Ampibian-Graphs-I-MBBS-23-24-Batch (1).pptx

Important for first year mbbs students

1. Amphibian Nerve muscle experiments Dr. Kalpana B Associate Professor Department of Physiology

2. At the end of class student should be able to: Explain the response of muscle to a brief single electrical stimulus . Discuss the effect of increasing strength of stimuli,two successive stimuli and multiple stimuli on muscle contraction Outline the effect of load, temperature and velocity on muscle contraction

3. Competency no 3.7

4. Instruments used in amphibian Experiments Kymograph Muscle Trough

5. Inductorium

6. Myograph board with stand

7. Simple muscle twitch

8. The contraction and relaxation of a muscle in response to a single adequate stimulus. Phase of contraction followed by relaxation phase. AB-latent period(LP) BC-contraction phase(CP) CD-relaxation phase(RP) 1. What are the duration of LP,CP,RP LP-0.01 s CP-0.04 s RP-0.05 s

9. 2. What are the causes of latent period? Time taken for impulse to travel from nerve-NMJ Time taken to stimulate muscle Time taken for excitation-contraction to occur Time taken for lever to overcome inertia Time taken to overcome the viscous resistance of muscle.

10. Effect of increasing strength of stimuli on muscle contraction

11. 1. What is the effect of increasing strength of stimuli on muscle contraction Amplitude of contraction increases with increase in the strength of stimuli.

12. 2.What are the factors that affect the magnitude of contraction Number of motor units activated by the stimulus the strength of stimulus the frequency of stimulus

13. Effect of 2 successive stimuli on muscle contraction 1 ) beneficial effect 2 ) superposition 3 ) summation

14. What is beneficial effect Second stimulus- immediately after the muscle relaxes following the first contraction. Availability of more Ca++ Second stimulus releases Ca ++ and adds to the remaining Ca ++ from the first contraction

15. 2. What is incomplete summation 2 stimuli-second stimulus falls during relaxation period of first twitch. Incomplete summation

16. 3. Define Summation Second stimulus is applied during contraction period of the first stimulus

17. Effect of multiple stimuli on muscle contraction 1.Staircase phenomenon/treppe 2. clonus 3. Tetanus

18. 1. Define treppe/staircase phenomenon progressive increase in force of contraction-first few contraction Maximum uniform tension/contraction is reached.

19. 2. What are the causes of staircase phenomenon Beneficial effect of higher Ca++ concentration Increased temperature in muscle. Decreased viscosity of sarcoplasm

20. 3. What is tetanus and clonous Tetanus Muscle is stimulated repeatedly at a very high frequency there is sustained contraction. Incomplete tetanus/clonus Frequency below tetanisable frequency Incomplete relaxation between contraction.

21. Genesis of Fatigue 1. Define Fatigue Repeated stimulus-tension developed in the muscle gradually decreases. Decrease in muscle tension as a result previous contractile activity.

22. 2. What are the changes in the fatigue curve? Decline in the amplitude of contraction. Decrease in shortening velocity Relaxation period is prolonged

23. 3. What is contraction reminder? Incomplete relaxation-state of partial contraction decrease in ATP and accumulation of metabolites

24. Effect of load on muscle contraction What is freeload(Preload) and afterload in the muscle ? Preload -load on muscle before contraction Afterload -load on muscle after muscle starts contracting Work efficiency of muscle increases in preload and in afterload it decreases.

25. 2 . What are the effect of load on muscle contraction in preload and afterload condition Afterload Latent period increases, amplitude of contraction decreases with increase load, contraction period decreases and work done is less. Preload Height of contraction increases, no change in contraction time.

26. 3. Give examples for preload and afterload in human beings Lifting heavy load is an example for afterload and throwing a stone is example for preload

27. Effect of temperature on muscle contraction Heat rigor Moderate high temp(40 · C)- increase in amplitude of muscle curve Cold rigor At low temperature. amplitude of contraction decreases. At high temp- above (60 · C) - coagulation of muscle proteins Stiffening and shortening of muscle fibers.

28. Effect of velocity on nerve conduction 1. What are the factors affects conduction velocity Diameter and myelination of nerve fiber Temperature

29. Isometric contraction What is active tension, passive tension and total tension on skeletal muscle Passive tension Muscle fiber is stretched passively Total tension Stretched muscle when stimulated Active tension Tension created by cross bridge movements

30. Summary

31. References Text book of practical physiology 4 th edition G K pal and Parvati pal Text book of practical physiology for MBBS A K Jain AEJ 42