Muscle Anatomy and Physiology

This set of flashcards covers important vocabulary related to muscle anatomy and physiology, particularly focusing on muscle tissue types, mechanisms of contraction, and the neuromuscular junction.

Neuromuscular Junction

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

Skeletal Muscle

Muscle that is attached to bones and is responsible for voluntary movements.

Muscle Fiber

A single muscle cell that makes up skeletal muscle.

T-tubules

Deep invaginations of the sarcolemma that extend into the muscle fiber.

Sarcoplasmic Reticulum

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

Myofibrils

Long, cylindrical structures in muscle fibers made up of myofilaments.

Sarcomere

The functional contractile unit of a muscle fiber defined by the area between two Z discs.

Actin

A protein that forms thin filaments in muscle fibers.

Myosin

A protein that forms thick filaments in muscle fibers.

Troponin

A protein complex involved in the muscle contraction mechanism.

Tropomyosin

A protein that blocks the binding sites on actin when muscle fibers are relaxed.

Power Stroke

The process where the myosin head pivots and pulls actin filaments toward the center of the sarcomere.

Calcium Ions (Ca2+)

Essential ions that trigger muscle contraction by binding to troponin.

Sliding Filament Theory

The theory that explains muscle contraction as the sliding of actin and myosin filaments across each other.

Contractility

The ability of muscle fibers to shorten and generate tension.

Excitability

The ability of muscle fibers to respond to stimuli with electrical changes.

Elasticity

The ability of muscle fibers to return to their resting length after contraction.

Extensibility

The capability of muscle fibers to be stretched beyond their resting length.

Motor Unit

A motor neuron and all the muscle fibers it innervates.

ACh (Acetylcholine)

A neurotransmitter that transmits signals from neurons to muscle fibers.

Action Potential

An electrical signal that triggers the contraction of muscle fibers.

Synaptic Clef

The gap between the synaptic knob and the motor end plate.

Sarcoplasm

The cytoplasm of a muscle fiber.

Z Disc

A structure that separates sarcomeres from each other.

M Line

The middle part of the sarcomere where thick filaments are anchored.

H Zone

The region in the A band where there is no overlap of thick and thin filaments.

I Band

The region in the sarcomere containing only thin actin filaments.

A Band

The region of the sarcomere that contains both thick and thin filaments.

Rigor Mortis

The stiffening of muscles after death due to lack of ATP.

Neuromuscular Transmission

The process of communication between a motor neuron and a muscle fiber.

Excitation-Contraction Coupling

The sequence of events by which an action potential in a muscle fiber leads to contraction.

Sarcoplasmic Calcium

Calcium that is released from the sarcoplasmic reticulum, necessary for muscle contraction.

G-actin

Globular actin monomers that polymerize to form F-actin.

F-actin

Filamentous actin polymers formed by G-actin.

Motor End Plate

The region of the sarcolemma that contains receptors for acetylcholine.

Action Potential Propagation

The process by which an action potential is transmitted across the muscle plasma membrane.

Calcium Channel

A protein that enables the movement of calcium ions across cell membranes.

Troponin-Ca2+ Complex

The formed complex when calcium binds to troponin, initiating muscle contraction.

Threshold Potential

The minimum depolarization required to activate an action potential in muscle fibers.

Henneman’s Size Principle

The principle stating that smaller motor units are recruited first as force increases.

Fatigue-Resistant Fibers

Muscle fibers that can sustain activity longer without fatigue.

Fast Fatigable Fibers

Muscle fibers that contract quickly but tire rapidly.

Whole-Muscle Properties

The collective characteristics of a muscle affecting its contraction strength and endurance.