Anatomy & Physiology I Unit Ten

1. Anatomy & Physiology I Unit Ten

2. Muscle Characteristics Contractility Excitability Conductivity Extensibility Elasticity

3. Muscle Characteristics The ability to contract Contraction results in movement Contraction occurs due to sliding filaments

4. Muscle Characteristics Muscles contract due to nerve activity Muscles can be under voluntary or involuntary control

5. Skeletal Muscle Characteristics Appear striated Under voluntary control Quick response time due to nerve stimulation of independently contracting muscle fibers Results in body movement and balance

6. Smooth Muscle Characteristics Appear non-striated Under involuntary control Relatively slow response time due to stimulation produced by pacemaker potentials Results in internal organ movements and glandular secretions

7. Cardiac Muscle Characteristics Appear striated Under involuntary control Quick response time due to pacemaker produced action potentials

8. Cardiac Muscle Characteristics Intercalated discs connecting fibers produce simultaneous contraction Results in heart beats and the movement of blood

9. Muscle Anatomy

10. Muscle Anatomy

11. Filament Arrangement

12. Actin Filament Composition

13. Myosin Action

14. The Power Stroke

15. Conduction in the Muscle Cell

16. Motor Unit

17. Muscle Contraction Sequence

18. Muscle Contraction Sequence

19. Muscle Contraction Sequence

20. Muscle Contraction Sequence

21. Muscle Contraction Sequence

22. Muscle Contraction Sequence

23. Muscle Energy Sources ATP - as noted previously, ATP is necessary for energizing myosin cross bridges and accumulating Ca2+ at the end of contraction

24. Muscle Energy Sources ADP - as noted previously, ADP cycles with ATP in the power stroke and is necessary for engaging and disengaging myosin cross bridges

25. Muscle Energy Sources

26. Atrophy vs. Hypertrophy Myoglobin is a pigment found in skeletal muscle cells that functions to take up and store oxygen for use in the cell Myoglobin provides a supply of ready oxygen needed for muscle contraction

27. Atrophy vs. Hypertrophy Atrophy is the decrease in the mass and size of muscle tissue due to inactivity Hypertrophy is the increase in the mass and size of muscle tissue due to increased activity

28. Atrophy vs. Hypertrophy Steroid hormones will increase protein synthesis in muscle tissue, producing hypertrophy Testosterone, found in males, is one such hormone that naturally increasing muscle size in males

29. Twitches and Summation

30. Summation and its Results

31. Tonus Tonus is an example of a graded response that is used to maintain position or posture

32. Definitions Isotonic contractions - contractions that result in the shortening of a muscle and movement Isometric contractions - contractions that do not shorten a muscle and result in no movement

33. Contraction Functions Isotonic contractions are used to produce movement in the body Isometric contractions are used to maintain tone, position and posture

34. Refractory Period

35. Muscle Disorders Muscular dystrophy: ~ sex linked recessive disease ~ affected muscles fill with fat & connective tissue causing muscle tissue to atrophy ~ caused by the lack of dystrophin

36. Muscle Disorders Myasthenia gravis: ~ may be an autoimmune disease ~ affected muscles develop weakness due to a reduced number of acetylcholine receptors ~ receptor numbers are gradually reduced as disease progresses

37. Muscle Disorders Strain: ~ also called a pulled muscle ~ excessive stretching or tearing of a muscle due to overuse or abuse

38. Muscle Disorders Shin splints: ~ irritation of the tibialis anterior ~ caused by excessive use of the muscle without prior conditioning ~ its inflammation causes swelling and intense pain