part of dr . hanaa

2. Muscular System
Locomotion
( movement of the parts or the whole body).

3. Types of muscles
• According to the histological structure
1- Striated muscles, contain striations.
2- Unstriated muscles, no striations (smooth).
• According to the position :
1- Skeletal muscles, present around the skeleton.
2- Cardiac muscles, present in the heart.
3- Visceral muscles, present in the viscera and urinary bladder.
• According to the ability of controlling the contraction:
1- Voluntary muscles, contract under our control.
2- Unvoluntary muscles, contract without control of us.

4. Skeletal muscle

9. • according to protein in myosin: two types:
a) Slow unit
* red - dark- respond slowly- long twitch duration (up to
100 ms) - low mitochondrial ATP ase activity ,
* Produce ATP slowly
* In large limp muscle
* Ex. marathon runners (more red fibers)
b) Fast unit
* Pale(white) - short twitch duration ( 7 ms) - * produce
ATP quickly – more powerful contractions – fine ,skilled
movement
* Ex. Weighlifters

10. Skeletal (voluntary; striated) muscle
• Attach to skeleton
• Function in movement (bone)
• Contract voluntary
C.N.S. neuromuscular junction
• Connect to the bone through the beginning
(origin) other end (insertion)
• If the origin formed of 2 parts(Biceps) or 3
(Triceps)
• Ends with tendons

11. Structure
Each muscle composed of many myofibrils(muscle
fibers).
Cylindrical shape, multinucleated.
Each myofibril composed of many myofibrils .
Each myofibril composed of many repeated sarcomeres.
Myofibrile appear as alternated dark and light bands.
Light band is called Isotropic band (I),
Dark band is called Anisotropic band (A).
Each sarcomere composed of many myofilaments.
( thin ) actin , troponin , tropomysin
( thick ) myosin .

18. Molecular structure:
Myosin:
• Thick helical protein filament.
• Consists of heads and tails.
• By proteiolytic enzyme(trypsin) broken into:
** light meromyosin (LMM) : H-zone
No ATPase activity and can’t combine with actin.
No heads at the H-zone.
** Heavy meromyosin (HMM) contain ATP ase activity , can
combine with actin.
• Release the heads from the tails if treated with pepsin enzyme.
• The head of the myosin molecule forms cross bridge with the
adjacent actin filament.

19. Actin:
•Thin filaments actin with small amount of tropomyosin and
troponin.
•In ionic environment of the cell, actin exist in the fibrous
form (F-actin) containing 2 chains of actin monomer coiled
around each other.
•In the absence of salts, actin becomes globular (G-actin).
•The change from F- actin to G- actin is reversible and is
called ( G F ) transformation;

20. • Troponin and tropomyosin
(Regulatory agent in muscle contraction)
At rest ,tropomyosin block the binding of actin to myosin.
• Troponin is formed of 3 subunits:
Troponin (I) inhibit the interaction of myosin to actin.
Troponin (C) which contain the binding sites of Ca++ that
initiate the contraction of the myofilaments.
Troponin (T) binds the other troponin component to
tropomyosin.

23. Classification according to the movement
:
• 1- a) Flexor; bends one part upon another.
• b) Extensor; straightens or extends part.
• 2- a) Adductor; draws a part towards the axis
• b) Abductor; draws a part away of the axis
• 3- a) Depressor; lowers a part.
• b) Elevator; elevate or raise a part.
• 4- a) Constrictor; constricts or close an organ.
• b) Dilator; cause dilation of the same organ.
• 5- Rotator Muscle; rotates on part on another

24. CARDIAC MUSCLES:
 They contract involuntary, and rythimitically.
 They obey all or non law.
They are auto stimulated (pace maker).
Striated muscle
 Pump blood
 Adapted for resistant to fatigue
**A lot mitochondria (aerobic respiration)
**Numerous myoglobins (O2 storing pigment)
**Good blood supply

25. Intercalated discs (support contration) double membrane separating
adjacent cells.
Cell junctions fuse together the plasma membranes of cardiac muscle cells,
allow the cells to contract as a unit.

26. Smooth muscle
Unstriated
 Walls of hollow organs
( gastrointestinal tube & respiratory system )
 Two types
 multi-unit: without interconnection,iris
 single-unit :(walls of viscera)

27. Spindle shape –single nucleus
 Arranged in sheets
 Few mitochondria(depend on anaerobic glycolysis)
 Contain myosin & actin (not arranged into
sarcomeres)
 Stimulated by
Autonomic nervous system ( involuntary)
Hormons ( vasoconstriction & vasodilators)
adrenalin

28. EFFECT OF STIMULUS:
a- In skeletal Muscle:
• Threshold Stimulus:
no responds occur.
• Minimal Stimulus:
responds by minimal observed line.
• Submaximal Stimulus:
increasing the stimulus, the number of
responding fibers increase
• Maximum Stimulus:
all muscle fibers contract.
• Supra-maximum Stimulus:
increasing the stimulus, no more effect.
B- In cardiac Muscle:
• Sub-minimal stimulus;
no responds occur.
• Threshold value;
all muscle fibers
respond,increasing
stimulus no more effect
will resulted.

31. Steps of Contraction:
• Release of transmitter at motor end
plate.
• Generation of action potential.
• Inward spread of depolarization
along T-tubules.
• Release of Ca++ ions.
• Binding of Ca++ ions to troponin C.
• Uncovering myosin binding sites on
actin.
• Formation of cross-Linkage between
actin and myosin
• Sliding of actin over myosin,
producing shortening.

33. Steps Of Relaxation:
•Ca++ ions pumped back
into sarcoplasmic
reticulum.
•Release of Ca++ ions from
troponin.
•Cessation of interaction
between actin and
myosin.

34. Changes accompanying muscle contraction:
Thermal Change:
Heat of contraction and relaxation.
PH Changes:
Accompanied the chemical changes, acid by
splitting ATP or base by breakdown of CP.
Electrical change:
Direct or indirect depolarization through the
connected nerve.
Chemical change:
(Aerobic or anaerobic) oxidative respiration,
CP is an immediate source of ATP ( phosphrelate
ADP).

35. Mechanical
changes:
Sliding of actin
filament over the
myosin filaments,
( cross bridge).