Muscle Tissue

Skeletal muscle

Muscle with long, striated, multinucleated muscle fibers controlled by the nervous system to produce voluntary movement of their attached bones

Cardiac muscle

Muscle with short, branched, striated single-nuclei muscle fibers that are controlled by an internal pacemaker to involuntarily pump blood in the heart

Smooth muscle

Muscle with short, spindley, single nucleus muscle fibers that are controlled by chemical signals to involuntarily move the walls of internal organs

Muscle fascicles

Bundles of muscle fibers in skeletal muscle

Muscle fibers

Muscle cells

Epimysium

Connective tissue wrapped around skeletal muscle

Perimysium

Connective tissue wrapped around muscle fascicles

Endomysium

Connective tissue wrapped around muscle fibers

Sarcolemma

Muscle fiber membrane

Myofibrils

Muscle fiber organelle with segments of sarcomeres

Sarcomeres

Functional unit of muscle fibers that shortens to create muscle contraction

T-tubules

Part of the sarcolemma that carries an action potential into the muscle fiber

Sarcoplasmic reticulum

Muscle fiber organelle that stores Ca⁺⁺ ions, releasing the ions in response to muscular action potentials

Actin

Thin myofilaments projecting from the z-disc

Myosin

Thick myofilaments projecting from the m-line

Troponin-tropomyosin complex

Molecules attached to actin that prevent it from binding to myosin

Sliding filament model

Sarcomere shortening created by Ca⁺⁺ ions binding to troponin, removing the troponin-tropomyosin complex from actin so it can connect to myosin

Z-disc

Borders of sarcomeres

A-band

Dark band of myosin on a sarcomere

I-band

Light band of actin on a sarcomere

H-zone

Band of myosin alone on a

M-line

Line in the middle of the sacrome where myosin projects from

Cross-bridge cycle

Action of myosin heads pulling on actin, powered by ATP