Gross Anatomy of the Muscular System

Flashcards covering key terms and concepts from the muscular system anatomy and physiology.

I band

The region of a sarcomere that contains only thin filaments (actin).

A band

The region of a sarcomere that contains both thick (myosin) and thin (actin) filaments.

H zone

The central part of the A band where there are only thick filaments (myosin).

Z line

The boundary between adjacent sarcomeres; it anchors the thin filaments.

M line

The middle line of a sarcomere that anchors thick filaments.

Cross bridge

The connection formed between myosin head and actin during muscle contraction.

Tropomyosin

A protein that blocks the binding sites on actin, preventing muscle contraction.

Troponin

A protein complex that binds calcium ions and causes tropomyosin to shift, allowing contraction.

Sarcomere

The basic contractile unit of muscle tissue.

Calcium ions (Ca2+)

Ions released from the sarcoplasmic reticulum that trigger muscle contraction.

Myofibril

A long, filamentous organelle found within muscle cells; composed of repeating sarcomeres.

Fascicle

A bundle of muscle fibers surrounded by a connective tissue sheath.

Epimysium

The outer connective tissue layer that surrounds the entire muscle.

Perimysium

The connective tissue that surrounds each fascicle within a muscle.

Endomysium

The connective tissue that surrounds each individual muscle fiber.

Diaphragm

The main muscle involved in respiration, located below the lungs.

Erector spinae

A group of muscles responsible for extending and rotating the back.

Rotator cuff

A group of muscles and their associated tendons that act to stabilize the shoulder.

Abduction

Movement away from the midline of the body.

Adduction

Movement toward the midline of the body.