1. Chapter 3 Support and locomotion – muscles and movement.
Year 13- Biology 2

2. By the end of this session I should be able to:
Describe the histology and ultrastructure of striated muscle.
Describe the sliding filament theroy of muscle contraction, including the roles of troponin and tropomyosin.
Describe the structure of a neuromuscular junction and explain how a nerve impulse causes muscle to contract.

3. Discussion pairs –two minutes
Give reasons why animals move from place to place:
1. To obtain food
2. To escape from predators
3. To find a mate
4. To distribute offspring
5. To reduce competition
6. To avoid danger
7. To maintain position
8. To avoid waste products

4. Muscular Movement
muscles are attached to bones to form lever systems for movement
muscle contraction creates a driving force when obtains energy from respiration;
when a muscle relaxes, energy is not necessary
There are 3 types of muscle:
Skeletal muscle,
Smooth muscles,
Cardiac muscle.

5. Three types of Muscle:
A. Smooth: involuntary control of internal organs for digestion, & blood vessels
B. Cardiac: involuntary control of the heart
C. Skeletal: Voluntary control of the skeletal muscles for movement

6. The Musculature System……..
Structure:
Voluntary Muscles
Striated-Skeletal
Involuntary Muscles
Cardiac- Heart
Smooth-Stomach
Striated Skeletal
Several nuclei
Box shaped, many mitochondria

7. Cardiac Muscle: Fewer Striations Fewer Mitochondria Large nuclei
Lattice work of spaces between some cells
Still square shape
One nuclei per cell

8. Smooth Muscle: Eye shaped One nuclei per cell No lattice work
No striations
Long & drawn out
Fewer Mitochondria

9. Skeletal muscle structure

10. Muscle structure

11. Actin / myosin filaments

12. Actin / myosin 2

13. Sarcomere structure Sarcomere Sarcolemma Z line A band I band H band
M line

14. Muscle structure

15. sarcolemma:
membrane of muscle fibre
sarcomere:
each repeating unit of cross striations
sarcoplasm: cytoplasm with a system of membranes called sarcoplasmic reticulum

16. dark band and
light band
Z line: central line of each light band;
2 Z lines marks a sarcomere
H zone: lighter region in dark band with a central dark line - M line
Myosin:
thick filaments
Actin:
thin filaments

18. actin

19. troponin
actin

20. tropomyosin
troponin
actin

21. tropomyosin
troponin
actin

22. myosin binding site
tropomyosin
troponin
actin

24. Ca2+
Ca2+
Ca2+
Ca2+

25. Ca2+
Ca2+
Ca2+
Ca2+
Calcium ions are released from the sarcolemma after stimulation from the T system

26. Ca2+
Ca2+
Ca2+
Ca2+

27. the calcium ions bind to the troponin and changes its shape

28. the calcium ions bind to the troponin and changes its shape

29. Ca2+
Ca2+
Ca2+
Ca2+

30. Ca2+
Ca2+
Ca2+
Ca2+

31. Ca2+
Ca2+
Ca2+
Ca2+
the troponin displaces the tropomyosin and exposes the myosin binding sites

32. Ca2+
Ca2+
Ca2+
Ca2+

33. Ca2+
Ca2+
Ca2+
Ca2+

34. Ca2+
Ca2+
Ca2+
Ca2+
the bulbous heads of the myosin attach to the binding sites on the actin filaments

35. Ca2+
Ca2+
Ca2+
Ca2+

36. Ca2+
Ca2+
Ca2+
Ca2+

37. Ca2+
Ca2+
Ca2+
Ca2+
the myosin heads change position to achieve a lower energy state and slide the actin filaments past the stationary myosin

38. Ca2+
Ca2+
Ca2+
Ca2+ A Pi A Pi A Pi

39. A Pi
Ca2+ A Pi
Ca2+ A Pi
Ca2+
Ca2+

40. ATP binds to the bulbous heads and causes it to become detachedPi
Ca2+ A Pi
Ca2+ A Pi
Ca2+
Ca2+
ATP binds to the bulbous heads and causes it to become detached

41. ATP binds to the bulbous heads and causes it to become detachedPi A Pi A Pi
Ca2+
Ca2+
Ca2+
Ca2+
ATP binds to the bulbous heads and causes it to become detached

42. hydrolysis of ATP provides the energy to “re-cock” the headsPi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
Ca2+
Ca2+
Ca2+
hydrolysis of ATP provides the energy to “re-cock” the heads

43. hydrolysis of ATP provides the energy to “re-cock” the headsPi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
Ca2+
Ca2+
Ca2+
hydrolysis of ATP provides the energy to “re-cock” the heads

44. Pi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
Ca2+
Ca2+
Ca2+

45. calcium ions are re-absorbed back into the T systemPi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
Ca2+
Ca2+
Ca2+
calcium ions are re-absorbed back into the T system

46. calcium ions are re-absorbed back into the T systemPi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
calcium ions are re-absorbed back into the T system

47. Pi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
the troponin reverts to its normal shape and the tropomyosin move back to block the myosin binding sites

48. Pi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
the troponin reverts to its normal shape and the tropomyosin move back to block the myosin binding sites

49. Pi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
the troponin reverts to its normal shape and the tropomyosin move back to block the myosin binding sites

50. phosphocreatine regenerates ATPPi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
phosphocreatine regenerates ATP

51. phosphocreatine regenerates ATPPi Pi Pi A Pi Pi Pi Pi A Pi Pi A
Ca2+
phosphocreatine regenerates ATP

52. phosphocreatine regenerates ATPPi Pi Pi A Pi Pi Pi A Pi Pi Pi A
Ca2+
phosphocreatine regenerates ATP

54. Neuromuscular junction: Note Ach = Acetylcholine

55. Sarcoplasmic
Reticulum

56. Sequence of events
1. An action potential arrives at the end of a motor neurone, at the neuromuscular junction.
2. This causes the release of the neurotransmitter acetylcholine.
3 This initiates an action potential in the muscle cell membrane (Sarcolemma).
4. This action potential is carried quickly into the large muscle cell by invaginations in the cell membrane called T-tubules.

57. Sequence of events
5. The action potential causes the sarcoplasmic reticulum to release its store of calcium into the myofibrils.
6. Ca2+ causes tropomoysin to be displaced uncovering myosin binding sites on actin.
7. Myosin cross bridges can now attach and the cross bridge cycle can take place.
Relaxation is the reverse of these steps