LAB 1B PHYSIOLOGY

• Intocostrin is an aqueous solution of curare, a medication that inhibits skeletal muscles due to its neuromuscular blocking properties
• Curare operates by passively interacting with protein molecules in the motor and plate regions, preventing acetylcholine molecules from entering this location
• Acetylcholine is no longer capable of binding to the receptor protein, resulting in the inability to exercise its effects
• The myoneural junction comprises three primary components:

  • Nerve terminal: transmits signals from the nervous system to muscles, initiating muscle contraction
  • Synaptic cleft: the gap between the nerve terminal and the muscle's plasma membrane
  • Motor End Plate: the postsynaptic part of the neuromuscular junction, a thickened section of the muscle's plasma membrane that folds to create junctional folds
• Preparation A:

  • Nerve did not contract upon stimulation after 10 minutes due to immersion in intocostrin
  • Muscle contracted initially and after 5 minutes but not after 10 minutes due to intocostrin causing competitive inhibition of acetylcholine action
• Preparation B:

  • Demonstrated consistent and prolonged effects with both nerve and muscle responses indicating ongoing stimulation and contraction over the entire 15-minute period as the myoneural junction was not involved
• Neuromuscular/myoneural junctions allow skeletal muscles to irritate independently
• Each muscle fiber can react differently to different nerve signals due to distinctive connections with motor neurons, allowing for precise control and independent irritability
• Intocostrin blocks nicotinic acetylcholine receptors at the neuromuscular junction, preventing acetylcholine from causing muscular contraction
• Curare attaches to nicotinic acetylcholine receptors, blocking the action of acetylcholine and resulting in muscle paralysis by interfering with the regular flow of signals between muscles and nerves