Question 1

Which of the following best describes the primary charge carriers responsible for electricity in biological fluids?

Accepted Answer

Electrolytes such as $$Na^+$$, $$K^+$$, $$Cl^-$$, and $$Ca^{2+}$$

Question 2

A neuron at rest has a transmembrane electrical potential. What is the main reason for this resting membrane potential?

Accepted Answer

Selective permeability of the membrane to $$K^+$$ and the action of the sodium-potassium pump

Question 3

Which equation is used to calculate the equilibrium potential for a single ion across a membrane?

Accepted Answer

Nernst equation: $$E = \frac{RT}{zF} \log \frac{[ion]_{outside}}{[ion]_{inside}}$$

Question 4

If the extracellular concentration of $$K^+ is 5 mM $$and the intracellular concentration is 150 mM, what is the sign of the equilibrium potential for $$K^+$$?

Accepted Answer

Negative

Question 5

Which of the following best explains why the inside of a resting neuron is negatively charged relative to the outside?

Accepted Answer

The sodium-potassium pump moves 3 $$Na^+$$ out and 2 $$K^+ in$$, resulting in a net loss of positive charge

Question 6

Which formula is used to calculate the resting membrane potential considering multiple ions and their relative permeabilities?

Accepted Answer

Goldman-Hodgkin-Katz equation: $$V_m = \frac{RT}{F} \ln \frac{P_{K^+}[K^+]_{out} + P_{Na^+}[Na^+]_{out} + P_{Cl^-}[Cl^-]_{in}}{P_{K^+}[K^+]_{in} + P_{Na^+}[Na^+]_{in} + P_{Cl^-}[Cl^-]_{out}}$$

Question 7

A patient is given a drug that inhibits the sodium-potassium pump. What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential becomes less negative (closer to zero)

Question 8

During depolarization of a neuron, which ion’s movement is primarily responsible for the change in membrane potential?

Accepted Answer

$$Na^+$$ moving into the cell

Question 9

Which of the following best describes the effect of opening $$K^+$$ channels in a neuron at rest?

Accepted Answer

Hyperpolarization

Question 10

A muscle cell is stimulated and its membrane depolarizes. What is the immediate consequence of this depolarization?

Accepted Answer

Rise in cytosolic $$Ca^{2+}$$ leading to contraction

Question 11

Which of the following statements about electric field lines in biological membranes is correct?

Accepted Answer

Electric field lines point from the anode to the cathode

Question 12

If a cell’s membrane becomes more permeable to $$Na^+$$, what will happen to the membrane potential?

Accepted Answer

It will become more positive (depolarize)

Question 13

Which of the following is NOT a consequence of membrane depolarization in excitable cells?

Accepted Answer

Hyperpolarization of the membrane

Question 14

A neuron’s resting membrane potential is measured at $$-70 mV. $$Which of the following best explains this value?

Accepted Answer

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

Question 15

Which of the following ions has the greatest influence on the resting membrane potential of most cells?

Accepted Answer

$$K^+$$

Question 16

A cell is placed in a solution with a high concentration of $$Na^+$$ outside and low concentration inside. According to the Nernst equation, what is the equilibrium potential for $$Na^+$$?

Accepted Answer

Positive

Question 17

Which of the following best describes the effect of the sodium-potassium pump on membrane potential?

Accepted Answer

It moves 3 $$Na^+$$ out and 2 $$K^+ in$$, making the cell more negative

Question 18

Which of the following would most likely cause hyperpolarization of a neuron?

Accepted Answer

Opening $$K^+$$ channels

Question 19

A patient’s neurons are found to have a resting membrane potential of $$-50 mV $$instead of the normal $$-70 mV. $$Which of the following could explain this change?

Accepted Answer

Decreased activity of the sodium-potassium pump

Question 20

Which of the following is a direct result of depolarization in a presynaptic neuron?

Accepted Answer

Exocytosis of neurotransmitters

Lecture #11

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