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

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

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

Each muscle served by one artery, one nerve, and one or more veins Enter/exit near central part and branch through connective tissue sheaths Every skeletal muscle fiber supplied by nerve ending that controls its activity Huge nutrient and oxygen need; generates large amount of waste

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

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

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

Sliding Filament Model Muscles contract by thin myofilament moving toward thick myofilament “Bridges” formed between the myofilaments pull the sarcomeres closer Requires ATP and Ca

Major events in muscle contraction/relaxation

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

Oxygen role in muscle contraction Hemoglobin - molecule that oxygen binds to in RBC 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 movement synergist - helper muscles antagonist - produces opposite movement

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

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

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

Stimuli 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 Recruitment - the amount of fibers involved in contraction - the more fibers the more strength

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

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

MUSCLES - FACIAL

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