Adult Critical Care Specialty (ACCS) Practice Exam

Neuromuscular blocking agents primarily affect which types of muscles?

1. Intercostal muscles

2. Cardiac muscle

3. Diaphragm

4. Skeletal muscle

The correct answer is: Cardiac muscle

Neuromuscular blocking agents primarily work on skeletal muscles, making the designation of skeletal muscle the correct response. These agents are designed to interfere with the transmission of nerve impulses to skeletal muscles by blocking the action of acetylcholine at the neuromuscular junction, which is critical for voluntary muscle contraction. Skeletal muscles are responsible for voluntary movements, such as those involved in breathing and movement of limbs, and they receive direct neural input from the peripheral nervous system. When neuromuscular blockers are administered, they prevent the skeletal muscles from receiving the necessary signals to contract, leading to muscle paralysis and facilitating procedures such as intubation or surgery. While the intercostal muscles, which assist in breathing, and the diaphragm, the primary muscle of respiration, are also skeletal muscles, the term strictly refers to the broader category of skeletal muscles in general. Cardiac muscle, on the other hand, is involuntary and operates under different mechanisms, which are unaffected by neuromuscular blocking agents. Thus, understanding that neuromuscular blockers act specifically on skeletal muscle helps clarify their application in clinical settings.