LAB 5 SYNAPTIC FATIGUE

• Primary objectives of the experiment:

  • To determine the primary seat of fatigue in an intact body
  • To investigate the effect of acetylcholine as the sylactse
• Differentiate between the synapse and the myoneural junction
• Materials and equipment needed:

  • Stimulating apparatus
  • Dissecting set
  • Frog
• Procedure:

  • Single pitch a frog and expose both sciatic nerves and gastrocnemius muscles
  • Stimulate the left sciatic nerve repeatedly until the right gastrocnemius muscle ceases to contract
  • Transfer the electrodes to the right sciatic nerve and stimulate it with the same intensity of stimulus
• In the study of fatigue in an intact body, it is important to consider the components of a reflex arc:

  • Receptor
  • Efferent nerve fiber
  • Synapses located in a central integrating station
  • Efferent nerve fiber
  • Effector organ
• Corresponding structures involved in the experiment:

  • Receptor: PROPRIOCEPTORS located in the muscle
  • Afferent and efferent nerve fibers: sciatic nerve
  • Synapses: located in the spinal cord
  • Effector organ: muscle
• Definition of synapses:

  • Functional connection between the axon of a presynaptic cell and the dendrite of another nerve cell
  • Involves a complex process allowing grading and modulation of neural activity
• When left sciatic nerve is stimulated repeatedly, both gastrocnemius muscles contract bilaterally due to connections on both sides at the CNS

  • Stimulation of right sciatic nerve also results in contraction of both muscles
• Primary seat of fatigue in an intact body is concluded to be the synapse, as stimulation of both sciatic nerves evoked responses on both gastrocnemius muscles