Question 1

Which of the following best describes the distribution of ions across the membrane of a resting neuron?

Accepted Answer

There is a higher concentration of Na$$^+$$ and Cl$$^-$$ outside the neuron, and a higher concentration of K$$^+$$ and proteins$$^-$$ inside.

Question 2

A resting neuron's membrane is said to be 'polarized.' What does this mean in terms of membrane potential?

Accepted Answer

The inside of the membrane is negative relative to the outside, typically around $$-70\ \mathrm{mV}.$$

Question 3

What is the primary function of the Na$$^+-K$^+$$ pump in maintaining the resting membrane potential?

Accepted Answer

It actively transports 3 Na$$^+$$ out of the cell and 2 K$$^+$$ into the cell, using ATP.

Question 4

Which of the following best distinguishes between leak channels, voltage-gated channels, and ligand-gated channels?

Accepted Answer

Leak channels are always open, voltage-gated channels open in response to changes in membrane potential, and ligand-gated channels open in response to binding of specific molecules.

Question 5

A patient is given a drug that blocks all voltage-gated Na$$^+$$ channels on neurons. What would be the most immediate effect on neuronal signaling?

Accepted Answer

Action potentials would be unable to initiate or propagate along the axon.

Question 6

Which of the following statements about synaptic (graded) potentials is TRUE?

Accepted Answer

They can summate spatially and temporally to influence the likelihood of an action potential.

Question 7

How does spatial summation differ from temporal summation in neurons?

Accepted Answer

Spatial summation involves multiple inputs at different locations simultaneously, while temporal summation involves repeated inputs at the same location over time.

Question 8

Where on a neuron do action potentials typically occur, and which type of ion channel is essential for their initiation?

Accepted Answer

Action potentials occur on the axon hillock and axon, requiring voltage-gated Na$$^+$$ channels.

Question 9

During the depolarization phase of an action potential, which of the following events occurs?

Accepted Answer

Voltage-gated Na$$^+$$ channels open, allowing Na$$^+ to $$enter the cell.

Question 10

A neuron receives two excitatory postsynaptic potentials (EPSPs) at the same synapse in rapid succession. What process is this an example of?

Accepted Answer

Temporal summation

Question 11

Which of the following best explains why action potentials are unidirectional along an axon?

Accepted Answer

Voltage-gated Na$$^+$$ channels become inactivated after opening, creating a refractory period that prevents backward propagation.

Question 12

If the resting membrane potential of a neuron is $$-70\ \mathrm{mV}$$ and the threshold for action potential initiation is $$-55\ \mathrm{mV}$$, what must occur for the neuron to fire an action potential?

Accepted Answer

The membrane potential must depolarize to at least $$-55\ \mathrm{mV}.$$

Question 13

A neuron is exposed to a toxin that increases the permeability of the membrane to K$$^+. $$What is the most likely effect on the resting membrane potential?

Accepted Answer

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

Question 14

Which of the following best describes the sequence of events during an action potential?

Accepted Answer

Depolarization (Na$$^+$$ influx) → Repolarization (K$$^+$$ efflux) → Hyperpolarization

Question 15

A patient has a genetic mutation that causes voltage-gated K$$^+$$ channels to open more slowly than normal. What effect would this have on the action potential?

Accepted Answer

The repolarization phase would be delayed, causing a longer action potential duration.

Question 16

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

Accepted Answer

Graded potentials can summate and decrease with distance, while action potentials are all-or-none and propagate without decrement.

Question 17

A neuron receives simultaneous excitatory inputs from three different presynaptic neurons at different locations on its dendrites. What is this phenomenon called?

Accepted Answer

Spatial summation

Question 18

If a neuron's membrane potential moves from $$-70\ \mathrm{mV} to$$ $$-90\ \mathrm{mV}$$, what has occurred?

Accepted Answer

Hyperpolarization

Question 19

Which of the following best explains how a change in membrane charge opens voltage-gated ion channels?

Accepted Answer

A change in membrane potential alters the conformation of the channel protein, opening the channel.

Question 20

A neuroscientist records the following sequence in a neuron: rapid Na$$^+$$ influx, followed by K$$^+$$ efflux, and then a brief period where the membrane potential is more negative than resting. What is this last phase called?

Accepted Answer

Hyperpolarization (afterpotential)

Neuronal Membrane Potentials and Synaptic Transmission: Study Guide

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