Muscle Structure and Function

A collection of vocabulary flashcards related to muscle structure and function, covering key concepts such as motor units, muscle contraction mechanisms, and types of muscle fibers.

Skeletal Muscle Functions

Locomotion, maintenance of posture, production of heat, support, and stabilization of joints.

Muscle Fiber

A muscle fiber or myocyte is a single muscle cell that contains myofibrils.

Myofibril

A long, thread-like structure within a muscle fiber that contracts.

Motor Unit

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

Small Motor Units

Motor units for fine control, for example, eye muscles.

Large Motor Units

Motor units used for gross motor functions, like the quadriceps.

Neuromuscular Junction (NMJ)

The chemical synapse between a motor neuron and a muscle fiber where acetylcholine (ACh) initiates muscle contraction.

Acetylcholine (ACh)

A neurotransmitter that binds to receptors on the motor endplate, causing muscle contraction.

Excitation-Contraction Coupling

The process linking the electrical excitation of the muscle cell to contraction, involving calcium release.

Crossbridge Cycle

The process where myosin heads attach to and pull on actin filaments.

Sliding Filament Theory

Explains muscle contraction by actin filaments sliding past myosin filaments.

Isotonic Contraction

When the muscle changes length while contracting.

Isometric Contraction

When the muscle generates force without changing length.

Muscle Twitch

A brief, single contraction of a muscle fiber in response to a stimulus.

Summation

The process where successive stimuli lead to stronger muscle contractions.

Tetanus

A sustained muscle contraction without any relaxation due to high-frequency stimuli.

Slow-Twitch Muscle Fibers (Type I)

Muscle fibers resistant to fatigue, used for endurance activities, relying on aerobic metabolism.

Fast-Twitch Muscle Fibers (Type II)

Muscle fibers that contract quickly and powerfully but fatigue easily, relying on anaerobic metabolism.

Action Potential

A rapid electrical signal that travels along the muscle cell membrane, leading to contraction.

T-tubules

Extensions of the muscle cell membrane that carry the action potential deep into the muscle fiber.

Muscle Relaxation

Occurs when calcium is pumped back into the sarcoplasmic reticulum, causing actin and myosin to disengage.

Muscle Fatigue

Occurs due to depletion of energy sources and accumulation of metabolic byproducts.