The nucleolus:
is the site of ribosome assembly in a cell.
8. What is a membrane potential?
a voltage or electrical charge across the plasma membrane
9. During interphase of the cell life cycle, the cell divides into two cells.
False
10. In their resting state, all body cells exhibit a resting membrane potential; therefore, all cells are polarized.
True
11. Which type of membrane junction is an example of a tight junction?
Junctions among epithelial cells lining the digestive tract.
12. ___________ is the diffusion of a solvent, such as water, across a selectively permeable membrane.
Osmosis
13. Drag the appropriate labels to their respective targets.
(left from top to bottom)
s, g1, cytokinesis
(right from top to bottom)
interphase, g2, mitosis, mitotic phase
14. During which phase of the cell cycle does DNA duplication, or replication, take place?
Interphase
When a double helix of DNA is replicated, two complete helices are formed. Together, these helices are called sister __________.
chromatids
During which phase of mitosis do sister chromatids line up at the center of the cell?
Metaphase
During which phase of mitosis do the sister chromatids move apart?
Anaphase
During which phase of mitosis do nuclear envelopes and the nucleoli reappear?
Telophase
During which phase of mitosis do the nuclear envelope and nucleoli disappear?
Prophase
What is the name of the process by which the cytoplasm divides in two?
Cytokinesis
15. Drag the appropriate labels to their respective targets.
(left top to bottom)
transcription, RNA processing, translation, polypeptide
(right top to bottom)
DNA, pre-mRNA, mRNA, ribosome
16. Which of the following is a difference between primary and secondary active transport:
In primary active transport, the transport protein gets phosphorylated; in secondary active transport, the transport protein is not phosphorylated.
17. Which of the following names the three main parts of a human cell?
Plasma membrane, cytoplasm, and nucleus.
18. Which of the following statements correctly describes the plasma membrane?
It is a dynamic fluid structure that is in constant flux.
19. Solutions with a higher concentration of solutes than the concentration inside the cell are:
Hypertonic
20. Which of the following forms of vesicular transport processes are used by flu viruses, diphtheria, and cholera toxins to enter our cells?
Receptor-mediated endocytosis
21. What must happen before a body cell can divide?
Its DNA must be replicated exactly so that identical copies of the cell's genes can be passed on to each of its offspring.
22. __________ is an adapter molecule which brings amino acids to the ribosome to build a protein.
t-RNA
23. Which of the following would not diffuse through the plasma membrane by means of simple diffusion?
Glucose
24. Drag the appropriate labels to their respective targets.
(from left to bottom right + bottom)
nonpolar tail of phospholipid molecule, polar head of phospholipid molecule, cholesterol, glycolipid, glycoprotein, peripheral proteins, integral proteins
25. Which of the following processes allows cells to concentrate material that is present only in very small amounts in the extracellular fluid?
Receptor-mediated endocytosis
26. Why is the selective permeability of the plasma membrane essential for normal cell function?
Selective permeability allows cells to exclude some substances and allow others to pass into or out of the cell.
27. Phagocytosis is a form of exocytosis.
False
28. Which of the following is a function of the rough endoplasmic reticulum?
synthesis of the cell's membranes
29. What are the two basic steps of polypeptide synthesis?
transcription and translation
30. What is the primary function of the mitochondria?
They are the main sites of ATP production.
31. Which cell organelle provides the majority of the ATP needed by the cell to carry out its metabolic reactions?
Mitochondrion
32. Which of the following statements is true?
During exocytosis, substances from the inside of the cell are moved outside.
33. What is the difference between active and passive transport across the plasma membrane?
Active transport is ATP dependent, whereas passive transport uses only the kinetic energy of the particles for movement across the plasma membrane.
34. Diffusion is a form of active transport.
false
35. Lysosomes perform digestive functions within a cell.
True
36. Which cell component helps to maintain the structural integrity of the cell?
cytoskeleton
37. Which organelle is responsible for building proteins?
ribosomes
38. Which of the following factors act to bind cells together?
Specialized junctions, wavy membrane contours, and glycoproteins
Chapter 24 (Metabolism) Homework
1. Redox reactions:
are characterized by one substance gaining an electron while another substance loses an electron.
2. Ammonia, which is a byproduct of protein metabolism, is converted to _____ in the ______.
urean; liver
3. Which nutrient molecule is the pivotal fuel molecule in the oxidative pathways?
glucose
4. Which of the following is a characteristic of the electron transport chain (ETC)?
The ETC occurs in the mitochondria.
5. ______ refers to reactions in which large molecules are broken down into smaller molecules.
catabolism
6. Drag the appropriate labels to their respective targets.
(left from top to bottom)
Krebs cycle, glycolysis, vis-substrate level phosphorylation
(right from top to bottom)
electron transport chain and oxidative phosphorylation, via oxidative phosphorylation
7. Which of the following is NOT a pathway in the oxidation of glucose?
gluconeogensis
8. Most ATP in cellular respiration is generated in glycolysis.
False
9. Glycolysis occurs in the ______ of cells and is an _______ process.
cytosol; anaerobic
10. What is the primary function of cellular respiration?
to generate ATP
11. Which of the following is not an end product of the Krebs cycle?
citric acid
Chapter 9 (Muscle) Homework
1. The smallest contractile unit of a muscle fiber is the:
sarcomere
2. What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
A myosin head binds to which molecule to form a cross bridge?
actin
What causes the myosin head to disconnect from actin?
binding of ATP
What causes the power stroke?
release of ADP and Pi
3. When muscles are contracting under oxygen deficient conditions, they will form ________ to ensure they maintain a supply of ATP.
lactic acid
4. Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release.
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
5. Thick myofilaments are made of:
myosin
6. Which of the following is correctly paired?
Skeletal muscle: voluntary control
7. Choose the false statement.
Skeletal muscle cells use creatine instead of ATP to do work.
8. Which type of muscle can contract without being stimulated by the nervous system?
cardiac
9. Which muscle characteristic describes the ability of muscle to respond to a stimulus?
excitability
10. What is the role of calcium in the cross bridge cycle?
Calcium binds to troponin, altering its shape.
What role does tropomyosin play in the cross bridge cycle?
The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form
How does troponin facilitate cross bridge formation?
Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin.
What, specifically, is a cross bridge?
myosin binding to actin
Which event causes cross bridge detachment?
ATP binding to the myosin head
Where in the cross bridge cycle does ATP hydrolysis occur?
during the cocking of the myosin head
How/when does the myosin head cock back to store energy for the next cycle?
After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.
BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?
Myosin heads would remain detached, unable to cock.
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.
