human anatomy

Agonist

A substance that activates a receptor to produce a biological response, often enhancing the effect of a neurotransmitter or hormone.

Antagonist

The muscle that opposes the agonist; it inhibits or dampens the biological response by blocking the receptor or reducing the effect of the neurotransmitter or hormone.

Aponeurosis

A flat sheet of connective tissue that connects muscles to the parts they move.

Concentric

A type of muscle contraction where the muscle shortens as it generates force.

Eccentric

A type of muscle contraction where the muscle lengthens while still generating force.

Endomysium

A connective tissue that surrounds individual muscle fibers.

Epimysium

A connective tissue sheath that surrounds the entire muscle.

Fascicle

A bundle of muscle fibers within a muscle.

Isometric

A type of muscle contraction where the muscle generates force without changing length.

Perimysium

A connective tissue sheath that surrounds a fascicle.

Peristalsis

The wave-like muscle contractions that move food through the digestive tract.

Sarcolemma

The plasma membrane of a muscle fiber.

Acetylcholine

A neurotransmitter that transmits signals across the neuromuscular junction.

Action Potential

A rapid rise and fall in voltage or membrane potential across a cellular membrane.

Cross Bridges

Structures formed when myosin heads bind to actin during muscle contraction.

Motor Neuron

A nerve cell that transmits signals to muscles, causing them to contract.

Motor Unit

A single motor neuron and all the muscle fibers it innervates.

Neuromuscular Junction

The synapse where a motor neuron meets a muscle fiber.

Sarcomeres

The basic contractile units of muscle fibers.

Synaptic Cleft

The gap between the nerve ending and the muscle fiber at the neuromuscular junction.

Contusion

A bruise, resulting from bleeding beneath the skin due to trauma.

Hernia

A condition where an internal organ pushes through a weak spot in the surrounding muscle or tissue.