Question 1

Which of the following best describes a graded potential in a neuron?

Accepted Answer

It is a transient change in membrane voltage that can vary in amplitude and may be depolarizing or hyperpolarizing.

Question 2

A neurotransmitter binds to a postsynaptic receptor and increases Na	extsuperscript{+} permeability. What is the most likely effect on the membrane potential?

Accepted Answer

The membrane will depolarize, moving closer to threshold.

Question 3

Which equation is used to calculate the equilibrium potential for a single ion across a membrane?

Accepted Answer

The Nernst equation: $E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$

Question 4

What property of graded potentials allows them to combine and potentially reach threshold for an action potential?

Accepted Answer

Summation, both spatial and temporal

Question 5

If a neurotransmitter opens K	extsuperscript{+} channels on the postsynaptic membrane, what is the expected effect?

Accepted Answer

Hyperpolarization, leading to an inhibitory postsynaptic potential (IPSP)

Question 6

Which of the following is TRUE about the passive decay of graded potentials?

Accepted Answer

Graded potentials decrease in amplitude as they spread from the site of origin.

Question 7

A neuron receives two EPSPs at the same time but at different locations on the dendrite. What is this phenomenon called?

Accepted Answer

Spatial summation

Question 8

Which of the following best distinguishes an action potential from a graded potential?

Accepted Answer

Action potentials are all-or-none events, while graded potentials vary in amplitude.

Question 9

Which formula is used to calculate the membrane potential considering multiple ions?

Accepted Answer

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

Question 10

A neuron is at rest with $V_m = -70$ mV. If the membrane becomes more negative, what term describes this change?

Accepted Answer

Hyperpolarization

Question 11

Which of the following is a consequence of temporal summation in neurons?

Accepted Answer

Multiple graded potentials arriving at the same location in rapid succession, increasing the likelihood of reaching threshold

Question 12

What is the effect of opening Cl	extsuperscript{-} channels on the postsynaptic membrane?

Accepted Answer

Hyperpolarization, making the cell less likely to fire an action potential

Question 13

Which of the following statements about EPSPs and IPSPs is correct?

Accepted Answer

IPSPs make the membrane potential more negative, moving it further from threshold.

Question 14

A neuron receives several subthreshold EPSPs in rapid succession at the same synapse. What is the likely outcome?

Accepted Answer

Temporal summation may allow the neuron to reach threshold and fire an action potential.

Question 15

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

Accepted Answer

They are all-or-none events.

Question 16

What is the main reason why graded potentials decay as they travel along the membrane?

Accepted Answer

Leakage of charge across the membrane

Question 17

Which of the following best describes the trigger zone of a neuron?

Accepted Answer

The region where action potentials are initiated if threshold is reached

Question 18

A patient is given a drug that increases the permeability of Na	extsuperscript{+} channels in neurons. What is the most likely effect?

Accepted Answer

Increased likelihood of depolarization and action potential firing

Question 19

Which of the following is required to initiate an action potential, but NOT a graded potential?

Accepted Answer

Threshold stimulus

Question 20

If a neuron receives both EPSPs and IPSPs simultaneously, what determines whether it will fire an action potential?

Accepted Answer

The net effect of all summed graded potentials at the trigger zone

Excitable Cells: Graded Potentials and Action Potentials

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