Current Presentation is about physiology of Muscle Contraction and Relaxation with basic understanding for Graduates of Medical and Allied health sciences.

1. Dr. Aniket A. Shilwant
BAMS, MD
MUSCLE
PHYSIOLOGY

2. Classification MUSCLE PHYSIOLOGY
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 Appearance
Striated / Non-Striated
 Control
Voluntary / Involuntary
 Location
Skeletal
Smooth
Cardiac

3. Histology MUSCLE PHYSIOLOGY
Epimysium
• Surrounds entire muscle
Perimysium
• Surrounds bundles of muscle fibers
Fascicles
Endomysium
• Surrounds individual muscle fibers
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4. Histology MUSCLE PHYSIOLOGY
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 Muscle Coverings -
 Epimysium
 Perimysium
 Endomysium
 Fascicle, Fasciculus
 Tendon
 Aponeurosis
 Sarcoplasm
 Sarcolemma

5. Histology MUSCLE PHYSIOLOGY
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Sarcoplasm –
1. Nuclei
2. Myofibril
3. Golgi apparatus, Mitochondria, Sarcoplasmic reticulum
4. Ribosomes
5. Glycogen droplets, Occasional lipid droplets
6. Sarcotubular System
7. Sarcomere

6. Sarco-tubular System MUSCLE PHYSIOLOGY
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Transverse / T tubules – ECF
Longitudinal / L tubules – S-ER
Cisternae
Calcium

7. Sarcomere MUSCLE PHYSIOLOGY
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8. MUSCLE PHYSIOLOGY
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Sarcomere
Portion between 2 Z lines
Main contractile unit
Main structural and functional unit
Contains alternate dark and light bands
Contains myofilaments
In between dark band there is A white portion = H zone
In H zone A single dark line = M line
M line made up of myosin

9. MUSCLE PHYSIOLOGY
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Myofilaments
ACTIN
Thin filament
Each filament contains about 300-400 molecules of actin
Enclosed completely by tropomyosin
MYOSIN
Thick filament
Each filament contains about 200 molecules of myosin
2parts – one head and one tail portion
Head portion has 2binding sites-one for actin and other for ATP

10. MUSCLE PHYSIOLOGY
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Myofilaments
TROPOMYOSIN
Has 40-60 molecules
Completely covers actin filament
TROPONIN
Troponin I- binded with actin
Troponin T- binded with tropomyosin
Troponin C- binded with calcium ions

11. Histology MUSCLE PHYSIOLOGY
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12. MUSCLE PHYSIOLOGY
Actomyosin complex
Muscular contraction is due to Actomyosin complex
It includes three stages:
1. Excitation-contraction coupling
2. Role of troponin and tropomyosin
3. Sliding mechanism
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MOLECULAR BASIS OF MUSCULAR CONTRACTION

13. MUSCLE PHYSIOLOGY
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Action potential at axon terminal
Ca+ Channel open
Entry of Ca from ECF into axon
Release of Ach
Ach Receptor complex
Na+ Channel open of muscle
Entry of Na+ from ECF into muscle
Development of Endplate potential
Generation of Action potential
Excitation-Contraction Coupling Reaction
Muscle Contraction
NEUROMUSCULAR JUNCTION

14. Neuro-Muscular Junction MUSCLE PHYSIOLOGY
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15. MUSCLE PHYSIOLOGY
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Excitation of muscle by nerve impulse
Generation of action potential in muscle fiber
Spread of action potential via T tubules
Action potential in Cisternae
Release of Ca+ ions
Ca ions attach actin filament
Muscle contraction
EXCITATION CONTRACTION COUPLING REACTION

16. Neuro-Muscular Junction MUSCLE PHYSIOLOGY
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17. MUSCLE PHYSIOLOGY
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Release of Ca ions from cisternae of L tubules
Binding of Ca ions and troponin
Pulling of tropomyosin
Actin is exposed
Myosin head attaches with actin
With the power stroke tilting of myosin head
Myosin head gets detached back to original position
Myosin head attaches with new actin molecule
Acto-myosin complex
Muscle contraction
SLIDING MECHANISM OR SLIDING THEORY

18. MUSCLE PHYSIOLOGY
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Sliding Theory

19. MUSCLE PHYSIOLOGY
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20. MUSCLE PHYSIOLOGY
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21. MUSCLE PHYSIOLOGY
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After work done muscle fiber portion repolarises
Ca ion gets back into L tubules
Decreased content of Ca content in Sarcoplasm
Ca ions also releases and detached from Troponin C
Myosin head completely detaches from actin
Muscle relaxed
MUSCLE RELAXATION

22. MUSCLE PHYSIOLOGY
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Entry of Ca from ECF inside muscle
Ca + Calmodulin = Ca-Calmodulin complex
Activation of kinase (dependant on Myosin)
Phosphorylation of Myosin
Sliding of actin filaments
Muscle contraction
SMOOTH MUSCLE CONTRACTION

23. MUSCLE PHYSIOLOGY
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Ca from L tubules, gets back into Sarcoplasm
Dissociation of Ca-Calmodulin complex
Muscle relaxed
SMOOTH MUSCLE RELAXATION

24. MUSCLE PHYSIOLOGY
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25. MUSCLE PHYSIOLOGY
• Textbook of Physiology – Guyton & Hall
• Ganong’s Review of Medical Physiology
• Textbook of Physiology –Vander’s
• Essentials of medical physiology – Prema & K Sembulingam
• Image sources – Internet
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REFERENCES

26. THANK YOU ALL!!!
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MUSCLE
PHYSIOLOGY
Dr. Aniket A. Shilwant
BAMS, MD
Associate Physiology
Sharir Kriya Dept.
GJPIASR, The CVM University
ayuraniket18@gmail.com