A nurse working in radiology administers iodine to a patient who is having a computed tomography (CT) scan.
The nurse working on the oncology unit administers chemotherapy to a patient who has cancer.
At the public health department, a nurse administers a measles mumps rubella vaccine to a 14-month-old child as a routine immunization.
Which branch of pharmacology best describes the actions of the three nurses?

Choice A rationale

Magnesium plays a role in muscle relaxation but is not primarily responsible for muscle contraction. It helps in stabilizing the muscle membrane by acting as a natural calcium blocker. Deficiency in magnesium can lead to muscle cramps and spasms, but it does not directly cause muscle contraction and relaxation processes.

Choice B rationale

Chloride is an essential electrolyte involved in maintaining fluid balance and acid-base balance, but it does not directly influence muscle contraction and relaxation. It works in conjunction with sodium to regulate osmotic pressure and acid-base balance.

Choice C rationale

Calcium is crucial for muscle contraction. It is released from the sarcoplasmic reticulum within the muscle cells and binds to troponin, causing a conformational change that allows actin and myosin to interact and generate contraction. During relaxation, calcium ions are pumped back into the sarcoplasmic reticulum.

Choice D rationale

Hydrogen ions are involved in pH balance and acid-base regulation but do not directly affect muscle contraction and relaxation. Excess hydrogen ions (acidosis) can impair muscle function, but they are not the primary factor in muscle contraction processes.

Choice A rationale

Clonic-tonic muscle contraction is related to convulsions and seizures but does not accurately define epilepsy. Epilepsy is a neurological disorder characterized by recurrent seizures due to abnormal electrical activity in the brain.

Choice B rationale

Epilepsy involves abnormal electrical discharges in the brain, not in the muscles. Muscle contractions are a symptom of seizures, not the cause of epilepsy.

Choice C rationale

Epilepsy is not a single disease; it encompasses various conditions characterized by recurrent seizures. It is a spectrum of disorders with different causes and manifestations.

Choice D rationale

This choice accurately describes epilepsy as characterized by sudden, recurrent, and transient disturbances in brain function due to abnormal electrical discharges in the brain.