hala muscular system

Cardiac Muscle

Striated, branched muscle tissue containing intercalated discs; found only in the heart

Connective Tissue Layers of Skeletal Muscle

Endomysium → Perimysium → Epimysium (deepest to most superficial)

T-Tubules

Extensions of the sarcolemma that carry action potentials deep into the muscle fiber

Sarcoplasmic Reticulum

Specialized smooth endoplasmic reticulum that stores and releases calcium ions

Myoglobin

Red oxygen-binding pigment that stores oxygen in muscle fibers

Myosin

Protein that forms the thick filaments of a sarcomere

A Band

Dark region of a sarcomere containing thick filaments and overlapping thin filaments

Myosin Cross-Bridges

Projections on myosin filaments that bind to actin during muscle contraction

Creatine Phosphate

High-energy compound that provides the fastest method of ATP regeneration in muscle

Muscle Fatigue

Decline in the ability of a muscle to maintain force production due to ATP depletion and other factors

Oxygen Debt

Increased oxygen requirement after exercise needed to restore normal muscle conditions

Muscle Twitch

A single contraction-relaxation cycle of a muscle fiber following stimulation

Latent Period

Time between stimulation and the beginning of muscle contraction

Fast-Twitch Fibers

Muscle fibers that contract rapidly, rely more on anaerobic metabolism, and fatigue quickly

Zygomaticus

Facial muscle that elevates the corners of the mouth during smiling

External Intercostal Muscles

Muscles that elevate the ribs during inspiration

Internal Intercostal Muscles

Muscles that depress the ribs during expiration

Pectoralis Major

Large chest muscle that flexes, adducts, and medially rotates the arm; pulls the arm toward the chest

Latissimus Dorsi

Large back muscle that extends, adducts, and medially rotates the arm; brings the arm down from a raised position

Rotator Cuff Muscles

Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis (SITS)

Biceps Brachii

Flexes the forearm at the elbow and assists in flexing the arm

Triceps Brachii

Extends the forearm at the elbow and assists in extending the arm

Iliopsoas

Primary hip flexor that flexes the thigh

Gluteus Maximus

Powerful hip extensor that extends the thigh

Medial Thigh Muscles (Adductor Group)

Group of muscles that adduct the thigh toward the body's midline

Quadriceps Group

Group of four muscles on the anterior thigh responsible primarily for knee extension

Anterior Thigh

Location of the quadriceps muscle group

Hamstring Group

Posterior thigh muscles consisting of biceps femoris, semitendinosus, and semimembranosus

Rectus Femoris

Quadriceps muscle located on the anterior thigh; not part of the hamstring group

Strain

Stretching or tearing of a muscle or tendon

Myasthenia Gravis

Autoimmune disorder in which antibodies destroy acetylcholine receptors, causing muscle weakness

Sliding Filament Theory

Mechanism of muscle contraction in which actin filaments slide past myosin filaments, shortening the sarcomere

Troponin

Regulatory protein that binds calcium ions and moves tropomyosin away from actin binding sites

Calcium Ions (Ca²⁺)

Bind to troponin to expose active sites on actin and initiate muscle contraction

Sarcomere

Functional contractile unit of skeletal muscle located between two Z-discs

Fascicle

Bundle of muscle fibers surrounded by perimysium

Endomysium

Connective tissue surrounding an individual muscle fiber

Perimysium

Connective tissue surrounding a fascicle

Epimysium

Connective tissue surrounding the entire muscle

Recruitment

Increase in contraction strength through activation of additional motor units

Hypertrophy

Increase in muscle size due to enlargement of muscle fibers from training

Antagonists

Muscles that oppose the action of another muscle

Insertion

Attachment point of a muscle on the movable bone

Frontalis

Facial muscle that raises eyebrows and wrinkles the forehead

Sternocleidomastoid

Muscle that rotates the head and flexes the neck

Trapezius

Muscle that elevates and adducts the scapula and assists in extending the head

Diaphragm

Primary muscle responsible for breathing

Rectus Abdominis

Muscle that flexes the vertebral column and compresses the abdomen

Deltoid

Muscle responsible for arm abduction

Gastrocnemius

Major calf muscle responsible for plantar flexion of the foot

Fibromyalgia

Chronic disorder characterized by widespread musculoskeletal pain, tenderness, and fatigue

Muscular Dystrophy

Group of inherited disorders causing progressive muscle weakness and degeneration

SITS Mnemonic

Supraspinatus, Infraspinatus, Teres Minor, Subscapularis (rotator cuff muscles)

ATP Regeneration Sequence

Creatine phosphate system → Anaerobic glycolysis → Aerobic cellular respiration

Sarcomere Bands

A Band = dark region; I Band = light region

Muscle Fiber Types

Slow-twitch = aerobic, fatigue-resistant; Fast-twitch = anaerobic, powerful, fatigue quickly