Question 1

Which of the following best describes the function of the axon hillock in a neuron?

Accepted Answer

It is the region where action potentials are initiated due to the summation of excitatory and inhibitory inputs.

Question 2

A neuron is placed in a solution that blocks all voltage-gated sodium ($$\mathrm{Na^+}) $$channels. What will be the most immediate effect on the neuron's ability to generate an action potential?

Accepted Answer

The neuron will be unable to reach threshold and initiate an action potential.

Question 3

Which of the following statements about the resting membrane potential ($$\mathrm{RMP}) of a $$typical neuron is CORRECT?

Accepted Answer

The $$\mathrm{RMP} is $$established because the membrane is more permeable to $$\mathrm{K^+}$$ than to $$\mathrm{Na^+}.$$

Question 4

A patient with multiple sclerosis (MS) experiences muscle weakness and vision problems. Which of the following best explains the physiological basis for these symptoms?

Accepted Answer

Destruction of the myelin sheath slows or blocks action potential propagation along axons.

Question 5

Which of the following best describes the effect of increasing axon diameter on the speed of action potential propagation?

Accepted Answer

It increases the speed of propagation by decreasing internal resistance.

Question 6

During the absolute refractory period of an action potential, which of the following is true?

Accepted Answer

Voltage-gated $$\mathrm{Na^+}$$ channels are inactivated and cannot reopen immediately.

Question 7

Which of the following best explains why action potentials propagate in only one direction along an axon?

Accepted Answer

The refractory period prevents the region behind the action potential from being re-excited immediately.

Question 8

A neuron receives simultaneous excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) at different locations on its dendrites. What is this process called?

Accepted Answer

Spatial summation

Question 9

Which of the following is a key difference between electrical and chemical synapses?

Accepted Answer

Chemical synapses are unidirectional and involve neurotransmitter release, while electrical synapses allow bidirectional ion flow through gap junctions.

Question 10

Which of the following best describes the role of the $$\mathrm{Na^+/K^+}$$ ATPase pump in neurons?

Accepted Answer

It actively transports $$3\ \mathrm{Na^+}$$ out of the cell and $$2\ \mathrm{K^+}$$ into the cell, maintaining the resting membrane potential.

Question 11

A neuron is exposed to a drug that increases the permeability of its membrane to $$\mathrm{K^+}. $$What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become more negative (hyperpolarized).

Question 12

Which of the following events occurs first during the generation of an action potential?

Accepted Answer

Opening of voltage-gated $$\mathrm{Na^+}$$ channels

Question 13

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin insulates the axon, allowing action potentials to jump between nodes of Ranvier via saltatory conduction.

Question 14

A postsynaptic neuron receives a neurotransmitter that opens ligand-gated chloride ($$\mathrm{Cl^-}) $$channels. What is the likely effect on the postsynaptic membrane?

Accepted Answer

It will hyperpolarize, making an action potential less likely.

Question 15

Which of the following best describes the 'all-or-none' property of action potentials?

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated; subthreshold stimuli do not produce action potentials.

Question 16

Which of the following mechanisms does NOT contribute to the termination of neurotransmitter action at a chemical synapse?

Accepted Answer

Continuous opening of voltage-gated $$\mathrm{Na^+}$$ channels

Question 17

A neuron receives two excitatory inputs in rapid succession at the same synapse, resulting in a larger depolarization. What is this phenomenon called?

Accepted Answer

Temporal summation

Question 18

Which of the following is TRUE regarding graded potentials?

Accepted Answer

They decrease in magnitude with distance from the site of stimulation.

Question 19

A neuron is exposed to a toxin that blocks the reuptake of neurotransmitters at the synaptic cleft. What is the most likely effect?

Accepted Answer

Neurotransmitter will remain in the synaptic cleft longer, prolonging its effect on the postsynaptic cell.

Physiology of Neurons: Structure, Function, and Electrical Activity

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