The Muscular System

Functions of Muscle Tissue Movement Facilitation Thermogenesis Postural Support Regulation of Organ Volume Pumps Blood (HEART)

Characteristics of Muscle Tissue Contractility ability to become short and thick while producing movement

Characteristics of Muscle Tissue Extensibility The ability of muscle tissue to be elongated or stretched Smooth muscle

Characteristics of Muscle Tissue Elasticity ability to return to its normal resting length Skeletal from being shorter—smooth—from extended

Characteristic of Muscle tissue Excitability (irritability) ability to receive and respond to a stimulus

Cardiac Muscle Forms heart wall (Myocardium) striated involuntary Fibers quadrangular & branching centrally located nucleus sarcolemmas connected by intercalated discs gap junctions

Smooth (Visceral) Muscle walls of hollow internal surfaces such as: blood vessels - stomach urinary bladder - intestines non striated involuntary can be stretched to great lengths allows for tremendous size variability

Skeletal Muscle attached to bones striated voluntary Multinucleated

Characteristics of Skeletal Muscle Muscle origin: where muscle begins--tendon attaches to immovable bone (proximal) Muscle insertion: where muscle ends--tendon attaches to moveable bone (distal) Belly (gaster): fleshy portion of muscle between tendons

Key terms Sarcolemma - muscle cell membrane Sarcoplasm = muscle cell cytoplasm

Key terms Myofilaments --contain contractile elements of muscle fiber Sarcomere: one section of contractile filaments

Actin Thin Myofilaments 2 regulatory proteins Tropomyosin- follows contour of filament Troponin = protein on tropomyosin Receptor site for Ca+

Myosin Thick Myofilaments globular head Aka cross bridges

SLIDING FILAMNET THEORY OF MUSCLE CONTRACTION SEE HANDOUT

Muscle--Nerve Interaction Motor Neuron = nerve cell that excites muscle fiber Motor Unit = motor neuron & all the muscle fibers it can effect

Neuromuscular Junction Neuromuscular Junction = place between nerve & muscle fiber Motor End Plate - location on muscle fiber next to the nerve

Acetylcholine Acetylcholine (Ach) = neurotransmitter released to begin muscle contraction (action potential) acetylcholine Receptors—on motor end plate-makes membrane more permeable to Na+

Roles of Skeletal Muscles Agonist--Antagonist Agonist (Prime Mover) Main muscle Antagonist opposite movement

Roles of Skeletal Muscles Synergist Synergist—assists agonist provides additional force

Roles of Skeletal Muscles Fixator Fixator (Stabilizer) stabilizes a body segment prime mover can act more effectively

SKELETAL MUSCLE ORGANIZATION Muscle fibers: elongated muscle cells Endomysium: membrane around muscle fibers Perimysium: membrane around fascicles Epimysium: membrane around entire muscle (fascia)

The end

Intramuscular Injections injections that penetrate the skin and subcutaneous tissue used for prompt absorption used when large doses are necessary Preferred Sites: Gluteus Medius Muscle Vastus Lateralis Muscle Deltoid Muscle

Muscle Diseases and Disorders

Abnormal Contractions an unintended muscular contraction not stimulated by normal mechanisms may be caused by dehydration, electrolyte imbalances or neurological disorders and abnormalities

Myalgia (Fibromyalgia) painful disorders of muscles, tendons, and surrounding soft tissue Chronic condition Treat symptoms no cure

Muscular Dystrophies muscle destroying diseases degeneration of individual muscle fibers progressive atrophy of skeletal muscles Usually due to a genetic defect

Myasthenia Gravis (MG) a weakness of skeletal muscle at neuromuscular junction an auto-immune disorder caused by antibodies that disable the Ach receptors at the motor end plate

Shinsplints strengthen tibialis anterior muscle pain in the lower leg which may be caused by: tendonitis of the tibialis anterior muscle inflammation of the periosteum stress fracture of the tibia exaggerated enlargement of muscles within the epimysium pulling away of the periosteum from the underlying bone Treatment: RICE strengthen tibialis anterior muscle