1. Human Physiology Unit Five

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. Sarcomere Contraction
The “all or none” law indicates that sarcomeres, when stimulated will contract fully - there is no partial contraction of sarcomeres

13. Actin Filament Composition

14. Myosin Action

15. The Power Stroke

16. Conduction in the Muscle Cell

17. Motor Unit

18. Muscle Contractions
Graded responses are due to the number of motor units recruited during a muscle contraction
The fewer the number of motor units recruited, the weaker the overall contraction
The greater the number of motor units recruited, the stronger the overall contraction

19. Muscle Contraction
Sequence of Events

20. Muscle Contraction Sequence

21. Muscle Contraction Sequence

22. Muscle Contraction Sequence

23. Muscle Contraction Sequence

24. Muscle Contraction Sequence

25. Muscle Contraction Sequence

26. Twitches and Summation

27. Summation and its Results

28. Contraction Types
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

29. Contraction Functions
Isotonic contractions are used to produce movement in the body
Isometric contractions are used to maintain tone, position and posture
Tonus is an example of a graded response that is used to maintain position or posture

30. The Anatomy of a Muscle Spindle

31. Motor Neuron Types
Lower motor neurons - neurons extending from the spinal cord that innervate skeletal muscle (Ex. - alpha and gamma motor neurons)
Higher motor neurons - neurons found in the brain that process information and control muscle contractions through lower motor neurons

32. The Muscle Stretch Reflex

33. Reciprocal Enervation

34. The Crossed Extensor Reflex

35. Muscle Energy Sources
ATP is necessary for energizing myosin cross bridges and accumulating Ca2+ at the end of contraction
ADP cycles with ATP in the power stroke and is necessary for engaging and disengaging myosin cross bridges

36. Muscle Energy Sources
At rest, skeletal muscle obtains most of its energy from the aerobic catabolism of fatty acids
Creatine phosphate is a compound found in skeletal muscle that will donate its phosphate groups to ADP during times of sustained muscle activity

37. Muscle Energy Sources

38. Muscles and Oxygen
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 for the production of the ATP needed for muscle contraction

39. Muscles and Oxygen
Lactic acid is produced by muscles when they enter into anaerobic respiration due to limited oxygen amounts
Lactic acid will be converted back to pyruvic acid in the liver after oxygen levels have returned to normal

40. Muscles and Oxygen
Oxygen debt is the amount of oxygen needed to restore oxygen concentrations on hemoglobin (RBCs) and myoglobin (skeletal muscle), as well as the oxygen needed to convert lactic acid back to pyruvic acid (liver)

41. 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

42. 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