. Neurobiology, lecture on Nerves, Neurons and Glia

Summers
USD Department of Biology

Neurobiology

text:
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

VI. Membrane Potential



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