Muscle Physiology

These flashcards cover key vocabulary and concepts related to muscle physiology as presented in the lecture notes.

Muscle Tissue Types

The three types of muscle tissue are skeletal, cardiac, and smooth, each having distinct structures and functions.

Neuromuscular Junction (NMJ)

The site where a motor neuron communicates with a muscle fiber, involving axon terminals, synaptic clefts, and receptors.

Sarcoplasmic Reticulum (SR)

A specialized endoplasmic reticulum in muscle cells that stores calcium ions essential for muscle contraction.

T-tubules

Transverse tubules that extend from the plasma membrane into the muscle fiber, facilitating action potential propagation.

Sarcomere

The functional unit of a skeletal muscle fiber, defined as the region between two Z discs, active in contraction.

Sliding-Filament Theory

A theory explaining muscle contraction whereby myosin filaments pull actin filaments past each other, shortening the sarcomere.

Excitation-Contraction Coupling

The process linking muscle excitation by nerve signals to muscle contraction through calcium release.

Myofibrils

Long, thread-like structures in muscle fibers composed of sarcomeres that facilitate muscle contraction.

Motor Unit

A functional unit consisting of a motor neuron and all the muscle fibers it innervates.

Isometric Contraction

A type of muscle contraction where muscle tension increases but the muscle length remains unchanged.

Isotonic Contraction

A type of muscle contraction where muscle tension causes the muscle to change length, either shortening (concentric) or lengthening (eccentric).

ATP hydrolysis

The process where ATP is broken down to release energy for muscle contractions, particularly in the cross-bridge cycle.

Calpain

An enzyme that breaks down proteins in muscle during relaxation, contributing to muscle fatigue.

Ligand-Gated Channels

Ion channels that open in response to the binding of a specific chemical messenger (ligand), such as acetylcholine.

Voltage-Gated Channels

Ion channels that open in response to changes in membrane potential, critical for action potential propagation.

EPOC (Excess Post-Exercise Oxygen Consumption)

The increased rate of oxygen intake following strenuous activity to repay oxygen debt and restore physiological conditions.

Smooth Muscle Characteristics

Smooth muscle is non-striated, involuntary, with a single nucleus, and performs slow, sustained contractions.

Cardiac Muscle Characteristics

Cardiac muscle is striated, involuntary, contains intercalated discs for synchronized contraction, and is fatigue resistant.

Fatigue in Muscle

The progressive loss of strength and contractility due to prolonged physical activity, depletion of energy sources, and accumulation of metabolic byproducts.