1. UNIT 3: MUSCLES

2. Types of Muscle tissue Skeletal: striated and voluntary- moves body Smooth: involuntary, non-striated Cardiac: heart, involuntary

3. Skeletal muscle

4. Epimysium: Covering of whole muscle Perimysium: Covers group of fibers= fasicle Endomysium: Covers each cell= muscle fiber

5. Tendon- fibrous CT that extends from epimysium to connect muscle to bone Aponeurosis- broad sheet of CT– extension of muscle’s fibrous wrapping to merge with another muscle Fascia- fibrous CT around muscle, outside epimysium and tendon Whole muscle is an organ

8. Skeletal/Striated Muscle Fiber Fiber= muscle cell Skeletal muscle made of bundles of fibers- extending the length of the muscle

9. Inside a Muscle Fiber Sarcolemma- plasma membrane Sarcoplasm- cytoplasm Sarcoplasmic reticulum (SR)- network of tubules and sacs similar to ER that works to pump and store Calcium ions for electrical impulse  muscle contraction

10. Triad: A T-tubule sandwiched between two ends of SR Transverse Tubules (T-tubules): extensions of plasma membrane (sarcolemma) that reach transversely, deeper through cell (in shape of T) –Carry nerve impulses into myofibril –Important for muscle contraction

12. Muscle fibers made of Myofibrils – bundles of very fine fibers--are responsible for muscle fiber contraction; their contraction shortens the entire cell due to their attachment to the sarcolemma

13. Myofilaments Protein filaments consisting mainly of proteins: thin filaments- actin, troponin and tropomyosin thick filaments- myosin Thick and thin alternate

14. Actin Globular molecules look like beads, form 2 strands twisted around each other

15. Myosin Molecules shaped like golf clubs– “heads” stick out and are chemically attracted to actin Heads are called cross bridges– they try to bridge gap between filaments

17. Short Unit of myofibril= Sarcomere Sarcomere is contractile unit

19. Regions of sarcomere A band- dArk, thicK wide stripe, contains myosin overlapping actin H band- in middle of A band- region of only myosin I band- lIght, thIn, either side of A-band, contains actin only Z line- dense plate/disk to which thin filaments anchor at ends in I-band, marks ends of one sarcomere

20. Changes when muscle contracts Muscle contraction shortens muscle, units of muscle fibers overlap Sarcomere shortens H-band disappears, A now solid dark Z-lines become closer together I-band becomes thinner

22. Sliding Filament Theory Flood of calcium ions binds to troponin, moving them off the active sites of Actin they normally block Myosin heads bind to Actin and pull the thin filaments toward center of sarcomere  SHORTENS SARCOMERE & ENTIRE MUSCLE FIBER

23. Muscle Contraction: shortens a muscle –Requires Calcium Calcium: charged ions released after nerve impulse- necessary to expose actin so myosin can bind Cross-bridge: myosin heads when they attach to actin

24. Troponin: sits on Actin –Inhibits enzyme ATPase & Tropomyosin Tropomyosin –Blocks binding site for myosin on actin –Wraps around edge of actin

25. Neuromuscular Junction: connection between nerve cell and sarcolemma of muscle fiber  where electrical impulse starts Releases Acetylcholine

26. Steps of Contraction 1.Nerve impulse goes from neuron to NMJ  releases ACh 2.ACh diffuses across NMJ and binds to muscle fiber  electrical impulse 3.Impulse moves along sarcolemma, down T-tubules, to SR

27. 4. Ca ions released from SR to sarcoplasm  bind to troponin 5. Tropomyosin moves to expose actin 6. Energized myosin heads bind to actin and use energy from ATP to pull actin toward center 7. Thin filaments pulled together  MUSCLE SHORTENS

28. Relaxation 1.After impulse Ca is pulled off troponin and SR reabsorbs it 2.Ca moved off of troponin  tropomyosin moves back, blocking actin 3.Myosin cross-bridges can’t attach to actin anymore 4.Myosin & Actin aren’t connected  MUSCLE LENGTHENS

29. Energy Sources for muscles ATP- acts like pulled rubber band tight –Pulls myosin off actin into cocked position –When it breaks down to ADP, it releases energy, making myosin pull on actin

31. Energy Sources for muscles Myoglobin- attracts and stores oxygen –Replenishes oxygen lost in muscles during exercise –Red color (contains Iron)

