1. Muscle

2. Muscle- Three Types SkeletalCardiacSmooth

4. Functional Characteristics Excitability (Irritability)- respond to stimulus Contractility- shorten forcibly Extensibility- stretched Elasticity- recoil to resting length

5. Muscle Functions Produces movement Maintains posture Stabilizes joints Generates heat

6. Gross Anatomy Skeletal Muscle One nerve One artery One or more veins

7. Connective Tissue Sheaths Endomysium- surrounds each muscle fiber Perimysium- surrounds bundles of muscle fibers called fascicles Epimysium- dense irregular CT that surrounds entire muscle

8. Quiz Picture

9. Attachments Direct- the epimysium is attached directly to bone ex: glute Indirect- the CT extends in a sheet (aponeurosis) or cord (tendon) to attach to bone ex: bicep

10. Histology of Muscle Fiber (Cell) Sarcoplasm- (cytoplasm) myoglobin and glycogen Myofibrils- (microfilaments) rod like structures containing the contractile units Sarcolemma – (cell membrane) connected to T-tubules

11. Quiz Picture

12. Sarcomere Functional unit of muscle fiber Quiz Picture

13. Banding Pattern of Sarcomere Striations- repeating A bands and I bands H Zone- lighter band in center of A Band Z Disc- darker band in center of I band M Line- dark line in middle of the H Zone

16. Filaments of Myofibril Thick Filaments- make up the A Band; Myosin Thin Filaments- make up I Band; Actin

17. Filaments Thick- Myosin - tail and 2 globular heads, cross bridges - tail and 2 globular heads, cross bridges – the function part – the function part Thin- Actin - subunits are function globular - subunits are function globular - 2 strands Tropomyosin, hold it together - 2 strands Tropomyosin, hold it together - and multiple units of Troponin,locks - and multiple units of Troponin,locks

19. Sarcoplasmic Reticulum/T Tubules ER of muscle; calcium release Wraps around each myofibril Terminal Cisternae- cross channels at A Band I Band Junctions T Tubules  connect sarcolemma to SR Triads  Connect of 2 SR and 1 T- tubule

20. Quiz Picture

22. How does all that anatomical structure, function physiologically? What is the importance of the membranes? Why is it important that T-tubules connect to SR? Why are there extra mitochondria? Why are thick and thin filaments build the way they are?

23. Muscle Contraction

24. 3 Parts 1. Neuromuscular Junction 2. Excitation-Contraction Coupling 3. Cross Bridge Formation

25. Part 1: Neuromuscular Junction Axon Terminal- release Ach (acetylcholine) Synaptic Cleft- space Junctional folds of sacrolemma of muscle cell- Ach receptors

28. Video Go to APFlix Events at Neuromuscular Junction

29. Action Potential Depolarization- change in membrane potential from more negative to more positive Repolarization- membrane returns to original negative state Refractory Period- during repolarization; cell cannot be stimulated until repolarization complete

31. Video APFlix Three (3) videos to review Action Potentials. Resting, Generation and Propagation of Action Potentials.

32. Part 2: Excitation-Contraction Coupling (Role of Ca) Upon change in membrane potential during depolarization from T-tubule calcium is released from SR Attaches to Troponin and uncovers active binding site for Myosin heads

34. Video APFlix Excitation-Contraction Coupling

35. Part 3: Cross Bridge Formation Video APFlix Cross Bridge Cycle

36. Muscle Contraction Neuromuscular junction/Generation of Action potential (1-9 Goes with Neuromuscular Junction Video 10-12 goes with Excitation–Contraction Coupling Video) 1.Stimulus travels down nerve to terminal end 2.Nerve impulse cause Ca +2 to enter end of nerve 3.Ca +2 changes shape of vesicles holding Ach (Acetylcholine) 4.ACh is released into and travels across synaptic cleft 5.ACh attached to Ach receptors on Sacrolemma 6.Binding of Ach open ion channels 7.Na + rushes into cell, K + rush out of cell 8.Shift of ions create an electrical impulse- Action Potential (AP) 9.ACh is absorbed back into nerve end or destroyed by Ache (Acetylcholinesterase) stopping deplorization 10.AP is propagated down Sacrolemma 11.AP enters T-Tubules and makes contact with Sarcoplasmic Reticulum (SR) 12. Channel on SR open allowing Ca +2 to rush into sarcoplasm of the cell

37. Muscle Contraction Filaments of Myosin racket or move the filaments of Actin closer together, Cross Bridge Cycle (Goes with Cross Bridge Cycle Video) 13.Calcium released from Sarcoplasmic Reticulum 14.Ca binds to Troponin 15.Troponin changes shape and shifts Tropomyosin, unlocking (opening) binding sites for Myosin heads 16.ATP has already charged or cocked the Myosin heads, which attached to Actin 17. ADP leave Myosin head, Myosin heads rackets and shift Actin strands closer to each other 18.New ATP attaches to Myosin head, recharging or cocking head, cycle continues as long as ATP and Ca is present 19.Ca leaves Troponin, Tropomyosin shift back closing off Actin binding sites 20.Muscle relaxes back to original position

38. Muscle Contraction Put all the steps together Stimulation comes down the nerve to neuromuscular junction All the steps of Excitation- Contraction Coupling

39. Muscle Contraction Nerve Stimulus Calcium into axon terminal Release Ach Ach crosses synaptic cleft Ach into receptors on sarcolemma which starts depolarization of membrane Na + into cell K + out, action potential travels down sarcolemma

40. Muscle Contraction Cont’ AP travels down T-tubules to SR SR release Ca Ca moves troponin/tropomyosin Myosin heads attach to actin Myosin heads move Sarcomere contracts

41. Motor Unit A motor neuron and all the muscle fibers it supplies

43. 43

44. Muscle Twitch Response of a motor unit to a single action potential; one single contraction

45. 3 Phases of a Twitch Myogram- graph of a twitch Myogram- graph of a twitch Latent Period- Nothing visible on graph Contraction- cross bridges active until peak Relaxation-relaxation

47. Wave Summation Occurs because in rapid contractions of muscle full relaxation is not reached so each stimulus causes more tension Produces smooth, continuous contractions Same stimulation delivered rapidly Tetanus- so fast that peaks fuse

49. Recruitment (Multiple Motor Unit Summation) Calling more and more motor units into play by increasing the amount of stimulation delivered to the muscle More to do with the force of contraction as more stimulus calls more motor units into play Increased stimulation delivered at same rate

50. LAB

51. Threshold Stimulus The stimulus at which the first observable contraction occurs

52. Maximal Stimulus The stimulus which produces the strongest contraction All motor units are recruited and contracting

53. Treppe Staircase Effect The increase seen in muscle tension achieved when it is stimulated over and over No change in force; not rapid Increased availability of calcium and better enzyme activity

55. Isotonic Contractions Muscle tension is generated and contraction occurs; work is done Eccentric contraction- contraction causes lengthening of muscle (reverse processes, letting weight down)

56. Isometric Contractions Muscle tension is generated but contraction does not occur No work gets done

57. Metabolic Pathways With or Without Oxygen (what are the names for those processes?) 3 types

61. FAST VS. SLOW MUSCLE FIBERS FAST TWITCH MUSCLE FIBERS Larger fibers for greater strength of contraction Extensive sarcoplamic reticulum for rapid release of Ca2+ Large amounts of enzymes for glycolysis Less blood supply and fewer mitochondria because oxidative metabolism is secondary Low blood supply and absence of large quantities of myoglobin give not-reddish appearance (white muscle) SLOW TWITCH MUSCLE FIBERS Smaller fibers innervated by smaller nerve fibers More extensive blood supply and greater number of mitochondria Fibers contain large amounts of myoglobin Myoglobin gives slow muscle a reddish appearance (red muscle) 61 Every muscle is composed of a mixture of fast and slow muscle fibers, along with ones between fast and slow. p. 306 Table 9.2

62. Fiber Contraction Speed: Fast Twitch 62 Figure 12-15: Fast-twitch glycolytic and slow-twitch muscle fibers

64. Muscle Fatigue Physiologically unable to contract even though the muscle is receiving stimuli Relative lack of ATP and decreased oxygen Oxygen Debit  extra oxygen needed to recovery after exercise

65. Exercise Effect on Muscle Aerobic- increase in blood vessels, number of mitochondria present; better endurance (slow twitch fibers) Resistance- increase in size of fibers more myofibrils not in number of fibers, more sarcomeres (fast twitch muscles)

66. Exercise Physiology – Training: Muscle Damage/Repair Overview damage occurs during lengthening (eccentric) movements (Weight Training) damage commonly occurs to sarcolemma, Z-disc T- tubules/SR, myofibrils, cytoskeleton Inflammatory response WBCs destroy healthy muscle cells as well as damaged ones. This causes the pain nerve fibers to be excited. repair begins ~1-2 d post-exercise (DOMS) Pain can be lessened by massage therapy 2h after intense exercise. 66

67. 67 Muscle Fiber Damage