Functions and Structure of Muscles

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Energy Systems

ATP-PC system, Glycolytic system, Oxidative system.

Contractility

Ability of muscles to contract or shorten.

Elasticity

Ability of muscles to return to their original shape after contraction or extension.

Extensibility

Ability of muscles to stretch without being damaged.

Cross Bridge

Binding of myosin to actin, forming a bridge for muscle contraction.

Muscle Fatigue

Caused by ATP depletion, lactic acid accumulation, and electrolyte imbalances.

Sarcolemma

Cell membrane of a muscle fiber.

H Zone

Center of the A band containing only myosin filaments.

M Line

Center of the H zone, stabilizing the sarcomere.

Neurotransmitters

Chemicals released at the neuromuscular junction, initiating muscle contraction.

Perimysium

Connective tissue surrounding bundles of muscle fibers.

Endomysium

Connective tissue surrounding individual muscle fibers.

Ion Channels

Control the flow of ions necessary for muscle contraction.

Sarcoplasm

Cytoplasm of a muscle cell.

A Band

Dark bands containing both actin and myosin filaments.

Action Potential

Electrical signal generated in the muscle cell, leading to contraction.

Slow Twitch Fibers

Endurance-oriented muscle fibers.

T-tubules

Invaginations of the sarcolemma that transmit signals deep into the muscle fiber.

Smooth Muscle

Involuntary muscle found in internal organs, contracts slowly.

Cardiac Muscle

Involuntary muscle found in the heart, contracts rhythmically and is striated.

Calcium

Ion involved in muscle relaxation when removed from troponin.

I Band

Light bands containing only actin filaments.

Posture

Maintenance of body position and support of the skeleton.

Motor Unit

Motor neuron and the muscle fibers it innervates.

Skeletal Muscle

Muscle attached to bones responsible for voluntary movement.

Myocyte

Muscle cell containing sarcolemma (cell membrane) and sarcoplasm (cell cytoplasm).

Sliding Filament Model

Muscle contraction occurs as actin and myosin filaments slide past each other, shortening the sarcomere.

Fast Twitch Fibers

Muscle fibers suited for power and speed.

Cardiac Muscle

Muscle found in the heart, responsible for pumping blood, involuntary.

Smooth Muscle

Muscle found in the walls of internal organs, responsible for involuntary movements.

Heat Generation

Muscles produce heat during contraction, contributing to body temperature regulation.

Joint Stability

Muscles provide support and stability to joints.

Power Stroke

Myosin undergoes a power stroke, causing actin to slide.

Epimysium

Outer layer of connective tissue surrounding the entire muscle.

Neuromuscular Junction

Point of connection between a nerve ending and a muscle fiber.

Excitation-Contraction Coupling

Process by which muscle contraction is initiated.

Muscle Relaxation

Process of muscle returning to its original state after contraction.

Actin and Myosin Filaments

Protein filaments responsible for muscle contraction.

ATP

Provides energy for the cross-bridge cycle and muscle contraction.

Excitability

Responsiveness of muscles to stimuli, such as nerve signals.

Z Disk

Separates one sarcomere from the next, anchoring actin filaments.

Muscle tissue

Specialized tissue composed of muscle fibers that can contract.

Myoglobin

Stores oxygen in muscle cells for aerobic energy production.

Nerves and Blood Vessels

Supply muscles with nutrients and signals for contraction.

Movement

Voluntary and involuntary motions facilitated by muscles.


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