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QUESTIONS AND ANSWER
Osmoreceptors located in the hypothalamus directly control the release of which
substance?
a. Angiotensin
b. Atrial natriuretic peptide
c. Aldosterone
d. Vasopressin (antidiuretic hormone, ADH)
,✔️ Correct Answer: D
Rationale: Osmoreceptors in the hypothalamus detect changes in serum osmolality and
stimulate or suppress the release of vasopressin (ADH) from the posterior pituitary. ADH
acts on the renal collecting ducts to increase water reabsorption, concentrating urine and
restoring normal serum osmolality. Angiotensin (Option A) is part of the renin-
angiotensin-aldosterone system. Atrial natriuretic peptide (Option B) is released from
cardiac atria in response to increased blood volume. Aldosterone (Option C) is released
from the adrenal cortex in response to angiotensin II and increased serum potassium.
Decreased neuromuscular excitability is often the result of which electrolyte imbalances?
a. Hypercalcemia and hypermagnesemia
b. Hypomagnesemia and hyperkalemia
c. Hypocalcemia and hypokalemia
d. Hypernatremia and hypomagnesemia
✔️ Correct Answer: A
Rationale: Calcium and magnesium both stabilize cell membranes and decrease
neuromuscular excitability. Elevated levels of calcium (hypercalcemia) and magnesium
(hypermagnesemia) depress neuronal firing and muscle contraction, leading to lethargy,
weakness, and diminished reflexes. Hypomagnesemia (Option B) and hypocalcemia
(Option C) increase excitability. Hypernatremia (Option D) typically causes central nervous
system irritability.
,Which clinical scenario is most likely to lead to hyponatremia?
a. Insufficient antidiuretic hormone (ADH) secretion
b. Excess aldosterone secretion
c. Administration of intravenous normal saline
d. Frequent nasogastric tube irrigation with water
✔️ Correct Answer: D
Rationale: Hyponatremia occurs when there is an excess of water relative to sodium in
the extracellular fluid. Frequent nasogastric tube irrigation with water introduces
hypotonic fluid, diluting serum sodium. Insufficient ADH (Option A) leads to diabetes
insipidus and hypernatremia. Excess aldosterone (Option B) causes sodium and water
retention but typically with potassium loss. Administration of normal saline (Option C)
contains sodium and would not cause hyponatremia.
An increase in the resting membrane potential (hyperpolarized state) is associated with
which electrolyte imbalance?
a. Hypokalemia
b. Hyperkalemia
c. Hypocalcemia
d. Hypercalcemia
✔️ Correct Answer: A
Rationale: Potassium is the primary intracellular cation and plays a critical role in
establishing the resting membrane potential. Hypokalemia results in hyperpolarization of
the cell membrane, making it more difficult to reach threshold for depolarization. This
, leads to muscle weakness, fatigue, and cardiac arrhythmias. Hyperkalemia (Option B)
causes depolarization and increased excitability. Calcium imbalances (Options C and D)
affect neuromuscular excitability but not directly through resting membrane potential.
Abnormalities in intracellular regulation of enzyme activity and cellular production of
adenosine triphosphate (ATP) are associated with which electrolyte imbalance?
a. Hyponatremia
b. Hypocalcemia
c. Hypophosphatemia
d. Hypokalemia
✔️ Correct Answer: C
Rationale: Phosphate is essential for ATP synthesis and enzyme function.
Hypophosphatemia leads to decreased ATP production, impairing cellular energy
metabolism. This affects multiple organ systems, including muscle weakness, cardiac
dysfunction, and respiratory failure. Severe hypophosphatemia causes depletion of ATP in
tissues, which is critical for cellular function. Options A, B, and D are not primarily
associated with ATP production and enzyme activity.
The fraction of total body water (TBW) volume contained in the intracellular space in
adult males is approximately: