Muscle Physiology Review

Flashcards summarizing key concepts about muscle physiology, including muscle twitch, excitation-contraction coupling, and muscle contraction types.

What is a muscle twitch?

A muscle twitch is the response of a muscle fiber to a single stimulus.

What are the three phases of a muscle twitch?

1. Latent Period, 2. Contraction Phase, 3. Relaxation Phase.

What shortens during muscle contraction?

The sarcomere shortens, not the filaments.

What is the link between the nerve signal and muscle contraction?

Excitation–Contraction Coupling (ECC).

What are the steps of Excitation–Contraction Coupling?

1. Action potential travels along muscle membrane, 2. Goes down T-tubules, 3. Sarcoplasmic reticulum releases Ca²⁺, 4. Ca²⁺ binds to troponin, 5. Tropomyosin moves → exposes binding sites, 6. Myosin binds actin → contraction starts.

What happens during relaxation of muscles?

Ca²⁺ is pumped back into the SR and binding sites are covered again.

How does the voltage of a stimulus affect muscle contraction?

Increasing stimulus voltage results in more motor units recruited, leading to greater force.

What is the difference between isotonic and isometric contractions?

Isotonic contractions change length while tension remains the same, whereas isometric contractions maintain the same length but change tension.

What is the Length–Tension Relationship?

Force depends on starting muscle length, with optimal length yielding maximum force.

What is Treppe?

The staircase effect where repeated stimuli after rest lead to a gradual increase in force due to more Ca²⁺ being available.

What is wave summation?

Wave summation occurs when a new stimulus is applied before full relaxation, causing contractions to add together.

What is complete tetanus?

Complete tetanus occurs when there is no relaxation between contractions, resulting in a smooth, sustained contraction.