Question 1

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

Accepted Answer

Sodium ions rush into the cell through voltage-gated sodium channels

Question 2

Which equation best represents the Nernst potential for potassium ($K^+$) across a neuronal membrane?

Accepted Answer

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

Question 3

A patient presents with muscle weakness due to a mutation in their voltage-gated sodium channels. Which phase of the action potential is most likely affected?

Accepted Answer

Depolarization

Question 4

Which of the following best describes the difference between leak channels and voltage-gated channels in neurons?

Accepted Answer

Leak channels are always open, allowing passive ion movement, while voltage-gated channels open in response to changes in membrane potential

Question 5

During the repolarization phase of the action potential, which ion movement is primarily responsible for returning the membrane potential toward resting values?

Accepted Answer

Efflux of potassium ions

Question 6

Which of the following statements about the sodium-potassium pump ($Na^+/K^+$ ATPase) is correct?

Accepted Answer

It moves 3 $Na^+$ ions out of the cell and 2 $K^+$ ions in per cycle, using ATP

Question 7

A neuron receives multiple excitatory postsynaptic potentials (EPSPs) at different locations on its dendrites at the same time. What is this phenomenon called?

Accepted Answer

Spatial summation

Question 8

Which of the following best explains why the lens and cornea of the eye lack blood vessels?

Accepted Answer

To maintain transparency for light transmission

Question 9

Which photoreceptor is most sensitive in low-light conditions, and what is the main reason for this?

Accepted Answer

Rods, because they contain more photopigment and are more sensitive to light

Question 10

A patient is diagnosed with myopia. Which of the following best describes their visual condition?

Accepted Answer

Light focuses in front of the retina, causing distant objects to appear blurry

Question 11

Which of the following is the correct sequence of events during an action potential?

Accepted Answer

Threshold reached → sodium channels open → sodium influx → potassium channels open → potassium efflux → repolarization

Question 12

Which of the following best describes the effect of light on a rod photoreceptor cell?

Accepted Answer

Light causes the rod cell to hyperpolarize and release less neurotransmitter

Question 13

Which of the following is a common cause of cataracts?

Accepted Answer

Misfolding of crystallin proteins in the lens

Question 14

Which of the following best explains colorblindness?

Accepted Answer

Deficiency or absence of one or more types of cone photoreceptors

Question 15

Which region of the brain receives visual information from the optic nerve?

Accepted Answer

Occipital lobe

Question 16

If a neuron is exposed to a drug that blocks voltage-gated potassium channels, what would most likely happen to the action potential?

Accepted Answer

Repolarization would be delayed, prolonging the action potential

Question 17

Which of the following best describes temporal summation in neurons?

Accepted Answer

Repeated synaptic inputs at the same location in rapid succession combine to reach threshold

Question 18

Which formula best describes the Goldman-Hodgkin-Katz equation for membrane potential ($V_m$)?

Accepted Answer

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

Question 19

Which of the following is true regarding the distribution of sodium ($Na^+$) and potassium ($K^+$) ions in a resting neuron?

Accepted Answer

$Na^+$ concentration is higher outside the cell, $K^+$ is higher inside

Action Potentials and Neural Signaling: Study Notes for Anatomy & Physiology

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