Question 1

Which of the following best describes the functional divisions of the nervous system?

Accepted Answer

The central nervous system (CNS) processes information, while the peripheral nervous system (PNS) transmits signals between the CNS and the rest of the body.

Question 2

Ouabain blocks Na+/K+ pumps in neurons. What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become less negative as sodium and potassium gradients dissipate.

Question 3

Which of the following statements correctly distinguishes local (graded) potentials from action potentials?

Accepted Answer

Local potentials are decremental and can vary in size, while action potentials are all-or-none and propagate without decrement.

Question 4

During the rising phase of an action potential (point B), which ion channels are primarily open and what is the direction of ion movement?

Accepted Answer

Voltage-gated Na+ channels are open, allowing Na+ to flow into the cell.

Question 5

How does the propagation of an action potential exemplify a positive feedback loop?

Accepted Answer

Opening of voltage-gated Na+ channels causes further depolarization, which opens more Na+ channels.

Question 6

If depolarization at the trigger zone led to a negative feedback loop instead of a positive one, what would be the result?

Accepted Answer

An action potential would not be generated because the system would counteract further depolarization.

Question 7

Multiple sclerosis causes degeneration of myelin. What is the primary effect on neuronal conduction?

Accepted Answer

Conduction speed decreases because myelin is necessary for saltatory conduction.

Question 8

In hypocalcemia, extracellular $$\mathrm{Ca$$^{2+}$$}$$ levels are low. How does this affect activity at a cholinergic synapse?

Accepted Answer

Neurotransmitter release decreases because $$\mathrm{Ca$$^{2+}$$} is $$required for vesicle fusion.

Question 9

A single EPSP depolarizes the trigger zone from $$-70\ \mathrm{mV} to$$ $$-60\ \mathrm{mV}$$, with threshold at $$-55\ \mathrm{mV}. $$Will an action potential be generated?

Accepted Answer

No, because the depolarization does not reach threshold.

Question 10

If two identical EPSPs occur immediately after each other, each depolarizing the membrane from $$-70\ \mathrm{mV} to$$ $$-60\ \mathrm{mV}$$, will an action potential be triggered?

Accepted Answer

Yes, because temporal summation can bring the membrane potential to threshold.

Question 11

If two EPSPs occur simultaneously, each depolarizing the membrane from $$-70\ \mathrm{mV} to$$ $$-60\ \mathrm{mV}$$, what form of summation occurs and will an action potential be triggered?

Accepted Answer

Spatial summation occurs, and an action potential will be triggered if the combined depolarization reaches threshold.

Question 12

Which equation best represents the effect of the Na+/K+ pump on ion gradients across the neuronal membrane?

Accepted Answer

$$3\ \mathrm{Na^+}$$ out, $$2\ \mathrm{K^+} in$$, per ATP hydrolyzed

Question 13

A neuron exposed to ouabain gradually loses its Na+ and K+ gradients. What is the most likely effect on its ability to generate action potentials?

Accepted Answer

The neuron will eventually be unable to generate action potentials due to loss of ion gradients.

Question 14

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 via saltatory conduction.

Question 15

A patient with hypocalcemia is experiencing muscle weakness. Which mechanism at the cholinergic synapse best explains this symptom?

Accepted Answer

Reduced $$\mathrm{Ca$$^{2+}$$}$$ impairs acetylcholine release, decreasing muscle stimulation.

Question 16

Which scenario best illustrates the concept of temporal summation in neuronal signaling?

Accepted Answer

Two EPSPs occur in rapid succession at the same synapse, combining to reach threshold.

Question 17

Which of the following is a plausible consequence of blocking voltage-gated Na+ channels during an action potential?

Accepted Answer

The neuron will fail to depolarize, preventing action potential initiation.

Guided Study: Functional Divisions and Physiology of the Nervous System

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