1. SKELETAL MUSCLE NOTES

2. Terms epi = upon peri = around endo = within or inner mys = muscle
sarco = flesh
lemma = husk
fasci = bundle

4. Structure of skeletal muscle fiber

5. A sarcomere

6. Twizzler analogy
Many packages of Twizzlers =
Fascicle

7. Twizzler analogy 2 1 package of Twizzlers = Muscle fiber
The packaging =
Sarcolemma

8. Twizzler analogy 3
1 bundle of twizzlers =
myofibril

9. Twizzler analogy 4
1 Twizzler strand =
Filament

10. Terms associated with skeletal muscles
Tendon- Attaches muscle to bone

11. Ligament- Attaches bone to bone

12. Origin- The location where the muscle is attached to the relatively immovable end of the bone

13. Insertion- end of the muscle that is attached to the movable bone

14. Prime mover- the muscle that provides most of the movement

15. Synergist- muscle that assists the prime mover

16. Antagonist- the muscle that opposes the action of the prime mover

17. Muscle Contraction

18. Neuromuscular Junction

19. Neuromuscular junction animation

20. Sliding Filament theory
Boat = Myosin (thick filament)
Oar = Myosin side arm
Water = Actin (thin filament)
Life ring = Calcium

21. Resting ATP is bound to myosin side arm.
ATP cleaves into ADP + P (high energy)

22. Step 1 Action potential
A nerve action potential releases acetylcholine into the synaptic cleft opening the Na+ channels.
Action potential spreads across sarcolemma releasing Ca into sarcoplasma

23. Step 2 Myosin-actin binding
Ca binds to troponin
A shape change in troponin moves tropomyocin out of the way of actin binding site
Actin and myosin bind using energy from cleaved ATP.

24. Step 3 Power Stroke
Side arm pivots so myosin and actin slide by each other shortening the sarcomere.
ADP and P released (low energy)

25. Step 4 ATP binding and actin-myosin release
A different ATP molecule binds to active site.
Actin released

26. Step 5 ATP cleavage Return to high energy state
Cycle will repeat if Ca still available.

27. A few thoughts
The boat (myosin) does not move far in one cycle, a muscle contraction requires many cycles
What happens if ATP is not available?
Muscle stays contracted- cramps
Why does rigor mortis occur?
ATP is not available to control Ca release so contractions are continuous 6-8 hours after death. Body relaxes hours as enzymes break down contractile structures

28. Sarcomere summary

29. Final animation
animation 2
Watch “Distonia: movie

30. Muscles of the Head

31. Anterior torso muscles

32. Posterior torso muscles

33. Anterior shoulder and arm

34. Anterior forearm

35. Anterior thigh

36. Lateral thigh

37. Posterior thigh