Muscle Physiology and Contraction

These flashcards cover key terms and concepts related to muscle physiology and contraction, providing definitions relevant for exam preparation.

Activation of motor neuron

The initial step in muscle contraction which controls motor units.

Neuromuscular Junction (NMJ)

The point where a motor neuron stimulates a muscle fiber.

Excitation-Contraction Coupling

The process where an electrical stimulus from a nerve meets a muscle, leading to muscle contraction.

Sarcoplasmic Reticulum

The specialized endoplasmic reticulum in muscle cells that stores calcium ions.

Myofilaments

The contractile proteins in muscle cells; include thick filaments (myosin) and thin filaments (actin).

Sliding Filament Mechanism

The theory that explains how muscles contract by the sliding of actin over myosin.

Motor Unit

A motor neuron and all the muscle fibers it innervates.

Acetylcholine (ACh)

The neurotransmitter released at the NMJ that stimulates muscle contraction.

Rigor Mortis

The postmortem stiffening of muscles due to lack of ATP.

Isometric vs. Isotonic Contraction

Isometric contraction generates tension without shortening, whereas isotonic contraction results in muscle shortening or lengthening.

Troponin

A protein that binds calcium ions and, upon binding, shifts tropomyosin to expose binding sites on actin.

Z-disc

The boundary between sarcomeres where thin filaments (actin) are anchored.

Calcium ions (Ca2+)

Essential ions that initiate muscle contraction by binding to troponin.

Cross-bridge

The connection formed when myosin heads bind to actin during contraction.

Excitation

The process of generating an action potential in the muscle fiber following stimulation.

T tubule

Transverse tubules that allow action potentials to penetrate deep into a muscle fiber.

Striations

The visible bands in a skeletal muscle fiber due to the arrangement of myofilaments.

Sarcolemma

The cell membrane of a muscle fiber.

Endomysium

The connective tissue that surrounds each muscle fiber.

Fascicle

A bundle of muscle fibers surrounded by perimysium.

Perimysium

The connective tissue sheath that surrounds a fascicle.

fascicle

bundles of fibers

1 fiber

bundle of my-fascicles

tubules

opening or folding in sarcolemma to penetrate charges

sarcoplasm reticulum

subway system around cells (transporter)

transverse tubule

has openings so electricity can go to bigger cells

sarcolemma

inside cell membrane

sarcoplasm

cytoplasm of muscle cell

Actin

thin protein 

myosin

thick protein

sarcomere

h band = thick filament

a band = thick filament

I band = thin filament

z disc- holds thin filament

m line= holes thick filament