MUSCULAR SYSTEM NHS - HUMAN ANATOMY/PHYSIOLOGY Dr. Smith CHAPTER 6

MUSCLES b Move bones - originate from mesoderm 600+ organs b ONLY CONTRACT - GET SHORTER b Muscular System made up of Skeletal, cardiac, Smooth b Striated Muscle Tissue: has cross strips or striations - skeletal and cardiac b Non - Striated: NO bands: IN - Voluntary b Cardiac - involuntary striations

Types of Muscle Tissue b Striated b Skeletal - - responsible for moving bones - voluntary b Cardiac - bulk of heart, has interclated disks - keeps muscle in contact - involuntary b NON-STRIATED b Smooth - involuntary, blood vessel walls, digestive system

STRUCTURE OF SKELETAL MUSCLE b Origin - muscle attachment to bone - no movement b Insertion - muscle attachment to moveable (joint) b Tendons - anchor muscle to bone - great strength/flexibility b Bursae and synovial membranes

Muscle Microscopy b Muscle fibers - muscle contractile cell b Composed of thick and thin myofilaments b Made of proteins Actin - thin filamentsActin - thin filaments Myosin - thick filamentsMyosin - thick filaments

SACROMERE (CONTRACTLIE UNIT) b Area from Z line to Z line

Sliding Filament Model b Muscles contract by myofilaments flowing towards each other.  “ Bridges ” formed between the myofilaments pull the sacromeres closer b Requires ATP and Ca

Major events in muscle contraction/relaxation

Energy Sources for Contraction b ATP molecules supply energy b Creatine Phosphate make possible the formation of ATP from ADP b Creatine phosphokinase makes creatine phosophate and stores additional energy

Oxygen role in muscle contraction b Hemoglobin - molecule that oxygen binds to in RBD  Myoglobin - molecule that oxygen “ loosely ” binds to in muscle - makes them red

Functions of Skeletal Muscle  Movement - muscle ’ s insertion bone moves toward the origin prime mover - main muscle responsible for movementprime mover - main muscle responsible for movement synergist - helper musclessynergist - helper muscles antagonist - produces opposite movementantagonist - produces opposite movement

FUNCTIONS OF MUSCULAR SYSTEM b Muscle tone maintains posture b Tonic contraction - does not move body parts - keeps posture - opposite of gravity b Hypothermia - decrease in body temperature b Hyperthermia - increase in body temperature POSTUREHEAT PRODUCTION

MUSCLE FATIGUE b THE DECREASING STRENGTH OF MUSCLE CONTRACTION b OXYGEN DEBT INCREASES FATIGUE b Lack of ACH, and lactic acid build up support fatigue b AEROBIC VS. ANAEROBIC RESPIRATION

NERVOUS SYSTEM AND MUSCLES b NERVOUS SYSTEM - IMPORTANT ROLE IN MUSCLE CONTRACTOIN - PARLYSIS - MULTIPLE SCLEROISIS b Muscle cells - stimulated by motor neurons b Chemicals released at neuromuscular junction

Stimuli b Threshold stimulus - minimum level of stimulation required for contraction.  “ All or nothing ” - Once a muscle ’ s threshold is reached all the muscle fibers contracts all the way b Recruitment - the amount of fibers involved in contraction - the more fibers the more strength

Types of Contraction b Twitch - quick, jerky response to stimuli b tetanic - sustained and steady contraction (tetanus b isotonic - muscle shortens - insertion moves toward origin b isometric - the same distance - tone of muscle increases - - repeated isometric makes muscles larger and stronger

Exercise on Skeletal Muscle b During inactivity, muscles shrink in mass - disuse atrophy b Exercise causes increase in muscle size - hypertrophy b Strength training - heavy resistance - increases myofilaments in muscle fiber b endurance training (aerobic) - increases # of blood vessels to/in muscles, increases mitochondria

MUSCLES - FACIAL

Movements of Muscles b Flexion - movement that makes angle between bones smaller b Extension - movement that makes angle between bone larger b Abduction - moving away from midline b Adduction - moving toward the midline b Rotation - movement around axis b Supination/Pronation - Movement to face up/ face down b Dorsiflexion/Plantary Flexion