GEN PHYSIO LAB EX 1-B

• Objective:

  • To prove that skeletal muscles possess independent irritability
  • To understand how curare exerts its effects at the myoneural junction
• Preparation:

  • Intocostrin is an aqueous solution of curare that inhibits skeletal muscles by neuromuscular blocking effect
  • Curare combines with protein molecules at the motor and plate region, blocking acetylcholine access and preventing its effects
• Materials and equipment:

  • Two watch glasses, two glass slides, intocostrin or lidocaine solution, frog
• Procedure:

  • Make two muscle nerve preparations and place them on watch glasses
  • Stimulate nerve of preparation A with minimal shocks and observe the response
  • Transfer the stimulus to the muscle of preparation A and note the response
  • Repeat the procedure three times at 5-minute intervals
  • Repeat the above steps with preparation B
  • Tabulate the results
• Report and Conclusion:

  • Muscle of preparation A did not contract after 10 minutes due to intocostrin causing competitive inhibition of acetylcholine action at the myoneural junction
  • Muscle of preparation B did not show any alteration in contraction since the myoneural junction was not involved
  • Skeletal muscle is capable of contraction even if the impulse does not pass the myoneural junction or the muscle was denervated, known as INDEPENDENT IRRITABILITY