Q: Which equation best represents the threshold voltage required to initiate an action potential at the axon hillock?

$$V_{threshold} = -55\ \text{mV}$$

Question 1

Which of the following best explains why action potential conduction is unidirectional in myelinated neurons?

Accepted Answer

The refractory period prevents the action potential from being generated at previously activated nodes.

Question 2

A neuron receives simultaneous excitatory inputs from three presynaptic neurons. What process allows these inputs to combine and potentially trigger an action potential?

Accepted Answer

Spatial summation

Question 3

Which equation best represents the threshold voltage required to initiate an action potential at the axon hillock?

Accepted Answer

$$V_{threshold} = -55\ 	ext{mV}$$

Question 4

During the absolute refractory period, what is the state of the voltage-gated sodium channels?

Accepted Answer

They are inactivated and cannot be reopened regardless of stimulus strength.

Question 5

Which of the following is a direct result of neurotransmitter binding to ligand-gated ion channels on the postsynaptic membrane?

Accepted Answer

Production of a graded potential in the postsynaptic neuron

Question 6

If a neurotransmitter opens a ligand-gated Cl- channel on the postsynaptic membrane, what is the likely effect?

Accepted Answer

Hyperpolarization and generation of an IPSP

Question 7

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next.

Question 8

A patient has a mutation that reduces the diameter of their axons. What effect would this have on conduction velocity?

Accepted Answer

Conduction velocity would decrease due to greater resistance.

Question 9

Which of the following is true regarding the removal of excess neurotransmitter from the synaptic cleft?

Accepted Answer

Excess neurotransmitter is removed by enzymatic hydrolysis or reuptake by the presynaptic neuron.

Question 10

Which of the following best describes the function of myelin in neurons?

Accepted Answer

Myelin insulates the axon and prevents leakage of charge, increasing conduction velocity.

Question 11

Which scenario would most likely result in an action potential in the postsynaptic neuron?

Accepted Answer

Multiple EPSPs generated simultaneously by several presynaptic neurons (spatial summation)

Question 12

Which of the following equations best represents the relationship between conduction velocity ($$v$$), axon diameter ($$d$$), and myelination?

Accepted Answer

$$v \propto d$$

Question 13

Which of the following is NOT a characteristic of the absolute refractory period?

Accepted Answer

A second action potential can be generated if the stimulus is strong enough.

Question 14

Which of the following best describes the effect of an EPSP on the postsynaptic membrane?

Accepted Answer

It depolarizes the membrane, moving it toward threshold.

Question 15

A neuron receives both EPSPs and IPSPs at the same time. What is the likely outcome?

Accepted Answer

The EPSPs and IPSPs may cancel each other out, preventing an action potential.

Question 16

Which of the following is true about ligand-gated ion channels?

Accepted Answer

They open when a ligand, such as a neurotransmitter, binds to them.

Question 17

Which of the following best describes the process of temporal summation?

Accepted Answer

One presynaptic neuron fires repeatedly, releasing more neurotransmitter.

Question 18

Which of the following is a consequence of opening ligand-gated K+ channels on the postsynaptic membrane?

Accepted Answer

Hyperpolarization and decreased likelihood of action potential

Question 19

Which of the following is true regarding the propagation of action potentials in unmyelinated neurons?

Accepted Answer

Action potentials are regenerated continuously along the entire axon.

Question 20

Which of the following best describes the role of the axon hillock in a multipolar neuron?

Accepted Answer

It is the site where the action potential is first generated.

Neurons, Synapses, and Signaling: Study Guide (Campbell Biology Ch. 48)

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