1. Chapter 11 Physiology of the Muscular System

2. General functions:  Movement  Heat Production  Posture

3. Function of the skeletal muscle tissue

4. Muscle cell:  Bundles of muscle fibers (cells)  Extends entire length of the cell  Same structures as cells, but with different names  Plasma membrane – sarcolemma  Cytoplasm – sarcoplasm  Many mitochondria and nuclei  Tubules and sacs – sarcoplasmic reticulum  Typical only to muscle cells – myofibrils bundles of fine fibers that allow contraction of the muscle

5. Cont.  Sarcomeres – fibers running lengthwise of the muscle and consist of A bands that look striped (striated)  T – tubules run transverse to the sarcomere fibers – allow for electrical signals to promote movement  Sarcoplasmic reticulum allows for calcium to be stored with in its sacs  Triad – these tubules ( T-tubules sandwiched between two SR sacs) allows for an electrical impulse to trigger movement

6. Myofilaments  Each muscle fiber has a thousand or more parallel subunits called myofibrils  Beside each myofibril are thousands of thick and thin myofilaments  Myofilaments composed of – myosin, actin, tropomysin, and troponin

7. Contraction  Shortening  Page 316 box 11-2

8. Excitation of the sarcolemma  Skeletal muscles normally at rest  Motor neurons receive message at the neuromuscular junction (synapse)  Can we say “gaposis”?  Neurotransmitter jumps the gap with messages and in turn releases acetylcholine  This initiates an electrical impulse causing excitation

10. Contraction  The previously discussed impulse conducted down muscle fibers (sarcolemma) and to the T-tubules  This triggers release of Calcium ions from the SR  This combines with troponin and exposes actin molecules  Actin then binds with myosin – this bends the myosin heads and with great force, pulls the filaments past them  This shortens the myofibers (called the sliding filament theory)

11. Relaxation  After the SR releases Ca into sarcoplasm, it begins to pull the Ca back into the sacs.  Only takes a few milliseconds  This shuts down the contraction process

12. ATP  Adenosine triphosphate  ENERGY!  Re-synthesis of this high energy bond must always take place since only small amounts are stored  Another high energy bond comes from creatine phosphate elevated with H.A.  Catabolism of both of these comes from catabolism of foods

13. Glucose / oxygen  Required for continued, efficient muscle function  Glucose is stored as glycogen  Oxygen can be stored by cells  During rest, oxygen is bound to protein molecules called myoglobin (red pigment) and contains iron to attract O-2

14. Aerobic vs anerobic respiration  Aerobic – oxygen  Anerobic – avoid the use of oxygen  Catabolic process that produces energy from glucose  Anerobic respiration results in lactic acid which causes a burning sensation during or after exercise

15. Why would an individual continue to breathe deeply after exercise is over?

18. Methemeglobinemia  Genetic flaw  Both parents must be carriers for the offspring to suffer from this abnormality.  Blood cannot bind to oxygen properly – blood is brown – not red in the arterial lumen  TMT: methylene blue q d

19. Heat production  Greatest source of heat production in the body is digestion  Next is muscle movement through exercise

20. Electrical Impedence Myography

21. Typical graph of Lou Gehrig’s Disease (motor neurons disintegrate) Serial measurements of the EIM parameter Θavg in selected muscles of a group of patients with ALS show decline as the disease progresses.

22. Tetanus  Smooth sustained types of contraction  Smooth/sustained – tetanic contractions or tetanus  Can be incomplete (short periods of relaxation) or complete (sustained)

23. Muscle tone  Tonic ( tone) contraction – continual, partial contraction – also called muscle tone  Flaccid – reduced tone  Spastic – increased tone

24. Strength  Graded strength principle – muscles contract at varying levels at various times  Variables - Metabolism, conscious stimuli, amount of load imposed

25. Exercise – effects on muscle structure  Disuse atrophy – wasting  Hypertrophy – enlargement  Strength training – mass  Endurance training (aerobic)- sustainability

26. Isometric vs isotonic contractions  Isotonic – tone/tension remains same length of muscle elongates while moving against a load  Concentric contractions – results in shortening of the muscle (pick up a book)  Eccentric contraction – movement causes lengthening of the muscle while in a contracted state (lower the book back to the table)  Isometric contraction – opposite isotonic – muscle length remains the same during contraction – does’t produce movement – just tension (yoga)

27. Abnormal contractions  Cramp – involuntary twitches – inflammation, irritation, nutrition, fluid imbalance  Convulsion – abnormal, uncoordinated tetanic contraction – brain wave abnormality, fever, neurological damage  Fibrillation – fibers contract out of timing with each other – flutter – no productive movement occurs

28. Cardiac muscle  Exclusive to the heart  Striated involuntary muscle  Pericardium, myocardium, endocardium

29. Smooth muscle  Involuntary  Visceral – walls of hollow organs – GI, U, Repro. – peristalsis  Multiunit – arrector pili of the skin, small blood vessels

30. Abnormalities  Strain  Myalgia  Contusion  Infection – poliomyelitis  Muscular dystrophy – genetic – atrophy replaced by adipose tissue  Myasthenia gravis – muscle weakness  Hernia – inguinal, umbilical, abdominal

31. Muscular dystrophy

33. Myasthenia gravis