Chapter 8: Muscles

Acetylcholine

A neurotransmitter involved in muscle contraction and other neural functions.

Action Potential

A brief electrical impulse that travels along a neuron or muscle cell membrane.

All or None Law

The principle that a muscle fiber contracts fully or not at all in response to a stimulus.

Antagonist

A muscle that opposes the action of another muscle (the agonist).

Belly

The thick, central part of a muscle.

Biceps

A muscle with two heads, such as the biceps brachii in the arm.

Biomechanics

The study of mechanical laws relating to movement in living organisms.

Blepharospasm

Involuntary contraction of eyelid muscles.

Contractility

The ability of a muscle to shorten forcibly when stimulated.

Dilator Muscles

Muscles that widen an opening (e.g., pupils).

Dystonia

A movement disorder causing involuntary muscle contractions.

Elasticity

The ability of a muscle to return to its original shape after stretching.

Excitability

The ability of a muscle to respond to stimuli.

Extensibility

The ability of a muscle to be stretched.

Fibromyalgia

A chronic disorder causing widespread muscle pain and fatigue.

Force

The strength or energy exerted by a muscle.

Heel Spur

A bony growth on the heel bone, often causing pain.

Hernia

Protrusion of an organ or tissue through a weak spot in muscle.

Insertion

The point where a muscle attaches to a movable bone.

Intramuscular

Within or into a muscle.

Isometric

Muscle contraction without a change in muscle length.

Isotonic

Muscle contraction with a change in length (shortening or lengthening).

Motor Unit

A motor neuron and all the muscle fibers it controls.

Muscle Fatigue

Temporary loss of muscle strength due to prolonged activity.

Muscle Spasm

Sudden, involuntary muscle contraction.

Muscle Strain

Overstretching or tearing of muscle fibers.

Muscle Tone

The continuous, low-level contraction of muscles at rest.

Muscular Dystrophy

A genetic disorder causing progressive muscle weakness.

Myalgia

Muscle pain.

Myasthenia Gravis

An autoimmune disorder causing muscle weakness.

Neuromuscular Junction

The point where a motor neuron meets a muscle fiber.

Origin

The fixed attachment point of a muscle.

Physiotherapy

Treatment to restore movement and function through exercise and therapy.

Plantar Fasciitis

Inflammation of the foot’s plantar fascia, causing heel pain.

Prime Mover

The main muscle responsible for a movement (agonist).

Rehabilitation

Therapy to recover strength and function after injury.

Remission

A period where disease symptoms lessen or disappear.

Rotator Cuff Injury

Damage to the shoulder’s stabilizing muscles.

Sarcolemma

The cell membrane of a muscle fiber.

Sarcoplasm

The cytoplasm of a muscle cell.

Shin Splints

Pain along the shinbone from overuse.

Smooth Muscle

Involuntary muscle found in organs (e.g., intestines).

Sphincter

A ring-shaped muscle that controls passage through an opening.

Sprain

Stretching or tearing of ligaments.

Strain

Stretching or tearing of muscles or tendons.

Strength

The ability of a muscle to exert force.

Synergists

Muscles that assist the prime mover in a movement.

Tennis Elbow

Inflammation of tendons in the elbow from overuse.

Tetanus

Sustained muscle contraction or a bacterial infection causing muscle spasms.

Torque

A rotational force produced by muscle contraction.

Torticollis

A condition where neck muscles contract abnormally, twisting the head.

Triceps

A muscle with three heads, such as the triceps brachii in the arm.

Vastus Lateralis

The largest part of the quadriceps muscle group.