Sheep Brain Dissection - Cccprofessorlou

Sheep Brain d organisms/preserved animals %28mammals%29/sheep organs/preserved sheep dissection.doMichigan State University Neuroscience ProgramBrain Bee Enrichment WorkshopOctober 6, 2012Material and information from this handout was adapted from the following sources:Barnard College: euroscience: Exploring the Brain, Bear et al., 2007The Sheep Brain: A Basic Guide, Cooley & Vanderwolf, 1979BrainFacts.org

Introduction to anatomical termsDorsal (Latin: dorsum back): the top of the brainVentral (Latin: venter belly): the underside of the brainAnterior: front of the brainPosterior: back of the brainCoronal cuts: parallel to the anterior/posterior axisHorizontal cuts: parallel to the dorsal/ventral axisMedial: towards the midlineLateral: towards the sideSagittal cuts: parallel to the medial/lateral axis

Surface structures of the brainThere are many structures of the brain that can be identified on the surface of the brain. Locatethe structures below (illustrated on the following page) and try to identify the functions of suchareas. **Be sure to ask your volunteer to help you if you need help associating functions todifferent brain areas.Sulcus (plural: sulci); the hillsGyrus (plural: gyri); the valleysMedial longitudinal fissureCentral sulcus (aka Sylvian fissure)CerebrumMatch the following structures with their functions:StructuresFunctionsCerebellumControls respiration, blood glucose levels, and heartrhythmsMedullaReceives sensory info & sends it to the brain, butalso receives motor info from the brain and sends itto the limbsPonsInvolved in motor learning and timing ofmovementsSpinal cordIncludes tracts that conduct signals from thecerebrum down to the cerebellum and medulla, andtracts that carry the sensory signals up into thethalamusOlfactory bulbs – What is the function of the olfactory bulbs? Compare the size of the olfactory bulbs in asheep relative to the total brain size compared to the olfactory bulbs in a human brain. What could account forthe size differences in the olfactory bulbs when comparing different species?

Primary Motor CortexParietal LobeTemporal LobeOccipital LobeFrontal LobePrimary Sensory Cortex

The cerebral cortex can be divided into 4 lobes. Identify each of these lobes and associate thedifferent functions listed below with the correct lobe of the brain (each lobe many have multiplefunctions from the list).A. Processing auditory informationB. Initiating and coordinating motor movementsC. Processing sensory informationD. Problem solving and planningE. Visual processingF. Attention and LanguageG. PersonalityH. Short-term memory and learned emotional responsesFrontal lobeA portion of the frontal lobe is defined as the primary motor cortex. Locate this structure on the sheepbrain. What is the role of the motor cortex?Parietal lobeA portion of the parietal lobe is defined as the primary sensory cortex What would happen if we wereto electrically stimulate this area in a sheep that was alive?The entire surface of the body is represented in the primary sensory cortex. Interestingly, some parts of thebody have more cortical space that others. The figure below (right) is known as the homunculus and illustrateswhat the body would look like based on the amount of cortical space devoted to each body region (larger bodyregions have more cortical space). What parts of the body do think are more sensitive to touch based on thisfigure?Occipital lobeTemporal lobe

Ventral view of the brainMammals have 12 pairs of cranial nerves. Some of these nerves are sensory nerves, other aremotor nerves, and some are both sensory and motor (mixed). Locate these 12 nerves on yoursheep brain, match each function with its associated nerve, and circle whether each nerve issensory, motor, or both.A.B.C.D.E.F.G.H.I.J.K.L.Controls muscles of the tongueControl muscles of the neck and shoulderVisionEye movements; pupillary constrictionEye movementsEye movementsSmellSensations of the skin, muscles and teeth; controls biting and chewingMediates visceral sensations; Innervates larynx, pharynx, gastrointestinal and cardiovascular systemsHearing and sense of balanceTaste and motor movements of the throatTaste, movements of the face, winking, smiling, secretion of tearsI.Olfactory Nerve – What would happen if we were to damage the olfactory nerve in a living sheep?(Sensory/Motor/Mixed)II.Optic Nerve – You may notice that each optic nerve (containing axons of ganglion cells from asingle eye) converge at the optic chiasm. What is happening here? (Sensory/Motor/ Mixed)III.Oculomotor Nerve – Based on the naming of this nerve, what do you think the function is?(Sensory/Motor/ Mixed)IV.Trochlear Nerve – (Sensory/Motor/ Mixed)V.Trigeminal Nerve – (Sensory/Motor/ Mixed)VI.Abducens Nerve – (Sensory/Motor/ Mixed)VII.Facial Nerve – (Sensory/Motor/ Mixed)VIII.Vestibulo-cochlear (Auditory) Nerve – (Sensory/Motor/ Mixed)IX.Glossopharyngeal Nerve – (Sensory/Motor/ Mixed)X.Vagus Nerve – (Sensory/Motor/ Mixed)XI.Spinal Accessory Nerve – (Sensory/Motor/ Mixed)XII.Hypoglossal Nerve – (Sensory/Motor/ Mixed)

