Question 1

Which of the following best explains why the resting membrane potential of a neuron is negative relative to the extracellular fluid?

Accepted Answer

Potassium ions leak out of the cell through open leak channels, causing a net loss of positive charge from the cytosol.

Question 2

A neuron is exposed to a toxin that blocks all voltage-gated sodium channels. What would be the most immediate effect on the neuron's ability to generate an action potential?

Accepted Answer

The neuron would be unable to reach threshold and initiate depolarization.

Question 3

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

Accepted Answer

It moves two potassium ions in and three sodium ions out per ATP hydrolyzed.

Question 4

A local potential causes the membrane potential of a neuron to change from $$-70\ \mathrm{mV} to$$ $$-60\ \mathrm{mV}. $$Which of the following best describes this event?

Accepted Answer

A depolarization has occurred.

Question 5

Which of the following best describes the difference between continuous and saltatory propagation of action potentials?

Accepted Answer

Saltatory propagation occurs in myelinated axons and is faster because the action potential jumps between nodes of Ranvier.

Question 6

During which phase of the action potential are voltage-gated potassium channels primarily responsible for returning the membrane potential toward the resting value?

Accepted Answer

Repolarization phase

Question 7

A patient has a genetic mutation that causes their neurons to lack myelin sheaths. Which of the following would most likely be observed in this patient?

Accepted Answer

Slower action potential conduction due to reliance on continuous propagation.

Question 8

Which of the following best describes the absolute refractory period?

Accepted Answer

A period when no stimulus, no matter how strong, can trigger another action potential.

Question 9

Which type of ion channel opens in response to a neurotransmitter binding to its receptor on the postsynaptic membrane?

Accepted Answer

Ligand-gated channel

Question 10

A postsynaptic neuron receives input from several presynaptic neurons, resulting in both EPSPs and IPSPs. What is the term for the process by which these inputs combine to determine whether an action potential will be generated?

Accepted Answer

Summation

Question 11

Which of the following best explains why Type A fibers conduct action potentials faster than Type C fibers?

Accepted Answer

Type A fibers have a larger diameter and are heavily myelinated.

Question 12

Which of the following events occurs first during synaptic transmission at a chemical synapse?

Accepted Answer

Voltage-gated calcium channels open in the presynaptic terminal.

Question 13

A neuron is exposed to a drug that prevents the reuptake of neurotransmitters from the synaptic cleft. What is the most likely effect on synaptic transmission?

Accepted Answer

Synaptic transmission will be prolonged due to increased neurotransmitter availability.

Question 14

Which of the following is a characteristic of local (graded) potentials?

Accepted Answer

They are decremental and reversible.

Question 15

If a postsynaptic potential moves the membrane potential from $$-70\ \mathrm{mV} to$$ $$-80\ \mathrm{mV}$$, what type of postsynaptic potential has occurred?

Accepted Answer

Inhibitory postsynaptic potential (IPSP)

Question 16

Which of the following mechanisms does NOT contribute to the termination of synaptic transmission?

Accepted Answer

Continuous opening of voltage-gated sodium channels

Question 17

A patient is diagnosed with a disorder that impairs the function of ligand-gated ion channels. Which of the following processes would be most directly affected?

Accepted Answer

Initiation of postsynaptic potentials at chemical synapses

Question 18

Which of the following best describes the role of voltage-gated calcium channels in synaptic transmission?

Accepted Answer

They trigger the release of neurotransmitter from the presynaptic neuron.

Question 19

A neuron receives a strong excitatory stimulus immediately after the absolute refractory period. What is the most likely outcome?

Accepted Answer

An action potential will be generated if the stimulus is strong enough to reach threshold during the relative refractory period.

Question 20

Which of the following is TRUE regarding electrical synapses?

Accepted Answer

They are found in the brain, cardiac muscle, and visceral smooth muscle.

Introduction to the Nervous System and Nervous Tissue: Electrophysiology and Synapses

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