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PHGY 210 (24)


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McGill University
PHGY 210
Ann Wechsler

Nervous systemMajor divisions1 Afferent Cell bodies outside of CNS2 Efferent Cell bodies in CNS3 Cranial nerves somatic visual olfactory taste auditory4 Spinal nerves somatic sensation Touch temperature pain proprioception5 Somatic efferent innervates only skeletal only excitatory motor neurons6 Autonomic efferent innervates motor neurons smoothcardiac muscle excitatoryinhibitory7 EntericDivisions of spinal cordThoracic nerves 12 segments shoulders chest upper abdomenCervical 8 segments that innervate neck shoulders arms handLumbar nerves 5 segments for lower abdominal wall hips and legsSacral nerves 5 segments genitals and lower digestive tractCoccygeal nerves 1 segmentCranial nerves 12 of them1012 go into brain stemOlfactory nerve and optic nerve do not go into the brain stemDevelopment of nervous systemEggdividing into ball of cellsinner cell mass blastocyststructurescavitiesweek 3blastocyst contains embryonic disctop layerneural plateDevelopment of neural tubeEctodermCNS and PNSMesodermDura layersEndodermDigestive system34 week Neural groove pinches off to form neural tubeectoderm layerTube becomes CNS and part of PNSNeural tubeTubes form neural tubes forms vesicles fore mid hindbrainForebraincerebral and thalamusMidbrainmidbrainHindPons Medulla and cerebellumTail becomes the spinal cordCavity in neural tube becomes the ventricles and the central canalCSF and ventricles2 circulatory system in brain CSF ventricle and the BLOODCSFProduced in ventricles 150mL of in head at any time2 biggest ventricleslateral ventriclesLining of ventricles Choroid plexus produces CSF takes bloodsecrete CSF into ventriclesCSFBrain floats in CSF produces 500ml dayCSF functions1 Cushions the CNS specific gravity of CSF and the brain are equal2 Provides nourishment to the brain3 Removes metabolic waste through absorption at arachnoid villiComposed of sterile colourless acellular fluid that contains glucosePassive circulation no pumpingCirculation Foramen of monro3rd ventriclecerebral aqueduct4th ventcentral canalExit routes 3 openings foramen of lushka 2 lateral and magendie CSF goes out to subarachnoid spacecomes up to the toparachnoid villi suck and empty CSF into dural sinus which is connected to venous blood supplyHydrocephalus Build up of CSFIntracranial pressureLeads to expansion of head2 types1 Communicating Ventricles can communicate with each other Problem in subarachnoid space potentially with arachnoid villi problem is outside CNS2 Noncommunicating Blockage between ventricles usually in cerebral aqueduct cause its smallpressure built up inside ventricles pushes brain against skullMeninges of CNSCover spinal cord and the brain1 Dura mater protects brain and spinal cord tough leather membraneDura layer opens up in a space along the midline at the top of the brain dural sinus 2 Arachnoid membrane3 Pia mater stuck to surface of gray matter cerebral cortexTrabeculae are pillars between the Pia and arachnoid that allow CSF to flow in betweenSubarachnoid spacespace between pia and arachnoid membraneBlood vessels in the subarachnoid spaceBlood supply to the brain1 Brain metabolizes a lot of glucose2 Very little glycogen in the brain3 Brain needs continuous supply of glucose and oxygen does not require insulin4 Disrupt supply can lead to loss of consciousness few minutesdeath5 Receives 15 of total blood but only 2 of body mass since it requires continuous supply of blood and O2Blood flow to the brainMainly going up carotid arterydivides into internalexternalinternal goes to the brain
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