11. Muscle tissue does not:
generate nerve impulses
12. The response of a motor unit to a single action potential of its motor neuron is called a:
muscle twitch
13. Slow oxidative muscle fibers are best suited for:
endurance activities
14. What is excitation-contraction coupling?
events leading to the sliding of myofilaments
15. The force of a muscle contraction is not affected by:
the amount of ATP in the muscle cells.
16. The sliding filament model of contraction states that:
during contraction, the thin filaments slide past the thick filaments so that actin and myosin filaments overlap.
17. In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate
How is acetylcholine (ACh) removed from the synaptic cleft?
acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisternae of the sarcoplasmic reticulum
18. Which of the following is true?
Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
19. Which organelle contains the contractile elements found in skeletal muscle?
myofibril
20. Skeletal muscle cells are grouped into bundles called __________.
fascicles
Synaptic vesicles at the neuromuscular junction contain __________.
acetylcholine
ACh receptors are found mainly in the __________.
sarcolemma
What most directly causes synaptic vesicles to release acetylcholine into the synaptic cleft?
calcium entering the axon terminal
Acetylcholine receptors are best characterized as what type of channel?
chemically gated Na+-K+ channels
When the chemically gated ion channels open, which ion is mainly responsible for depolarizing the sarcolemma?
sodium
What is the primary mechanism by which ACh is cleared from the synaptic cleft?
broken down by acetylcholinesterase
What would happen if acetylcholine was not removed from the synaptic cleft?
Multiple action potentials would occur in the muscle fiber.
21. Which muscle fiber type is best suited for endurance activities?
slow oxidative fibers
22. Which protein inhibits skeletal muscle contraction, and what ion removes the inhibition?
Tropomyosin; calcium ions
23. Which energy production process provides the majority of the energy for muscle activity?
aerobic respiration
24. The distance between Z-discs ______ during muscle contraction.
decreases
25. Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase.
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron.
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
26. The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
Calcium ions are stored in the sarcoplasmic reticulum.
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ATP binds to the myosin head
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end?
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
27. The first step toward generating a skeletal muscle contraction is:
stimulation of the muscle by a nerve ending.
28. Which of the following factors influence the velocity and duration of muscle contraction?
load placed on the muscle
29. The major role of the sarcoplasmic reticulum is to regulate:
intracellular levels of Ca2+.
30. What is a cross bridge cycle?
thick filaments pulling thin filaments toward the center of the sarcomere
Chapter 11 (Nervous) Homework
1. Which of the following types of neurons carries impulses away from the CNS?
motor
2. What type of conduction takes place in unmyelinated axons?
Continuous conduction
An action potential is self-regenerating because __________.
depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the largest diameter
3. Which of the following best describes the Na+ and K+ concentrations across a neuron's plasma membrane?
The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside.
What is the major role of the Na+-K+ pump in maintaining the resting membrane potential?
maintaining the concentration gradients for Na+ and K+ across the cell membrane
Which of the following is the clearest example of a neuronal membrane's selective permeability?
K+ ions can diffuse across the membrane more easily than Na+ ions
Which of the following would increase the membrane permeability to K+?
more K+ leakage channels
Suppose a drug is developed that blocks K+ leakage channels. The drug prevents ions from passing through those channels. If this drug was applied to a neuron, what would be the most immediate effect on that neuron?
The resting membrane potential would become less negative (more positive).
Imagine you changed the concentration of K+ outside a neuron such that the resting membrane potential changed to -80 mV (from the normal resting value of -70 mV). What have you changed?
the electrical gradient for K+ and the concentration gradient for K+
What is the electrochemical gradient of an ion?
the sum of the electrical and concentration gradients for that ion
Hypothetically, what would be the most immediate effect of doubling the number of Na+ leakage channels in the plasma membrane?
The resting membrane potential would become less negative (more positive).
4. Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?
Resting membrane potential (RMP)
Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?
Leak channels
On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?
The inside surface of the plasma membrane is much more negatively charged than the outside surface.
The plasma membrane is much more permeable to K+ than to Na+. Why?
There are many more K+ leak channels than Na+ leak channels in the plasma membrane.
The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.
The presence of concentration gradients and leak channels
What prevents the Na+ and K+ gradients from dissipating?
Na+-K+ ATPase
5. Drag the appropriate labels to their respective targets.
(first 2 from top to bottom)
dendrites, chromatophilic substances
(3 in the middle)
cell body, axon, Shwann cell
(last 2 on the right from top to bottom)
node of ranvier, axon terminals
6. What part of the nervous system performs information processing and integration?
CNS - central nervous system
7. What does the difference in the K+ and Na+ concentration on either side of the plasma membrane (and permeability of the membrane to those ions) generate?
resting membrane potential
8. The sodium-potassium pump ejects two Na from the cell and then transports three K back into the cell in order to stabilize the resting membrane potential.
false
9. Which neuroglia are the most abundant and versatile of the glial cells?
astrocytes
10. Which membrane potential results in depolarization without a nerve impulse being generated?
excitatory postsynaptic potential
11. Which of the following is the conducting region of the neuron?
axon
12. A postsynaptic cell can be a neuron, a muscle cell, or a secretory cell. What is an example of a presynaptic cell?
a neuron
Which component has a role in the postsynaptic cell during synaptic activity?
chemically gated channels
What is the role of calcium in synaptic activity?
Calcium influx into the synaptic terminal causes vesicle fusion
What is the role of neurotransmitter at a chemical synapse?
Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane
Neurotransmitter is released from presynaptic neurons through what mechanism?
exocytosis
What type of channel on the postsynaptic membrane binds neurotransmitter?
a chemically gated channel
In addition to diffusion, what are two other mechanisms that terminate neurotransmitter activity?
reuptake and degradation
Events that occur during synaptic activity are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Voltage-gated calcium channels open (b) Neurotransmitter binds to receptors (c) Action potential arrives at axon terminal (d) Neurotransmitter is removed from the synaptic cleft (e) Neurotransmitter released into synaptic cleft (f) Graded potential generated in postsynaptic cell
(c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft
13. During the action potential of a neuron, which ion is primarily crossing the membrane during the depolarization phase, and in which direction is the ion moving?
Na+ is entering the cell.
What is happening to voltage-gated channels at this point in the action potential?
Na+ channels are inactivating, and K+ channels are opening
During what part of the action potential do voltage-gated Na+ channels begin to inactivate (their inactivation gates close)?
at the end of the depolarization phase, as the membrane potential approaches its peak value
The repolarization phase of the action potential, where voltage becomes more negative after the +30mV peak, is caused primarily by __________.
K+ ions leaving the cell through voltage-gated channels
During an action potential, hyperpolarization beyond (more negative to) the resting membrane potential is primarily due to __________.
