Chapter 10 – Muscle Tissue

A comprehensive set of vocabulary flashcards covering structure, function, and organization of skeletal muscle tissue, contraction mechanics, fiber types, and muscle terminology from Chapter 10.

Skeletal Muscle

Voluntary muscle tissue that pulls on bones to produce movement.

Cardiac Muscle

Involuntary, rhythmic muscle tissue that pumps blood through the heart and vessels.

Smooth Muscle

Involuntary muscle tissue that moves fluids and solids through internal passageways.

Excitability

Ability of muscle tissue to respond to stimuli by changing membrane potential.

Contractility

Capacity of muscle fibers to shorten and generate tension.

Extensibility

Ability of muscle to contract over a range of resting lengths.

Elasticity

Muscle’s ability to recoil to its original length after stretching.

Epimysium

Dense connective tissue that surrounds an entire skeletal muscle.

Perimysium

Connective tissue that divides a muscle into fascicles.

Endomysium

Delicate connective tissue surrounding individual muscle fibers.

Tendon

Cord-like structure formed by merged mysia that connects muscle to bone.

Aponeurosis

Broad sheet of connective tissue that connects muscle to muscle.

Ligament

Dense connective tissue band that connects bone to bone.

Sarcolemma

Plasma membrane of a muscle fiber.

Sarcoplasm

Cytoplasm of a muscle cell.

Myofibril

Contractile organelle composed of repeating sarcomeres inside a muscle fiber.

Myofilament

Protein filament (actin or myosin) that makes up a sarcomere.

Actin

Thin filament protein involved in muscle contraction.

Myosin

Thick filament protein whose heads form cross-bridges with actin.

Sarcomere

Smallest functional unit of a muscle fiber; extends from Z line to Z line.

Z Line (Z Disc)

Boundary of a sarcomere where thin filaments are anchored.

I Band

Light band containing only thin filaments.

A Band

Dark band that includes the entire length of thick filaments and overlap zone.

H Band

Central region of A band containing only thick filaments.

M Line

Center of sarcomere where thick filaments attach.

Titin

Elastic protein that connects thick filaments to Z line, providing recoil.

Sliding Filament Theory

Model explaining muscle contraction as thin filaments sliding toward the M line.

Calcium Ion (Ca²⁺)

Trigger released from sarcoplasmic reticulum that initiates contraction.

Troponin

Regulatory protein that binds Ca²⁺ and moves tropomyosin off actin sites.

Tropomyosin

Protein that blocks myosin-binding sites on actin at rest.

Neuromuscular Junction (NMJ)

Synapse between a motor neuron and a skeletal muscle fiber.

Acetylcholine (ACh)

Neurotransmitter released at NMJ to stimulate muscle fibers.

Motor End Plate

Specialized region of sarcolemma with ACh receptors.

Synaptic End Bulb

Axon terminal containing vesicles of ACh.

Motor Unit

A motor neuron and all the muscle fibers it innervates.

Muscle Tone

Continuous, passive tension in resting muscles that stabilizes joints and posture.

Muscle Spindle

Sensory receptor within muscle that monitors stretch and helps regulate tone.

Muscle Hypertrophy

Increase in muscle size due to enlargement of existing fibers.

Muscle Atrophy

Decrease in muscle size and strength from disuse.

Type I Fiber

Slow-twitch, red, fatigue-resistant muscle fiber rich in mitochondria and myoglobin.

Type IIa Fiber

Fast-twitch oxidative, intermediate fiber with moderate myoglobin and endurance.

Type IIb Fiber

Fast-twitch glycolytic, large white fiber that contracts powerfully but fatigues quickly.

Parallel Muscle

Muscle with fascicles parallel to its long axis (e.g., biceps brachii).

Convergent Muscle

Muscle with broad origin and converging fibers to a single tendon (e.g., pectoralis major).

Unipennate Muscle

Pennate muscle with fibers on one side of a tendon (e.g., extensor digitorum).

Bipennate Muscle

Pennate muscle with fibers on both sides of a central tendon (e.g., rectus femoris).

Multipennate Muscle

Pennate muscle with branches of tendon within muscle (e.g., deltoid).

Circular Muscle (Sphincter)

Muscle with fibers arranged in concentric rings (e.g., orbicularis oris).

Origin

Stationary attachment point of a muscle.

Insertion

Movable attachment point of a muscle.

Prime Mover (Agonist)

Muscle chiefly responsible for a specific movement.

Antagonist

Muscle whose action opposes that of the agonist.

Synergist

Muscle that assists the prime mover.

Fixator

Muscle that stabilizes a joint by simultaneous contraction with agonist and antagonist.

Myoblast

Embryonic cell that fuses to form a multinucleate muscle fiber.

Myosatellite Cell

Stem cell that aids in repair of damaged muscle tissue.