1. Skeletal Cardiac Smooth
Muscles
Skeletal
Cardiac
Smooth
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Muscles

2. Muscles Specialized tissue
Convert chemical energy into mechanical energy
The energy obtained from nutrients
Enable the muscles to contract
Move different skeletal bones around joints
Cardiac muscle to pump blood
Smooth muscle to contract eg- GIT
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Muscles

3. Types of Muscles There are three types of muscles Smooth
Skeletal (striated)
Cardiac (which is also striated)
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Muscles

4. Types of Muscles Cardiac Muscle Skeletal Muscle
Syncytial smooth Muscle
Multiunit smooth Muscle
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5. Skeletal Muscles Structure Muscle cell (muscle fiber)
Long cylindrical multinucleated cell
Lie parallel to each other
Force of action is directed along the fiber’s long axis
Length varies from few mm to 30 cm or more
Width is about 0.15 mm
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Muscles

6. Skeletal Muscles Level of organization
Fine layer of connective tissue (endomysium)
Wraps each muscle fiber
It separates it from neighboring fiber
Endomysium
Muscle fiber
Perimysium
Muscle fibers
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Muscles

7. Skeletal Muscles Another layer: perimysium
Surround a bundle of up to 150 muscle fibers
Fascicules
A fascia
Fibrous connective tissue surround the entire muscle
Endomysium
Muscle fiber
Perimysium
Muscle fibers
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Muscles

8. Skeletal Muscles Beneath the endomysium lie The sarcolema
Thin elastic membrane
Enclose the fiber’s cellular contents
Contain the plasma membrane
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9. Skeletal Muscles Plasma membrane
Conduct electrochemical wave of depolarization
Over the surface of fiber
Insulates one fibre from another during depolarization
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10. (Connective tissue sheath) Fascicules within sheath of perimyesium
Epimysium
(Connective tissue sheath)
Fascicules within sheath of perimyesium
Bundles of fibers.
Muscles fibers are enclosed by own sheath of endomyesium
Sarcoplasmic reticulum
From H.Taher Sherief; Physiology Book(CD)
22-Feb-19
Muscles

11. Skeletal Muscles Within the muscle fiber
Aqueous protoplasm (sarcoplasm) which contains
Enzymes, fat, glycogen particles
Nuclei (about 250 per mm length)
Genes, mitochondria, organelles
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Muscles

12. Sarcoplasmic Reticulum
Nucleus
Sarcoplasmic reticulum
Longitudinal network of tubular channels and vesicles
Allows the wave of depolarization
To spread from outer surface to inner environment
Myofibrils
Sarcolemma
Terminal cisterna (lateral sacs)
Z disc
sarcoplasmic reticulum (SR)
Z-disc
Triad
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Muscles

13. Sarcoplasmic Reticulum
Nucleus
Through the T tubules
To initiate muscle contraction
Contain Ca++ pump in their membrane
Pump Ca++ from sarcoplasm into vesicles
Sarcoplasmic reticulum
Myofibrils
Sarcolemma
Terminal cisterna (lateral sacs)
Z disc
sarcoplasmic reticulum (SR)
Z-disc
Triad
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Muscles

14. Skeletal Muscles Chemical composition 75% water 20% proteins
5% minerals & nutrients
Salts, high energy phosphates, urea, lactate
Na+, Ca++, Mg++, Cl- phosphorous,
Fat, carbohydrate, AA
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Muscles

15. Skeletal Muscles Ultra-structure
A single multinucleated muscle fibre contain
Smaller functional units
Lie parallel to long axis
Myofibrils
Myofibrils contain even smaller units
Myofilaments
Actin
Troponin
Tropomyosin
myosin
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Muscles

16. Ultra-structure
MYOFIBRILS ARE MADE OF REPEATING ASSEMBLIES OF THICK AND THIN FILAMENTS
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Muscles

17. (Connective tissue sheath) Fascicules within sheath of perimyesium
Epimysium
(Connective tissue sheath)
Fascicules within sheath of perimyesium
Bundles of fibers.
Muscles fibers are enclosed by own sheath of endomyesium
Sarcoplasmic reticulum
Actin
From H.Taher ; Physiology Book(CD)
22-Feb-19
Muscles

18. Myosin Filament Made up of 4 protein chains 2 myosin molecules
Double helix
Tail segment
Heavy meromysin (HMM)
Light meromysin
Light chains
Myosin globular head
Light Meromysin
Tail, Heavy Meromysin (HMM)
Myosin globular head
LMM
HMM
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Muscles

19. Myosin Filament Globular head 4 light chains Cross-bridge formation
ATPase
4 light chains
2 associated with each myosin molecule globular heads
Light chains
Myosin globular head
Light Meromysin
Tail, Heavy Meromysin (HMM)
Myosin globular head
LMM
HMM
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Muscles

