Skeletal striated multinucleate voluntary 10 100 m Smooth

Skeletal – striated, multinucleate, voluntary, 10 -100 m Smooth - found in walls of hollow visceral organs; ex. stomach, bladder, respiratory passages; visceral, nonstriated, involuntary; discuss peristalsis Cardiac – in heart only, striated, involuntary, intercalcated disks

Muscle function: • produce movement • maintain posture • stabilize joints • generate heat • move substances within the body Functional Characteristics: • Excitability- respond to a stimulus • Contractility- ability to shorten forcibly when adequately stimulated • Extensibility- the ability to be stretched • Elasticity- the ability of a muscle fiber to resume its resting length after being stretched

Skeletal Muscle Tissue

Smooth Muscle Tissue

Cardiac Muscle Tissue

Gross Anatomy Skeletal Muscle

bundle of muscle fibers Muscle Anatomy muscle fiber (cell) myofibril sarcomere

Muscle Fiber

Myofibril

Z lines Sarcomere

Sarcomere A band

Sarcomere I bands

Actin and Myosin Filaments actin myosin

Myosin (Thick) Filament

Actin (Thin) Filament

Sliding Filament Hypothesis

Actin (Thin) Filament No Calcium Ion tropomyosin

Actin (Thin) Filament Calcium Ion Present myosin binding sites tropomyosin

Actin & Myosin Interaction

Actin & Myosin Interaction

Actin & Myosin Interaction

Actin & Myosin Interaction

Actin & Myosin Interaction

Biology 100 Human Biology motor neurons spinal cord neuromuscular junctions Motor Unit muscle fibers muscle bundle

Neuromuscular junctions muscle fibers branching axon to motor unit

Stimulation of Skeletal Muscle

axon sarcomere myofibrils plasma membrane

T tubules sarcoplasmic reticulum

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Relaxation of Skeletal Muscle

Stimulation of Skeletal Muscle

Stimulation of Skeletal Muscle

Muscle Twitch period of relaxation period of contraction latent period stimulus

Contraction Response single twitches summatio n tetanus action potentials in motor neuron

Slow-Twitch Versus Fast -Twitch Muscle Fibers

Energy for muscle contraction: ATP is the only energy source ATP (ATPase + H 2 O) ADP + Pi ATP is Generated by: 1. creatine phosphate ADP + creatine phosphate creatine + ATP 2. lactic acid fermentation From stored glycogen via anaerobic glycolysis; glucose pyruvic acid (no O 2) lactic acid O 2 3. aerobic respiration Krebs CO 2 + H 2 O + ATP

Fast glycolitic: white muscle fibers, low myoglobin, anaerobic glycolysis, few mitochondria, fast twitch fibers, high glycogen stores, short bursts, fatigues easily Slow oxidative: red muscle, aerobic, high myoglobin, low glycogen stores, lots mitochondria, slow, tonic, long distance Fast oxidative: red pink, aerobic, fast, high myoglobin, intermediate amt. of mitochondria, intermediate glycogen, intermediate fatigue resistance Ratio- red: white (all 3 types in body) Ex. fish- long distance blue fin tuna- mostly red meat quick bursts- yellow tail- more white meat

Long distance Runner- aerobic respiration Sprinter- anaerobic respiration

Effects of Exercise Hypertrophy- excessive enlargement of muscle tissue Atrophy- disuse Muscles must be physically active if they are to remain healthy Cast- muscle strength can decrease at a rate of 5%/ Cast day; can use e- stimulus Avoid muscle injuries: -warm up muscles- walk fast 5 minutes -then stretch- avoids pulls and tares

Steroids Anabolic steroids • similar to testosterone • large doses required for good effect • Side effects: • overall - kidney and heart damage, aggressiveness • females - sterility, facial hair, breast & uterine atrophy • males - baldness, atrophy of testis

Muscle Disorders • cramp- sustained spasm or tetanic contraction; may be due to low blood sugar levels, electrolyte depletion, dehydration how to care for cramp: RICE • strain- muscle pull • spasm- tics • hernia- protrusion of organ through body cavity wall may be due to heavy wts.

Isotonic and Isometric Contractions Isotonic contraction • Contraction with a change in length • The muscle shortens and movement occurs. Isometric contraction • Contraction without any change in length • The muscle does not shorten and there is no movement produced even though the muscle contracts.

Isotonic and Isometric Contractions Isometric Isotonic