Question 1

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

Accepted Answer

Graded potentials can be summed and decrease in amplitude with distance, while action potentials are self-propagating and maintain constant amplitude.

Question 2

A neuron receives multiple excitatory and inhibitory inputs at its dendrites. What determines whether an action potential will be generated at the axon hillock?

Accepted Answer

The amplitude of the summed graded potentials reaching the axon hillock and whether it reaches threshold.

Question 3

Which type of ion channel is primarily responsible for the rising phase (depolarization) of the action potential?

Accepted Answer

Voltage-gated sodium channels

Question 4

During the absolute refractory period, why can a neuron not fire another action potential?

Accepted Answer

Voltage-gated sodium channels are either open or inactivated, preventing further depolarization.

Question 5

Which equation best represents the change in membrane potential ($$V_m) $$due to the movement of ions across the membrane?

Accepted Answer

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

Question 6

A patient is exposed to a neurotoxin that blocks voltage-gated potassium channels. What effect would this have on the action potential?

Accepted Answer

The repolarization phase would be delayed, prolonging the action potential.

Question 7

Which of the following mechanisms is NOT involved in the removal of neurotransmitter from the synaptic cleft?

Accepted Answer

Direct phosphorylation by protein kinases

Question 8

If the resting membrane potential of a neuron is $$-70\ \mathrm{mV}$$ and the threshold for action potential is $$-55\ \mathrm{mV}$$, what minimum depolarization is required to trigger an action potential?

Accepted Answer

$$15\ \mathrm{mV}$$

Question 9

Which statement best explains how neurons encode the intensity of a stimulus?

Accepted Answer

By increasing the frequency of action potentials.

Question 10

A neuron is exposed to a drug that increases the permeability of its membrane to potassium ions. What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become more negative (hyperpolarized).

Question 11

Which of the following is TRUE regarding the propagation of an action potential along an axon?

Accepted Answer

The action potential is self-propagating and maintains constant amplitude.

Question 12

Which of the following best describes the role of voltage-gated calcium channels at the axon terminal?

Accepted Answer

They trigger the fusion of synaptic vesicles with the presynaptic membrane, leading to neurotransmitter release.

Question 13

During the undershoot (hyperpolarization) phase of the action potential, which channels are primarily responsible for the membrane potential becoming more negative than the resting potential?

Accepted Answer

Voltage-gated potassium channels

Question 14

Which of the following is a property of graded potentials but NOT of action potentials?

Accepted Answer

They can be summed together to reach threshold.

Question 15

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

Accepted Answer

The neuron will be unable to maintain its resting membrane potential.

Question 16

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 propagation.

Question 17

Which of the following would most likely result in an inhibitory postsynaptic potential (IPSP)?

Accepted Answer

Opening of ligand-gated potassium or chloride channels

Question 18

A neuron receives two simultaneous graded potentials: one depolarizing (+10 mV) and one hyperpolarizing (-5 mV). What is the net effect at the axon hillock?

Accepted Answer

A net depolarization of +5 mV

Question 19

Which of the following is the correct sequence of events during synaptic transmission at a chemical synapse?

Accepted Answer

Action potential arrives at axon terminal → voltage-gated calcium channels open → synaptic vesicles fuse with membrane → neurotransmitter released

Lecture #14

Guida di studio - Domande di pratica

Study guide - Flashcard