Muscle Tissue and Contraction Flashcards

Flashcards about muscle tissue and contraction.

Skeletal Muscle

Found attached to bones, striated in appearance, and under voluntary control.

Cardiac Muscle

Found in the heart, striated in appearance, and under involuntary control.

Smooth Muscle

Found in the walls of internal organs, not striated, and under involuntary control.

Sarcolemma

The plasma membrane of a muscle cell.

Sarcoplasm

The cytoplasm of a muscle cell.

Sarcoplasmic Reticulum

The smooth endoplasmic reticulum of a muscle cell, which stores calcium ions.

Myofiber/Muscle Fiber

Alternative names for skeletal muscle cells.

Fascicles

Bundles of muscle fibers.

Myofiber

A single muscle cell.

Myofibril

A long, cylindrical structure within a muscle cell composed of sarcomeres.

Myofilaments

The protein filaments (actin and myosin) that make up a sarcomere.

Sarcomere

The functional unit of muscle contraction, located between two Z-discs.

Myofilaments: Actin

Thin filaments composed of the protein actin, associated with troponin and tropomyosin.

Myofilaments: Myosin

Thick filaments composed of the protein myosin, which has a head that binds to actin.

Z-discs

The boundaries of a sarcomere.

M-line

The midline of a sarcomere.

A band

The region of a sarcomere containing myosin filaments; does not change width during contraction.

H zone

The region of a sarcomere containing only myosin filaments; decreases in width during contraction.

I bands

The region of a sarcomere containing only actin filaments; decreases in width during contraction.

T-tubules

Invaginations of the sarcolemma that transmit action potentials into the muscle fiber.

Myosin Head

The part of the myosin protein that binds to actin, enabling muscle contraction.

Myosin Binding Sites

Located on the actin filaments; where myosin heads bind during muscle contraction.

Tropomyosin

A protein that blocks myosin-binding sites on actin when the muscle is at rest preventing contraction.

Sarcoplasmic Reticulum

The smooth endoplasmic reticulum of a muscle fiber that stores calcium ions.

Terminal Cisternae

Enlarged regions of the sarcoplasmic reticulum that store calcium ions to release upon muscle stimulation.

Troponin

A protein complex that binds calcium ions and moves tropomyosin away from the myosin-binding sites on actin, initiating muscle contraction.

Synapse

The junction between a neuron and another cell (e.g., muscle cell, gland).

Neuromuscular Junction

The synapse between a motor neuron and a muscle fiber. Also called a myoneural junction or motor end plate.

Excitation-Contraction Coupling

The sequence of events by which an action potential in the sarcolemma leads to muscle contraction.

Muscle Fiber Types

Type I (slow oxidative), Type IIa (fast oxidative), and Type IIb (fast glycolytic).

Motor Unit

A single motor neuron and all the muscle fibers it innervates.

Wave Summation

The addition of successive neural stimuli to produce greater contraction.

Tetanus (Incomplete/Unfused)

A sustained muscle contraction with partial relaxation between stimuli.

Tetanus (Complete/Fused)

A sustained muscle contraction without any relaxation between stimuli; generates more tension than incomplete tetanus.

Rigor Mortis

The stiffening of muscles after death due to lack of ATP; lack of ATP prevents detachment of myosin heads from actin.

Muscle Tone

A state of sustained partial contraction of muscles that is essential for posture, balance and readiness.

Isotonic Contraction

A muscle contraction in which the muscle changes length while maintaining a constant tension; -iso means same, -tonic means tension.

Isometric Contraction

A muscle contraction in which the muscle length remains the same while tension increases; -iso means same, -metric means length.

Concentric Contraction

A type of isotonic contraction in which the muscle shortens while generating force.

Eccentric Contraction

A type of isotonic contraction in which the muscle lengthens while generating force.