Question 1

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

Accepted Answer

It is the electric potential of the inside of the cell relative to the outside, typically around $$-70\ \mathrm{mV}.$$

Question 2

What is the primary mechanism responsible for maintaining the negative resting membrane potential in neurons?

Accepted Answer

The activity of $$\mathrm{Na^+/K^+}$$ pumps, which move $$3\ \mathrm{Na^+}$$ out and $$2\ \mathrm{K^+} in.$$

Question 3

Which property allows neurons and muscle cells to change their membrane potentials?

Accepted Answer

Excitability

Question 4

A graded potential that depolarizes the membrane is most likely caused by:

Accepted Answer

Opening of ligand-gated $$\mathrm{Na^+}$$ channels

Question 5

Which of the following statements about action potentials is TRUE?

Accepted Answer

They follow the all-or-none law and always reach the same amplitude once threshold is reached.

Question 6

What is the threshold membrane potential for opening voltage-gated $$\mathrm{Na^+}$$ channels in neurons?

Accepted Answer

$$-55\ \mathrm{mV}$$

Question 7

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

Accepted Answer

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

Question 8

What is the main difference between graded potentials and action potentials?

Accepted Answer

Graded potentials vary in magnitude and decrease with distance, while action potentials are all-or-none and propagate without decrement.

Question 9

Which of the following best explains the absolute refractory period?

Accepted Answer

It is the period during which $$\mathrm{Na^+}$$ channels are inactive and no stimulus can trigger another action potential.

Question 10

Saltatory conduction in myelinated neurons is characterized by:

Accepted Answer

Action potentials leaping from one node of Ranvier to the next.

Question 11

Which factor increases the speed of action potential conduction in neurons?

Accepted Answer

Increased myelination

Question 12

A stronger stimulus is encoded in a neuron by:

Accepted Answer

Increasing the frequency of action potentials

Question 13

Which of the following is TRUE about electrical synapses?

Accepted Answer

They are joined by gap junctions allowing ions and molecules to pass directly between cells.

Question 14

At a chemical synapse, what is the role of synaptic vesicles?

Accepted Answer

They store neurotransmitters for release into the synaptic cleft.

Question 15

Otto Loewi’s experiment demonstrated that synaptic transmission at the neuromuscular junction is:

Accepted Answer

Chemical, involving neurotransmitter release.

Question 16

Which of the following best describes the function of the $$\mathrm{Na^+/K^+}$$ pump during the after-hyperpolarization phase?

Accepted Answer

It quickly reestablishes the resting potential by moving $$3\ \mathrm{Na^+}$$ out and $$2\ \mathrm{K^+} in.$$

Question 17

Which of the following is a correct sequence of events during the generation of an action potential?

Accepted Answer

Opening of voltage-gated $$\mathrm{Na^+}$$ channels, followed by opening of voltage-gated $$\mathrm{K^+}$$ channels.

Question 18

Which of the following is TRUE about the synapse in the peripheral nervous system (PNS)?

Accepted Answer

The second cell can be a muscle or gland, forming a neuromuscular junction.

Question 19

Which statement about graded potentials is correct?

Accepted Answer

They can be depolarizing or hyperpolarizing and vary in magnitude.

Electrical Activity in Neurons and Synaptic Transmission: Cell Biology Study Notes

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