Muscular system 7.

Epimysium

A fascia that surrounds muscles.

Perimysium

Connective tissue that surrounds fasiculi (bundles of muscle fibers).

Endomysium

Thin connective tissue that surrounds individual muscle fibers.

Neuromuscular Junction (NMJ)

The synapse or junction between a motor neuron and a muscle fiber.

Action Potential

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

Ligand-gated Ion Channels

Ion channels that open or close in response to the binding of a molecule (ligand) such as a neurotransmitter.

Voltage-gated Ion Channels

Ion channels that open or close in response to changes in membrane potential.

Depolarization

The process during the action potential when the inside of the cell becomes less negative.

Repolarization

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

Excitation-Contraction Coupling

Mechanism where an action potential leads to muscle fiber contraction.

Cross-Bridge Cycle

The process through which myosin heads pull actin filaments, resulting in muscle contraction.

Treppe

A graded response occurring when a muscle is rested, leading to progressively stronger contractions.

Isometric Contraction

Muscle contraction where the muscle length does not change but tension increases.

Isotonic Contraction

Muscle contraction where the muscle changes length while maintaining constant tension.

Slow-twitch Fibers

Muscle fibers that contract slowly, have high endurance, and are rich in myoglobin.

Fast-twitch Fibers

Muscle fibers that contract quickly, have less endurance, and are tailored for short bursts of strength.

Rigor Mortis

A postmortem state where muscles become stiff due to calcium binding to myosin without ATP.

Acetylcholinesterase

An enzyme that breaks down the neurotransmitter acetylcholine in the synaptic cleft.

Muscle Fatigue

The decline in the ability of a muscle to generate force, often due to depletion of ATP.

Sarcoplasmic Reticulum

A specialized smooth endoplasmic reticulum in muscle cells that stores calcium ions.

Calmodulin

A calcium-binding protein that plays a critical role in smooth muscle contraction.

Muscle Twitch

A single contraction of a muscle fiber in response to a single action potential.