Question 1

A patient presents with muscle weakness and loss of sensation in the limbs. MRI reveals demyelination in the CNS. Which neuroglial cell is most likely affected, and what is the primary consequence for nerve conduction?

Accepted Answer

Oligodendrocyte; slowed saltatory conduction

Question 2

During an action potential, which ion movement is primarily responsible for the depolarization phase, and what is the effect on membrane potential?

Accepted Answer

$$\mathrm{Na^+}$$ influx; membrane becomes less negative

Question 3

A toxin blocks voltage-gated potassium channels in neurons. What effect would this have on the action potential?

Accepted Answer

It would prolong repolarization, delaying return to resting potential.

Question 4

Which of the following best describes the role of astrocytes in the CNS?

Accepted Answer

Regulating the extracellular environment and supporting the blood-brain barrier

Question 5

A patient is unable to feel pain or temperature on one side of the body after a spinal cord injury. Which type of nerve fiber is most likely damaged?

Accepted Answer

Somatic sensory fibers

Question 6

If the sodium-potassium pump ($$3\ \mathrm{Na^+}$$ out, $$2\ \mathrm{K^+} in) is $$inhibited by a drug, what will happen to the resting membrane potential over time?

Accepted Answer

It will become less negative as $$\mathrm{Na^+}$$ accumulates inside.

Question 7

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin allows action potentials to jump between nodes of Ranvier, a process called saltatory conduction.

Question 8

A neuron receives both excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) at the same time. What determines whether an action potential will be generated?

Accepted Answer

The sum of all EPSPs and IPSPs at the axon hillock reaching threshold

Question 9

Which neurotransmitter is released at neuromuscular junctions to stimulate skeletal muscle contraction?

Accepted Answer

Acetylcholine

Question 10

A patient is given a drug that blocks acetylcholinesterase. What is the expected effect at the neuromuscular junction?

Accepted Answer

Prolonged muscle contraction due to increased acetylcholine

Question 11

Which of the following best describes the direction of axonal transport called 'anterograde'?

Accepted Answer

From cell body to axon terminal

Question 12

A patient with multiple sclerosis (MS) experiences muscle weakness and vision problems. Which process is most directly impaired in their neurons?

Accepted Answer

Saltatory conduction

Question 13

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

Accepted Answer

Action potentials occur fully if threshold is reached, or not at all.

Question 14

A neuron is exposed to a drug that increases chloride ($$\mathrm{Cl^-}) $$permeability. What is the likely effect on the postsynaptic membrane?

Accepted Answer

It will hyperpolarize, making action potentials less likely.

Question 15

Which of the following is a function of microglial cells in the CNS?

Accepted Answer

Phagocytosing pathogens and debris

Question 16

A patient is diagnosed with a tumor that blocks the flow of cerebrospinal fluid (CSF). Which neuroglial cell type is most likely involved in the normal circulation of CSF?

Accepted Answer

Ependymal cells

Question 17

Which of the following best describes the effect of endorphins in the nervous system?

Accepted Answer

They act as natural opiates, reducing pain perception.

Question 18

A neuron has a resting membrane potential of $$-70\ \mathrm{mV}. If $$the membrane becomes more negative, reaching $$-80\ \mathrm{mV}$$, what is this process called?

Accepted Answer

Hyperpolarization

Question 19

Which of the following best explains why the sodium-potassium pump is essential for maintaining the resting membrane potential?

Accepted Answer

It actively transports $$3\ \mathrm{Na^+}$$ out and $$2\ \mathrm{K^+} in$$, maintaining ionic gradients.

Question 20

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

Accepted Answer

Action potentials cannot be initiated.

Nervous System & Nervous Tissue: Study Guide

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