White versus gray matterYou may notice that some areas of the brain are white (e.g. optic nerve; white matter), while others are a darkercolor (more ivory or gray; gray matter). What could account for these differences? Think about the differentcomponents of a neuron (see diagram below) and how this may influence the color differences you see. Also,many of the white structures you see are nerves. What part of the neuron makes up 010/04/neuron-psychologist.htmlDiseases of the nervous system: Multiple sclerosis (MS)MS is an autoimmune disorder that is caused by the body’s own immune system attacking the myelinsheath of axons. Why is the loss of myelin a problem?Two common areas that are damaged in MS are the optic tract and the cerebellum. What kinds of symptomsmay patients with MS have based on this information?

Midline view of the brainWe will now be making the first cut to observe some medial structures of the brain. Place thebrain in the dissection pan and cut down the longitudinal fissure, the sulcus that marks theseparation of the left and right cerebral hemispheres. Try to make a single smooth cut down themiddle.Margaret Bell, MSUIdentify the structures in bold and match them with their associated function (listed below)A. “Little brain”; balance and motor learningB. Relay station of the brain; relays sensory, spatial, and motor information to the cortexC. Consists of the superior and inferior colliculi (receive visual and auditory information); Containsnuclei that regulate reward mechanisms and moodD. Receives sensory information and sends it to the brain, but also receives motor information from thebrain and sends it to the limbsE. “Bridge”; Connects midbrain to the medullaF. Connects the left and right hemisphereG. Links the nervous system to the endocrine system; controls body temperature, hunger, thirst, fatigue,sleep, & circadian rhythmsH. Autonomic functions such as respiration, heart rate, blood pressureI. Endocrine gland; main site of melatonin productionCorpus callosum – If this structure was cut in a living sheep, what wouldn’t be able to take place?ThalamusHypothalamusPineal body

MidbrainPonsMedullaSpinal cordCerebellumThe ventricular system (Lateral ventricle, Third ventricle, Cerebral aqueduct, Fourth ventricle)The brain contains multiple cavities or chambers filled with cerebrospinalfluid (CSF). What do you think is the purpose of this fluid in the brain?Besides filling the ventricles, CSF also surrounds the brain. Why might thisbe nd brain.htm

Coronal SectionsNow put the two halves of the brain together to make three coronal cuts (shown below) andlocate the labeled structures.Cut #1 - Through the anterior portion of the corpus callosumCut #1LateralVentricleThe caudate nucleus and putamen are part of the basal ganglia. What is the primary functionof the basal ganglia?What neurodegenerative disease is associated with a loss of dopamine neurons that project tothe basal ganglia?

Cut #2 – Through the thalamus and hypothalamusCut #2What is the function of the hippocampus? What is the name of a neurodegenerative diseasethat effects this structure?Cut #3 – Through the caudal end of the cerebrum (anterior to the cerebellum), through thesuperior colliculus and in between the midbrain and the ponsCut #3

Hippocampal formation and dorsal brainstemObserve the sheep brain that has had the cerebellum and the caudal portion of the cerebralcortex removed. Find the structures labeled in the figure below.

Ventral view of the brain Mammals have 12 pairs of cranial nerves. Some of these nerves are sensory nerves, other are motor nerves, and some are both sensory and motor (mixed). Locate these 12 nerves on your sheep brain, match each function with its associated nerve, and circle whether each nerve is sensory, motor, or both.