EMG and Muscle Contraction

These flashcards cover key concepts related to muscle tissue types, structure, contraction mechanisms, and physiological responses.

Muscle Tissue Types

Cardiac (striated, involuntary), Smooth (nonstriated, involuntary), Skeletal (striated, voluntary).

Myofibril

Bundles of protein filaments that contract muscle by shortening.

Sarcomere

The region between two Z-lines; the functional unit of muscle contraction.

Action Potential

A change in electrical potential that initiates muscle contraction.

Excitation-Contraction Coupling

The process where an action potential leads to muscle contraction through calcium ion release.

Cross-Bridge Formation

When myosin heads bind to active sites on actin, forming a connection essential for contraction.

Muscle Twitch

The mechanical response of a muscle fiber to a single stimulus, including latency, contraction, and relaxation periods.

Summation

The increased force production in muscle fibers by applying additional stimuli before relaxation.

Tetanus

A sustained muscle contraction without relaxation due to frequent stimulation.

Muscle Fatigue

A decrease in muscle tension following frequent stimulation, often due to metabolic disruptions.

Fast Glycolytic Fibers

Muscle fibers that produce quick bursts of force but fatigue rapidly.

EMG (Electromyography)

A technique measuring electrical activity in muscles to assess muscle response.

Peripheral Nuclei

Multiple nuclei located between the sarcolemma and myofibrils in skeletal muscle cells.

Calcium Ions

Essential ions that bind to troponin to initiate muscle contraction.

Central Drive

Neural signals from the brain that increase motor unit activation and firing rates to counter fatigue.

Sarcolemma

The cell membrane of a muscle fiber, enclosing the sarcoplasm.

Sarcoplasmic Reticulum (SR)

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

T-tubules (Transverse Tubules)

Invaginations of the sarcolemma that allow action potentials to rapidly penetrate the muscle fiber.

Actin

A thin filament protein that forms the backbone of the sarcomere and has binding sites for myosin heads.

Myosin

A thick filament protein with heads that bind to actin, crucial for muscle contraction.

Motor Unit

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

Neuromuscular Junction

The specialized synapse between a motor neuron and a muscle fiber where neurotransmitters transmit signals.

Troponin

A protein complex on actin filaments that binds calcium ions to initiate muscle contraction by moving tropomyosin.

Tropomyosin

A protein that covers myosin-binding sites on actin in relaxed muscle, preventing cross-bridge formation.

ATP (Adenosine Triphosphate)

The primary energy currency used for muscle contraction, powering myosin head movement and calcium pumping.