⚰️ SET 26: Rigor Mortis AND ⚡ SET 27: Muscle Twitch AND 📈 SET 28: Strength of Muscle Contraction

What is rigor mortis?

Stiffening of muscles after death

When does rigor mortis begin?

About 3–4 hours after death

What causes calcium to increase during rigor mortis?

Breakdown of sarcoplasmic reticulum and sarcolemma

What effect does calcium have in rigor mortis?

It triggers cross-bridge formation

Why can muscles not relax during rigor mortis?

ATP is no longer produced

When does rigor mortis peak?

Around 12 hours after death

When does rigor mortis disappear?

After 48–60 hours as proteins break down

What is a muscle twitch?

A single contraction-relaxation response to a stimulus

What are the three phases of a twitch?

Latent, contraction, and relaxation

What happens during the latent phase?

Signal travels with no visible contraction

What happens during the contraction phase?

Muscle shortens and generates force

What happens during the relaxation phase?

Muscle returns to resting state

How does a single muscle fiber respond to stimuli?

It produces the same force each time

How does a whole muscle increase force?

By recruiting more motor units

What is multiple motor unit summation?

Increasing force by activating more motor units

What is multiple-wave summation?

Increasing force by increasing stimulus frequency

Why does higher frequency increase force?

Calcium builds up in muscle fibers