lecture3

lecture3 - Lecture 3! nervous! Nerve cells:! ow of signal:!...

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nervous Lecture 3
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Nerve cells: fow oF signal: dendrites cell body axon axon terminal next cell (can be meters long) synapse (chemical or electrical)
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Three general class of neurons for a functioning nervous system sensory receptor (light, heat, pressure, touch , smell, . ..) cell body 1. afferent neuron 3. efferent neuron 2. interneurons 1. Afferent Neurons: convey information to the central nervous system. Serve as receptors to bring in information. Don't have dendrites 3. Efferent Neurons: convey information away from the central nervous system to target (effector) cells 2. Interneurons: connect the afferent and efferent neurons in the central nervous system. They process the information from the afferents to give the proper efferent response. They are much more abundant than afferent or efferent neurons. central nervous system target cell (muscle, gland, . ..
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Glial cells make up " 90% of the cells in the nervous system. They don't convey information. Rather they serve to support nerve cells. Schwann cells - myelinate peripheral neurons oligodendrocytes - myelinate CNS neurons astrocyte - control composition of CNS extracellular Fuid (ion and glucose concentration, permeability of capillaries). [New data suggests a more active role in modulating neuronal signaling] microglia - immune functions ependymal cells - form sheets that line the brain ventricles (cavities)
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ECF ICF •for nerve cells, the ion (Na + , K + , Ca 2+ , Cl - ,...) composition of the intra- cellular and extracellular compartments is important •ions require speci±c channels to cross the membrane (in or out) How do nerve cells communicate? First we have to look at properties of nerve cell membranes:
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•ion channels facilitate movement of ions across membranes the are selective for particular ions (i.e., K + , or Na + or Cl - ....) •at least 400 ion channel structures have been identified in the human genome, of which only about 100 have been functionally tested. •some types of channels are always open (example, K + leak channels) •some channels open and close depending on the membrane voltage - they are called voltage gated : the interaction of these charged groups is sensitive to the charge on the membrane, and determine whether the channel is open or closed •some channels open and close depending on the binding of a chemical messenger
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lecture3 - Lecture 3! nervous! Nerve cells:! ow of signal:!...

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