Question

select the correct answer.
hyponatremia is a condition in which the sodium in the blood is too low. uncontrolled spasms, which are sudden, involuntary contractions of muscles,
are among the symptoms of hyponatremia. why do they occur?
a. sodium is needed to generate an action potential.
b. sodium makes up most of the myelin sheath.
c. sodium is the signaling molecule that transmits impulses across a synapse.
d. sodium controls voluntary movement, and potassium controls involuntary movement.

Explanation:

To solve this, we analyze each option:

• Option A: Action potentials in neurons (which control muscle contractions) rely on sodium ion influx. Low sodium (hyponatremia) disrupts action potential generation, leading to muscle spasms. This is correct.
• Option B: Myelin sheath is mainly lipids (like phospholipids) and proteins, not sodium. Eliminate B.
• Option C: Neurotransmitters (e.g., acetylcholine) transmit impulses across synapses, not sodium. Eliminate C.
• Option D: Both voluntary and involuntary movements involve action potentials with sodium/potassium, and this option misstates their roles. Eliminate D.

Answer:

A. Sodium is needed to generate an action potential.