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Sheep brain Dissection
1. Place the brain on a dissecting tray, top side up, so that you are looking down at the cerebrum.
2. Each of the grooves is called a sulcus; each of the ridges or folds is called a gyrus. These terms are not especially important, but you may later come across the plural terms “sulci” and “gyri”, and now you know what they mean.
3. Compare the sheep brain to the life-sized models of the human brain. Look closely.
How exactly are they different? How are they similar?
4. Try to identify the four lobes of the cerebrum:
Frontal lobes are at the front.
This controls motor functions in sheep. Human frontal lobes are much larger and control more “human” abilities and behaviors.
Parietal lobes are behind the frontal lobes.
These receive and process touch sense information.
Temporal lobes are on the sides of the brain.
These receive and process auditory information.
Occipital lobes are at the back of the brain
These receive and process visual signals.
5. Find the cerebellum, just underneath the occipital lobe.
This controls muscle coordination.
6. Turn the brain over.
7. Look for three parts of the brainstem: the medulla, the pons and the midbrain.
The brainstem is responsible for basic functions like heartbeat, respiration and digestion. The midbrain also produces the important chemical dopamine which makes us feel good after we do anything that aids our survival (eat, win a contest, try to reproduce, etc.)
8. Also look for the beginning of the spinal cord.
9. Look for the olfactory bulbs underneath the frontal lobes.
The olfactory bulbs receive smells, and these are processed nearby.
10. You may be able to see parts of the optic nerves crisscrossing as they travel from where the eyes would have been back to the occipital lobes. These nerves transmit light signals from the eyes to the occipital lobes.
11. Place the brain on the tray, top side up once more. Using a scalpel, carefully cut the brain exactly in half lengthwise.
12. Using the picture on page 22 handout (the back of this sheet), try to identify the
Thalamus – where sensory information is first received before being relayed to various parts of the cerebral cortex.
Hypothalamus – just under the thalamus, an area that regulates basic functions like hunger, temperature, fluid balance and governs the pituitary gland that controls hormones. (The pituitary gland may or may not have been removed when the brain was dissected from the sheep.)
Pineal Gland or Pineal Body – a small gland that produces the chemical melatonin which helps regulate your “body clock” and sleep/wake cycle.
Corpus callosum – a thick white network of axons that makes important connections between the left and right sides of the brain.
13. Notice how the inside of the cerebellum forms an interesting tree-like pattern. Here you can clearly see the distinction between the gray portion of nerves (gray matter = cell bodies) and the white portion of nerves (white matter = axons) in the brain.
14. It may be possible to cut off the cerebellum then lift off the top layers of the cerebrum to expose the hippocampus and amygdala, but this is very tricky. The amygdala generates fear and anger, and the nearby hippocampus helps make long term memories.
Why is the close proximity of the hippocampus and the amygdala essential for survival?
15. Carefully dispose of the brain in the main garbage area, and wash your tray and utensils when finished.
http://www.hometrainingtools.com/articles/brain-dissection-project.html