Question 1

Which phase of the action potential is characterized by the rapid influx of Na$$^+$$ ions into the neuron, and what is the primary cause of this influx?

Accepted Answer

Depolarization phase; opening of voltage-gated sodium channels

Question 2

During which phase of the action potential do potassium ions (K$$^+) $$move out of the neuron, and what is the effect on membrane potential?

Accepted Answer

Repolarization; membrane potential returns toward resting value

Question 3

What is the typical resting membrane potential of a neuron, and which ions are primarily responsible for maintaining this potential?

Accepted Answer

$$-70 mV$$; sodium (Na$$^+) $$and potassium (K$$^+)$$

Question 4

What is the role of the sodium-potassium ATPase pump in maintaining the resting potential of a neuron?

Accepted Answer

It actively transports 3 Na$$^+$$ out and 2 K$$^+$$ into the cell, using ATP.

Question 5

If a neuron fails to reach the threshold potential, what will be the result?

Accepted Answer

No action potential will be generated.

Question 6

Which of the following best describes saltatory conduction in myelinated axons?

Accepted Answer

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

Question 7

In multiple sclerosis, the myelin sheath deteriorates. What is the most likely effect on nerve impulse transmission?

Accepted Answer

Impulse transmission slows down and becomes less reliable.

Question 8

What triggers the release of neurotransmitters from synaptic vesicles at the synaptic terminal?

Accepted Answer

Influx of calcium ions (Ca$$^{2+})$$

Question 9

Which of the following neurotransmitters is most directly involved in muscle contraction at the neuromuscular junction?

Accepted Answer

Acetylcholine

Question 10

A patient is exposed to a toxin that blocks voltage-gated sodium channels. What is the most immediate effect on neuronal signaling?

Accepted Answer

Action potentials cannot be initiated.

Question 11

Which of the following best explains why ions cannot freely diffuse across the neuronal plasma membrane?

Accepted Answer

Ions are charged and require specific protein channels to cross the hydrophobic lipid bilayer.

Question 12

During the falling phase of the action potential, which ion channel is primarily open, and what is the direction of ion movement?

Accepted Answer

Potassium channel; K$$^+$$ moves out of the cell

Question 13

Which of the following is the correct sequence of events during synaptic transmission?

Accepted Answer

Action potential arrives at terminal → Ca$$^{2+}$$ channels open → Neurotransmitter released → Neurotransmitter binds to postsynaptic receptors

Question 14

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

Accepted Answer

An action potential is either fully generated if threshold is reached, or not generated at all.

Question 15

Which glial cell type is responsible for forming myelin sheaths in the central nervous system?

Accepted Answer

Oligodendrocytes

Question 16

A neuron is at rest with a membrane potential of $$-70 mV. If $$the membrane becomes more negative (e.g., $$-80 mV$$), what is this process called?

Accepted Answer

Hyperpolarization

Question 17

Which of the following is NOT a function of glial cells?

Accepted Answer

Transmitting electrical signals

Question 18

What would happen if the sodium-potassium ATPase pump stopped functioning in a neuron?

Accepted Answer

The concentration gradients of Na$$^+$$ and K$$^+$$ would dissipate, and the resting potential would be lost.

Question 19

Which of the following best explains why the action potential only travels in one direction along an axon?

Accepted Answer

Voltage-gated sodium channels become inactivated immediately after opening, preventing backward propagation.

General Biology: Neurons, Nervous System, and Sensory Systems Study Guide

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