20. Myosin Filament
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Muscles

21. Actin Filaments Made up of Double helix
2 strands of actin molecules twisted together
Double helix
Can exists as
Globular proteins
Fibrilar proteins
Actin filament
Tropomyosin
Troponin
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Muscles

22. Actin Filaments Troponin complex Tropomyosin
Attaches tropomyosin to actin
Tropomyosin
Covers active sites on actin
Tropomyosin
Troponin
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Muscles

23. Other Muscle Proteins Others include
 -actinin distributed along Z band
-actinin found in actin filament
M protein
C protein
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Muscles

24. Muscle Contraction Pure myosin and actin
Combine to form
Actomyosin
Sliding filament theory of muscle contraction
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Muscles

25. Cross bridge Z - line Z - line
Sarcomere showing the region of overlap between thick and thin filaments
Sarcomere shortening in response to crossbridge formation
Increase in the degree of overlap
RELAXED
CONTRATING
FULLY CONTRACTED
From: Physiology textbook CD by Hassen T. Sherief
22-Feb-19
Muscles

26. Mechanism of Muscle Contraction
At rest
Interaction between actin and myosin
Prevented by troponin tropomyosin complex
Active sites
Inhibitor
Actin filament
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Muscles

27. Mechanism of Muscle Contraction
In the presence of Ca++
Ca++ bind to troponin C
Leads to conformational change of tropomyosin
Uncovering of active sites
Active sites
Inhibitor
Actin filament
Ca++
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Muscles

28. Mechanism of Muscle Contraction
Myosin bind to actin
Bending of globular head
While still attached to actin
Moves the actin molecule
Active sites
Inhibitor
Actin filament
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Muscles

29. Mechanism of Muscle Contraction
The bending of globular head
Exposes ATP binding site
ATP bind on myosin head
Detachment from actin
Active sites
Inhibitor
Actin filament
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Muscles

30. Mechanism of Muscle Contraction
ATP is hydrolyzed to ADP and energy
ADP, energy
Incorporated into myosin head
Straightening of bent head to 900
Ready to attach to next active sight
Active sites
Inhibitor
Actin filament
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31. Mechanism of Muscle Contraction
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32. 22-Feb-19
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33. Excitation Contraction Coupling
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34. 22-Feb-19
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35. Excitation Contraction Coupling
Arrival of AP on motor end plate
NMJ transmission
AP along sarcolema
Spread through
T-tubules AP
T-tubule AP
Sarcoplasmic ret
Ca++
Ca++
Mg++
Ca++/Mg++ ATPase
Voltage gated channels
Ca++
Ca++
Ca++
Ca++
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Muscles

36. Excitation Contraction CouplingAP
Opening of voltage gated
Ca++ channels
Ca++ move from
Sarcoplasmic reticulum
Into sarcoplasm
 Ca++ concentration
T-tubule AP
Sarcoplasmic ret
Ca++
Ca++
Mg++
Ca++/Mg++ ATPase
Voltage gated channels
Ca++
Ca++
Ca++
Ca++
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Muscles

37. Actin Filaments Ca++ bind to troponin C Actin and myosin
Conformational change of tropomyosin
Uncovering of active sites
Actin and myosin
Crossbridge formation
Muscle contraction
Actin filament
Tropomyosin
Troponin
Active site
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Muscles

38. Excitation Contraction Coupling
Relaxation occur
Active pumping of Ca++ into sarcoplasmic reticulum
Ca++/Mg++ ATPases AP
T-tubule AP
Sarcoplasmic ret
Ca++
Ca++
Mg++
Ca++/Mg++ ATPase
Voltage gated channels
Ca++
Ca++
Ca++
Ca++
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Muscles

39. Actin Filaments There is a
↓ in the Concentration of Ca++ in the cytoplasm
Closure of active sites
relaxation
Actin filament
Tropomyosin
Troponin
Active site
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40. Excitation Contraction coupling
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41. 22-Feb-19
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42. Length – Tension Relationship
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43. Length – Tension relationship
During muscle contraction the isometric force exerted by the muscle
Depend on the
Actual length of the muscle fibers
The force developed
Related to degree of overlap between
Actin and myosin
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44. 22-Feb-19
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45. Cross-bridges Mechanical link The interaction between
Between thick and thin filament
The interaction between
Myosin head and
Actin filament
Cause the head to
Tilt towards the arm
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Muscles

46. Cross-bridges This drags the actin filament This is the power stroke
Towards centre of the sarcomere
This is the power stroke
The number of cross bridges determine
Force produced by muscle fibre
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Muscles

47. Cross-bridges Each of the cross-bridge
Operate independently of the others
The greater the number of cross-bridges
Attaching to actin
The greater the force of contraction
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Muscles