K+ ions diffusing through voltage-gated channels
During the hyperpolarization phase of the action potential, when the membrane potential is more negative than the resting membrane potential, what happens to voltage-gated ion channels?
K+ channels close. Na+ channels go from an inactivated state to a closed state.
Tetraethylammonium (TEA) blocks voltage-gated K+ channels such that K+ cannot pass even when the channels are open. However, TEA leaves K+ leakage channels largely unaffected. How would you expect the action potential to change if you treated a neuron with TEA?
The action potential would depolarize as usual, but the repolarization phase would take longer, causing the action potential to be more broad in time.
14. Which of the following types of glial cells monitor the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?
microglia
15. Which of the following are gaps found along a myelin sheath?
nodes of ranvier
16. Neurons and nerve cells are different names for the same thing.
true
17. What type of stimulus is required for an action potential to be generated?
a threshold level stimulus
18. Where do most action potentials originate?
Initial segment
What opens first in response to a threshold stimulus?
Voltage-gated Na+ channels
What characterizes depolarization, the first phase of the action potential?
The membrane potential changes from a negative value to a positive value.
What characterizes repolarization, the second phase of the action potential?
Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na+ channels change shape, and their activation gates open.
19. The small space between the sending neuron and the receiving neuron is the
synaptic cleft.
A molecule that carries information across a synaptic cleft is a
neurotransmitter.
When calcium ions enter the synaptic terminal,
they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.
When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,
ion channels in the plasma membrane of the receiving neuron open.
If a signal from a sending neuron makes the receiving neuron more negative inside,
the receiving neuron is less likely to generate an action potential.
20. The diffusion of what ion, across the neuronal membrane, is responsible for the local currents that depolarize regions of the axon to threshold?
Na+ (sodium)
An action potential in one segment of axon causes adjacent sections of axon membrane to reach threshold through what mechanism?
the generation of local currents
During action potential propagation in an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?
The previous axonal segment is in the refractory period.
In a myelinated axon, how do the nodes of Ranvier differ from other segments of the same axon?
The nodes are more permeable to ions
Where are action potentials regenerated as they propagate along a myelinated axon?
at the nodes of Ranvier
How do action potential propagation speeds compare in myelinated and unmyelinated axons?
Propagation is faster in myelinated axons.
The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.
saltatory conduction
The myelin on myelinated neurons can be degraded or destroyed in diseases such as multiple sclerosis-a process called demyelination. If a myelinated neuron was affected by demyelination, how would this affect action potentials in that neuron?
The speed of action potential propagation would be slower.
21. Which of the following PNS neuroglia help to form myelin sheaths around larger nerve fibers in the PNS?
schwann cells
22. Drag the labels to identify the sequence of events that occurs at a synapse.
synaptic response to an action potential
an action potential arrives... --> calcium channels open... --> vesicles containing neurotransmitters... --> Neurotransmitter molecules Diffuse... --> the Neurotransmitter molecules bind...
23. Which of the following is not one of the basic functions of the nervous system?
neural genesis
24. How is an action potential propagated along an axon?
An influx of sodium ions from the current action potential depolarizes the adjacent area.
Why does the action potential only move away from the cell body?
The areas that have had the action potential are refractory to a new action potential.
The velocity of the action potential is fastest in which of the following axons?
a small myelinated axon
25. The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
K+; Na+
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
What is the value for the resting membrane potential for most neurons?
–70 mV
The Na+–K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
Na+ is pumped out of the cell and K+ is pumped into the cell.
The concentrations of which two ions are highest outside the cell.
Na+ and Cl–
26. Which of the following types of glial cells produce the myelin sheaths that insulate the neural fibers in the CNS?
Oligodendrocytes
27. Which of the following allows us to consciously control our skeletal muscles?
the somatic nervous system
28. Which part of the neuron is responsible for generating a nerve impulse?
axon
29. Which of the following does not factor into the rate of impulse propagation?
The number of axon collaterals extending from a truncated axon.
30. Where in the neuron is an action potential initially generated?
axon hillock
The depolarization phase of an action potential results from the opening of which channels?
voltage-gated Na+ channels
The repolarization phase of an action potential results from __________.
the opening of voltage-gated K+ channels
Hyperpolarization results from __________.
slow closing of voltage-gated K+ channels
What is the magnitude (amplitude) of an action potential?
100 mV
31. Which of the following is true of axons?
each neuron has a single axon
32. Which neurotransmitter(s) is/are the body's natural pain killer?
endorphins
33. Drag the appropriate labels to their respective targets.
(first 3 top to bottom)
receptive region, Biosynthetic center and receptive region, impulse generating and conducting region
(middle)
impulse direction
(last on the right)
secretory region
34. In a synapse, neurotransmitters are stored in vesicles located in the __________.
presynaptic neuron
An action potential releases neurotransmitter from a neuron by opening which of the following channels?
voltage-gated Ca2+ channels
Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.
chemically gated; postsynaptic
Binding of the neurotransmitter to its receptor causes the membrane to __________.
either depolarize or hyperpolarize
The mechanism by which the neurotransmitter is returned to a presynaptic neuron’s axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?
acetylcholine
35. Unmyelinated fibers conduct impulses faster than myelinated fibers.
false
chapter 13/15 (senses) homework
1. Ringing in the ears is called:
tinnitus
2. What part of the eye constitutes the blind spot?
optic disc
3. The receptor organ for hearing is the _____
spiral organ of corti
4. Choose the correctly paired terms.
nyctalopia. night blindness
5. The visible colored portion of the eye is the:
iris
6. _________ are receptors that can respond to changes in pressure.
mechanoreceptors
7. The final step in perceiving sound is:
the auditory cortex is stimulated
8. Which of the following is a characteristic of the lens?
the lens focuses light on the retina
9. There are ____ auditory ossicles in the ear.
three
10. Which of the following is the basic taste quality responsible for a "beef taste"?
umami
11. Which photoreceptors respond to very dim light?
rods
12. Which of the following is not used to classify sensory receptors?
The number of dendritic endings present
13. The distance between two consecutive wave crests is the_______
wavelength
14. Which structure in the eye provides nutrition to all eye layers?
choroid
15. Complex receptors are also called sense organs.
true
16. Taste is independent of smell.
false
17. Choose the false statement about nerves.
The majority of a nerve's bulk is due to axons.
18. Which accessory eye structures function to produce the tears that cleanse and protect the eye?
lacrimal glands
19. The receptors for smell are activated when:
dissolved odorants bind to the receptors in the cilium membranes.
20. What is the vestibular apparatus?
the equilibrium receptors in the semicircular canals and vestibule
21. Choose the false statement about the olfactory epithelium.
It is made of simple squamous epithelium.
