Neurobiology |
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Principles of Neural Science - Kandel, Schwartz and Jessell: Read pages 19-34, 67-86 for this lecture end |
VI. Nerves, Neurons and Glia back to V. Development of Neural Systems A. Neurons are single cells of nervous tissue 1. include (in order and direction of transmitted signal): dendrites, cell body (soma), axon (may be myelinated), terminal (bouton), and synapse a. synaptic cleft is the space through which a neuron communicates with another cell (often another neuron) 2. Nerves are assemblies of axons a. Central: nuclei = clustered soma; Peripheral: ganglia = grouped cell bodies B. Glia (=glue) surround and support neurons 1. 10 - 50X more glia than neurons 2. oligodendrocytes (CNS) and Schwann cells (PNS) insulate / myelinate large axons 3. produce NGF & neurotrophins; guiding development, neurite outgrowth and maintaining mature neurons a. also remove debris after injury or neuronal death 4. buffer [K+] in the extracellular space 5. remove transmitters from synaptic cleft 6. form tight junctions along capillaries of the brain = Blood Brain Barrier C. Membranes and neural signals 1. neural transmissions are carried along axonal membranes by ion (Na+, K+, Cl-) movement across the membrane 2. non-transmitting cells have an unequal balance of ions such that there is a resting potential of -40 to -80 mV 3. input to the cell may increase (hyperpolarize) this potential or reduce (depolarize) it a. multiple inputs make local membrane potential graded 4. signals are stimulated by threshold (~ -25 to -55 mV) depolarization = Action Potential a. axon region with the voltage-gated Na+ channels and therefore lowest threshold is the trigger zone or integrative component, which sums input from all regional depolarizations 5. conductile axon propagates all-or-none action potential
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