1. To understand the cellular processes for synthesis of ATP.
To compare and contrast aerobic and anaerobic processes in the muscle cell.
To examine the differences in ATP synthesis among different types of muscle cells

2. Structure of Adenosine Triphosphate (ATP)
Note: ATP has three phosphate groups. The structure of a phosphate group (Pi) is:
• The bond between the last two phosphate groups is high energy

3. (1) (2) (3) Regeneration of ATP 1.direct phosphorylation of CP
2.anaerobic glycolysis
3.Oxidative phosphorylation of glycogen, glucose, fat
(1)
(2)
(3)

4. Metabolism of Skeletal Muscles
Phosphcreatine:
Rapid source of renewal of ATP.
ADP combines with creatine phosphate.
Phosphocreatine concentration (20-40 mM) is 4-8 times concentration of ATP (5mM).

5. Sources of Glucose
• Two sources of glucose to muscles:
1. Blood glucose.
2. Breakdown of glycogen into glucose
within the muscle cell

6. Anaerobic Pathway: Lactic Acid
glucose
glycogen
glucose
lactic acid
pyruvic acid 2
Anaerobic Pathway: Lactic Acid

7. Aerobic Pathway O2 O2 CO2 H2O glucose glycogen glucose 2 myoglobin 36
pyruvic acid
acetyl CoA 2
myoglobin 36 O2
CO2
H2O

8. Regeneration of ATP
1.direct phosphorylation of CP: 1ATP produced per CP
2.anaerobic glycolysis: 2 ATP per glucose
3.Oxidative phosphorylation of glycogen, glucose, fat; ?? ATP per glucose

9. glucose pyruvic acid lactic acid acetyl CoA myoglobin O2 H2O CO2
glycogen
pyruvic acid
lactic acid
acetyl CoA
myoglobin O2
H2O
CO2
creatine

11. White muscle fiber
Red muscle fiber

12. Features of White Muscle Fibers
Characteristics of white muscle fibers:
Large in diameter
Light in color due to reduced or absent myoglobin
Surrounded by only a few capillaries
Have relatively few mitochondria
Have a high glycogen content
6. Synthesize ATP mainly by glycolysis

13. Features of Red Muscle Fibers Characteristics of red muscle fibers:
Half the diameter of white muscle fibers
Dark red in color due to a large quantity of myoglobin
Surrounded by many capillaries
Have many mitochondria
Have a low glycogen content
6. Synthesize ATP mainly by the Krebs cycle and oxidative phosphorylation

15. Factors Affecting Muscle Tension
Three factors which affect muscle tension in a whole muscle:
1. Frequency of stimulation
2. Number of motor units recruited
3. Degree of muscle stretch

16. Contraction of Motor Units
To examine the components of a motor unit.
To understand the relationship between motor unit size and precision of muscle movement.
To explore the relationship of motor units to muscle tone.

18. Types of Muscle Contractions
Relaxation
Latent period
Contraction phase
Twitch:
Muscle is stimulated with a single electrical shock (above threshold).
Quickly contracts and then relaxes.
Increasing stimulus increases the strength of the twitch (up to maximum).

19. Relation between force and shortening velocity
Velocity of contraction is maximal when load is zero
Velocity decreases when load increases
Power is maximal at intermediate velocity

20. Temporal Summation of Two Stimuli
Effect of Time Interval on Second Contraction

21. Types of Muscle Contractions
Summation:
If second electrical shock is administered before complete relaxation of muscle.

22. Types of Muscle Contractions
Incomplete tetanus:
Stimulator delivers an increasing frequency of electrical shocks.
Relaxation period shortens between twitches.
Strength of contraction increases.
Complete tetanus:
Fusion frequency of stimulation.
No visible relaxation between twitches.
Smooth sustained contraction.

23. Second & Third Factor Affecting Muscle Tension
Three factors which affect the development of muscle tension:
1. Frequency of Stimulation
2. Number of Motor Units Recruited
3. Degree of Muscle Stretch

24. Length-Tension Relationship

26. Slow- and Fast-Twitch Fibers
Slow-twitch (type I fibers):
High oxidative capacity:
Resistant to fatigue.
Have rich capillary supply.
Numerous mitochondria and aerobic enzymes.
Use ATP slowly
Red muscle (dark-colored meat of fish and fowl)

27. Classification of fiber types
1. Tonic fibers: contract slowly, do not produce twitches and AP,
postural muscle and extraocular muscles
2.Three types of twitch (or phasic) fibers
a. slow twitch (or type I) fibers
b. fast twitch oxidative (or type IIa) fibers
c. fast-twitch glycolytic (or type IIb) fibers

28. Slow- and Fast-Twitch Fibers
Fast-twitch (type IIa fibers):
Adapted to respire aerobically.
Specialized for repetitive movement
Relatively resistant to fatigue.
Numerous mitochondria and aerobic enzymes
Flight muscles of migratory birds

29. Slow- and Fast-Twitch Fibers
Fast-twitch (type IIB fibers):
Adapted to respire anaerobically.
Have large stores of glycogen.
Have few capillaries.
Have few mitochondria.
White breast muscle of domestic fowl.

31. Ration for different fiber types
Fast-twitch fibers: rapid movement of its limb or fins, use large amount of ATP.
Slow muscles: move slowly, use less amount of energy
Trade-off

33. Cardiac Muscle Contain actin and myosin arranged in sarcomeres.
Contract via sliding-filament mechanism..
Adjacent myocardial cells joined by gap junctions.
AP spread through cardiac muscle through gap junctions.
Behaves as one unit.
All cells contribute to contraction.

36. Cardiac muscle
A small, elongated cell, single nucleus, connected together by gap junction, myogenic (contraction initiated in the muscle fibers themselves).
Contains contractile fibers and conducting fibers (peacemaker fibers)
Initiation and sustain of contraction depend on a signal from pacemaker fibers and spreads as APs through the heart by gap junctions.

37. Skeletal muscle: short AP with a few milliseconds
Cardiac muscle:
Long AP and long refractory period with several hundred milliseconds

39. Features of smooth muscle
Lack of sarcomeres & T-tubules (non-striated)
Thick and thin filaments are anchored on dense bodies
Walls of hollow organs
Support visceral functions (not for locomotion and other behavior)
Very slow contraction & prolonged contracted activity
Low energy requirement
Myogenic (single-unit) and neurogenic (multi-unit)
Stretch more than skeletal muscle
Synthesis and secrete proteins (collagen & elastin)

40. Small spindle-shaped cells, one central located nucleus, diameter 2-10 mm, length 100-500 mm

41. Smooth Muscle Contraction
Depends on rise in free intracellular Ca++ .
Ca++ binds with calmodulin.
Ca++ calmodulin complex joins with and activates myosin light chain kinase.
Myosin heads are phosphorylated.
Myosin head binds with actin.
Relaxation occurs when Ca++ concentration decreases.

42. Inactive myosin kinase Active myosin kinaseCa 2+
Calmodulin Ca 2+
-calmodulin
Inactive myosin kinase
Active myosin kinase
ATP P i
ADP
Inactive myosin
Phosphor
ylated myosin
(can bind with actin)
Fig. 8-30, p.351

43. Caldesmon inhibits myosin-actin binding in smooth muscle.
Remove caldesmon by Ca 2+-Calmodulin or phosphorylation

44. Binding Ca 2+ to myosin light chain
Phyosphorylation of myosin light chain by Ca2+-calmodulin or PKC