Functions of Muscle 1.Producing Movement Locomotion Manipulation Respond quickly

Functions of Muscle 2. Maintaining Posture Defy gravity

Functions of Muscle 3. Stabilizing Joints

Functions of Muscle 4. Generate Heat Important in maintaining body temperature

Naming Muscles 1. Location 2. Shape 3. Size 4. Direction of fibers 5. Number of origins 6. Location of attachements 7. Action

Muscle Tissue Skeletal (striations, voluntary, tires easily, strong) Smooth (found in hollow organs, force things through passage, involuntary, slow) Cardiac (heart, involuntary)

Gross Anatomy of Muscle Each skeletal muscle fiber is supplied with a nerve ending that controls activities

Microscopic Anatomy Muscle Muscle fibers Long, cylindrical, oval nuclei, multiple nuclei, HUGE

Microscopic Anatomy Muscle Sarcoplasm- cytoplasm of muscle cells Myoglobin- red pigment, stores oxygen

Microscopic Anatomy Muscle Myofibrils Muscle fibers have many of these Contain contractile elements of skeletal muscle cells

Microscopic Anatomy Muscle Striations A Band I Bands H Zone M Line Z Disc

Microscopic Anatomy Muscle A and I Bands Aligned with one another Gives the stripped appearance

Microscopic Anatomy Muscle H Zone Visible only in relaxed muscle In the A Band

Microscopic Anatomy Muscle M Line In H Zone

Microscopic Anatomy Muscle Z Disc In the I Band Midline line

Microscopic Anatomy Muscle Sarcomere Muscle segment Region between 2 Z Discs Smallest contractile unit of muscle

Microscopic Anatomy Muscle Myofilaments Within sarcomeres Thick and thin filaments Thick- actin Thin- myosin

Microscopic Anatomy Muscle Myosin Rod-like tail with 2 “heads” Heads link the actin with myosin (form cross bridges) Actin binding sites ATP binding sites Enzymes-Split ATP to generate energy for contraction

Microscopic Anatomy Muscle Actin Contains tryptomyosin- block active sites in relaxed muscle Troponin- binds to actin, contains Calcium releasing sites for muscle contraction

Microscopic Anatomy Muscle Sarcoplasmic Reticulum Surround each myofibril Regulate intracellular levels of Calcium Contract- release calcium GO signal for contraction

Sliding Filament Model of Contraction Contraction- myosin heads attach to actin forming cross bridges Relaxation- cross bridges inactive

Sequence of Events in Muscle Contraction 1. Action potential stimulates sarcolemma 2. Sarcolemma releases Calcium 3. Myosin binding sites on actin are exposed

Sequence of Events in Muscle Contraction 4. Cross bridge formation (myosin hooks onto actin) 5. Power Stroke- myosin pulls on actin sliding it towards sarcomere, ATP  ADP + P (MOVEMENT)

Sequence of Events in Muscle Contraction 6. Cross bridge detachment- ATP is replaced which causes myosin to detach from actin 7. Myosin head returns to normal position (ready for next stimuli)

Motor Unit

Muscle Fatigue Oxygen is limited and ATP production fails to meet ATP needs Physiological inability to contract even though muscle still receives stimuli Lactic acid buildup

Oxygen Debt Extra amount of oxygen body must take in to restore muscles & rid the body of lactic acid (liver)

Exercise and Muscles Aerobic exercise Increase in capillaries Increased number of mitochondria

Smooth Muscle Contractions like skeletal muscle Calmodulin helps with contraction since smooth muscle does not have troponin

Muscular Dystrophy Inherited muscle destroying diseases Duchenne Muscular Dystrophy Sex linked recessive (boys) No cure but medication has developed

Disuse Atrophy Don’t work out, bed rest, immobility Degeneration and loss of muscle mass Decrease at 5% each day Replaced by cartilage (rehabilitation impossible)