Muscle Types and Contraction Summary

These flashcards cover key vocabulary and concepts from the lecture notes related to muscle types, structure, and contraction mechanisms.

Skeletal Muscle

Striated, voluntary muscle attached to bones, multinucleated with peripheral nuclei, responsible for body movement.

Cardiac Muscle

Striated, involuntary muscle found in the heart, has a single central nucleus, responsible for pumping blood.

Smooth Muscle

Non-striated, involuntary muscle found in the walls of hollow organs, has a single central nucleus, responsible for moving substances through internal passages.

Myofiber

A single muscle cell that is long and cylindrical.

Myofibril

Long, threadlike structures inside myofibers made up of sarcomeres.

Sarcomere

The unit of contraction in a muscle, made up of actin and myosin.

Actin

Thin filament involved in muscle contraction, has tropomyosin wrapped around it.

Myosin

Thick filament in muscle that has heads that bind to actin during contraction.

Tropomyosin

Protein that wraps around actin and blocks myosin-binding sites when the muscle is at rest.

Troponin

A protein complex on actin that binds calcium and moves tropomyosin to expose binding sites.

Rigor Mortis

The stiffening of muscles after death due to ATP depletion, locking myosin and actin together.

Power Stroke

The step in muscle contraction where myosin heads change shape to pull actin toward the center of the sarcomere.

Motor Unit Recruitment

The activation of additional motor units to generate a stronger muscle contraction as stimulus strength increases.

Threshold Potential

The minimum stimulus strength required to trigger an action potential in a motor neuron, leading to muscle contraction.

Calcium's role in muscle contraction

Calcium enables actin-myosin binding by moving tropomyosin away from binding sites on actin.

Effect of ATP in muscle function

ATP powers muscle contraction and relaxation; without it, myosin cannot detach from actin.