Bio22 Lab - Exercise 13 (Nervous Response: Decerebrated Frog) Discusses how a decerebrated frog reacts to different stimuli. Discusses why this is so. References: Campbell et. al., Biology Hallare, Student Handbook in Gen. Zoology Part 2

1. Nervous Physiology
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.