Anatomy and Physiology: Muscle Tissue

Comprehensive vocabulary flashcards covering muscle tissue types, cellular structures, sliding filament theory, metabolism, and functional properties.

Skeletal Muscle

A voluntary muscle tissue attached to bones that is striated and contains multinucleated fibers.

Cardiac Muscle

An involuntary muscle tissue found only in the heart characterized by branched fibers, striations, and intercalated discs.

Smooth Muscle

An involuntary, nonstriated muscle tissue found in organs and blood vessels with spindle-shaped cells and a single nucleus.

Excitability

The ability of muscle tissue to respond to stimuli by generating electrical signals or action potentials.

Calcium Ions ($Ca^{++}$)

The ions essential for muscle contraction that are stored in the sarcoplasmic reticulum and bind to troponin in striated muscle.

Contractility

The functional property of muscle describing its ability to shorten with force.

Extensibility

The functional property of muscle describing its ability to stretch.

Elasticity

The functional property of muscle describing its ability to recoil to its original length.

Epimysium

The connective tissue layer that surrounds the entire muscle and provides structural support.

Perimysium

The connective tissue layer that surrounds bundles of muscle fibers called fascicles.

Endomysium

The connective tissue layer that surrounds individual muscle fibers and contains nutrients and extracellular fluid.

Sarcolemma

The specialized plasma membrane of a muscle fiber.

Sarcoplasmic Reticulum (SR)

A specialized smooth endoplasmic reticulum in muscle fibers that stores and releases $Ca^{++}$.

Sarcomere

The basic functional unit of skeletal muscle that extends from one Z-disc to the next.

Actin

The protein that makes up the thin filaments of a sarcomere.

Myosin

The protein that makes up the thick filaments of a sarcomere which contains heads that pull on actin.

Troponin

A regulatory protein in skeletal and cardiac muscle that contains binding sites for $Ca^{++}$.

Tropomyosin

A regulatory protein that covers the myosin-binding sites on actin filaments when the muscle is relaxed.

Z-disc

The structure that marks the boundaries of a sarcomere and provides an attachment point for thin filaments.

H zone

The area in the center of a sarcomere that contains only thick filaments.

M line

The central line of the sarcomere consisting of proteins that stabilize the thick filaments.

Neuromuscular Junction (NMJ)

The specific site where a motor neuron meets a skeletal muscle fiber to allow communication.

Acetylcholine (ACh)

The neurotransmitter released by motor neurons that diffuses across the synaptic cleft to initiate muscle excitation.

T-tubules

Invaginations of the sarcolemma that carry electrical signals deep into the muscle fiber.

Cross-bridge cycle

The repeated process of myosin heads binding to actin, pivoting (power stroke), detaching, and re-cocking using ATP.

Sliding Filament Theory

The explanation of muscle contraction stating that thin filaments slide past thick filaments, shortening the sarcomere without changing filament length.

Rigor Mortis

A state following death where myosin heads remain locked to actin because ATP production has stopped.

Creatine Phosphate

A high-energy molecule that provides rapid ATP regeneration for short, explosive activities lasting about $15\,\text{seconds}$.

Anaerobic Glycolysis

The metabolic process that breaks down glucose without oxygen to produce $2\,\text{ATP}$ and lactic acid, supporting activity for $15-60\,\text{seconds}$.

Aerobic Respiration

The most efficient way to produce ATP (approximately $36\,\text{ATP}$ per glucose) using oxygen in the mitochondria.

Oxygen Debt

The extra oxygen needed after exercise to restore ATP, rebuild creatine phosphate, and remove lactic acid.

Hypertrophy

An increase in muscle size and bulk caused by the increased production of myofibrils and sarcomeres within fibers.

Atrophy

A decrease in muscle size due to reduced use or disease, leading to the loss of myofibrils and sarcomeres.

Isotonic Contraction

A type of contraction where muscle tension remains constant while the muscle length changes to move a load.

Isometric Contraction

A type of contraction where the muscle produces tension without changing its length, such as maintaining posture.

Motor Unit

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

Recruitment

The process by which the nervous system increases muscle force by activating additional and larger motor units.

Muscle Twitch

A single muscle contraction and relaxation cycle produced by one motor neuron action potential.

Tetanus

A state of continuous, sustained muscle contraction resulting from very frequent stimuli without a relaxation phase.

Treppe

Also known as the staircase effect, it is the gradual increase in muscle tension when a resting muscle is stimulated repeatedly.

Muscle Tone

The small amount of constant tension in skeletal muscles maintained by the alternating activation of motor units.

Slow Oxidative (SO) Fibers

Fatigue-resistant muscle fibers that use aerobic metabolism and contain many mitochondria and high myoglobin; best for endurance.

Fast Glycolytic (FG) Fibers

Large-diameter fibers designed for short bursts of power that use anaerobic glycolysis and fatigue quickly.

Intercalated Discs

Structures in cardiac muscle that contain gap junctions for electrical signaling and desmosomes for mechanical anchoring.

Mesoderm

The embryonic tissue layer from which most muscle tissue develops.

Satellite Cells

Stem-like cells located in skeletal muscle that proliferate and fuse to repair damaged muscle fibers.

Fibrosis

The replacement of muscle tissue with collagen-based scar tissue following severe injury.

Calmodulin

The regulatory protein in smooth muscle that binds to calcium to eventually activate myosin kinase.