Parts of muscle

Epimysium

Outermost part of muscle

Dense later of collagen fibers that covers the entire muscle

Perimysium

Covers muscle fascicles

Made of collagen and elastic fibers, blood vessels, and nerves.

Endomysium

Surrounds individual muscle fibers/cells

Made of elastic fibers, capillaries, and nerves

Muscle Fiber

Muscle Cell

Sarcolemma

Structure of Muscle Fiber/Cell;

Plasma membrane that surrounds each muscle fiber

Myofibril

Structure of Muscle Fiber/Cell;

Organelles inside muscle fibers. Contains myofilaments

Myofilaments

Structure of Muscle Fiber/Cell;

Within the myofibril. Responsible for muscle contraction

Made of myosin and actin proteins/filaments

Sarcoplasmic Reticulum

Structure of Myofibril;

Wraps each myofibril. Stores calcium needed for muscle contraction

Terminal cisternae

Structure of Myofibril;

Expanded end of the sarcoplasmic reticulum.

T-tubule

Structure of Myofibril;

Tube that is continuous with the sarcolemma. Forms a passageway through muscle fibers and myofibrils. Responsible for carrying an electrical signal from a nerve, to the sarcoplasmic reticulum to release calcium needed for muscle contraction.

Triad

Structure of Myofibril;

One T-Tubule and two terminal cisternae. Where the electrical signal in the T-tubule stimulates release of Ca++ from SR

I-Band

Structure of Myofilament

Light in color, spot with just actin proteins

A-Band

Structure of Myofilament

Dark in color. Spot with just mostly myosin proteins and some actin

H-Zone

Structure of Myofilament

Thick but no thin filaments. Resembles an H

Sarcomere

Structure of Myofilament

From Z-line to Z-line

Z-Line

Structure of Myofilament

Where actin filaments are anchored. Myosin is also anchored to Z-line with stabilizing proteins called titin.

Zone of Overlap

Structure of Myofilament

Where Myosin and actin filaments overlap