22. ______ are collections of neuron cell bodies associated with nerves in the PNS.
ganglia
23. Nerves that only carry impulses away from the central nervous system (CNS) are called:
motor nerves
24. Eye color is determined by the level of brown pigment present.
true
25. Which of the following is not a requirement for something to be tasted?
The tastant must contact the basal cells of the taste buds.
26. Where are equilibrium receptors located?
In the semicircular canals and in the vestibule of the ear.
27. The boundary between the external and middle ear is the:
tympanic membrane
28. Which of the following is true of receptors for dynamic equilibrium?
The receptors for dynamic equilibrium respond to rotation forces.
29. Which of the following correctly matches the equilibrium receptor to the type of equilibrium it monitors?
maculae/static equilibrium
30. Most taste buds are located:
on the tongue
31. Which of the following is a role of the vitreous humor?
It supports the posterior surface of the lens.
32. The peripheral nervous system (PNS) includes the brain and spinal cord.
false
33. Which type of sensory receptor allows us to feel an insect landing on our skin?
mechanoreceptor
chapter 16 (endocrine) homework
1. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.
diabetes
type 2
type1
both type 1 and type 2
2. What is required for the production of anterior pituitary gland hormones?
hormonal stimuli
3. Which of the following hormone pairs are antagonists that regulate blood calcium ion levels?
parathyroid hormone/calcitonin
4. Which of the following pairs correctly match the adrenal gland zone or area with the class of hormones it produces?
zona glomerulosa/mineralocorticoids
5. Which hormone(s) is/are essential to our ability to deal with stress?
glucocorticoids
6. Which of the following hormones helps the body avoid dehydration and water overload?
Antidiuretic hormone
7. Which of the following homeostatic imbalances is characterized by persistent elevated blood glucose levels, dramatic losses in muscle and bone protein, and water and salt retention, leading to hypertension and edema?
Cushing's syndrome
8. What type of hormones bind to receptors located on the cell membrane?
water-soluble hormones, such as insulin and epinephrine
Which intracellular substance degrades cAMP, thus inactivating the response to a hormone?
phosphodiesterase
Growth factor hormones, such as insulin, bind to which type of receptor?
tyrosine kinase receptors
Which is the correct order of events for hormones activating Gs proteins?
activation of G protein, binding of GTP, activation of adenylate cyclase, conversion of ATP to cAMP
Which second messenger causes the release of calcium from the endoplasmic reticulum?
IP3
Which of the following adrenergic receptors increase cAMP levels?
β receptors
9. _____ is the situation when one hormone cannot exert its full effects without another hormone being present.
permissiveness
10. Which of the following is not an endocrine gland?
adenoid
11. Which of the following hormones has intracellular receptors?
cortisol
What is the mechanism of action of lipid-soluble hormones?
activation of genes, which increases protein synthesis in the cell
After a lipid-soluble hormone is bound to its intracellular receptor, what does the hormone complex do?
acts as a transcription factor and binds to DNA, activating a gene
Which hormone’s receptor is always bound to DNA, even when the receptor is empty?
thyroid hormone
What keeps intracellular receptors from binding to DNA before a hormone binds to the receptor?
chaperone proteins (chaperonins)
12. Major hormones circulate to virtually all tissues.
true
13. The stimuli causing endocrine glands to secrete their hormones in direct response to changing blood levels of certain critical ions and nutrients are called ______________.
humoral stimuli
14. Which pancreatic hormone functions to lower blood glucose levels?
insulin
15. Which of the following is not a property of endocrine glands?
they have ducts
16. Which of the following occurs in situations where more than one hormone produces the same effects at the target cell and their combined effects are amplified?
synergism
17. Which of the following hormones stimulates the adrenal cortex to release glucocorticoids that help the body to resist stressors?
Adrenocorticotropic hormone
18. Which hormone is the body's major metabolic hormone?
thyroid hormone
19. Hyperparathyroidism is a rare condition where the bones soften and deform.
true
20. The hypothalamus is known to control the activity of the anterior pituitary, which has traditionally been called the "master endocrine gland."
true
21. Which of the following organs does NOT produce a hormone or hormones?
lungs
22. Hormones that regulate the secretory action of other endocrine glands are called ____________.
tropins
23. Hormones are long-distance chemical signals that travel in blood or lymph throughout the body.
true
24. Which of the following hormones mainly serves to stimulate milk production by the breasts?
prolactin
25. Which of the following is a hormone produced by the posterior pituitary?
none of these
26. When blood glucose levels are high
The pancreas releases insulin
A liver cell responds to insulin by
Taking in glucose and converting it to glycogen.
What cells in the body respond to glucagon by breaking down glycogen and releasing glucose?
Liver cell
Body cells that respond to insulin include
Liver cells, as well as most other cells of the body
When blood glucose levels are low
The pancreas releases glucagon, which eventually causes blood glucose levels to increase
The body's tendency to maintain relatively constant internal conditions is called
homeostasis.
27. What is the primary function of hormones?
alter cell activity
28. The anatomical effects of acromegaly can usually be reversed by surgically removing the tumor from the anterior pituitary.
false
29. Which of the following is not a homeostatic imbalance related to underactivity of the thyroid gland?
graves' disease
30. Up-regulation involves the loss of receptors and prevents the target cells from overreacting to persistently high hormone levels.
false
31. Which of the following glands is found atop the kidneys?
adrenal
32. Which of the following is NOT a major type of stimulus that triggers endocrine glands to manufacture and release hormones?
enzymatic
1. Drag the appropriate labels to their respective targets
(From Top to Bottom)
Chemical level, cellular level, Tissue level, Organ level, Organ System level
2. Which of the following is true of negative feedback mechanisms?
The output shuts off the original stimulus or reduces its intensity
3. Drag the appropriate labels to their respective targets.
(starting with top half to bottom half)
(from left to right)
Stimulus, Receptors, control centers, effectors, balance
(from right to left)
receptors, control center, effectors
4. Which of the following best demonstrates the principle of complementarity of structure and function?
Bones can support and protect body organs because they contain hard mineral deposits.
5. Drag each image to the appropriate location in the sequence.
High Blood glucose levels
Blood glucose becomes high --> Pancreas releases insulin -->Insulin binds to receptors on target cells --> cells take in glucose --> Blood glucose returns to normal
6. Drag the appropriate labels to their respective targets.
(from left to right)
Stimulus, receptor, input, control center, output, response, balance (middle)
7. What does the principle of complementarity of structure and function mean?
Function reflects structure and structure determines function.
