Question 1

Which equation would you use to calculate the equilibrium potential for potassium ($$K^+) $$across a neuronal membrane, and what is the correct formula?

Accepted Answer

$$E_{ion} = 61 \log \frac{[ion]_{out}}{z[ion]_{in}}$$

Question 2

A patient presents with hyperkalemia (elevated blood $$K^+). $$How does this affect the resting membrane potential and neuronal excitability?

Accepted Answer

The membrane potential becomes less negative, making neurons more excitable.

Question 3

Which of the following best describes the difference between graded potentials and action potentials?

Accepted Answer

Graded potentials can be summed, while action potentials cannot be summed.

Question 4

Which equation would you use to calculate the membrane potential considering multiple ions, and what is the correct formula?

Accepted Answer

$$V_m = 61 \log \frac{P_K[K^+]_{out} + P_{Na}[Na^+]_{out} + P_{Cl}[Cl^-]_{in}}{P_K[K^+]_{in} + P_{Na}[Na^+]_{in} + P_{Cl}[Cl^-]_{out}}$$

Question 5

During the rising phase of an action potential, which ion channels open and what is the result?

Accepted Answer

Voltage-gated $$Na^+$$ channels open, causing depolarization.

Question 6

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

Accepted Answer

The neuron will not be able to repolarize efficiently, prolonging the action potential.

Question 7

Which of the following best explains why action potentials only travel in one direction along an axon?

Accepted Answer

The absolute refractory period prevents backward conduction due to inactivated $$Na^+$$ channels.

Question 8

According to Ohm’s Law, what happens to the current ($$I) if $$the resistance ($$R) of $$the cell membrane increases while voltage ($$V) $$remains constant?

Accepted Answer

Current decreases.

Question 9

Which of the following is a real-life consequence of demyelinating diseases such as multiple sclerosis?

Accepted Answer

Decreased speed or failure of action potential conduction due to current leak.

Question 10

A graded potential is initiated at the dendrite and travels toward the axon hillock. What two factors cause the graded potential to decrease in strength as it moves?

Accepted Answer

Current leak and cytoplasmic resistance.

Question 11

Which of the following best describes the role of voltage-gated $$Na^+$$ channel inactivation gates during the action potential?

Accepted Answer

They close slowly to stop $$Na^+$$ influx, ending the depolarization phase.

Question 12

Which of the following scenarios would most likely result in a neuron failing to fire an action potential in response to a normally suprathreshold stimulus?

Accepted Answer

The neuron is in the absolute refractory period.

Question 13

Which of the following is NOT a mechanism for terminating neurotransmitter activity at a synapse?

Accepted Answer

Continuous exocytosis of neurotransmitter vesicles.

Question 14

A patient with hypokalemia (low blood $$K^+) is $$likely to experience which of the following symptoms, and why?

Accepted Answer

Muscle weakness due to neurons being hyperpolarized and less excitable.

Question 15

Which of the following best explains why a stronger stimulus results in more neurotransmitter release at a synapse?

Accepted Answer

A stronger stimulus increases the frequency of action potentials, leading to more neurotransmitter release.

Question 16

Which of the following is true regarding the coding of stimulus strength in the nervous system?

Accepted Answer

Stimulus strength is coded by the frequency of action potentials.

Question 17

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 18

Which of the following is the correct sequence of events for neurotransmitter release at a chemical synapse?

Accepted Answer

Action potential arrives, voltage-gated $$Ca^{2+}$$ channels open, $$Ca^{2+}$$ influx, exocytosis of vesicles, neurotransmitter binds postsynaptic receptor.

Neurons: Cellular and Network Properties – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards