Question 1

Which of the following best describes the main function of the central nervous system (CNS)?

Accepted Answer

To integrate sensory information and coordinate appropriate responses.

Question 2

A neuron at rest has a membrane potential closest to the equilibrium potential of which ion, and why?

Accepted Answer

Potassium, because the membrane is much more permeable to potassium ions at rest.

Question 3

Which of the following equations is used to calculate the equilibrium potential for a single ion across a membrane?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$$

Question 4

A patient is diagnosed with multiple sclerosis, a disease that damages myelin sheaths. Which of the following would most likely be observed in their neurons?

Accepted Answer

Decreased speed of action potential propagation due to loss of saltatory conduction.

Question 5

Which type of glial cell is primarily responsible for forming the myelin sheath in the central nervous system?

Accepted Answer

Oligodendrocyte

Question 6

During the depolarization phase of an action potential, which of the following occurs?

Accepted Answer

Voltage-gated sodium channels open, allowing Na$$^+ to $$enter the cell.

Question 7

A graded potential differs from an action potential in that:

Accepted Answer

It can be summed and is decremental, decreasing in strength as it spreads.

Question 8

If the resting membrane potential of a neuron is $$-70\ \mathrm{mV}$$ and the threshold for action potential is $$-55\ \mathrm{mV}$$, what minimum depolarization is required to trigger an action potential?

Accepted Answer

$$15\ \mathrm{mV}$$

Question 9

Which of the following best explains why action potentials are unidirectional along an axon?

Accepted Answer

The refractory period prevents the action potential from traveling backward.

Question 10

A neuron is exposed to tetrodotoxin (TTX), which blocks voltage-gated sodium channels. What is the most likely effect on the neuron?

Accepted Answer

It will be unable to generate action potentials.

Question 11

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next, increasing conduction speed.

Question 12

Which of the following is a correct statement about the sodium-potassium pump?

Accepted Answer

It moves 3 Na$$^+$$ ions out and 2 K$$^+$$ ions in per ATP hydrolyzed.

Question 13

A neuron receives two subthreshold excitatory stimuli in rapid succession at the same synapse. What is this phenomenon called, and what is its effect?

Accepted Answer

Temporal summation; it increases the likelihood of action potential generation.

Question 14

Which of the following best describes the role of voltage-gated potassium channels during an action potential?

Accepted Answer

They open during repolarization to allow K$$^+$$ efflux.

Question 15

A neuron has a resting membrane potential of $$-70\ \mathrm{mV}. If $$the extracellular potassium concentration increases, what will happen to the resting membrane potential?

Accepted Answer

It will become less negative (depolarize).

Question 16

Which of the following is a key difference between ligand-gated and voltage-gated ion channels?

Accepted Answer

Ligand-gated channels open in response to neurotransmitter binding, while voltage-gated channels open in response to changes in membrane potential.

Question 17

Which of the following best explains why graded potentials are decremental?

Accepted Answer

They lose strength as they spread due to leakage of charge across the membrane.

Question 18

A neuron is classified as multipolar if it:

Accepted Answer

Has one axon and two or more dendrites.

Question 19

Which of the following best describes the effect of the refractory period on the frequency of action potentials?

Accepted Answer

It limits the maximum frequency at which a neuron can fire action potentials.

Anatomy & Physiology: The Nervous System – Structure, Function, and Electrical Signaling

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