8. Which level of structural organization is considered to be the highest level?
Organismal
9. Which of the following is the simplest level of structural organization in the human body?
Chemical
10. In a homeostatic control mechanism, which component monitors the environment?
Receptor
11. Which life process in the body sustains all others?
Metabolism
12. Which of the following is not an example of maintaining boundaries?
When your hand is exposed to extreme heat, you involuntarily pull your hand away from the painful stimulus.
13. Which represents the correct order in which the elements interact in a homeostatic control system?
The receptor, the control center and the effector.
14. Drag the appropriate labels to their respective targets.
(from left to bottom right)
Digestive system, respiratory system, integumentary system, urinary system, Cardiovascular system (middle)
15. The regulation of body temperature is an example of which type of homeostatic control?
negative feedback
16. Which body systems are absolutely essential for homeostasis?
nervous and endocrine systems
Chapter 3 (Cells) Homework
1. Which of the following is characteristic of cilia?
They are whiplike, motile cellular extensions that occur in large numbers on the exposed surfaces of certain cells.
2. Which of the following is not a concept of the cell theory?
Cells are given life through a process known as spontaneous generation.
3. DNA replication is performed by:
DNA polymerase.
4. The plasma membrane is made primarily of_________.
Phospholipids
5. Some types of cells move freely through the body, while others are bound into tightly knit communities.
True
6. Which of the following is not a primary function of peroxisomes?
They contain powerful enzymes called free radicals.
7. The nucleolus:
is the site of ribosome assembly in a cell.
8. What is a membrane potential?
a voltage or electrical charge across the plasma membrane
9. During interphase of the cell life cycle, the cell divides into two cells.
False
10. In their resting state, all body cells exhibit a resting membrane potential; therefore, all cells are polarized.
True
11. Which type of membrane junction is an example of a tight junction?
Junctions among epithelial cells lining the digestive tract.
12. ___________ is the diffusion of a solvent, such as water, across a selectively permeable membrane.
Osmosis
13. Drag the appropriate labels to their respective targets.
(left from top to bottom)
s, g1, cytokinesis
(right from top to bottom)
interphase, g2, mitosis, mitotic phase
14. During which phase of the cell cycle does DNA duplication, or replication, take place?
Interphase
When a double helix of DNA is replicated, two complete helices are formed. Together, these helices are called sister __________.
chromatids
During which phase of mitosis do sister chromatids line up at the center of the cell?
Metaphase
During which phase of mitosis do the sister chromatids move apart?
Anaphase
During which phase of mitosis do nuclear envelopes and the nucleoli reappear?
Telophase
During which phase of mitosis do the nuclear envelope and nucleoli disappear?
Prophase
What is the name of the process by which the cytoplasm divides in two?
Cytokinesis
15. Drag the appropriate labels to their respective targets.
(left top to bottom)
transcription, RNA processing, translation, polypeptide
(right top to bottom)
DNA, pre-mRNA, mRNA, ribosome
16. Which of the following is a difference between primary and secondary active transport:
In primary active transport, the transport protein gets phosphorylated; in secondary active transport, the transport protein is not phosphorylated.
17. Which of the following names the three main parts of a human cell?
Plasma membrane, cytoplasm, and nucleus.
18. Which of the following statements correctly describes the plasma membrane?
It is a dynamic fluid structure that is in constant flux.
19. Solutions with a higher concentration of solutes than the concentration inside the cell are:
Hypertonic
20. Which of the following forms of vesicular transport processes are used by flu viruses, diphtheria, and cholera toxins to enter our cells?
Receptor-mediated endocytosis
21. What must happen before a body cell can divide?
Its DNA must be replicated exactly so that identical copies of the cell's genes can be passed on to each of its offspring.
22. __________ is an adapter molecule which brings amino acids to the ribosome to build a protein.
t-RNA
23. Which of the following would not diffuse through the plasma membrane by means of simple diffusion?
Glucose
24. Drag the appropriate labels to their respective targets.
(from left to bottom right + bottom)
nonpolar tail of phospholipid molecule, polar head of phospholipid molecule, cholesterol, glycolipid, glycoprotein, peripheral proteins, integral proteins
25. Which of the following processes allows cells to concentrate material that is present only in very small amounts in the extracellular fluid?
Receptor-mediated endocytosis
26. Why is the selective permeability of the plasma membrane essential for normal cell function?
Selective permeability allows cells to exclude some substances and allow others to pass into or out of the cell.
27. Phagocytosis is a form of exocytosis.
False
28. Which of the following is a function of the rough endoplasmic reticulum?
synthesis of the cell's membranes
29. What are the two basic steps of polypeptide synthesis?
transcription and translation
30. What is the primary function of the mitochondria?
They are the main sites of ATP production.
31. Which cell organelle provides the majority of the ATP needed by the cell to carry out its metabolic reactions?
Mitochondrion
32. Which of the following statements is true?
During exocytosis, substances from the inside of the cell are moved outside.
33. What is the difference between active and passive transport across the plasma membrane?
Active transport is ATP dependent, whereas passive transport uses only the kinetic energy of the particles for movement across the plasma membrane.
34. Diffusion is a form of active transport.
false
35. Lysosomes perform digestive functions within a cell.
True
36. Which cell component helps to maintain the structural integrity of the cell?
cytoskeleton
37. Which organelle is responsible for building proteins?
ribosomes
38. Which of the following factors act to bind cells together?
Specialized junctions, wavy membrane contours, and glycoproteins
Chapter 24 (Metabolism) Homework
1. Redox reactions:
are characterized by one substance gaining an electron while another substance loses an electron.
2. Ammonia, which is a byproduct of protein metabolism, is converted to _____ in the ______.
urean; liver
3. Which nutrient molecule is the pivotal fuel molecule in the oxidative pathways?
glucose
4. Which of the following is a characteristic of the electron transport chain (ETC)?
The ETC occurs in the mitochondria.
5. ______ refers to reactions in which large molecules are broken down into smaller molecules.
catabolism
6. Drag the appropriate labels to their respective targets.
(left from top to bottom)
Krebs cycle, glycolysis, vis-substrate level phosphorylation
(right from top to bottom)
electron transport chain and oxidative phosphorylation, via oxidative phosphorylation
7. Which of the following is NOT a pathway in the oxidation of glucose?
gluconeogensis
8. Most ATP in cellular respiration is generated in glycolysis.
False
9. Glycolysis occurs in the ______ of cells and is an _______ process.
cytosol; anaerobic
10. What is the primary function of cellular respiration?
to generate ATP
11. Which of the following is not an end product of the Krebs cycle?
citric acid
Chapter 9 (Muscle) Homework
1. The smallest contractile unit of a muscle fiber is the:
sarcomere
2. What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
A myosin head binds to which molecule to form a cross bridge?
actin
What causes the myosin head to disconnect from actin?
binding of ATP
What causes the power stroke?
release of ADP and Pi
3. When muscles are contracting under oxygen deficient conditions, they will form ________ to ensure they maintain a supply of ATP.
lactic acid
4. Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release.
