Chapter 9: Skeletal Muscle Tissue and Muscle Organization

Skeletal Muscle

Muscle tissue that can be controlled voluntarily, attaches to bones and performs movement.

Cardiac Muscle

Involuntary muscle found only in the heart.

Smooth Muscle

Involuntary muscle found in the walls of hollow organs.

Epimysium

Connective tissue that surrounds an entire muscle.

Perimysium

Connective tissue that surrounds individual bundles (fascicles) of muscle fibers.

Endomysium

Connective tissue that surrounds each muscle fiber.

Neuromuscular Junction

The synapse where communication between a neuron and a muscle fiber occurs.

Sarcoplasm

The cytoplasm of a skeletal muscle cell.

Sarcoplasmic Reticulum (SR)

An internal membrane system similar to endoplasmic reticulum in muscle cells.

Transverse (T) Tubules

Deep indentations of the sarcolemma that carry action potentials into the muscle cell.

Myofibrils (Muscle Fibers)

Organized structures within muscle fibers made up of myofilaments

Sarcomeres

Repeating functional units within myofibrils.

Sliding Filament Theory

Theory explaining how muscle fibers exert tension and shorten during contraction.

Action Potential

Electrical impulse that stimulates muscle contraction.

Acetylcholine (ACh)

Chemical released by neurons to stimulate muscle contraction.

Muscle Twitch

A single momentary muscle contraction response to a single stimulus.

Muscle Tone

Constant tension maintained in a muscle even at rest.

Hypertrophy

Enlargement of muscles due to excessive stimulation.

Atrophy

Decrease in muscle size and strength due to inadequate stimulation.

Fast Fibers

Skeletal muscle fibers that produce rapid, powerful contractions.

Slow Fibers

Skeletal muscle fibers that contract slowly and can sustain longer activity.

Intermediate Fibers

Skeletal muscle fibers that are similar to fast fibers but more resistant to fatigue.

Parallel Muscle

Muscle with fascicles that run parallel to its long axis.

Convergent Muscle

Muscle with fascicles that converge towards a single tendon or insertion point.

Pennate Muscle

Muscle with fascicles that form an oblique angle to the tendon.

Circular Muscle (Sphincter)

Muscle with fibers arranged concentrically around an opening.

Agonist (Prime Mover)

Muscle that provides the primary force for an action.

Antagonist

Muscle that opposes the action of the agonist.

Lever

A rigid structure that moves on a fixed point (fulcrum) to create movement.

Aging Effects on Muscles

Reduces size, elasticity, and power of muscle tissues, and decreases recovery from injuries.