Question 1

During the resting state of an action potential, which channels are open and what is the primary mechanism maintaining the resting membrane potential?

Accepted Answer

Only leakage channels for Na+ and K+ are open, and the Na+/K+ ATPase pump maintains the resting membrane potential.

Question 2

What is the primary event that triggers the depolarization phase of an action potential?

Accepted Answer

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

Question 3

Which equation best represents the Nernst equation for calculating the equilibrium potential for potassium ($$K^+) $$ions?

Accepted Answer

$$E_{K} = \frac{RT}{zF} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$$

Question 4

A neuron receives both excitatory and inhibitory inputs. Which scenario will most likely result in the generation of an action potential?

Accepted Answer

EPSPs predominate and bring the axon hillock to threshold ($$-55 mV).$$

Question 5

Which of the following best describes the 'all-or-none' phenomenon of action potentials?

Accepted Answer

Action potentials occur only if depolarization reaches threshold; otherwise, they do not occur at all.

Question 6

Which statement accurately describes saltatory conduction in myelinated axons?

Accepted Answer

Action potentials jump from one myelin sheath gap to the next, increasing conduction speed.

Question 7

During the repolarization phase of an action potential, which ion movement is primarily responsible for returning the membrane potential to its resting state?

Accepted Answer

K+ efflux out of the cell.

Question 8

Which neurotransmitter is typically excitatory at neuromuscular junctions in skeletal muscle but inhibitory in cardiac muscle?

Accepted Answer

Acetylcholine

Question 9

A patient is administered lidocaine during a dental procedure. What is the primary effect of lidocaine on neuronal action potentials?

Accepted Answer

It blocks voltage-gated Na+ channels, preventing depolarization and action potential generation.

Question 10

Which of the following best explains how the central nervous system distinguishes between a weak and a strong stimulus?

Accepted Answer

By the frequency of action potentials generated per second.

Question 11

Which equation represents the Goldman-Hodgkin-Katz equation for membrane potential, considering multiple ions?

Accepted Answer

$$V_m = \frac{RT}{F} \ln \left( \frac{P_{K^+}[K^+]_{out} + P_{Na^+}[Na^+]_{out} + P_{Cl^-}[Cl^-]_{in}}{P_{K^+}[K^+]_{in} + P_{Na^+}[Na^+]_{in} + P_{Cl^-}[Cl^-]_{out}} \right)$$

Question 12

Which type of synapse is most abundant in embryonic nervous tissue and allows rapid, bidirectional communication?

Accepted Answer

Electrical synapse

Question 13

Which neurotransmitter is most commonly associated with inhibitory postsynaptic potentials (IPSPs)?

Accepted Answer

GABA

Question 14

What is the effect of opening chemically gated Cl- channels on the postsynaptic membrane?

Accepted Answer

Hyperpolarization, making the membrane potential more negative.

Question 15

Which of the following best describes the function of neuromodulators?

Accepted Answer

They affect the strength of synaptic transmission by influencing neurotransmitter synthesis, release, degradation, or reuptake.

Question 16

Which step in chemical synaptic transmission is considered the rate-limiting step?

Accepted Answer

Synaptic delay: the time needed for neurotransmitter release, diffusion, and receptor binding.

Question 17

A neuron is exposed to a neurotoxin that blocks the Na+/K+ ATPase pump. What is the most likely consequence?

Accepted Answer

The neuron will be unable to restore ionic conditions after an action potential.

Question 18

Which of the following synaptic connections is least common in the nervous system?

Accepted Answer

Axoaxonal synapse

Question 19

Which neurotransmitter is synthesized from the amino acid tryptophan and is involved in emotional behaviors and the biological clock?

Accepted Answer

Serotonin

Question 20

Which type of receptor is associated with rapid, brief responses and is typically ligand-gated?

Accepted Answer

Channel-linked receptor

Action Potentials and Synaptic Transmission in the Nervous System

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