Muscular System

Primary Functions of the Muscular System

Includes movement, posture, and heat production.

Secondary Functions of the Muscular System

Includes joint stability, circulation, and respiration.

Epimysium

The outermost connective tissue layer encasing the entire muscle.

Perimysium

The intermediate connective tissue layer that surrounds a fascicle.

Endomysium

The innermost connective tissue layer surrounding the plasma membrane of a muscle cell.

Sarcoplasm

The inner contents of muscle cells, equivalent to cytoplasm.

Sarcolemma

The plasma membrane of muscle cells.

Myofibrils

Structures within muscle fibers containing repeating units called sarcomeres.

Sarcomere

The functional, contractile unit of the muscle fiber composed of actin and myosin.

Actin

A thin filament involved in muscle contraction, providing a binding site for myosin.

Myosin

A thick filament that interacts with actin to produce muscle contraction.

Z disc

Anchoring protein for thin filaments; delineates the boundaries of a sarcomere.

A Bands

Dark bands containing thick myosin filaments overlapping with thin actin filaments.

I Bands

Light bands composed solely of thin actin filaments.

H zone

A light band at the center of an A band, lacking thin filaments.

M line

A dark band at the center of the H zone, composed of anchoring proteins.

Titin

An elastic protein that connects the thick filaments of neighboring sarcomeres.

Label the following Sarcomere:

1. Myosin, 2. Actin, 3. Z-line, 4. A-band, 5. Sacromere 6. H-zone, 7. I-band, 8. M-line

T-Tubules

Extensions of the plasma membrane that help transmit the action potential into the cell.