Overview of Muscle Contraction and Cell Structure

These flashcards cover key vocabulary terms related to muscle structure and function based on the provided lecture notes.

Contractile organelle

An organelle, such as mitochondria, that is involved in contraction, specifically in muscle cells.

Muscle fiber

A muscle fiber is a single muscle cell. It is long and thin and contains many myofibrils.

Myofilaments

Small protein filaments within myofibrils; there are three types: thick, thin, and elastic.

Thick filament

Composed of myosin; a major component in muscle contraction.

Myosin molecule

Has two heads and a tail, forms thick filaments, and interacts with actin during contraction.

Thin filaments

Composed of actin, troponin, and tropomyosin; interact with myosin during contraction.

Active site

The indentation in globular actin where myosin heads temporarily bind during contraction.

Tropomyosin

A protein that blocks the binding site on actin, preventing contraction until calcium is present.

Troponin

A protein that, when bound to calcium, causes tropomyosin to move, allowing contraction to occur.

Sarcolemma

The plasma membrane of a skeletal muscle cell.

T tubules

Extensions of the sarcolemma that allow electrical impulses to travel deep into the muscle cell.

Sarcoplasmic reticulum

An organelle that stores calcium within muscle cells.

Striations

The alternating dark and light bands in muscle fibers, associated with A bands (dark) and I bands (light).

Sarcomere

The functional and structural unit of a muscle fiber, extending from one Z disk to another.

H zone

The central region of the A band in a sarcomere where there are no overlapping thin filaments.

Elastic filaments

Filaments that attach thick filaments to the Z disc, providing elasticity to the sarcomere.

Excitation-contraction coupling

The process linking the electrical impulse from a neuron to muscle contraction.

Cross bridge cycle

The process where myosin heads repeatedly bind, move, and detach from actin, pulling the muscle fibers during contraction.

Acetylcholine (ACh)

A neurotransmitter released at the neuromuscular junction that stimulates muscle contraction.

Action potential

A change in electrical charge that propagates along a muscle cell to trigger contraction.