Question 1

Which of the following best explains why the resting membrane potential of a neuron is typically around $$-70 mV$$?

Accepted Answer

There is a greater permeability to $$K^+$$ ions than $$Na^+$$ ions, and the sodium-potassium pump maintains ionic gradients.

Question 2

A patient is exposed to a toxin that blocks all voltage-gated $$Na^+$$ channels in neurons. What would be the most immediate effect on neuronal signaling?

Accepted Answer

Action potentials would not be generated, preventing long-distance signaling.

Question 3

Which of the following scenarios best illustrates spatial summation in a postsynaptic neuron?

Accepted Answer

Multiple presynaptic neurons fire simultaneously at different locations on the postsynaptic neuron, combining their effects.

Question 4

During which phase of the action potential are voltage-gated $$K^+$$ channels open and $$Na^+$$ channels are inactivating?

Accepted Answer

Repolarization

Question 5

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

Accepted Answer

If threshold is reached, an action potential will fire completely; if not, it will not fire at all.

Question 6

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

Accepted Answer

The membrane potential will become more negative (hyperpolarized).

Question 7

Which of the following is a key difference between graded potentials and action potentials?

Accepted Answer

Graded potentials can summate and decay over distance, while action potentials are self-propagating and do not decay.

Question 8

If a neuron is in the absolute refractory period, which of the following is true?

Accepted Answer

No stimulus, regardless of strength, can trigger another action potential.

Question 9

Saltatory conduction is faster than continuous conduction because:

Accepted Answer

Myelin sheaths allow the action potential to jump from node to node, reducing ion leakage.

Question 10

Which of the following best describes the effect of an excitatory postsynaptic potential (EPSP) on a neuron?

Accepted Answer

It opens ligand-gated cation channels, causing depolarization.

Question 11

A neuron receives repeated stimulation from a single presynaptic neuron in rapid succession. This is an example of:

Accepted Answer

Temporal summation

Question 12

Which of the following would most likely increase the conduction velocity of an action potential along an axon?

Accepted Answer

Increasing the degree of myelination

Question 13

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

Accepted Answer

Some $$K^+$$ channels remain open, and $$Na^+$$ channels reset.

Question 14

Which of the following best explains why graded potentials decay over distance, but action potentials do not?

Accepted Answer

Action potentials are regenerated by voltage-gated channels along the axon, while graded potentials are not.

Question 15

A neuron is exposed to a drug that blocks all chemically gated (ligand-gated) channels. Which process would be most directly affected?

Accepted Answer

Generation of graded potentials at the postsynaptic membrane

Question 16

Which of the following is true regarding the relative refractory period?

Accepted Answer

A stronger-than-normal stimulus can generate another action potential.

Question 17

If the sodium-potassium pump ($$3 Na^+$$ out, $$2 K^+ in) is $$inhibited in a neuron, what is the most likely consequence?

Accepted Answer

The resting membrane potential will gradually depolarize.

Question 18

Which of the following best describes the role of voltage-gated ion channels in the propagation of an action potential?

Accepted Answer

They open and close in response to changes in membrane potential, regenerating the action potential along the axon.

Question 19

A patient has a genetic mutation that causes their axons to lack myelin sheaths. Which of the following symptoms would you most likely expect?

Accepted Answer

Slower nerve impulse conduction and possible signal loss

Question 20

Which of the following is a direct result of opening ligand-gated cation channels at the postsynaptic membrane?

Accepted Answer

Generation of an excitatory postsynaptic potential (EPSP)

Neurophysiology: Membrane Potentials and Action Potentials

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