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
5. Thick myofilaments are made of:
myosin
6. Which of the following is correctly paired?
Skeletal muscle: voluntary control
7. Choose the false statement.
Skeletal muscle cells use creatine instead of ATP to do work.
8. Which type of muscle can contract without being stimulated by the nervous system?
cardiac
9. Which muscle characteristic describes the ability of muscle to respond to a stimulus?
excitability
10. What is the role of calcium in the cross bridge cycle?
Calcium binds to troponin, altering its shape.
What role does tropomyosin play in the cross bridge cycle?
The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form
How does troponin facilitate cross bridge formation?
Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin.
What, specifically, is a cross bridge?
myosin binding to actin
Which event causes cross bridge detachment?
ATP binding to the myosin head
Where in the cross bridge cycle does ATP hydrolysis occur?
during the cocking of the myosin head
How/when does the myosin head cock back to store energy for the next cycle?
After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.
BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?
Myosin heads would remain detached, unable to cock.
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.
11. Muscle tissue does not:
generate nerve impulses
12. The response of a motor unit to a single action potential of its motor neuron is called a:
muscle twitch
13. Slow oxidative muscle fibers are best suited for:
endurance activities
14. What is excitation-contraction coupling?
events leading to the sliding of myofilaments
15. The force of a muscle contraction is not affected by:
the amount of ATP in the muscle cells.
16. The sliding filament model of contraction states that:
during contraction, the thin filaments slide past the thick filaments so that actin and myosin filaments overlap.
17. In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate
How is acetylcholine (ACh) removed from the synaptic cleft?
acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisternae of the sarcoplasmic reticulum
18. Which of the following is true?
Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
19. Which organelle contains the contractile elements found in skeletal muscle?
myofibril
20. Skeletal muscle cells are grouped into bundles called __________.
fascicles
Synaptic vesicles at the neuromuscular junction contain __________.
acetylcholine
ACh receptors are found mainly in the __________.
sarcolemma
What most directly causes synaptic vesicles to release acetylcholine into the synaptic cleft?
calcium entering the axon terminal
Acetylcholine receptors are best characterized as what type of channel?
chemically gated Na+-K+ channels
When the chemically gated ion channels open, which ion is mainly responsible for depolarizing the sarcolemma?
sodium
What is the primary mechanism by which ACh is cleared from the synaptic cleft?
broken down by acetylcholinesterase
What would happen if acetylcholine was not removed from the synaptic cleft?
Multiple action potentials would occur in the muscle fiber.
21. Which muscle fiber type is best suited for endurance activities?
slow oxidative fibers
22. Which protein inhibits skeletal muscle contraction, and what ion removes the inhibition?
Tropomyosin; calcium ions
23. Which energy production process provides the majority of the energy for muscle activity?
aerobic respiration
24. The distance between Z-discs ______ during muscle contraction.
decreases
25. Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase.
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron.
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
26. The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
Calcium ions are stored in the sarcoplasmic reticulum.
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ATP binds to the myosin head
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end?
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
27. The first step toward generating a skeletal muscle contraction is:
stimulation of the muscle by a nerve ending.
28. Which of the following factors influence the velocity and duration of muscle contraction?
load placed on the muscle
29. The major role of the sarcoplasmic reticulum is to regulate:
intracellular levels of Ca2+.
30. What is a cross bridge cycle?
thick filaments pulling thin filaments toward the center of the sarcomere
Chapter 11 (Nervous) Homework
1. Which of the following types of neurons carries impulses away from the CNS?
motor
2. What type of conduction takes place in unmyelinated axons?
Continuous conduction
An action potential is self-regenerating because __________.
depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the largest diameter
3. Which of the following best describes the Na+ and K+ concentrations across a neuron's plasma membrane?
The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside.
What is the major role of the Na+-K+ pump in maintaining the resting membrane potential?
maintaining the concentration gradients for Na+ and K+ across the cell membrane
Which of the following is the clearest example of a neuronal membrane's selective permeability?
K+ ions can diffuse across the membrane more easily than Na+ ions
Which of the following would increase the membrane permeability to K+?
more K+ leakage channels
Suppose a drug is developed that blocks K+ leakage channels. The drug prevents ions from passing through those channels. If this drug was applied to a neuron, what would be the most immediate effect on that neuron?
The resting membrane potential would become less negative (more positive).
Imagine you changed the concentration of K+ outside a neuron such that the resting membrane potential changed to -80 mV (from the normal resting value of -70 mV). What have you changed?
the electrical gradient for K+ and the concentration gradient for K+
What is the electrochemical gradient of an ion?
the sum of the electrical and concentration gradients for that ion
Hypothetically, what would be the most immediate effect of doubling the number of Na+ leakage channels in the plasma membrane?
The resting membrane potential would become less negative (more positive).
4. Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?
Resting membrane potential (RMP)
Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?
Leak channels
On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?
The inside surface of the plasma membrane is much more negatively charged than the outside surface.
The plasma membrane is much more permeable to K+ than to Na+. Why?
There are many more K+ leak channels than Na+ leak channels in the plasma membrane.
The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.
The presence of concentration gradients and leak channels
What prevents the Na+ and K+ gradients from dissipating?
Na+-K+ ATPase
5. Drag the appropriate labels to their respective targets.
(first 2 from top to bottom)
dendrites, chromatophilic substances
(3 in the middle)
cell body, axon, Shwann cell
(last 2 on the right from top to bottom)
node of ranvier, axon terminals
6. What part of the nervous system performs information processing and integration?
CNS - central nervous system
7. What does the difference in the K+ and Na+ concentration on either side of the plasma membrane (and permeability of the membrane to those ions) generate?
resting membrane potential
8. The sodium-potassium pump ejects two Na from the cell and then transports three K back into the cell in order to stabilize the resting membrane potential.
false
9. Which neuroglia are the most abundant and versatile of the glial cells?
astrocytes
10. Which membrane potential results in depolarization without a nerve impulse being generated?
excitatory postsynaptic potential
11. Which of the following is the conducting region of the neuron?
axon
12. A postsynaptic cell can be a neuron, a muscle cell, or a secretory cell. What is an example of a presynaptic cell?
a neuron
Which component has a role in the postsynaptic cell during synaptic activity?
chemically gated channels
What is the role of calcium in synaptic activity?
Calcium influx into the synaptic terminal causes vesicle fusion
What is the role of neurotransmitter at a chemical synapse?
Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane
Neurotransmitter is released from presynaptic neurons through what mechanism?
exocytosis
What type of channel on the postsynaptic membrane binds neurotransmitter?
a chemically gated channel
In addition to diffusion, what are two other mechanisms that terminate neurotransmitter activity?
reuptake and degradation
Events that occur during synaptic activity are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Voltage-gated calcium channels open (b) Neurotransmitter binds to receptors (c) Action potential arrives at axon terminal (d) Neurotransmitter is removed from the synaptic cleft (e) Neurotransmitter released into synaptic cleft (f) Graded potential generated in postsynaptic cell
(c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft
13. During the action potential of a neuron, which ion is primarily crossing the membrane during the depolarization phase, and in which direction is the ion moving?
Na+ is entering the cell.
What is happening to voltage-gated channels at this point in the action potential?
Na+ channels are inactivating, and K+ channels are opening
During what part of the action potential do voltage-gated Na+ channels begin to inactivate (their inactivation gates close)?
at the end of the depolarization phase, as the membrane potential approaches its peak value
The repolarization phase of the action potential, where voltage becomes more negative after the +30mV peak, is caused primarily by __________.
K+ ions leaving the cell through voltage-gated channels
During an action potential, hyperpolarization beyond (more negative to) the resting membrane potential is primarily due to __________.
K+ ions diffusing through voltage-gated channels
During the hyperpolarization phase of the action potential, when the membrane potential is more negative than the resting membrane potential, what happens to voltage-gated ion channels?
K+ channels close. Na+ channels go from an inactivated state to a closed state.
Tetraethylammonium (TEA) blocks voltage-gated K+ channels such that K+ cannot pass even when the channels are open. However, TEA leaves K+ leakage channels largely unaffected. How would you expect the action potential to change if you treated a neuron with TEA?
The action potential would depolarize as usual, but the repolarization phase would take longer, causing the action potential to be more broad in time.
14. Which of the following types of glial cells monitor the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?
microglia
15. Which of the following are gaps found along a myelin sheath?
nodes of ranvier
16. Neurons and nerve cells are different names for the same thing.
true
17. What type of stimulus is required for an action potential to be generated?
a threshold level stimulus
18. Where do most action potentials originate?
Initial segment
What opens first in response to a threshold stimulus?
Voltage-gated Na+ channels
What characterizes depolarization, the first phase of the action potential?
The membrane potential changes from a negative value to a positive value.
What characterizes repolarization, the second phase of the action potential?
Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na+ channels change shape, and their activation gates open.
19. The small space between the sending neuron and the receiving neuron is the
synaptic cleft.
A molecule that carries information across a synaptic cleft is a
neurotransmitter.
When calcium ions enter the synaptic terminal,
they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.
When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,
ion channels in the plasma membrane of the receiving neuron open.
If a signal from a sending neuron makes the receiving neuron more negative inside,
the receiving neuron is less likely to generate an action potential.
20. The diffusion of what ion, across the neuronal membrane, is responsible for the local currents that depolarize regions of the axon to threshold?
Na+ (sodium)
An action potential in one segment of axon causes adjacent sections of axon membrane to reach threshold through what mechanism?
the generation of local currents
During action potential propagation in an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?
The previous axonal segment is in the refractory period.
In a myelinated axon, how do the nodes of Ranvier differ from other segments of the same axon?
The nodes are more permeable to ions
Where are action potentials regenerated as they propagate along a myelinated axon?
at the nodes of Ranvier
How do action potential propagation speeds compare in myelinated and unmyelinated axons?
Propagation is faster in myelinated axons.
The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.
saltatory conduction
The myelin on myelinated neurons can be degraded or destroyed in diseases such as multiple sclerosis-a process called demyelination. If a myelinated neuron was affected by demyelination, how would this affect action potentials in that neuron?
The speed of action potential propagation would be slower.
21. Which of the following PNS neuroglia help to form myelin sheaths around larger nerve fibers in the PNS?
schwann cells
22. Drag the labels to identify the sequence of events that occurs at a synapse.
synaptic response to an action potential
an action potential arrives... --> calcium channels open... --> vesicles containing neurotransmitters... --> Neurotransmitter molecules Diffuse... --> the Neurotransmitter molecules bind...
23. Which of the following is not one of the basic functions of the nervous system?
neural genesis
24. How is an action potential propagated along an axon?
An influx of sodium ions from the current action potential depolarizes the adjacent area.
Why does the action potential only move away from the cell body?
The areas that have had the action potential are refractory to a new action potential.
The velocity of the action potential is fastest in which of the following axons?
a small myelinated axon
25. The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
K+; Na+
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
What is the value for the resting membrane potential for most neurons?
–70 mV
The Na+–K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
Na+ is pumped out of the cell and K+ is pumped into the cell.
The concentrations of which two ions are highest outside the cell.
Na+ and Cl–
26. Which of the following types of glial cells produce the myelin sheaths that insulate the neural fibers in the CNS?
Oligodendrocytes
27. Which of the following allows us to consciously control our skeletal muscles?
the somatic nervous system
28. Which part of the neuron is responsible for generating a nerve impulse?
axon
29. Which of the following does not factor into the rate of impulse propagation?
The number of axon collaterals extending from a truncated axon.
30. Where in the neuron is an action potential initially generated?
axon hillock
The depolarization phase of an action potential results from the opening of which channels?
voltage-gated Na+ channels
The repolarization phase of an action potential results from __________.
the opening of voltage-gated K+ channels
Hyperpolarization results from __________.
slow closing of voltage-gated K+ channels
What is the magnitude (amplitude) of an action potential?
100 mV
31. Which of the following is true of axons?
each neuron has a single axon
32. Which neurotransmitter(s) is/are the body's natural pain killer?
endorphins
33. Drag the appropriate labels to their respective targets.
(first 3 top to bottom)
receptive region, Biosynthetic center and receptive region, impulse generating and conducting region
(middle)
impulse direction
(last on the right)
secretory region
34. In a synapse, neurotransmitters are stored in vesicles located in the __________.
presynaptic neuron
An action potential releases neurotransmitter from a neuron by opening which of the following channels?
voltage-gated Ca2+ channels
Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.
chemically gated; postsynaptic
Binding of the neurotransmitter to its receptor causes the membrane to __________.
either depolarize or hyperpolarize
The mechanism by which the neurotransmitter is returned to a presynaptic neuron’s axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?
acetylcholine
35. Unmyelinated fibers conduct impulses faster than myelinated fibers.
false
chapter 13/15 (senses) homework
1. Ringing in the ears is called:
tinnitus
2. What part of the eye constitutes the blind spot?
optic disc
3. The receptor organ for hearing is the _____
spiral organ of corti
4. Choose the correctly paired terms.
nyctalopia. night blindness
5. The visible colored portion of the eye is the:
iris
6. _________ are receptors that can respond to changes in pressure.
mechanoreceptors
7. The final step in perceiving sound is:
the auditory cortex is stimulated
8. Which of the following is a characteristic of the lens?
the lens focuses light on the retina
9. There are ____ auditory ossicles in the ear.
three
10. Which of the following is the basic taste quality responsible for a "beef taste"?
umami
11. Which photoreceptors respond to very dim light?
rods
12. Which of the following is not used to classify sensory receptors?
The number of dendritic endings present
13. The distance between two consecutive wave crests is the_______
wavelength
14. Which structure in the eye provides nutrition to all eye layers?
choroid
15. Complex receptors are also called sense organs.
true
16. Taste is independent of smell.
false
17. Choose the false statement about nerves.
The majority of a nerve's bulk is due to axons.
