What term describes a muscle's ability to receive and respond to stimuli?

• A. Excitability
• B. Contractility
• C. Extensibility
• D. Elasticity

Answer: (A)

Excitability is a muscle's ability to receive and respond to stimuli. When a motor neuron sends a signal to a muscle fiber, the membrane responds by depolarizing and generating an action potential, which triggers the release of calcium and leads to contraction. This responsiveness to nerves and other stimuli is what sets excitability apart from other muscle properties.

Contractility refers to the ability to shorten forcefully when stimulated and produce movement. Extensibility is the capacity to be stretched beyond its resting length without damage. Elasticity is the ability to return to the original length after being stretched. So, excitability specifically captures the initial stimulus detection and response that allow a muscle to ultimately contract.