Chapter 11

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 vsanerobic 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 ImpedenceMyography

21. Typical graph of Lou Gehrig’s Disease(motor neurons disintegrate)

22. Tetanus • Smooth sustained types of contraction • Smooth/sustained – tetaniccontractions 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 – arrectorpili 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