Sheep Brain Dissection Guide Good Luck!! Laurie Hayes To begin • Get gloves and a rubber apron or lab coat. Goggles are available if you would like them. • Pick up dissection tray, dull probe, pins and labels • Obtain a sheep brain and share this with a partner (or 2) • Rinse the sheep brain to remove preservative Meninges of the Brain Brain is protected by the skull and 3 layers of membranes called meninges Observe Meninges • Examine the brain to see if there is a tough outer coat…This is the DURA MATER (literally means “tough mother”) • Now look for the stringy, web-like ARACHNOID MATER (literally means spider mother) beneath and stuck to the dura mater. The space under the arachnoid, the subarachnoid space, is filled with cerebrospinal fluid and contains blood vessels. • Look deeper and see an thin transparent membrane that follows the contour of the ridges (gyri) and valleys (sulci) of the brain. This is the PIA MATER ( means tender mother) Questions?? • What is the function of the meninges? • Describe the following meninges: Dura mater, Arachnoid mater, and Pia mater • What is meningitis? Main Brain Regions • Identify the cerebrum, brain stem) and cerebellum on your brain • Draw picture of sheep brain and label structures Cerebrum Cerebellum Brain stem Questions?? • Which part of the brain allows for 1) Balance 2) Breathing 3) Hearing and Vision Human vs Sheep • Compare the various areas of the sheep brain (cerebrum, brain stem, cerebellum) to the human brain. #4. How is it the same and How is it different? Human brain Identify Dorsal Structures • With the dorsal side up, identify the cerebral hemispheres, gyri, sulci,and longitudinal fissure on your sheep brain Questions?? • What does the longitudinal fissure divide? • What is the difference between gyri and sulci? • What is the purpose of the gyri and sulci? Lobes of the Cerebrum • Find the 4 lobes of the brain-frontal, parietal, occipital, and temporal • Using pins label each lobe • Teacher check Questions???? • Name the lobe that functions in a) Hearing b) Vision c) Touch d) Movement Corpus Callosum • At the longitudinal fissure, gently separate the two hemispheres and look down between them for the thick band of white fibers. This is the corpus callosum • What is its function? Identify Ventral Structures • Place the sheep brain ventral side up. • Identify the olfactory bulb, optic nerve, optic chiasm • Using pins label each structure. • Draw and label the structures in lab writeup Questions?? • How does the human brain’s olfactory bulb differ from the sheeps? • Which is able to smell more odors? • Look at the optic chiasma. What happens to the optic nerve (vision) at the optic chiasma? • Which side of the occipital lobe (right or left) “sees” for the right eye? Brain Stem • Look at the three parts of the brain stem-the midbrain (cerebral peduncle and mammilary body), pons and medulla oblongata • Pin and label parts • Teacher check Function • Mammillary bodies serve as relay stations for reflexes related to sense of SMELL • Cerebral Pedunclegroup of myelinated nerves Questions?? • Label your diagram with parts of midbrain and brain stem • What is the function of the medulla oblongata and pons? • Could you survive without them? • Why or Why not? Identify dorsal structures • Carefully pull the cerebellum away from the cerebrum. Don’t break any structures off. • Identify the pineal body, superior colliculi, and inferior colliculi. Functions-Reflex Centers • Inferior Colliculimovement of head and trunk in response to sound stimuli • Superior Colliculimovement of eyes, head and neck in response to visual stimuli Pineal Gland • Produces the hormone melatonin at night • Melatonin is the sleep hormone Questions?? • What is the function of the Pineal body? Midsagittal Section • Obtain a brain the has been cut in half • Locate the brain stem parts: the medulla oblongata, the pons, cerebrum, and cerebellum Cerebellum • Look at the cross section of the cerebellum. The inner structure is called the arbor vitae (living tree). Why is this a good name for it? Midsagittal Section • Locate the corpus callosum, thalamus,lateral ventricle, fourth ventricle and cerebral aqueduct Questions – What is the function of the ventricles? – The cerebral aquaduct allows for the circulation of the cerebral spinal fluid through the ventricles. What do you think would happen if the duct became blocked? – How would that affect brain tissue? The End!! Good bye or in sheep language BAA BAA