Question 1

Which of the following best explains why the resting membrane potential of a neuron is typically negative?

Accepted Answer

The membrane is more permeable to K+ than Na+ at rest, allowing K+ to diffuse out, leaving behind negative charges.

Question 2

A patient is exposed to a toxin that blocks all voltage-gated Na+ channels in neurons. What would be the most immediate effect on neuronal signaling?

Accepted Answer

Action potentials could not be initiated, preventing long-distance signaling.

Question 3

Which equation is used to calculate the equilibrium potential for a single ion, such as K+?

Accepted Answer

$$E_X = \frac{RT}{zF} \ln \frac{[X]_{out}}{[X]_{in}}$$

Question 4

A neuron receives two simultaneous stimuli at different locations on its dendrites, each producing a subthreshold graded potential. What is this process called, and what is the likely outcome?

Accepted Answer

Spatial summation; the graded potentials may add together to reach threshold and trigger an action potential.

Question 5

Which of the following best describes the absolute refractory period of an action potential?

Accepted Answer

A period when no new action potential can be generated, regardless of stimulus strength, due to inactivated Na+ channels.

Question 6

Which of the following is a key difference between graded potentials and action potentials?

Accepted Answer

Graded potentials decay with distance, while action potentials are regenerated along the axon and do not decay.

Question 7

A neuron is exposed to a drug that increases the permeability of the membrane to Cl− ions. What is the most likely effect on the postsynaptic membrane?

Accepted Answer

It will hyperpolarize, decreasing the likelihood of an action potential.

Question 8

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 9

Which neurotransmitter is most likely to produce an inhibitory postsynaptic potential (IPSP) in the central nervous system?

Accepted Answer

GABA (γ-aminobutyric acid)

Question 10

A patient has a mutation that causes all their ligand-gated ion channels to remain closed, even in the presence of neurotransmitter. Which process would be most directly affected?

Accepted Answer

Generation of postsynaptic potentials (EPSPs and IPSPs)

Question 11

Which of the following best describes the role of the sodium-potassium ATPase pump in maintaining the resting membrane potential?

Accepted Answer

It actively transports 3 Na+ out of the cell and 2 K+ into the cell, maintaining the concentration gradients.

Question 12

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

Accepted Answer

Stronger stimuli produce higher frequency of action potentials.

Question 13

Which type of neural circuit is most likely involved in the withdrawal reflex, where a single stimulus leads to activation of multiple effectors?

Accepted Answer

Diverging circuit

Question 14

Which of the following best describes the effect of opening voltage-gated Na+ channels during the initiation of an action potential?

Accepted Answer

Na+ flows into the cell, causing depolarization.

Question 15

Which of the following is a property of direct-acting neurotransmitters?

Accepted Answer

They bind directly to and open ion channels, producing rapid responses.

Question 16

A neuron receives both excitatory and inhibitory inputs simultaneously. Which of the following best describes the outcome?

Accepted Answer

The net effect on the membrane potential will depend on the sum of all EPSPs and IPSPs at the axon hillock.

Question 17

Which of the following is true about the relative refractory period?

Accepted Answer

A stronger-than-normal stimulus can generate another action potential.

Question 18

Which of the following best explains why graded potentials decay with distance?

Accepted Answer

Current is lost through the leaky plasma membrane, causing the voltage to decline with distance.

Question 19

Which of the following neurotransmitters is classified as both excitatory and inhibitory, depending on the receptor type?

Accepted Answer

Acetylcholine

Question 20

Which of the following best describes parallel processing in neuronal circuits?

Accepted Answer

Input travels along several pathways, allowing different parts of the brain to process information simultaneously.

Physiology of the Nervous System: Membrane Potentials, Action Potentials, and Synaptic Transmission

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