1. Muscular System

2. Muscular System
Over 600 muscles
45% of body weight is muscles

3. Characteristics a. Excitability – respond to stimuli
Usually the stimulus is electrical or chemical

4. Characteristics
b. Contractility - shorten

5. Characteristics
c. Extensibility – be stretched or extended

6. Characteristics
d. Elasticity – recoil and resume length

7. Functions
a. Provides movement

8. Functions
b. Maintains posture

9. Functions
c. Stabilizes joints

10. Functions
d. Generates heat

11. 3 main types of muscle tissue

12. a. Skeletal muscle – move your skeleton
Voluntary muscle – we consciously control them
Striated – has narrow bands
Each cell has many nuclei

14. b. Smooth muscle – found in internal organs
Involuntary muscle – don’t consciously control them
Not striated – no narrow bands
Each cell only has one nucleus

16. C. Cardiac Muscle – found only in the heart
Involuntary muscle
Striated and branched
Each cell has only one nucleus

18. 35. Skeletal muscle anatomy
A. Muscle – organ made of several tissues
a. Surrounded by epimysium sheath

19. Skeletal muscle anatomy
B. Fascicle – portion of the muscle
a. Surrounded by perimysium sheath

20. Skeletal muscle anatomy
C. Muscle fiber – single, multinucleated cell
a. Surrounded by endomysium sheath

21. Cross section of muscle fibers

22. Muscle fibers

23. Muscle fibers
b. Sarcolemma – cell membrane c. Sarcoplasm – muscle cytoplasm d. Nucleus - many

24. Muscle fibers
e. Myoglobin – red pigment that stores oxygen f. Mitochondria – lots for energy g. Myofibrils – organelle made of bundles of myofilaments

26. Myofibrils a. Responsible for contraction b. 2 myofilaments
Actin – thin one
Myosin – thick one

27. 10,000 or more along each myofibril
c. Sarcomeres – functional unit of contraction, area between 2 z-lines
10,000 or more along each myofibril

28. Myofibril
d. I-band – light region, actin only e. A-band – dark region, myosin only f. H-zone – center of A-band, both actin and myosin g. Z-line – dark zigzag line in center of I-band

29. Sliding Filament Theory
a. Actin filaments slide past myosin
b. Z lines get closer together
c. Sarcomere shortens-neither actin or myosin get shorter.

30. Movement A. Tendons – attach muscle to bone
a. Tendons pull on bones and make them work like levers

31. Puppet on a String

32. Movement B. Contracting – shortening and fattening of muscle cells
C. Relaxing – returning back to beginning length
D. Muscles can only pull; they cannot push

33. Movement E. Most muscles work in pairs
This provides movement in two directions
When one muscle contracts, the other relaxes

34. Movement F. Flexor – the muscle that bends a joint
G. Extensor – the muscle that straightens a joint

35. Movement
H. triggered by electrical impulses through nerve cells

36. Movement
I. A sodium solution is released which causes the filaments to lock (contract) J. To unlock, calcium solution is released to relax the fibers as you propel forwards.
Nerve cell attaches to the sarcomere of each muscle fiber

37. Muscle Size
Who has more muscles?

38. Muscle Size A. The number of muscle fibers (cells) doesn’t change
they just get larger because more myofibrils are added to the cells

39. B. Hypertrophy - increase in number and size of myofibrils

40. C. Atrophy - decrease in size due to lack of use
If you don’t use it, it will shut down!

41. Muscle fibers and Exercise
A. Two types of fibers: a. Slow-twitch - endurance b. Fast-twitch - explosive
Those that want to build up fast-twitch or slow twitch fibers need to look at the exercise that will help them

42. Anaerobic Exercise a. Use fast-twitch fibers
b. Requires brief, high energy expenditure
Weightlifting – high weight, low reps
Sprinting
c. Depletes oxygen quickly
d. Excess lactic acid, turn to glucose

43. e. Builds the big muscles

44. Aerobic Exercise a. Use slow-twitch fibers
b. Prolonged and constant energy
Weightlifting – low weight, high reps
Long distance running, cycling
c. Uses same oxygen that is received
d. No lactic acid

45. e. Leans and tones the muscles

46. Body building
D. a form of body modification involving intense muscle hypertrophy
Eugen Sandow, the "Father of Modern Bodybuilding"

47. a. Testosterone – hormone that stimulates hypertrophy
Do girls have it?
Yes, boys produce times more than girls

48. b. Steroid - synthetic testosterone hormone to artificially build muscle