48. Cross bridge Z - line Z - line
Sarcomere showing the region of overlap between thick and thin filaments
Sarcomere shortening in response to crossbridge formation
Increase in the degree of overlap
RELAXED
CONTRATING
FULLY CONTRACTED
From: Physiology textbook CD by Hassen T. Sherief
22-Feb-19
Muscles

49. 22-Feb-19
Muscles

50. Smooth Muscles
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Muscles

51. Smooth Muscles Responsible for contractility
Hollow organs
Blood vessels, GIT, urinary bladder, uterus
Structure differ from that of skeletal muscle
Can develop isometric force per cross sectional area
Equal to or greater than that of skeletal muscle
Speed of contraction
A fraction of that of skeletal muscle
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Muscles

52. Smooth Muscles Does not show cross striation
Under microscope
It is also known as INVOLUNTARY muscle because
Its function is not under our voluntary will
Its activities arises spontaneously
Or through the autonomic nervous system
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53. Smooth Muscles Smooth muscle from different tissue differ In structure
Organization in sheets, bundles
In property
Response to different types of stimuli, innervations
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54. Smooth Muscles But in general individual cells
Are long and spindle shaped
About 50 to 500 μm long
Are 5 to 10 μm wide
Have one nucleus per cell
Guyton Textbook of Physiology
22-Feb-19
Muscles

55. Smooth Muscles Are surrounded by a cell membrane Have myosin and actin
Exhibit invagination (surface vesicles, caveoli)
Have myosin and actin
Contain sarcoplasmic reticulum
Guyton Textbook of Physiology
22-Feb-19
Muscles

56. Multi-Unit Type Multi-unit smooth muscle
Composed of individual muscle fibres
Each with its own nerve inervation
Can function independently
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57. Multi-Unit Type Each muscle fibre is
Discrete and operates independently
There is no spontaneous contraction
Activity controlled by the autonomic nervous system
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58. Multi-Unit Type The axon terminal Found in the
Makes several synaptic contacts on the membrane
Found in the
Iris, ciliary body
Around hair follicles
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59. Unitary (Single unit) Type
Unitary (single unit), visceral smooth muscle
Individual cells join together to form a sheet of cells
When one cell is excited
Then all contract as a single unit
Guyton Textbook of Physiology
22-Feb-19
Muscles

60. Unitary (Single unit) Type
Found in the walls of viscera
Digestive system, urinary bladder, ureters
Blood vessels
Guyton Textbook of Physiology
22-Feb-19
Muscles

61. Unitary (Single unit) Type
Cells are aggregated together into sheets or bundles
The cell membranes adhere to each other at several points
Tight and gap junctions
Where ions can flow freely from one fibre to next
Force generated in one muscle fibre can be transmitted into the next
Guyton Textbook of Physiology
22-Feb-19
Muscles

62. The Contractile Process in Smooth Muscles:
Contain both myosin and actin
Not arranged in orderly way as in skeletal muscles
Do not have troponin and tropomyosin
Instead there is
Caldesmon
Calponin
Guyton Textbook of Physiology
22-Feb-19
Muscles

63. The Contractile Process in Smooth Muscles:
The actin filaments
Are attached to dense bodies
Contraction is achieved by the
Sliding action of filaments like in skeletal muscles
Guyton Textbook of Physiology
22-Feb-19
Muscles

64. Molecular Basis for Contraction
Initiated by calcium as it is in skeletal muscles
Smooth muscle
Has poorly developed sarcoplasmic reticulum
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65. Molecular Basis for Contraction
Stimulation by nerves, or stretching
Causes membrane depolarization
Opening voltage gated calcium ion channels
Influx of calcium ions from the extra cellular fluid
Electromechanical coupling
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66. Molecular Basis for Contraction
Stimulation by hormones, drugs
Causes activation of receptors
Release of Ca++ ions from sarcoplasmic reticulum
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67. Molecular Basis for Contraction
Calcium ions bind to calmodulin
Myosin light chain kinase (MLCK) is activated
Activated MLCK Catalyses the phosphorylation of the myosin head
Actin then bind with myosin
Producing muscle contraction
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Muscles

68. Cessation of Contraction
Myosin is de-phosphorylated by a phosphatase
However, the cross bridges remain attached to actin
This produces sustained contraction
Latch mechanism (phenomenon)
Relaxation of smooth muscle occurs
When there is dissociation of calcium-calmodulin complex
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69. Control of Smooth Muscle Contraction
Low levels of Ca++
Caldesmon blocks actin binding sites
Muscle RELAXED
High Ca++ levels
Ca++ Calmodulin complex
Removes caldesmon and
Activates myosin light chain kinase (MLCK)
Which phosphorylates myosin
Promoting cycling
Caldesmon
bound to Ca++- calmodulin complex
From: Physiology textbook CD by Hassen T. Sherief
22-Feb-19
Muscles