4) What is the correct sequence of events in a stretch-sensitive sensory neuron?

Question

4) What is the correct sequence of events in a stretch-sensitive sensory neuron? (4.5 points)

action potential(s)

action potential propagation

graded potential (receptor potential)

neurotransmitter release

opening of mechanically-gated ion channels

opening of voltage-gated calcium channels

opening of voltage-gated sodium channels

sensory stimulus (muscle stretch)

summation of graded potentials

5) What is the correct sequence of signal transduction? (There can be missing steps, but the sequence must be correct.) (4 points)

a) sensory stimulus -> receptor potential in afferent -> action potential(s) in afferent -> neurotransmitter release by afferent

b) neurotransmitter release by afferent -> action potential(s) in efferent -> neurotransmitter release by efferent -> end plate potential -> muscle contraction

c) synaptic potential in efferent -> action potential(s) in efferent -> neurotransmitter release by efferent -> muscle contraction

d) All of the above are correct. e) None of the above are correct.

8) Where are interneurons found? (3 points) a) only in the brain

b) only in the spinal cord
c) only in the CNS
d) throughout the nervous system e) only in spinal nerves

12) In a typical neuron, where would you expect to observe a graded potential? Choose ALL that apply. Base your answer on what we discussed in lecture. (5 points)

a) dendrite
b) presynaptic terminal c) trigger zone

13) In a typical neuron, where would you expect to find voltage-gated Na+ channels? Choose ALL that apply. Base your answer on what we discussed in lecture. (5 points)

a) dendrite
b) presynaptic terminal c) trigger zone

14) Curare was once used as the sole anesthetic for surgery until it was realized that the patients’ sense of feeling was unaffected. Patients experienced the pain of surgery, but could not react until the curare “wore off”. Predict how curare could block patients from reacting to pain but not from feeling pain. (3.5 points)

a) Curare affects transmission of information between sensory neurons and their postsynaptic cells, but not between motor neurons and their postsynaptic cells

b) Curare affects transmission of information between motor neurons and their postsynaptic cells, but not between sensory neurons and their postsynaptic cells

c) Curare affects transmission of information between both sensory neurons and their postsynaptic cells, and motor neurons and their postsynaptic cells

17) If a neurotransmitter caused ion channels to open and sodium ions flowed into the cell, the cell would (depolarize, hyperpolarize); if chloride ions flowed out of the cell, the cell would (depolarize, hyperpolarize). (3 points)

a) depolarize, depolarize
b) depolarize, hyperpolarize
c) hyperpolarize, depolarize
d) hyperpolarize, hyperpolarize

20) A graded potential is a transient depolarization or hyperpolarization of an excitable cell. Why does the membrane potential return to its resting value (e.g., -65 mV)? Choose ALL that apply. (4 points)

a) because of the effects of the Na/K pump and/or other membrane pumps
b) because ion channels open, and ions flow returning the membrane potential to its resting

value
c) because concentrations have not changed d) because only leakage channels are open

30) Batrachotoxin, a toxin from the poison dart frog, was used historically for hunting on the end of a dart to paralyze prey. This toxin selectively binds sodium (Na+) voltage-gated channels causing a conformational change that decreases the voltage required for channel opening, increases the permeability of the channel to sodium and calcium, and prolongs the open state of the channel.

What does “decreasing the voltage required for channel opening” mean about the change in voltage required to cause opening of the channel? Select ALL that apply. (5 points)

a) It takes less depolarization to open and will now open at a more positive value b) It takes more depolarization and will now open at a more negative value
c) Threshold has changed.
d) It takes less depolarization to open and will now open at a more negative value e) It takes more depolarization and will now open at a more positive value

35) Which of the following would NOT influence the time necessary for an action potential to be propagated the length of a particular neuron? (3 points)

a) absence of nodes of Ranvier
b) diameter of the axon
c) length of the axon
d) presence or absence of a myelin sheath
e) type of neuron (e.g., whether axon is sensory or motor)

36) Which of the following is the most direct result of depolarizing the presynaptic membrane of an axon terminal? (3 points)

a) an EPSP or IPSP is generated in the postsynaptic cell
b) ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft c) synaptic vesicles fuse with the membrane
d) the postsynaptic cell produces an action potential
e) voltage-gated Ca++ channels in the membrane open

37) Release of neurotransmitter by presynaptic neurons can have what effect on the membrane potential of postsynaptic neurons? (3 points)

a) depolarization
b) hyperpolarization c) both
d) neither

38) Organophosphate insecticides are acetylcholinesterase inhibitors. What would be the most pronounced effect you would expect to observe in the postsynaptic potential (produced by acetylcholine binding to acetylcholine receptors) after an organophosphate insecticide was applied? (4 points)

a) decreased amplitude in the graded potential b) increased amplitude in the graded potential c) inhibition of the post-synaptic potential
d) prolonged post-synaptic potential

39) When a second EPSP, due to activating the same synapse, arrives at the trigger zone before the effects of a first have disappeared, what occurs? (3 points)

a) decrease in speed of impulse transmission b) extinction of the impulse
c) hyperpolarization
d) spatial summation

e) temporal summation

40) The duration of a graded potential can be influenced most directly by which of the following? Choose ALL that apply. (5 points)

a) How long the neurotransmitter remains bound to the receptor.

b) How quickly the ion channels open in the postsynaptic cell.

c) The number of postsynaptic receptors present.

d) The rate at which the neurotransmitter is degraded or removed from the synaptic cleft.

Explanation / Answer

Ans 4) The sequence are given below:-

1. Sensory stimulus (muscle stretch)

2. Graded potential

3. Action Potential Propagation

4. Opening of voltage gated Sodium Channel.

5. Opening of Voltage gated Calcium channel

6. Opening of mechanically-gated ion channels

7. Action Potential.

8. Summation of graded potential.

9. Neurotransmitter release

Ans 8) Interneurons are found in " c) Central Nervous System (CNS). " This means they are mainly found in brain and spinal cord.

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