Amphibian graph & charts.pptx

Amphibian graph and charts for medical students

1. Amphibian graph & charts By Shama Physiology Department

2. General introduction Gastrocnemius- sciatic preparation by dissecting Frog Why Frog? Easily available, cold blooded animals, tissue can survive in vitro without oxygenationand temp0erature control. Easy to handle

3. Appliances used in amphibian experiments Stimulating device Recording device Lucas chamber, kymograph, galvanic current

4. Procedure of preparation Stunning of Frog- blow on its head against the edge of table. Pithing of frog – destroy brain and spinal cord Dissection of sciatic nerve Dissection of gastrocnemius muscle. Ringer solution ( NaCl, CaCl2, KCl , NaHCO3)

5. Simple muscle twitch- An adequate stimulus applied to the nerve of a skeletal muscle gives rise to a brief contraction of the muscle followed by relaxation.

6. Causes of latent period:- Conduction of impulse along nerve Neuro muscular transmission Excitation- contraction coupling Stretching of SEC Inertia of lever

7. Action potential & SMT

8. Effect of Temperature on SMT By changing temperature of ringer solution First, record in warm ringer solution (38 ° -40°) then cold ringer solution (10 -12 °) cos cold ringer inactivates muscles & it is defficult to revive it. Should not exceed 42° coz it may denatured muscle proteins. What is heat rigor?

9. Effect of 2 successive stimuli on skeletal muscle contraction Summation means increase in the activity of a tissue produced by multiple stimulation. 2 types of summation:- summation of stimuli and summation of contraction. If second stimulus falls during latent period of muscle, no additional response will be there (completely refractory) If applied later, second response leading to development of tension (summation of effects) due to beneficial effects (release of Ca++, increase in temp, decrease in viscosity, decrease in inertia of recording)

10. Effect of 2 successive stimuli on skeletal muscle contraction

11. Effect of increasing strength of stimulus on skeletal muscle contraction Threshold of excitation of different motor neurons which supply a single skeletal muscle varies. Therefore, with the increase in strength of stimulus more and more motor units get recruited and the height of contraction increases. Each motor neuron and all muscle fibers it supplies constitute a motor unit.

12. Dubois Raymond induction coil consist of primary and secondary coil. Induced current is stronger at break than at make. Tap key to start giving stimulus

13. Effect of increasing strength of stimulus on skeletal muscle contraction. Height of muscle contraction at make and break shocks

14. Effect of load on skeletal muscle contraction. Load applied to muscle n 2 ways: Afterload & pre-load ways After-loaded is the condition in which the load starts to act on muscle after contraction has begun. Example: lifting of a weight from ground under normal condition. Pre-loaded is the condition in which the load acts on the muscle before it begins to contract. Example: continuous contraction of antigravity muscle to maintain body posture.

15. Muscle movements and contraction

16. Pre-load & After-load

17. Calculation of work done

18. Effect of increasing frequency of stimuli on skeletal muscle (12.5mm/sec) Treppe & staircase phenomenon- when a series of maximal stimuli are applied to muscle at a frequency so successive stimuli fall during relaxation phase therefore, it occurs an increase in tension developed. Clonus: successive stimuli falls during mid relaxation period. Tetanus: repeated maximal stimuli during contraction phase, activation of contractile mechanism occurs repeatedly before any relaxationand fuse into a continuous contraction.

19. Effect of increasing frequency of stimuli on skeletal muscle contraction

20. Genesis of Fatigue in skeletal muscle (640mm/sec) Fatigue is a temporary reduction of working capacity of a cell, organ or organism. Reversible phenomenon. No longer response because of Lack of of nutrition Accumulation of waste metabolites Depletion of Ach stores

21. Genesis of Fatigue ( contration remainder due to incomplete relaxation following depletion of ATP)

22. Determination of conduction velocity of sciatic nerve (640mm/sec) Stimulate the nerve at its muscle end (M-curve) Stimulate the nerve at its vertebral end (V-curve)

23. Conduction velocity of sciatic nerve

24. Factors affect conduction velocity of nerve Diameter of nerve fiber Presence or absence of myelination. Temperature Conducting media in which nerve is placed. RMP

25. THANK YOU