Muscular System Review Flashcards

Comprehensive vocabulary flashcards covering the structural organization, physiological mechanisms, anatomical muscle groups, and pathologic conditions of the muscular system.

Muscular System

An organ system consisting of skeletal, smooth, and cardiac muscle that permits movement of the body, maintains posture, and circulates blood.

Muscle Fibers

Specialized cylindrical cells that compose muscle tissue, characterized by their primary function of contractibility.

Fascia

A layer of fibrous connective tissue that separates individual muscles from each other and from the overlying skin.

Epimysium

A connective tissue sheath that surrounds an entire skeletal muscle.

Perimysium

A connective tissue wrapper that surrounds a bundle of muscle fibers known as a fascicle.

Endomysium

A delicate connective tissue layer that surrounds each individual skeletal muscle cell or fiber.

Fascicle

A discrete bundle of skeletal muscle fibers bound together by perimysium.

Tendon

A tough, cord-like connective tissue structure that attaches muscle to bone.

Ligament

A connective tissue structure that connects bone directly to bone.

Sarcolemma

The specialized plasma membrane surrounding a muscle fiber cell.

Transverse Tubules (T Tubules)

Tubelike inward folds of the sarcolemma occurring at regular intervals that extend deep into the center of the muscle fiber.

Terminal Cisternae

Enlarged regions of the smooth sarcoplasmic reticulum positioned adjacent to T tubules.

Muscle Triad

A functional three-structure complex composed of a central T tubule flanked by two terminal cisternae of the sarcoplasmic reticulum.

Sarcoplasm

The cytoplasm of a muscle fiber containing cytoplasm, organelles, and bundles of protein myofilaments.

Myofibrils

Long threadlike structures made of protein filaments that extend the length of a muscle fiber.

Myofilaments

Protein filaments comprising thick filaments (myosin) and thin filaments (actin) that make up a sarcomere.

Sarcomere

The basic structural and functional contractile unit of a muscle fiber, extending from one Z disk to the next adjacent Z disk.

Z Disks

Network structures of protein fibers that serve as attachment anchors for actin myofilaments and demarcate sarcomere boundaries.

Myosin

The protein that forms the thick filaments within a sarcomere.

Actin

The protein that forms the thin filaments within a sarcomere.

Calcium Ion ($\text{Ca}^{2+}$)

An essential ion for muscle contraction that binds to troponin, causing a conformational shift in tropomyosin to expose actin attachment sites.

Muscle Cramp

An uncontrollable, forcible contraction caused by ATP depletion that prevents myosin heads from detaching from actin.

Muscle Fatigue

A temporary state of reduced work capacity that protects muscle fibers and supportive tissues from structural damage.

Smooth Muscle

Non-striated, involuntary muscle consisting of single, spindle-shaped (fusiform) cells with one central nucleus, found in hollow visceral organs and blood vessels.

Cardiac Muscle

Striated, autorhythmic, involuntary muscle composed of branching uninucleate cells joined by intercalated discs, located in the heart wall.

Intercalated Disks

Specialized cell junctions containing desmosomes and gap junctions that connect adjacent cardiac muscle cells and permit synchronized contraction.

Aponeuroses

Broad, sheetlike tendons that attach muscle to bone or other connective tissues.

Retinaculum

A transverse band of dense connective tissue that holds down tendons passing across the wrist and ankle joints.

Origin

The relatively fixed, most stationary attachment point of a muscle.

Insertion

The mobile attachment point of a muscle attached to the bone undergoing the greatest movement during contraction.

Action

The specific anatomical movement produced by the contraction of a muscle.

Buccinator

A cheek muscle, known as the 'trumpeter’s muscle,' that flattens the cheek during whistling or blowing.

Orbicularis Oris

The circular muscle surrounding the mouth, known as the 'kissing muscle,' that closes and protrudes the lips.

Orbicularis Oculi

The circular muscle surrounding the eye orbit responsible for closing the eyes, squinting, blinking, and winking.

Zygomaticus

The facial muscle known as the 'smiling muscle' that elevates the upper lip and the corner of the mouth.

Sternocleidomastoid

A neck landmark muscle attaching to the sternum, clavicle, and mastoid process that rotates the head individually or flexes the neck bilaterally.

Triangle of Auscultation

An anatomical triangular landmark on the back bounded by the latissimus dorsi, trapezius, and medial border of the scapula.

Rotator Cuff Muscles

A group of four shoulder-stabilizing muscles abbreviated SITS: Supraspinatus, Infraspinatus, Teres minor, and Subscapularis.

Supraspinatus

The most commonly injured rotator cuff muscle located above the spine of the scapula, prone to degeneration due to poor blood supply.

Rectus Abdominis

An anterior abdominal muscle, commonly called the 'six pack,' that runs vertically along the front of the abdomen to compress abdominal contents.

Biceps Brachii

A two-headed muscle of the anterior upper arm that flexes the elbow and shoulder and supinates the forearm.

Gluteus Maximus

The largest and heaviest muscle in the human body, located in the buttocks, which extends the hip and abducts and laterally rotates the thigh.

Sartorius

The longest muscle in the human body, situated in the anterior compartment of the thigh.

Quadriceps Femoris

The largest muscle group in the human body responsible for knee extension, composed of the rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis.

Hamstring Muscles

The posterior thigh muscle group consisting of the biceps femoris, semitendinosus, and semimembranosus.

Myasthenia Gravis

An autoimmune disorder causing skeletal muscle weakness that rapidly worsens during exertion and improves after rest.

Muscular Hypertrophy

An increase in muscle fiber size and overall muscle mass caused by increased myofibrils when protein synthesis exceeds protein breakdown.

Muscle Atrophy

A reduction in muscle size and strength caused by a decrease in myofibrils due to disuse, starvation, nerve injury, disease, or aging.

Tendinitis

Inflammation of a tendon or its attachment site resulting from repetitive overuse of a muscle.

Duchenne Muscular Dystrophy (DMD)

An X-linked inherited muscle disease caused by an abnormal gene that produces nonfunctional dystrophin protein, leading to progressive muscle weakness.