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Chapter 9

BGYB30 Chapter 9 textbook notes

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University of Toronto Scarborough
Biological Sciences

MAMMILIAN PHSYSIOLOGY Chapter 9 the central nervous system Affective Behaviours: Behaviours that have to do with feelings and emotions Cognitive Behaviours: Behaviours related to thinking The CNS consists of the brain and the spinal cord Early Development In the very early embryo, the cells that become the CNS lay flatted on a region called the neural plate. At about 20 days old, the neural plate starts migrating towards the midline to form a hollow neural tube. By 23 days the neural tube is almost complete. The neural tube remains hollow and eventually will become the CNS. The cells in the inside of the tube either become ependyma (connective tissue that separates fluids) or undifferentiated stem cells. The cells on the outside become the neurons and the glial cells. The neural crest cells become the neurons of the PNS. By 4 weeks, 3 distinct divisions of the CNS are obvious: the forebrain, the midbrain, and the hindbrain. At this point, the forebrain is no bigger than the other parts www.notesolution.comBy week 6, growth of the forebrain outpaces the other regions and the embryo has developed all 7 regions of the CNS present at birth: the cerebrum, the diencephalon, the midbrain, the cerebellum, the Pons, the medulla oblongata, and the spinal cord Also by week 6, ventricles form and the neural tube becomes the central canal of the CNS By week 11, the cerebrum is much more developed than the other regions and is the most obvious structure when the infant is born Grey & White Matter The tissue of the CNS are divided into 2 groups: white matter and grey matter Grey Matter: Grey matter consists of unmyelinated nerve cell bodies, dendrites and axons terminals. They usually form layers over certain parts of the brain or form clusters of neurons with the same function (called nuclei) White Matter: White matter is made up mostly of myelinated axons and contains very few cell bodies. The white colour comes from the myelin (bundles of axons that connect to different regions of the CNS are known at tracts. Tracts = nerves in the PNS) Bone and Connective Tissue Support of the CNS The brain is encased in a bony skullcranium and the spinal cord is protected and runs www.notesolution.com
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