NCCAA Re-certification Practice Exam

Hypokalemia, which is characterized by low potassium levels in the blood, negatively affects neuromuscular transmission primarily by decreasing the release of acetylcholine (ACh) at the neuromuscular junction. Potassium plays a crucial role in maintaining the resting membrane potential of neurons and muscle cells. When potassium levels are low, it can lead to hyperpolarization of the nerve and muscle cell membranes.

This hyperpolarization can make it more difficult for these cells to reach the threshold for action potentials, which are necessary to trigger the release of ACh from nerve endings. As a result, the decreased release of ACh leads to reduced stimulation of the muscle fibers, which can impair muscle contraction.

Understanding the role of potassium in action potential generation and neurotransmitter release is key to grasping why hypokalemia causes a decrease in ACh availability at the neuromuscular junction, rather than increasing its release or having no effect at all. This can ultimately contribute to symptoms such as weakness and fatigue in affected individuals.