Question 1

Which of the following best explains how the kidney can produce urine that is hyperosmotic to blood?

Accepted Answer

The countercurrent multiplier system in the loop of Henle creates an osmotic gradient in the medulla, allowing water reabsorption in the collecting duct.

Question 2

A patient with a mutation in the gene encoding aquaporin-2 channels is likely to experience which of the following symptoms?

Accepted Answer

Severe dehydration due to inability to concentrate urine, resulting in diabetes insipidus.

Question 3

Which hormone acts most rapidly to decrease blood osmolarity after dehydration, and what is its mechanism of action?

Accepted Answer

Antidiuretic hormone (ADH); it increases aquaporin insertion in the collecting duct via a cAMP-mediated pathway.

Question 4

Which of the following best describes the effect of aldosterone on the distal tubule?

Accepted Answer

It increases the expression of ENaC and Na+/K+ ATPase, leading to increased Na+ and water reabsorption.

Question 5

Which of the following equations correctly represents the Nernst equation for the equilibrium potential of an ion?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{outside}}{[ion]_{inside}} \right)$$

Question 6

A neuron has a resting membrane potential of $$-70 mV $$and an equilibrium potential for K$$^+$$ ($$E_K) of$$ $$-90 mV. If $$the membrane potential is suddenly changed to $$-80 mV$$, what is the direction of K$$^+$$ flow?

Accepted Answer

K$$^+$$ will flow out of the cell to bring the membrane potential toward $$E_K.$$

Question 7

Which of the following best explains why action potentials travel in only one direction along an axon?

Accepted Answer

Voltage-gated Na$$^+$$ channels become inactivated after opening, preventing backward propagation.

Question 8

Which of the following is a direct effect of antidiuretic hormone (ADH) on the collecting duct?

Accepted Answer

Increased insertion of aquaporin water channels into the apical membrane.

Question 9

Which adaptation allows mammals living in arid environments to conserve water most effectively?

Accepted Answer

Long loops of Henle that create a steep osmotic gradient in the medulla.

Question 10

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

Accepted Answer

Action potentials will not be generated, leading to loss of neuronal communication.

Question 11

Which of the following best describes the role of the Na$$^+/K$^+$$ ATPase in neurons?

Accepted Answer

It maintains the resting membrane potential by pumping 3 Na$$^+$$ out and 2 K$$^+ in $$per ATP hydrolyzed.

Question 12

Which of the following is a key difference between ionotropic and metabotropic neurotransmitter receptors?

Accepted Answer

Ionotropic receptors directly gate ion channels, while metabotropic receptors activate second messenger pathways.

Question 13

Which of the following scenarios would most likely result in the generation of an action potential in a postsynaptic neuron?

Accepted Answer

Multiple excitatory postsynaptic potentials (EPSPs) summate temporally and/or spatially to reach threshold at the axon hillock.

Question 14

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin insulates the axon, allowing action potentials to jump between nodes of Ranvier in saltatory conduction.

Question 15

Which of the following is a correct statement about the renin-angiotensin-aldosterone system (RAAS)?

Accepted Answer

A drop in blood pressure triggers renin release, leading to angiotensin II formation, which stimulates aldosterone release and increases Na$$^+$$ and water reabsorption.

Question 16

Which of the following best describes the effect of atrial natriuretic peptide (ANP) on kidney function?

Accepted Answer

ANP opposes the actions of RAAS and ADH, promoting Na$$^+$$ and water excretion to lower blood volume.

Question 17

Which of the following is a real-world example of how understanding kidney adaptations in animals can inform human medicine?

Accepted Answer

Studying bears' ability to regenerate kidney tissue after hibernation may provide insights into treating human kidney disease.

Question 18

Which of the following best describes the historical significance of Luigi Galvani's experiments with frog legs?

Accepted Answer

They provided early evidence that nerves use electrical signals to communicate with muscles.

Lecture 6 Neurons, Synapses, and Kidney Regulation: Structure, Function, and Comparative Physiology

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