Question

multiple choice question

threshold is which of the following in terms of muscle physiology?

a volume of liquid
a distance
a voltage

Explanation:

Define threshold in muscle physiology

In Muscle Physiology, threshold refers to the minimum stimulus strength required to elicit a response (contraction). Specifically, this stimulus is electrical in nature and is measured as a change in membrane potential.

Identify the physical quantity of the threshold

The electrical potential difference across the sarcolemma (muscle cell membrane) is measured in volts or millivolts. Therefore, the threshold stimulus required to open voltage-gated channels and trigger an action potential is a specific level of electrical potential, which is a voltage.

Evaluate the given options

• "A volume of liquid": Incorrect, as volume does not describe electrical excitability.
• "A distance": Incorrect, as physical distance does not trigger membrane depolarization.
• "A voltage": Correct, because threshold is the minimum voltage level (typically around \(-55\text{ mV}\)) needed to generate an action potential.

Answer:

• A volume of liquid
• A distance
• A voltage (Correct answer)