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.
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Option A. Sodium is needed to generate an action potential.

Explanation:

Action potentials are generated by the special types of the voltage-gated channels which are embedded in the plasma membrane of the cell.

These channels are shut when the membrane potential is near zero and the voltage-gated channels open only when the membrane potential is more than the threshold voltage.

When the channels are open then they allow the flow of sodium ions which ultimately changes the electrochemical gradient which rises the membrane potential. This rise in membrane potential generates the action potential.

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.