PHGY 209 CNS Lecture II

PHGY 209 CNS Lecture II - PHGY 209 CNS Lecture II November...

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PHGY 209 CNS Lecture II November 1, 2008 Cranial nerves 12 pairs of cranial nerves. 10 of them project in and out of the brain stem. Olfactory nerves and optic nerves does not go through the brain stem, they go directly into the brain. Early development of the nervous system Fertilized egg blastocyst (with inner cell mass) inner embryonic disk (week 3) You have what’s called a neural plate at week 3 Ectoderm, mesoderm, and endoderm. Ectoderm is the neural plate, it becomes the CNS, mesoderm becomes muscle and tissues (including dura mater) and the endoderm becomes your digestive tract. At 3 ½ weeks, nerve plate folds up into a neural groove. At week 4, the neural groove becomes the neural tube. The neural tube becomes CNS and part of the PNS. The neural crest cells becomes part of the PNS. Mesoderm becomes part of the dura. Development of the neural tube Vesicles develope during week 4 into forebrain, midbrain, and hindbrain. Forebrain developes into the cerebral hemispheres, thalamus, Midbrain developes into the midbrain Hindbrain becomes the poins, medulla, and cerebellum Tail part of the neural tube becomes the spinal cord. The cavity inside the neural tube becomes the ventricles and the central canal. Cerebrospinal fluid In an adult brain, there are 150 ml of CSF. Two major cavities in each hemisphere called the lateral ventricles. Third ventricle – in the midline Fourth ventricle central canal. CSF is produced by the chloroid plexus . It takes blood and extract from it CSF and put it into the ventricles. Chloroid plexus produce CSF about 0.5 L per day. Functions of the CSF: support and cushion the CNS, provide nourishment to the brain (glucose), removes metabolic waste through absorption at the arachnoid villi (get CSF out of your head). CSF is not
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PHGY 209 CNS Lecture II - PHGY 209 CNS Lecture II November...

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