1. PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART B 6 The Muscular System

2. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Contraction of Skeletal Muscle  Muscle fiber contraction is “all or none”  A muscle fiber will contract fully or not at all  Muscle fibers do not partially contract  For a stronger reaction, more motor fibers or units have to be recruited  The minimum level needed to cause a muscle contraction is called the threshold stimulus

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings All or None Principal continued  Within a skeletal muscle, not all fibers may be stimulated during the same interval  Different combinations of muscle fiber contractions may give differing responses  Graded responses—different degrees of skeletal muscle shortening

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Contraction of Skeletal Muscle  Graded responses can be produced by changing  The frequency of muscle stimulation  The number of muscle cells being stimulated at one time

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Graded Strength Principle  Skeletal muscle organs do not follow the all or none principle  1. If many fibers of a muscle organ become fatigued, the entire muscle will suffer some loss in its ability to generate maximum force of a contraction  The more fibers contracting = more strength

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Graded Strength Principle  2. How many fibers stimulated depends on how many motor units are recruited.  The more intense and frequent a stimulus, the more motor units are recruited and the stronger the contraction  After threshold stimulus is achieved, a continued increase in stimulus strength produces a proportional increase in muscle strength until the maximal level of contraction is achieved.

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Graded Strength Principle  3. The strength a muscle can develop is related to the length of its fibers  Too short or too long and it can’t develop tension  4. The heavier the load, the stronger the contraction.

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Myography  Muscle graph, used to study muscle contractions  Threshold stimulus needed to make muscle contract  Latent period  Impulse travels to sarcolemma and t- tubules  SR releases CA  Ca takes troponin and tropomyosin from the actin

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Myography  Contraction Phase  Myofilaments slide past each other  Z lines are drawn in  Relaxation  Ca goes back to SR  Crossbridges break  Troponin and tropomyosin go back  Z lines go back

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses  Twitch  Single, brief contraction  Not a normal muscle function

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses Figure 6.9a

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses  Tetanus (summing of contractions)  One contraction is immediately followed by another  The muscle does not completely return to a resting state  The effects are added

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses Figure 6.9b

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses  Unfused (incomplete) tetanus  Some relaxation occurs between contractions  The results are summed

15. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses Figure 6.9c

16. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Treppe or Staircase  Also called treppe or staircase phenomenon  Shows that a muscle will contract more forcefully once it has contracted a few times  This is why athletes warm-up  Not sure why it happens but think Ca does not go all the way back to the SR between contractions

17. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses  Fused (complete) tetanus  No evidence of relaxation before the following contractions  The result is a sustained muscle contraction

18. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Graded Responses Figure 6.9d

19. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Response to Strong Stimuli  Muscle force depends upon the number of fibers stimulated  More fibers contracting results in greater muscle tension  Muscles can continue to contract unless they run out of energy

20. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Physiological Fatigue vs. Psychological Fatigue  Repeated stimulation lessens a muscle’s excitability and contractility and results in muscle fatigue  In muscle fatigue the muscle does not repond to the strongest stimuli  Physiological fatigue is caused by a lack of ATP  Rarely occurs

21. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Physiological Fatigue vs. Psychological Fatigue  Physiological fatigue produces that exhausted feeling that causes us to stop muscular activity  In physiological fatigue we can’t contract our muscles but in psychological fatigue we simply will not contract our muscles.

22. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Abnormal muscle contractions  Convulsions  Abnormal uncoordinated tetanic contractions  Fibrillation  Individual fibers contract asynchronoously rather than at one time  Produces a flutter of the muscle, but no movement  Common in the heart

23. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction  Initially, muscles use stored ATP for energy  ATP bonds are broken to release energy  Only 4–6 seconds worth of ATP is stored by muscles  After this initial time, other pathways must be utilized to produce ATP  ATP is formed in the mitochondria  Adensine Triphosphate

24. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction  Direct phosphorylation of ADP by creatine phosphate (CP)  Muscle cells store CP  CP is a high-energy molecule  After ATP is depleted, ADP is left  CP transfers energy to ADP, to regenerate ATP  CP supplies are exhausted in less than 15 seconds

25. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction Figure 6.10a

26. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anerobic Glycolysis (Lactic Acid System)  Glucose is a type of sugar  If in the blood it is glucose  If in the liver it is glycogen  Anerobic means without oxygen

27. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anerobic Glycolysis  Glucose Molecule splits (C6 H12 O6)  Lactic Acid (C3H6O3)Lactic Acid  Lactic Acid loses two Hydrogens and becomes Pyruvic Acid (C3 H4 O3)  The hydrogen has to find someplace to go  If there is enough O2, it will take it to the electron transport system  If not enough O2, it will combine with the pyruvic acid and go back to lactic acid

28. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anerobic Glycolysis  When your body reaches its limit of LA this energy system shuts down  Through training you can teach your body to handle more lactic acid  This system lasts from 30 seconds to 3 minutes

29. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction Figure 6.10b

30. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction  Anaerobic glycolysis and lactic acid formation  Reaction that breaks down glucose without oxygen  Glucose is broken down to pyruvic acid to produce some ATP  Pyruvic acid is converted to lactic acid  This reaction is not as efficient, but is fast  Huge amounts of glucose are needed  Lactic acid produces muscle fatigue

31. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction Figure 6.10c

32. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Energy for Muscle Contraction  Aerobic respiration  Takes at least 3 minutes to get into  Used for long term events  Pyruvic Acid goes through the Kreb’s cycle in the mitochondria  End up with 32 ATP

33. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anerobic Threshold  Point of exercise when you switch from aerobic to anerobic  Lactic Acid builds up again  If you exceed this threshold, you don’t get any training benefits

34. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anerobic Threshold  To run the fastest race possible, you must run just under your anerobic threshold and at the proper distance from the finish line, increase your speed so that the max L.A. accumulation will occur at the finish line.

35. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  You enter recovery having an oxygen debt  Oxygen debt is the amount of oxygen needed to convert lactic acid back to glucose  This is why you breathe hard after exercise  also why metabolism stays up after exercise Recovery

36. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  To rid the body of Lactic acid you use heat to increase blood flow to the muscle and get rid of it faster or do a slow jog which will use oxygen and help get rid of lactic acid Recovery

37. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Fast and Slow Twitch Muscle Fiber  Myoglobin is large protein molecule that takes oxygen to muscles  If it has a lot of myoglobin it is called red muscle fibers  also called slow twitch fibers  contracts many times before it gets tired

38. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  If it doesn’t have as much myoglobin it is called white muscle fibers  fatique more quickly  Intermediate fibers  somewhere in between the two Fast and Slow Twitch Muscle Fiber

39. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Tonic Contraction  Is a continual partial contraction  A small number of the total number of fibers contract  Also called muscle tone  It is the muscles of normal individuals when they are awake  If you go unconscious you can’t sit or stand  tonic- is more than normal tone  Flaccid- is less than normal tone

40. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Muscle Contractions  Isotonic contractions  Means same tension  The muscle shortens and movement occurs  Isometric contractions  Means same length  Tension in the muscles increases  The muscle is unable to shorten or produce movement  Most body movements are a combination of the two

41. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Effect of Exercise on Muscles  Exercise increases muscle size, strength, and endurance  Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue  Makes body metabolism more efficient  Improves digestion, coordination  Resistance (isometric) exercise (weight lifting) increases muscle size and strength

42. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Effect of Exercise on Muscles  Atrophy is when a muscle shrinks in mass  Hypertrophy is an increase in muscle size

43. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  myopathies are muscle disorders  muscle strain involves the overstretching or tearing of muscle fibers  muscle sprain if injury occurs in a joint and a ligament is damaged  muscle myositis is muscle inflammation Diseases

44. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  bacteria and viruses can infect muscles and cause muscle soreness when you get the flu  often produce a myelitis which is a muscle infection Muscle Infections

45. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  is a viral infection of the nerves that control skeletal movement  can cause paralysis and death if affects lungs  uncommon in U.S. because of vaccinations, but common in other countries Poliomyelitis

46. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  two types of immunity  one is a dead virus and can not cause the disease  one is a live virus and can cause the disease  there is no cure for polio Poliomyelitis

47. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  muscle weakness in the face and throat  immune system attacks muscle cells at the neuromuscular junction so muscle can’t be stimulated Myasthenia Gravis

48. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  weakness of the abdominal muscle can lead to the protrusion of an abdominal organ through the abdominal wall  usually an intestine  is reducible if it can be put back in Hernias

49. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  strangulated is when it is not reducible and blood flow to the intestines is stopped  emergency surgery is needed Hernias

50. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  characterized by the wasting away of muscle tissue  Duchenne’s MD is the most common and understood  replaces muscle with fat and fibrous tissue  usually affects skeletal muscles, but facial muscles not affected Muscular Dystrophy

51. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  can affect cardiac muscle  starts about age 3 and usually fatal by age 21  occurs mainly in boys and is an x- linked or sex-linked genetic disorder Muscular Dystrophy