Question 1

Which of the following best describes the resting membrane potential (RMP) of a typical neuron?

Accepted Answer

The inside of the neuron is negative relative to the outside, with a typical value of -70mV.

Question 2

During the depolarization phase of an action potential, which ion moves into the neuron and through which type of channel?

Accepted Answer

Sodium (Na+) moves into the neuron through voltage-gated sodium channels.

Question 3

What is the threshold value for initiating an action potential in a neuron?

Accepted Answer

$$-55\,	ext{mV}$$

Question 4

Which statement best explains the 'all or none' principle of action potentials?

Accepted Answer

Once threshold is reached, an action potential is generated to its fullest extent, regardless of stimulus strength.

Question 5

What is the primary function of acetylcholinesterase at the synapse?

Accepted Answer

It breaks down acetylcholine into acetate and choline, terminating the signal.

Question 6

Which of the following best describes saltatory conduction?

Accepted Answer

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

Question 7

A patient is exposed to a toxin that blocks voltage-gated calcium channels at the axon terminal. What effect would this have on synaptic transmission?

Accepted Answer

Neurotransmitter release would be inhibited, preventing signal transmission to the postsynaptic cell.

Question 8

Which sequence correctly describes the events at a chemical synapse?

Accepted Answer

Action potential arrives → calcium enters axon terminal → neurotransmitter released → neurotransmitter binds postsynaptic receptor → postsynaptic ion channels open

Question 9

Which of the following is TRUE regarding the refractory period of a neuron?

Accepted Answer

A neuron cannot generate a new action potential during the refractory period.

Question 10

If the extracellular fluid (ECF) of a neuron becomes depleted of sodium ions (Na+), what would be the most likely effect on action potential generation?

Accepted Answer

Action potentials would be inhibited because sodium influx is necessary for depolarization.

Question 11

Which of the following best describes the role of chemically-gated ion channels at the postsynaptic membrane?

Accepted Answer

They open in response to neurotransmitter binding, allowing Na+ and K+ to flow and generating a graded potential.

Question 12

A neuron receives a sub-threshold stimulus. What is the most likely outcome?

Accepted Answer

A slight change in membrane potential occurs, but no action potential is generated.

Question 13

Which of the following ions is most abundant in the intracellular fluid (ICF) of a neuron?

Accepted Answer

Potassium (K+)

Question 14

During repolarization of the neuron, which event occurs?

Accepted Answer

K+ channels open and K+ leaves the cell.

Question 15

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

Accepted Answer

Action potentials jump between nodes of Ranvier in myelinated axons, reducing the distance traveled.

Question 16

If acetylcholinesterase is inhibited at the synapse, what would be the most likely effect?

Accepted Answer

Acetylcholine would accumulate, causing prolonged stimulation of the postsynaptic cell.

Question 17

Which of the following is a real-life example of the importance of the refractory period in neurons?

Accepted Answer

It prevents the heart from beating too rapidly by ensuring each contraction is followed by a rest period.

Question 18

Which equation best represents the change in membrane potential during depolarization?

Accepted Answer

$$V_{m} = V_{rest} + \Delta V_{Na+}$$

Question 19

A patient is diagnosed with a genetic disorder that causes defective chemically-gated ion channels on the postsynaptic membrane. Which symptom would most likely be observed?

Accepted Answer

Impaired synaptic transmission, leading to muscle weakness or paralysis.

Neurophysiology: Membrane Potentials, Action Potentials, and Synaptic Transmission

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