All the basic info regarding skeletal muscle

1. DR.NAILA GHOURI

2. STRUCTURE OF SKELETAL MUSCLE
 Each skeletal muscle consist of elongated fiber called
as MUSCLE FIBER.
 It is a complete cell with cytoplasm called as
sarcoplasm and bounded by an outer membrane called
sarcolemma
 It has many nuclei
 Each muscle fiber
Consist of many
Small fibers called
MYOFIBRILS.

4.  MYOFIBRILS
 Contain special part SARCOMERE, found in straight
line.
 Actual unit of contraction.
 Each sarcomere is separated from each sarcomere by a
line called Z-LINE

5.  Between 2 Z-lines 2 zones are present
1. DARK ZONE
2. LIGHT ZONE
 These zones are responsible for the striation on
skeletal muscle.
 Myofibril
Consist of many
Small parts called
As MICRO
FILAMENTS.

6.  MICROFILAMENTS:
 They are of two types
 Around each thick myosin filament 6 thin
filaments are present.
THICK FILAMENTS THIN FILAMENTS
MYOSIN ACTIN
TROPOMYOSIN
TROPONIN

8.  Dark band is called as A-band
 Light band is called I-band
 Between 2 dark A bands a clear line is present called
H-line
 In the centre of light I-band a black line is present
called as Z-line
 The region between 2 Z-lines is SARCOMERE

9. SARCOMERE

10.  Thick filaments have cross bridges which are thick and
swollen along the ends called as BULBOUS HEADS.
 During contraction these cross bridges connect with
the actin filament.

12. MECHANISM OF MUSCLE
CONTACTION

13.  It indicates that filaments do not contract but they
slide over each other so that is why this theory is called
as SLIDING FILAMENT THEORY.
 This theory was proposed by HUXLEY
 Due to this sliding movement muscle contracts and
reduces in size.
 In 1 sec each cross bridge shows its movement 50-100
times or more than that.
 This shows that muscles contract very rapidly.
 Drawback :Due to the utilization of energy and rapid
movement they get tired very early

14. Why muscles get fatigue ??
why why
Why why
Why why why why

15. MUSCLE FATIGUE:
 When muscles become functionless temporarily it is
called as muscle fatigue.
 Muscle require energy for their contraction which they
obtain from anaerobic respiration and
fermentation (without O2)
 As a result glucose will b converted to lactic acid.
 If this anaerobic respiration continues then this end
product will start to accumulate in the muscles leading
to the muscle fatigue.

17. I am so tired please let me take
some deep breaths!!!!!

18.  Now the heavy exercise is stopped and muscles are
allow to respire in presence of sufficient oxygen which
is called as Aerobic respiration.
 The amount of O2 required to remove lactic acid from
tired or exhausted muscle is called as OXYGEN DEBT.
 It will convert lactic acid into CO2 and H2O or
directly into glycogen
 As a result muscles will again become normal and are
ready to perform their normal function.
 Exercise is good for keeping the muscles strong 

19. FACTORS AFFECTING MUSCLE
CONTRACTION
 NERVE IMPULSE :
 Signals are received from nervous system through
motor nerves that tells the muscle to contract.
 In absence of this message muscles are unable to
contract.
 Example , POLIO

20.  CALCIUM:
 Ca ions are released from sarcoplasmic reticulum of
muscle fiber in response to the nerve impulse.
 A substance ACETYLCHOLINE is released from from
neurons leading to more Ca+ release.
 These calcium ions now attach to troponin molecule.
 As a result binding site for myosin bulbous heads will
get exposed on actin filament.
 Now actin and myosin start their sliding movement.
 When nerve impulse complete its action then
everything will start working in backward direction.

24.  ENERGY:
 Energy is required for muscle contraction which is
obtained from food.
 This food energy is stored in the form of glycogen.
 From glycogen it is transferred to CREATINE
PHOSPHATE.
 In the last step ATP will b synthesized which is an
energy rich compound and helps in muscle
contraction.

26. I am so strong !!!!

27. ABNORMAL MUSCLE
CONTRACTION
 TETANY:
 When striated muscles start contraction automatically
it is termed as tetany
 Cause: deficiency of Ca+ in blood
 Result: nerves stimulate the muscles and before
getting their actual position actin and myosin start to
contract abnormally.
 There will b continous contraction.

28.  CRAMPS :
 It is a muscle pull.
 Usually occurs in arm.
 Also an abnormal contraction like tetany but with
different cause.
 Cause :
1. Reduced sugar in blood
2. Dehydration
3. Electrolyte imbalance
4. Extra exercise
5. Decreased blood supply