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BIOL 241 (4)

Unit 2 - CNS - Full Textbook Notes

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BIOL 241
Heidi Engelhardt

CHAPTER 9 THE CENTRAL NERVOUS SYSTEMEvolutionFlatworms no distinction between CNS and PNSSegmented worms ganglia present along nerve cord simple reflexes can be integrated Higher invertebrates complex reflexes controlled through neural networks Higher arthropods specific regions of the brain are associated with complex behavioursVertebrate forebrain region includes cerebrum dedicated to mainly processing olfactory information Cerebrum is smooth in less intelligent beings in humans it is deeply folded It allows reasoning and cognition Cerebellum in hindbrain for coordinating movement and balance AnatomyCNSbrain and spinal cordEarly embryocells that will become nervous system lie in neural plate Neural plate cells migrate toward midline and create a neural tube Neural crest cells from lateral edges are dorsal to neural tube Cells lining neural tube become epithelial ependymal or neural stem cells Outer cell layers of neural tube become neural and glia of CNS Neural crest cells become sensory and motor neurons of PNS Anterior of neural tubebrain Posteriorspinal cordGray matter unmyelinated nerve cell bodies dendrites axon terminals nucleiWhite matter myelinated axons and few cell bodies Tracts bundles of axons that connect different regions of CNS Meninges three layers of membrane that lie between bones and tissues of CNS Help stabilize neural tissueDura mater thickest associated with veins that drain blood from brain Arachnoid loosely tied to inner membrane Pia mater inner membrane thin adheres to surface of brain and spinal cord associated with arteries that supply blood to brain Cerebrospinal fluid physically protects delicate tissue chemically exchanges solutes with interstitial fluidBloodbrain barrier functional barrier between interstitial fluid and blood Isolates main control centre from potentially harmful substances in blood Highly selective capillaries shelter brain from toxins hormones ions neuroactive substances Edothelial cells form tight junctions with one another that prevent solute movement between cells Formation is induced by paracrine signals from astrocytes brain tissue itself that creates BBB Selectively permeable due to transport proteins capillary endothelium uses selected membrane carrierschannels to move nutrients from blood into brain interstitial fluid other transporters move wastes from interstitial fluid into plasma any water soluble molecule that is not transported here cannot cross BBB
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