Muscle system exam ANT & PHYIS

Functions of the muscular system

Produce movement, maintain posture and body position, stabilize joints, generate heat as they contract.

Skeletal muscle

Voluntary muscle attached to bones of the skeleton.

Cardiac muscle

Involuntary muscle that makes up most of the wall of the heart and is responsible for the pumping action of the heart.

Smooth muscle

Involuntary muscle tissue found in arteries, glands, skin, and visceral organs.

Epimysium

Surrounds whole muscle; lies beneath fascia.

Fascia

Band of connective tissue beneath the skin that separates the muscles from internal organs.

Perimysium

Surrounds fascicles within a muscle.

Fascicles

Groups of muscle fibers.

Endomysium

Surrounds individual muscle fibers within a fascicle.

Skeletal Muscle Fibers

Multinucleated with many myofibrils: long, parallel structures composed of actin and myosin.

Sarcomere

A repeating unit composed of actin and myosin filaments.

Actin

Thin protein filaments.

Myosin

Thick protein filaments.

Z lines

Mark the boundaries of each sarcomere.

H zone

Marks the center of the sarcomere.

Muscle contraction

Occurs when sarcomeres shorten due to the sliding of actin and myosin filaments.

A band

Actin and myosin overlap.

I band

Contains only actin.

M line

Anchors myosin.

Troponin

A regulatory globular protein that acts as the calcium sensor, found in cardiac and skeletal muscle.

Tropomyosin

A long, double-stranded regulatory protein coiled around Actin, Covers the myosin-binding sites on actin in a resting muscle, preventing contraction,

Neuromuscular junction

Where a neuron meets the muscle fiber to activate contraction.

Action potential

Nerve impulse that stimulates the neuron to release ACh.

Muscle fatigue

Loss in the ability to contract the muscle, caused by blood supply interruption, exhaustion of acetylcholine, lactic acid build up, or lack of ATP, K+, Na+, or Ca++.

Isometric contraction

Muscle changes tension but not length.

Isotonic contraction

Muscle changes length but not tension.

Concentric contraction

Muscle shortens.

Eccentric contraction

Muscle lengthens.