Question 1

Which of the following best describes the primary reason for the existence of a resting membrane potential in animal cells?

Accepted Answer

The unequal distribution of ions across the cell membrane and selective permeability to certain ions.

Question 2

A neuron is exposed to a drug that increases the permeability of its membrane to sodium ions ($$Na^+). $$What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become less negative (depolarize).

Question 3

Which equation is used to calculate the equilibrium potential for a single ion, and what is its general form?

Accepted Answer

The Nernst equation: $$E_{ion} = \frac{61}{z} \log \frac{[ion]_{out}}{[ion]_{in}}$$

Question 4

If the extracellular concentration of $$K^+$$ increases significantly, what will happen to the resting membrane potential of a typical neuron?

Accepted Answer

It will become less negative (depolarize).

Question 5

Which of the following is NOT a type of local cell-to-cell communication?

Accepted Answer

Endocrine signaling via hormones in the bloodstream.

Question 6

A cell releases a chemical messenger that acts on itself. This is an example of:

Accepted Answer

Autocrine signaling.

Question 7

Which of the following best explains why the equilibrium potential for $$Na^+ is $$positive while that for $$K^+ is $$negative?

Accepted Answer

The chemical gradients for $$Na^+$$ and $$K^+$$ are in opposite directions, requiring opposite electrical gradients to reach equilibrium.

Question 8

Which of the following is a correct application of the Goldman-Hodgkin-Katz (Goldman) equation?

Accepted Answer

Calculating the resting membrane potential by considering the relative permeabilities and concentrations of multiple ions.

Question 9

A patient is given a drug that blocks voltage-gated $$K^+$$ channels. What is the most likely effect on the action potential of a neuron?

Accepted Answer

Repolarization will be delayed, prolonging the action potential.

Question 10

Which of the following is an example of antagonistic control in physiological systems?

Accepted Answer

Sympathetic and parasympathetic neurons regulating heart rate in opposite directions.

Question 11

Which of the following statements about ligand-receptor interactions is TRUE?

Accepted Answer

A ligand binds to a specific site on a protein, and this interaction can be reversible or irreversible.

Question 12

A cell is exposed to an antagonist that binds to a receptor but does not activate it. What is the most likely effect?

Accepted Answer

The normal ligand cannot bind, so the receptor is not activated.

Question 13

Which of the following best describes the function of second messengers in signal transduction pathways?

Accepted Answer

They amplify the signal inside the cell after receptor activation.

Question 14

Which of the following is a correct example of a G protein-coupled receptor (GPCR) pathway?

Accepted Answer

Activation of adenylyl cyclase, increasing $$cAMP$$ levels as a second messenger.

Question 15

A mutation causes a cell to overexpress a receptor for a hormone. What is the most likely effect on the cell's response to that hormone?

Accepted Answer

The cell will become more sensitive to the hormone (upregulation).

Question 16

Which of the following best explains why proteins are selective in their binding to ligands?

Accepted Answer

Proteins have specific binding sites with molecular complementarity to their ligands.

Question 17

Which of the following is an example of paracrine signaling?

Accepted Answer

A cell releases a growth factor that acts on neighboring cells to stimulate division.

Question 18

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

Accepted Answer

It helps maintain the concentration gradients of $$Na^+$$ and $$K^+$$ across the cell membrane.

Question 19

A patient is given a drug that acts as a competitive inhibitor for an enzyme. Which of the following best describes how this drug works?

Accepted Answer

It binds to the active site of the enzyme, preventing the substrate from binding.

Cellular Communication and Membrane Potentials in Anatomy & Physiology

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