Muscle Contraction and Fiber Physiology

Flashcards covering the protein structure, regulatory mechanisms, and physiological processes of skeletal muscle contraction.

Dystrophin protein complex

A complex that generates force for muscle contraction by anchoring myofibrils to the sarcolemma.

Actin

Monomers organized into two thin, intertwined protein filaments.

Myosin

Thick filaments consisting of two strands, each with a globular head containing a binding site for actin and an elongated tail.

Regulatory proteins

Proteins such as tropomyosin and troponin that control when contraction occurs by modulating the interaction between actin and myosin.

Tropomyosin

A short, thin, string-like protein twisted into a filament.

Troponin

A globular or ball-like protein attached to tropomyosin that contains a binding site for $Ca^{2+}$.

A-band

A region within the sarcomere that spans the full length of thick (myosin) filaments and remains constant in length during contraction.

H-zone

The lighter region in the center of the A-band containing only thick filaments.

I-band

A region containing only thin filaments that are not pulled inward in a resting, relaxed muscle.

Nebulin

An actin-binding protein anchored in the Z-disc that extends the length of the thin filament.

Connectin (titin)

A cable-like protein that extends from Z-discs to the M line through the core of each thick filament.

Incomplete tetany

A state of continuous contraction where muscle contractions overlap due to rising stimulation frequency.

Fatigue

A reduction in muscle tension caused by prolonged stimulation.

Synaptic knob

The end of a neuron's axon that holds vesicles containing acetylcholine (ACH).

Excitation-contraction coupling

The process where a nerve signal triggers the release of ACH, leading to an electrical signal that reaches the sarcoplasmic reticulum to release $Ca^{2+}$, enabling sarcomeres to contract.

Aerobic cellular respiration

A process occurring in the mitochondria that uses oxygen, pyruvate, fatty acids, and amino acids to create large amounts of ATP.

Fast glycolytic fibers

Large, powerful muscle fibers that use glycolysis for ATP, have little myoglobin, and appear white.