Q: Which of the following best describes the sequence of ion channel activity during an action potential in a neuron?

Na\textsuperscript{+} channels open rapidly, Na\textsuperscript{+} enters causing depolarization, Na\textsuperscript{+} channels inactivate while K\textsuperscript{+} channels open, K\textsuperscript{+} exits causing repolarization.

Q: During the absolute refractory period, why can't another action potential be generated?

Na\textsuperscript{+} channels are open or inactivated, so no new action potential can occur.

Question 1

Which of the following best describes the sequence of ion channel activity during an action potential in a neuron?

Accepted Answer

Na	extsuperscript{+} channels open rapidly, Na	extsuperscript{+} enters causing depolarization, Na	extsuperscript{+} channels inactivate while K	extsuperscript{+} channels open, K	extsuperscript{+} exits causing repolarization.

Question 2

During the absolute refractory period, why can't another action potential be generated?

Accepted Answer

Na	extsuperscript{+} channels are open or inactivated, so no new action potential can occur.

Question 3

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 4

A neuron receives several excitatory and inhibitory signals at its dendrites. Which process determines whether an action potential will be generated?

Accepted Answer

The spatial and temporal summation of graded potentials at the axon hillock.

Question 5

Which of the following is an example of paracrine signaling?

Accepted Answer

A cell releasing a signal that acts on nearby cells in the same tissue.

Question 6

Which of the following best describes the role of kinases in cellular signaling?

Accepted Answer

Kinases add phosphate groups to proteins, which can activate or inhibit their function.

Question 7

A postsynaptic neuron receives neurotransmitter that opens ligand-gated Cl	extsuperscript{--} channels. What is the likely effect on the membrane potential?

Accepted Answer

Hyperpolarization, making an action potential less likely.

Question 8

Which of the following scenarios best illustrates the concept of signal transduction?

Accepted Answer

A neurotransmitter binds to a receptor, leading to the opening of ion channels and a change in membrane potential.

Question 9

Which of the following statements about graded potentials is correct?

Accepted Answer

Graded potentials can be depolarizing or hyperpolarizing and their effects can sum temporally or spatially.

Question 10

A patient is exposed to a toxin that blocks voltage-gated Ca	extsuperscript{2+} channels at the axon terminal. What is the most likely effect?

Accepted Answer

Neurotransmitter release will be inhibited, preventing synaptic transmission.

Question 11

Which of the following best explains why a cell only responds to certain chemical signals?

Accepted Answer

The cell must have a specific receptor for the signal.

Question 12

Which of the following is a correct statement about the difference between fast and slow cellular responses to signals?

Accepted Answer

Fast responses involve modifying existing proteins, while slow responses involve changing protein synthesis.

Question 13

Which of the following best describes the effect of phosphorylation on protein function?

Accepted Answer

Phosphorylation can either activate or inhibit proteins, depending on the protein.

Question 14

A neuron is exposed to a drug that prevents the removal of neurotransmitter from the synaptic cleft. What is the most likely consequence?

Accepted Answer

The postsynaptic cell will be continuously stimulated or inhibited.

Question 15

Which of the following equations best represents the Nernst equation for calculating the equilibrium potential for an ion?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{outside}}{[ion]_{inside}} \right)$$

Question 16

Which of the following best describes the role of the axon hillock in neuronal signaling?

Accepted Answer

It is the region where graded potentials are integrated and action potentials are initiated if threshold is reached.

Question 17

A mutation causes a neuron to lack voltage-gated K	extsuperscript{+} channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed, causing a prolonged action potential.

Question 18

Which of the following is an example of autocrine signaling?

Accepted Answer

A cell releases a signal that binds to receptors on its own surface, affecting its own activity.

Question 19

Which of the following best explains why the effect of a chemical signal can differ between two cell types?

Accepted Answer

Each cell type may express different receptors or signaling pathways for the same signal.

Question 20

Which of the following best describes the process of saltatory conduction?

Accepted Answer

Action potentials 'jump' from one node of Ranvier to the next, increasing conduction velocity.

Synapses and Signal Transduction in the Nervous System

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