1. Chapter 9 The Muscular System

2. Skeletal Muscle Structure
Tendon –
Fascia – outermost
covering; covers entire muscle & continuous
w/tendon; separates
muscle from adjacent
muscles
Aponeuroses-

3. Skeletal Muscle Structure
Coverings:
Epimysium – covers entire muscle
(under fascia)
Perimysium –
Endomysium –
covers each fiber (cell)
Sarcolemma –

4. Skeletal Muscle Structure – Cont.
Sarcoplasmic reticulum (SR) channels for transport
Myofibrils – threads that compose muscle fibers; contain protein filaments:
1. actin –
2. myosin –

5. Skeletal Muscle Structure

6. Muscle Fiber (muscle cell)
Cisternae of SR –
enlarged portions
Transverse tubules
(T-tubules) –
important
in muscle contraction
Sarcoplasm –

7. Breakdown of Skeletal Muscle

8. Parts of a Sarcomere (functional unit of a muscle)

9. Parts of a Sarcomere Z lines – end points M line – I band – on either
side of Z line; actin
filaments only
H zone – on either
side of M line;
myosin filaments only
A band –

10. Parts of a Sarcomere

11. 4 Proteins in Muscle Cells:

13. Troponin & Tropomyosin
4 proteins are found in muscle cells: actin, myosin, troponin & tropomyosin
troponin – appear
as globules; provide
a binding site for Ca+²
tropomyosin –

14. Sliding Filament Theory (How Muscles Contract)
Muscle fiber stimulated by release of ACh from synaptic vesicles of neuron
Transverse tubules (T-tubules) carry impulse deep into muscle fibers
Ca²+ bind to troponin, tropomyosin moves, exposing binding sites on actin filaments

15. Cross Bridge Animation

16. Sliding Filament Theory (How Muscles Contract )
Linkages form b/t actin & myosin
Actin filaments move inward, shortening the sarcomere
The enzyme cholinesterase (or AChesterase) decomposes ACh

17. Sliding Filament Theory
Relaxed muscle – binding sites on actin are covered by tropomyosin

18. Sliding Filament Theory
Ca²+ binds to troponin
Tropomyosin
slides out of the way
Myosin binds to actin &
pulls inward
Sarcomeres
shorten & muscle
contracts

19. Sliding Filament Animation

20. Sliding Filament Theory

21. Neuromuscular Junction – junction b/t motor neuron & muscle
Motor end plate – end
of muscle fiber; many
nuclei & mitochon-
dria located here

22. Neuromuscular Junction
Neurotransmitters
(ntm) chemicals that
help carry impulses
Motor unit –
Synaptic vesicles –
store neurotransmitter;
most common – acetylcholine (ACh)

24. Electron Micrograph Neuromuscular Junction

25. Neuromuscular Junction Animation

26. Energy for Muscle Contraction
ATP (adenosine triphosphate)
When ATP is converted to ADP (adenosine diphosphate) by losing the last phosphate, energy is released.

27. Energy for Muscle Contraction
Cells depend on cellular respiration
of glucose to synthesize ATP
An additional source is creatine phosphate

28. Energy for Muscle Contraction
Creatine phosphate stores excess energy
Anaerobic respiration (in the absence of O2) provides few ATP’s, while aerobic resp. (in the presence of O2) provides many ATP’s

29. Creatine Phosphate
High amts. of ATP - ATP is used to Low amts. of ATP – CP is used synthesize CP, which stores energy to resynthesize ATP.
for later use.

30. Importance of Myoglobin
l.a. carried by blood to
liver; liver can convert
l.a. to glucose, but
requires ATP (ATP being
used for muscle contraction)
myoglobin –

31. Aerobic vs. Anaerobic Respiration

32. Aerobic vs. Anaerobic Respiration
Carried by blood to liver; liver can convert l.a. to glucose, but requires ATP (ATP being used for muscle contraction)
Imp. b/c blood supply
during muscle contr.
may decrease
As l.a. accumulates, O2 debt occurs

33. Oxygen Debt
Strenuous exercise leads to O2 deficiency & lactic acid buildup
ATP provides energy for muscle contraction
Amt. of O2 needed to convert accumulated l.a. to glucose & restore ATP levels =
L.A. accumulation leads to muscle fatigue b/c pH of muscle cell is lowered & muscle cannot contract

34. Muscle Cramp Muscle cramp –
Rigor mortis – takes up to 72 hrs. to occur; sarcolemma becomes more permeable to Ca+² & ATP levels insufficient

35. Myogram Pattern or graph of a muscle contraction
A single contraction is
called a
3 parts:
Latent (lag) phase –
brief pd. of delay
b/t when the stimulus is applied & actual contraction occurs
Contraction
Relaxation –

36. Patterns of Contraction
a) Muscle Twitch –
b) Staircase Effect
many stimuli closely
spaced w/complete
relaxation in b/t; each
contraction generate
incr. force

37. Patterns of Contraction
c) Summation – when
the 2nd stimulus occurs
during the relaxation
pd. of 1st contr.; the
2nd contr. generates
more force
d) Tetany –

38. Muscle Facts
If a muscle is stimulated twice in quick succession, it may not respond the 2nd time – called refractory period
Threshold –
All-or-none – increasing the strength of the stimulation does NOT incr. the degree of contraction (a muscle contracts completely or not at all)

39. More Facts
Incr. stimulation from motor neurons causes a greater # of motor units to contract & vice versa
Called recruitment of motor units
Incr. the rate of stimulation also incr. the degree of contraction
Muscle tone –

40. Hypertrophy vs Atrophy
Hypertrophy- with intense exercise where muscle exerts more than 75% of its max tension there is an increase in actin and myosin fibers and increase muscle fiber diameter.
Inc diameter=
Atrophy-

41. Origin & Insertion Origin – end of muscle that attaches to stationary
bone
Insertion –
During contr., insertion
is pulled toward origin

42. Muscle Functions in Groups
Prime mover – responsible for most of the movement (ex.- biceps)
Synergist – aids the prime mover
Antagonist –

43. Structural Differences of 3 Types of Muscle
Skeletal Muscle
Smooth Muscle
Cardiac Muscle
Cells elongated w/multiple nuclei/cell
Cells spindle-shaped w/1 nucleus/cell
No T-tubules
T-tubules lg.; releases lg. amts. of Ca++; can contract longer (Ca channel blockers)
Striated/voluntary
Striated/invol.

45. Functional Differences of 3 Types of Muscle
Skeletal Muscle
Smooth Muscle
Cardiac Muscle
Needs nerve impulse for contraction
Displays rhythmicity & cells stimulates each other (as in peristalsis)
Ca+² binds to calmodulin
Ca+² binds to troponin
Not affected by hormones
Hormones may affect rate of contr.
Slower to contract but can maintain contraction longer

46. Functional Differences - Continued
Skeletal Muscle
Smooth Muscle
Cardiac Muscle
Not affected by stretching
Stretching of fibers may stimulate contr.
(ex.-stomach)
Remains in a refractory pd. until contraction ends (tetany won’t occur)

47. Fast vs Slow Twitch Fibers
Fast vs Slow Twitch Video

48. Fast Twitch vs. Slow Twitch Muscle
Contracts quickly, tires easily (sprinter)
Contracts slowly, tires slowly (long distance)
More mitochondria
Less myoglobin
Red muscle
Composes smaller muscles (eyes, hands, etc.)