Muscular System

Skeletal Muscle

Attached to bones, striated, and voluntarily controlled.

Cardiac Muscle

Located in the heart, striated, and involuntarily controlled.

Smooth Muscle

Located in blood vessels and hollow organs, non-striated, and involuntarily controlled.

Muscle Functions

Movement, maintain posture, respiration, production of body heat, communication, heart beat, contraction of organs and vessels.

Contractility

The ability of muscle to shorten forcefully.

Excitability

The capacity of muscle to respond to a stimulus.

Extensibility

The ability to be stretched beyond its normal resting length and still contract.

Elasticity

The ability of the muscle to recoil to its original resting length after being stretched.

Epimysium

The connective tissue sheath surrounding each skeletal muscle.

Fascicles

Groups of muscle cells within a skeletal muscle, surrounded by perimysium.

Endomysium

The connective tissue covering surrounding each skeletal muscle fiber.

Sarcolemma

The cell membrane of a muscle fiber, containing T tubules.

Myofibrils

Bundles of protein filaments within muscle fibers, consisting of actin and myosin.

Sarcomere

The basic structural and functional unit of a skeletal muscle, extending from one Z disk to the next.

Z Disks

Protein fibers that anchor actin myofilaments and separate sarcomeres.

Action Potential

A rapid change in charge across the cell membrane that triggers muscle contraction.

Depolarization

The process where the inside of the cell membrane becomes more positively charged.

Repolarization

The return of the cell membrane to its resting potential after depolarization.

Neuromuscular Junction

The synapse where a nerve fiber connects with a muscle fiber.

Motor Unit

A group of muscle fibers stimulated by a single motor neuron.

Acetylcholine

The neurotransmitter that stimulates skeletal muscles.

Muscle Twitch

A single contraction of a muscle fiber in response to a stimulus, consisting of latent, contraction, and relaxation phases.

Summation

The process where individual muscle contractions combine to produce a stronger contraction.

Slow Twitch Fibers

Muscle fibers that contract slowly, fatigue slowly, and use aerobic respiration.

Fast Twitch Fibers

Muscle fibers that contract quickly, fatigue quickly, and use anaerobic respiration.

Muscle Fatigue

A temporary state of reduced work capacity in muscle fibers.

Isometric Contraction

A contraction with increased muscle tension but no change in length.

Isotonic Contraction

A contraction with a change in muscle length but no change in tension.

Muscle Tone

The constant tension produced by muscles over long periods.

Cardiac Muscle

Striated muscle found in the heart, autorhythmic, and connected by intercalated disks.

Smooth Muscle

Non-striated muscle controlled involuntarily, found in organs.

Tendon

Connects skeletal muscle to bone.

Aponeuroses

Broad, sheet-like tendons.

Agonists

Muscles that work together to produce a movement.

Antagonists

Muscles that oppose the actions of agonists.

Muscle Nomenclature

Muscles are named based on location, size, shape, orientation, origin/insertion, number of heads, and function.

Muscles of Mastication

Include temporalis, masseter, and pterygoids.

Diaphragm

Muscle that moves during quiet breathing.

Trapezius

Muscle that extends the neck and shoulders.

Quadriceps Femoris

Group of four muscles in the thigh that extend the knee.