Bio22 Lab - Exercise 13 - Nervous Response (decerebrated frog)
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The decerebrated frog experiment tested the animal's responses to various stimuli, including touch, electric shock, heat, and chemicals, despite the removal of the forebrain. The results showed that the frog still reacted, indicating the cerebellum's role in motor control remains functional. This suggests that certain reflexive actions can occur without higher brain functions.
Bio22 Lab - Exercise 13 - Nervous Response (decerebrated frog)
- 2. Introduction O “The forebrain, which contains the olfactory bulb and cerebrum, has activities that include processing of olfactory input (smells), regulation of sleep, learning, and any complex processing. The midbrain, located centrally in the brain, coordinates routing of sensory input. The hindbrain, part of which forms the cerebellum, controls involuntary activities, such as blood circulation, and coordinates motor activities, such as locomotion.” - Campbell et. al., Biology, Tenth Ed. p. 1085 (2014)
- 3. Hypotheses O Null Hypothesis: The decerebrated frog will not respond to the stimuli. O Alternative Hypothesis: The decerebrated frog will respond to the stimuli.
- 4. Procedure 1. Make the frog sleep using Chloroform (CHCl3). 2. Open the frog of the mouth. 3. Cut the upper portion of the head from just behind the eyes (between the eyes and tympanum). 4. Expose the frog to the different stimuli.
- 6. Touch O With forceps, pinch the hind toe gently, then firmly. O Response: The frog pulled back from the forceps
- 7. Electric Shock O Apply the electrodes from the secondary coil of an induction coil (adjusted for a light shock) to the hind foot and then close the switch key for an instant. O Response: The frog jerked.
- 8. Heat O Bring a hot iron rod (such as a soldering iron) close to some part of the trunk or a limb. O Reaction: After a while, the frog tried to flip over.
- 9. Chemical O Moisten a small disc of filter paper in 10% acetic acid and apply it to different parts of the body (abdomen, back, arm, hind leg, toe). After each test, wash the skin well with water. O Reaction: After a while, the frog tried to flip over.
- 10. Righting the Body O Turn the frog on its back and see whether the animal can regain its normal position. O Reaction: The frog tried to move back to its normal position.
- 11. Compensatory movement O Place the frog in a petri dish, then rotate the dish, first clockwise, then counter clockwise; also tilt the dish from side to side. O Reaction: The frog tried to right itself.
- 12. Summary of Responses: Stimuli Response (+/-) Touch + (delayed) Electric shock + Heat + (delayed) Chemical + (delayed) Righting the body + Compensatory movement + Overall +
- 13. Conclusion & Discussion O The decerebrated frog reacted to the different stimuli despite not having a forebrain. This is so because the part of the brain that controls locomotion, the cerebellum, remains intact.