BIOB30 Ch8 (273-end)

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Biological Sciences
Joanne Nash

1 BIOB30 Chapter 8Neurons Cellular and Network Properties CelltoCell Communication in the Nervous SystemThe specificity of neural communication depends on several factors o The signal molecules secreted by the neurons o The target cell receptors for these chemicals o The anatomical connections between neurons and their targets occur at synapses Neurons Communicate at SynapsesEach synapse has two parts o The presynaptic cells axon terminal o The postsynaptic cells membraneIn a neural reflex information moves from the presynaptic to postsynaptic cell o The postsynaptic cell isnt always a neuron o In most neurontoneuron synapses the axon terminal is next to the dendrites or cell body of the postsynaptic neuronSometimes on axon or axon terminalCells average 10000 synapses can be more than 150000 Electrical SynapsesElectrical synapsespass an electrical signal or current directly from the cytoplasm of one cell to another through gap junctions o Rectifying synapsegap junctions in which current can only flow in one directionOccur mainly in CNS neurons o Also found in glial cells cardiac and smooth muscle and in nonexcitable cells that use electrical signalsThe advantage is a rapid conduction of signals that can synchronize activity within a network of cellsGap junctions also allow diffusion of chemicals Chemical SynapsesChemical synapsesthe electrical signal of the presynaptic cell is converted into a chemical signal neurotransmitters that crosses the synaptic cleft to the bind with receptors on the postsynaptic cell initiating an electrical responseo Most neurons in the nervous system use this o An electrical response is a rapid responseA second messenger pathway is a slower responseNeurotransmitter synthesis can occur at the nerve cell body or the axon terminal o But since axon terminals dont have organelles for protein synthesis the proteins must be made in the cell body
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