Brain Sheep Dissection

Purpose: To examine the parts of the sheep brain and compare it with the part of the human brain and relate functions of the brain. Materials: Sheep's brain, brain models, lab manual, disposable gloves, dissecting tray, and instruments. Procedure: Place the brain on a dissection tray with the dorsal side up. The parts of the brain, cerebrum, medial longitudinal fissure, central sulci, cerebellum, and the four lobes can be located on the dorsal side. Turning the brain on the ventral side facing up on the dissection tray, medulla, pons, brain stem and spinal cord can be located. The olfactory bulb, which lies below the frontal lobe, the optic chiasma formed by the crossover of the optic nerves can be located, also the twelve cranial nerves can be located. Then face the brain on a dissection tray dorsal side facing up. Using a scalpel cut through the corpus callosum connecting the left and right hemispheres. The four ventricles can be seen in this cross-section; the third and fourth connected by an aqueduct. The location of the thalamus, hypothalamus, pineal body, pons, medulla and other brain structures can be seen in this cross-section. When all structures of the brain have been examined, dispose of the dissected brain in the specific location. Results: a) External structures: brain stem, transverse cerebral fissure, cerebellum, olfactory bulb, optic nerve, oculomotor nerve, trochlear nerve, facial nerve, vestibulocochlear nerve, hypoglossal nerve, infundibulum, mammillary body, cerebral peduncle, pons, trigeminal nerve, abducens nerve, medulla oblongata. b) Internal structures: cerebral hemisphere, corpus callosum, frontal lobe, fornix, interthalamic adhesion, cerebral peduncle, optic chiasma, parietal lobe, cerebellum, pineal gland, arbor vitae, corpora quadrigemina, fourth ventricle, medulla oblongata, pons. Conclusion: After completing the dissection I realized many things I did not know about the brain before, for example, there are so many structures with specific and unique function within the brain that helps us to function effectively. Questions: 1. The sheep’s brain has more developed olfactory bulb when compared to the human brain because because animals usually depend on their olfactory senses to smell and send information to the brain. Humans depend on other senses, like vision and auditory to sense information and send to the brain. 2. The human brain is rounded, whereas the sheep’s brain is elongated/ oval in shape. 3. The human brain has a larger frontal lobe than the sheep’s brain. 4. The human brain and sheep brain have the major difference that humans can think, write, invent or create with their brains, whereas sheep cannot. Give examples of any 5 of these differences: ● The human brain has the ability to think logically and critically to make decisions. ● The human brain has the ability to write language ● The human brain has the ability to draw connections and conclusions to create an idea. ● The human brain has the ability to remember; long term memories and short term memories. ● The human brain has the ability to use technology. 5. By examining the sheep brain, a) What conclusions might you draw about how the brain works? The brain works through the trillions of nerve cells in the brain in patterns that coordinate our thought, emotion, behavior, movement, and sensation. The nerves in the brain connect the brain to the rest of your body, so communication occurs quickly. All the parts of your brain work together, each part is responsible for a specific function controlling all aspects of your body. b) What conclusions might you draw about brain function based upon brain structure? Brain function is based on where the structure is located, in the anterior, medial or posterior regions of skull, human brain can be divided into three major parts, which are the, forebrain, midbrain and hindbrain. These major divisions are composed into smaller sections, with each sections performing a specific role. 6. In the 1950’s brain researcher Roger Sperry and his colleagues studies patients with brain hemispheres had been functionally separated. What part of the brain was severed or not functioning in order for the test subjects to have independently-functioning cerebral hemispheres? Corpus Callosum was severed and not functioning in order for the test subjects to have independently-functioning cerebral hemispheres. 7. Explain the case of Phineas Gage Gage suffered a major personality changes after a brain trauma. John Martin Harlow, the doctor noted an iron was found behind his head after an accident. Harlow cleaned Gage’s wounds by removing small fragments of bone and then closed the larger wound at the top of Gauge’s head with straps. Gage’s wounds were not treated surgically, but were instead left open to drain into the dressings. The damage to Gage’s frontal cortex had resulted in a complete loss of social inhibitions, which often led to inappropriate behaviour. In effect, the tamping iron had performed a frontal lobotomy on Gage. Gage’s skull was damaged in three places: there is a small wound under the left zygomatic arch where the tamping iron entered; the orbital bone in the base of the skull behind the orbit of the eye; and the third, and largest, wound is in the top of the skull, where the tamping iron exited. The exit wound was enormous, and never healed. 8. Explain the end result of frontal lobotomy This means cutting a lobe of the brain, the frontal lobe. Only a small percentage of people supposedly got better or stayed the same, for many people, lobotomy had negative effects on a patient's personality, initiative, inhibitions, empathy and ability to function on their own; basically can turn into a vegetative state. 9. What are the effects if Electrical or mechanical stimulation of the: a) The Motor Cortex The effects of stimulation of Motor Cortex causes muscle activity. b) The Somatosensory Cortex The effects of stimulation of Somatosensory Cortex causes sensory perceptions.