32. Energy Sources for muscles Creatine Phosphate (CrP) –Resynthesizes ATP when muscles run out –Back up energy for 20 extra seconds contraction –Only small amount of ATP stored in muscle

33. Energy Sources for muscles If you run out of ATP/CP  muscle stiffness ATP is REQUIRED to detach myosin and turn off contraction After death… Rigor Mortis

34. Rigor Mortis in Meat -Cold shortening -Is meat stretchable? Why/why not? -Is meat muscle contracted?

35. Rigor Mortis in Meat Electrical stimulation- flexes and relaxes muscles immediately after animal is butchered

36. HOMEWORK due MON Research Protein Powder (supplement) Write a paragraph or bullets explaining… –What does it do? How does it work? –Does it build muscle? –Who should take it?

37. Muscle Tension Twitch- a single stimulation triggers a quick jerk of a muscle Lasts <0.1sec – phases: latent, contraction, relaxation

38. Kahoot: What happens after a motor neuron stimulus, before contraction happens?

39. Summation A series of stimuli occur rapidly so muscle doesn’t have time to relax in between contractions

40. Tetanus: smooth, sustained muscle contractions (common) Incomplete tetanus: shorts periods of relaxation occur between peak tension

41. Complete tetanus: more frequent stimuli make peaks of tension seem to fuse into a single, sustained peak  constant contraction

42. Motor Units Motor unit=neuron (nerve cell) + muscle fibers to which it attaches Motor neurons branch and can attach to many muscle fibers One motor unit may stimulate a small or large part of a muscle Less muscle fibers per motor unit = more precise movement (ex: fingers)

43. Effects of Lactic Acid When do your muscles burn? Exercise uses anaerobic processes (no oxygen) in short term  produces lactic acid Lactic acid accumulates when less Oxygen available Why do you still breathe heavily AFTER you stop exercising?

44. Types of muscle fibers White (Fast): have little myoglobin, fastest twitch speed, few mitochondria, muscles fatigue quicker –Example: in eyes & fingers for quick motions

45. Red fast: lots of myoglobin & oxygen, moderate twitch speed/fatigue resistance Red slow: slow twitch speed, most myoglobin, able to stay contracted longer, not easily fatigued; postural muscles

46. Most muscle tissues contain mixture of red and white fibers Athletic training can produce changes in mix of fiber types

47. Kahoot question! Which person would have the highest concentration of Red SLOW muscle fibers?

48. Kahoot question! Which body part would have the highest concentration of White muscle fibers?

49. Muscle Tone- Tonic Tonic Contraction: low level of continuous contraction  Muscle tone –Even though muscle relaxes, small number of motor units stay contracted –Important for maintaining posture

50. –Falling asleep… –Defined calf muscles…

51. Muscle Tone- Isotonic Isotonic contraction: “same tension”  muscle changes in length but tension/tone stays constant  myosin cross bridges “WIN” tug-of-war

52. Isotonic Contraction –Concentric: muscle shortens Pick up a book –Eccentric: muscle lengthens Lower the book you picked up  muscle contracts and gets longer

53. Muscle Tone- Isometric Isometric contraction: increased tension (work) but no movement (same length) –Motions usually combination of both types –Example: Shoulder Isometric holds it in place While arm moves: Isotonic Youtube vid: https://www.youtube.com/watch?v=PHTUl wCnCe8

54. Kahoot questions! What type of contraction?

55. Cardiac muscles- in between skeletal and smooth Automaticity- instead of nerve junction, cardiac muscle stimulates itself Aerobic- uses oxygen –Can’t sustain tetanus –Doesn’t fatigue easily

56. Smooth Muscles Non-striated: random arrangement of myosin/actin Anchored filament- filaments connected to plasma membrane, then crisscross the cell –When muscle contracts, it “balls up” –More freedom of movement Lack of motor neuron stimulation- self- excitation

57. Smooth Muscle Single unit smooth muscle arranged in sheets Act as large unit to push contents along organ –Example: in digestive system Multiunit smooth muscle has many independent cells– neurons attached to give more precise controlled movement Example: in skin – goosebumps in eye– dilate pupils

58. All or nothing concept What is the difference between lifting a light weight and a heavy weight? –Type of contraction?

59. All or nothing concept A BUNDLE of muscle FIBERS contract all or nothing – when stimulated by SINGLE motor unit The ENTIRE muscle does NOT contract all or nothing More motor units recruited= stronger overall contraction; more work