18. Which accessory eye structures function to produce the tears that cleanse and protect the eye?
lacrimal glands
19. The receptors for smell are activated when:
dissolved odorants bind to the receptors in the cilium membranes.
20. What is the vestibular apparatus?
the equilibrium receptors in the semicircular canals and vestibule
21. Choose the false statement about the olfactory epithelium.
It is made of simple squamous epithelium.
22. ______ are collections of neuron cell bodies associated with nerves in the PNS.
ganglia
23. Nerves that only carry impulses away from the central nervous system (CNS) are called:
motor nerves
24. Eye color is determined by the level of brown pigment present.
true
25. Which of the following is not a requirement for something to be tasted?
The tastant must contact the basal cells of the taste buds.
26. Where are equilibrium receptors located?
In the semicircular canals and in the vestibule of the ear.
27. The boundary between the external and middle ear is the:
tympanic membrane
28. Which of the following is true of receptors for dynamic equilibrium?
The receptors for dynamic equilibrium respond to rotation forces.
29. Which of the following correctly matches the equilibrium receptor to the type of equilibrium it monitors?
maculae/static equilibrium
30. Most taste buds are located:
on the tongue
31. Which of the following is a role of the vitreous humor?
It supports the posterior surface of the lens.
32. The peripheral nervous system (PNS) includes the brain and spinal cord.
false
33. Which type of sensory receptor allows us to feel an insect landing on our skin?
mechanoreceptor
chapter 16 (endocrine) homework
1. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.
diabetes
type 2
type1
both type 1 and type 2
2. What is required for the production of anterior pituitary gland hormones?
hormonal stimuli
3. Which of the following hormone pairs are antagonists that regulate blood calcium ion levels?
parathyroid hormone/calcitonin
4. Which of the following pairs correctly match the adrenal gland zone or area with the class of hormones it produces?
zona glomerulosa/mineralocorticoids
5. Which hormone(s) is/are essential to our ability to deal with stress?
glucocorticoids
6. Which of the following hormones helps the body avoid dehydration and water overload?
Antidiuretic hormone
7. Which of the following homeostatic imbalances is characterized by persistent elevated blood glucose levels, dramatic losses in muscle and bone protein, and water and salt retention, leading to hypertension and edema?
Cushing's syndrome
8. What type of hormones bind to receptors located on the cell membrane?
water-soluble hormones, such as insulin and epinephrine
Which intracellular substance degrades cAMP, thus inactivating the response to a hormone?
phosphodiesterase
Growth factor hormones, such as insulin, bind to which type of receptor?
tyrosine kinase receptors
Which is the correct order of events for hormones activating Gs proteins?
activation of G protein, binding of GTP, activation of adenylate cyclase, conversion of ATP to cAMP
Which second messenger causes the release of calcium from the endoplasmic reticulum?
IP3
Which of the following adrenergic receptors increase cAMP levels?
β receptors
9. _____ is the situation when one hormone cannot exert its full effects without another hormone being present.
permissiveness
10. Which of the following is not an endocrine gland?
adenoid
11. Which of the following hormones has intracellular receptors?
cortisol
What is the mechanism of action of lipid-soluble hormones?
activation of genes, which increases protein synthesis in the cell
After a lipid-soluble hormone is bound to its intracellular receptor, what does the hormone complex do?
acts as a transcription factor and binds to DNA, activating a gene
Which hormone’s receptor is always bound to DNA, even when the receptor is empty?
thyroid hormone
What keeps intracellular receptors from binding to DNA before a hormone binds to the receptor?
chaperone proteins (chaperonins)
12. Major hormones circulate to virtually all tissues.
true
13. The stimuli causing endocrine glands to secrete their hormones in direct response to changing blood levels of certain critical ions and nutrients are called ______________.
humoral stimuli
14. Which pancreatic hormone functions to lower blood glucose levels?
insulin
15. Which of the following is not a property of endocrine glands?
they have ducts
16. Which of the following occurs in situations where more than one hormone produces the same effects at the target cell and their combined effects are amplified?
synergism
17. Which of the following hormones stimulates the adrenal cortex to release glucocorticoids that help the body to resist stressors?
Adrenocorticotropic hormone
18. Which hormone is the body's major metabolic hormone?
thyroid hormone
19. Hyperparathyroidism is a rare condition where the bones soften and deform.
true
20. The hypothalamus is known to control the activity of the anterior pituitary, which has traditionally been called the "master endocrine gland."
true
21. Which of the following organs does NOT produce a hormone or hormones?
lungs
22. Hormones that regulate the secretory action of other endocrine glands are called ____________.
tropins
23. Hormones are long-distance chemical signals that travel in blood or lymph throughout the body.
true
24. Which of the following hormones mainly serves to stimulate milk production by the breasts?
prolactin
25. Which of the following is a hormone produced by the posterior pituitary?
none of these
26. When blood glucose levels are high
The pancreas releases insulin
A liver cell responds to insulin by
Taking in glucose and converting it to glycogen.
What cells in the body respond to glucagon by breaking down glycogen and releasing glucose?
Liver cell
Body cells that respond to insulin include
Liver cells, as well as most other cells of the body
When blood glucose levels are low
The pancreas releases glucagon, which eventually causes blood glucose levels to increase
The body's tendency to maintain relatively constant internal conditions is called
homeostasis.
27. What is the primary function of hormones?
alter cell activity
28. The anatomical effects of acromegaly can usually be reversed by surgically removing the tumor from the anterior pituitary.
false
29. Which of the following is not a homeostatic imbalance related to underactivity of the thyroid gland?
graves' disease
30. Up-regulation involves the loss of receptors and prevents the target cells from overreacting to persistently high hormone levels.
false
31. Which of the following glands is found atop the kidneys?
adrenal
32. Which of the following is NOT a major type of stimulus that triggers endocrine glands to manufacture and release hormones?
enzymatic