Question 1

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

Accepted Answer

It is negative inside relative to outside, primarily due to K$$^+$$ leak channels.

Question 2

A cell has the following ion concentrations: [K$$^+$$]$$_{in} = 140 mM$$, [K$$^+$$]$$_{out} = 5 mM. $$Using the Nernst equation $$E = \frac{RT}{zF} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$$, what is the sign of the equilibrium potential for K$$^+$$?

Accepted Answer

Negative, because K$$^+$$ will tend to leave the cell, making the inside more negative.

Question 3

During the rising phase of the action potential, which of the following best explains the rapid depolarization?

Accepted Answer

Opening of voltage-gated Na$$^+$$ channels, allowing Na$$^+ to $$enter the cell.

Question 4

If the extracellular fluid (ECF) is hypertonic relative to the intracellular fluid (ICF), what will happen to a red blood cell placed in this solution?

Accepted Answer

The cell will shrink as water leaves the cell.

Question 5

Which of the following is a non-penetrating solute commonly used in physiology experiments?

Accepted Answer

NaCl

Question 6

A neuron is exposed to a drug that increases the permeability of its membrane to Cl$$^-. $$What effect will this have on the membrane potential?

Accepted Answer

It will hyperpolarize the membrane, making it more negative inside.

Question 7

Which of the following best describes the function of the Na$$^+/K$^+-$$ATPase pump in maintaining the resting membrane potential?

Accepted Answer

It actively transports 3 Na$$^+$$ out and 2 K$$^+ in$$, maintaining concentration gradients.

Question 8

If a cell's membrane potential is at the equilibrium potential for K$$^+$$, what is true about the net movement of K$$^+$$ ions?

Accepted Answer

There is no net movement of K$$^+$$ ions across the membrane.

Question 9

A solution contains 100 mM NaCl and 100 mM glucose. What is the total osmolarity of the solution? (Assume complete dissociation of NaCl.)

Accepted Answer

$$300\ 	ext{mOsm}$$

Question 10

Which of the following best explains why the resting membrane potential is closer to the equilibrium potential for K$$^+$$ than for Na$$^+$$?

Accepted Answer

The membrane is more permeable to K$$^+$$ than to Na$$^+ at $$rest.

Question 11

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

Accepted Answer

Opening of voltage-gated K$$^+$$ channels.

Question 12

If the ECF is 400 mOsm and the ICF is 300 mOsm, and the membrane is impermeable to solutes, what will happen to a cell placed in this ECF?

Accepted Answer

Water will leave the cell, causing it to shrink.

Question 13

Which of the following is NOT a primary function of a neuron?

Accepted Answer

Secretion of digestive enzymes.

Question 14

A patient is given an intravenous solution of pure water. What is the most likely effect on their red blood cells?

Accepted Answer

Cells will swell and may burst due to water entering.

Question 15

Which of the following best describes the direction of the electrical force (EF) acting on K$$^+$$ ions at rest?

Accepted Answer

EF pushes K$$^+$$ into the cell because the inside is negative.

Question 16

Which of the following statements about the GHK (Goldman-Hodgkin-Katz) equation is correct?

Accepted Answer

It accounts for the relative permeabilities of multiple ions to determine membrane potential.

Question 17

If a cell is placed in a solution containing a penetrating solute, what is the effect on cell volume after equilibrium is reached?

Accepted Answer

Cell volume will return to normal as the solute equilibrates across the membrane.

Question 18

Which of the following best describes the process of depolarization in a neuron?

Accepted Answer

The membrane potential becomes less negative (more positive).

Question 19

A neuron receives simultaneous excitatory and inhibitory inputs. Which of the following best describes what happens at the axon hillock?

Accepted Answer

The neuron integrates all inputs, and if threshold is reached, an action potential is generated.

Membrane Potentials, Neuronal Physiology, and Osmolarity: Study Guide

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