Question 1

Which of the following best describes the function of Schwann cells in the peripheral nervous system?

Accepted Answer

They wrap around axons to form insulating myelin sheaths, increasing the speed of action potential conduction.

Question 2

A patient is diagnosed with multiple sclerosis, a disease characterized by the loss of myelin in the central nervous system. Which glial cell type is primarily affected?

Accepted Answer

Oligodendrocytes

Question 3

According to the Nernst equation, what would be the equilibrium potential for potassium ($$K^+) if $$the extracellular concentration is 5 mM and the intracellular concentration is 150 mM? Use the simplified Nernst equation: $$E_{ion} = 61 \log \left( \frac{[ion]_{out}}{[ion]_{in}} \right) (in mV).$$

Accepted Answer

$$E_{K^+} = 61 \log \left( \frac{5}{150} \right) = -89 mV$$

Question 4

Which of the following best explains why action potentials travel faster in myelinated axons compared to unmyelinated axons?

Accepted Answer

Myelin insulates the axon, allowing saltatory conduction between nodes of Ranvier, which increases conduction velocity.

Question 5

A neuron receives multiple graded potentials at its dendrites. Which of the following factors will NOT contribute to the loss of strength of these graded potentials as they travel toward the axon hillock?

Accepted Answer

The presence of voltage-gated sodium channels

Question 6

During the rising phase of the action potential, which of the following events occurs?

Accepted Answer

Voltage-gated sodium channels open, allowing $$Na^+ to $$enter the cell.

Question 7

Which of the following best describes the absolute refractory period of an action potential?

Accepted Answer

It is the period when sodium channels are resetting and no new action potential can be initiated, regardless of stimulus strength.

Question 8

A researcher is studying the effect of axon diameter on conduction velocity. If the diameter of an unmyelinated axon is doubled, what is the expected effect on the speed of action potential propagation?

Accepted Answer

The speed will increase because the internal resistance decreases.

Question 9

Which of the following is a function of astrocytes in the central nervous system?

Accepted Answer

Maintaining water-potassium balance and contributing to the blood-brain barrier

Question 10

A neuron is at its resting membrane potential of $$-70 mV. A $$depolarizing stimulus causes the membrane potential to reach threshold. What is the next event in the sequence of an action potential?

Accepted Answer

Voltage-gated sodium channels open, causing $$Na^+ to $$enter the cell.

Question 11

Which of the following best describes the role of the axon hillock in a neuron?

Accepted Answer

It is the region where graded potentials are integrated and action potentials are initiated if threshold is reached.

Question 12

A patient has a genetic mutation that causes voltage-gated sodium channels to remain inactivated longer than normal after an action potential. What is the most likely effect on neuronal signaling?

Accepted Answer

The absolute refractory period will be prolonged, reducing the maximum firing frequency.

Question 13

Which of the following equations predicts the membrane potential resulting from the combined effect of all permeant ions?

Accepted Answer

The Goldman-Hodgkin-Katz (GHK) equation

Question 14

A neuron is exposed to a toxin that blocks voltage-gated potassium channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed, causing the action potential to last longer.

Question 15

Which of the following best describes saltatory conduction?

Accepted Answer

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

Question 16

A neuron has a resting membrane potential primarily determined by the concentration gradient of which ion?

Accepted Answer

Potassium ($$K^+)$$

Question 17

Which of the following is a correct statement about graded potentials?

Accepted Answer

They lose strength as they move through the cell due to current leak and cytoplasmic resistance.

Question 18

A patient presents with a loss of sensation in the limbs. Which type of neuron is most likely affected?

Accepted Answer

Sensory (afferent) neuron

Question 19

Which of the following best explains why the refractory period prevents backward conduction of the action potential?

Accepted Answer

The membrane behind the action potential is hyperpolarized and cannot be depolarized immediately.

Question 20

A squid giant axon has a diameter of 0.9 mm. If a mammalian nerve contains 100 axons, each with the same diameter as the squid giant axon, what would be the total cross-sectional area of the mammalian nerve? (Area of a circle: $$A = \pi r^2$)

Accepted Answer

$$A = 100 	imes \pi 	imes (0.45)^2$ = 63.6 mm$^2$$

Ch8A Neurons: Cell and Network Properties – Organization and Anatomy of the Nervous System

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