Question 1

Which of the following best describes the main factor responsible for the negative resting membrane potential ($$-70 mV) in a $$typical neuron?

Accepted Answer

The selective permeability of the membrane to potassium ions ($$\mathrm{K^+}) $$and the presence of negatively charged proteins inside the cell

Question 2

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

Accepted Answer

Sodium channels open, allowing $$\mathrm{Na^+} to $$enter the cell

Question 3

A patient receives a drug that blocks voltage-gated sodium channels. What is the most likely effect on neuronal action potentials?

Accepted Answer

Action potentials will not be generated

Question 4

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

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated

Question 5

What is the primary difference between continuous and saltatory conduction of action potentials?

Accepted Answer

Saltatory conduction is faster because the action potential jumps from node to node, while continuous conduction is slower and occurs along the entire axon

Question 6

Refer to the synaptic transmission diagrams. What is the role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) at $$the synaptic terminal?

Accepted Answer

They trigger the fusion of synaptic vesicles with the presynaptic membrane, leading to neurotransmitter release

Question 7

Which enzyme is responsible for terminating the action of acetylcholine at the synaptic cleft?

Accepted Answer

Acetylcholinesterase

Question 8

A neuron is exposed to a sub-threshold stimulus. What is the expected outcome?

Accepted Answer

A small depolarization occurs, but no action potential is generated

Question 9

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

Accepted Answer

Acetylcholine will accumulate, causing prolonged stimulation of the postsynaptic cell

Question 10

Which of the following best describes the sequence of events at a chemical synapse?

Accepted Answer

Action potential arrives, calcium enters, vesicles release neurotransmitter, neurotransmitter binds to postsynaptic receptors

Question 11

During the repolarization phase of an action potential, which ion movement is primarily responsible?

Accepted Answer

$$\mathrm{K^+}$$ efflux

Question 12

A neuron is unable to generate a new action potential immediately after firing. This period is known as:

Accepted Answer

Refractory period

Question 13

Which of the following would most likely occur if the extracellular concentration of $$\mathrm{K^+}$$ increased significantly?

Accepted Answer

The resting membrane potential would become less negative (depolarized)

Question 14

Which statement best explains why action potentials travel in only one direction along an axon?

Accepted Answer

The refractory period prevents the action potential from traveling backward

Question 15

A patient is exposed to a toxin that prevents the reuptake of choline into the presynaptic neuron. What is the most likely effect?

Accepted Answer

Decreased synthesis of acetylcholine

Question 16

Which of the following is a correct sequence of events during synaptic transmission, as shown in the diagrams?

Accepted Answer

Action potential arrives, calcium enters, neurotransmitter is released, neurotransmitter binds to postsynaptic receptor

Question 17

Which of the following best describes the effect of a threshold stimulus on a neuron?

Accepted Answer

It opens enough sodium channels to initiate an action potential

Question 18

If a neuron is exposed to a chemical that blocks potassium channels, what is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed or inhibited

Question 19

Which of the following is true regarding the distribution of ions in a resting neuron?

Accepted Answer

The intracellular fluid (ICF) is rich in potassium and negatively charged proteins

Neurophysiology: Resting Membrane Potential, Action Potentials, and Synaptic Transmission

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