Patient Care Technician (PCT) AAH Practice Exam

What is the primary role of calcium (Ca++) in the body?

1. Regulating blood sugar

2. Excitability of neurons and muscle cells

3. Transporting oxygen in the blood

4. Maintaining fluid balance

The correct answer is: Excitability of neurons and muscle cells

Calcium plays a crucial role in the body, particularly in the excitability of neurons and muscle cells. It is essential for initiating muscle contractions, including both involuntary muscles (like the heart) and voluntary muscles (the muscles under your control). When a nerve impulse reaches a muscle cell, calcium ions are released into the cell, triggering the interaction between actin and myosin, the proteins responsible for muscle contraction. Additionally, calcium is vital for neurotransmitter release at synapses in the nervous system. When an impulse travels down a neuron, calcium ions enter the neuron and facilitate the release of neurotransmitters, allowing communication between nerve cells. This function underscores why calcium is often categorized as a significant player in both muscle physiology and neural activity. The other choices, while important functions in the body, do not pertain to the primary role of calcium. Regulating blood sugar is primarily managed by hormones like insulin. Transportation of oxygen in the blood is mainly the function of hemoglobin within red blood cells, and maintaining fluid balance involves various electrolytes, with sodium playing a more central role. Thus, the primary function of calcium is appropriately associated with the excitability of neurons and muscle cells.