Fast signals in the nervous system primarily supply which type of muscles?

Fast signals in the nervous system are crucial for the function of skeletal muscles, as they enable rapid contractions necessary for activities requiring quick and precise movements, such as running or jumping. Skeletal muscles are under voluntary control and are innervated by motor neurons that transmit signals quickly. This speed allows for immediate responses to stimuli, which is essential for maintaining balance, coordination, and executing fine motor skills.

In contrast, smooth muscles and cardiac muscles are influenced by slower-paced signals. Smooth muscles, found in organs and blood vessels, typically respond to autonomic signals that modulate their contractions over a longer time frame, allowing for sustained actions like peristalsis or blood vessel constriction. Cardiac muscle, while responsive to signals from the nervous system, operates mainly through its intrinsic conduction system, allowing the heart to beat rhythmically and autonomously without the need for rapid signaling. Gland cells also respond more slowly to hormonal signals rather than rapid nerve impulses.

Thus, the primary reliance of fast signals in the nervous system on skeletal muscles highlights their role in voluntary, quick-response movements, differentiating them from the other muscle types and cells mentioned.