In this chapter, students will be able to understand: Define synapse, distinguish between electrical and chemical synapses by structure and by the way they transmit information, distinguish between excitatory and inhibitory postsynaptic potentials, describe how synaptic events are integrated and modified,. | 11 Fundamentals of the Nervous System and Nervous Tissue: Part C The Synapse A junction that mediates information transfer from one neuron: To another neuron, or To an effector cell The Synapse Presynaptic neuron—conducts impulses toward the synapse Postsynaptic neuron—transmits impulses away from the synapse PLAY Animation: Synapses Types of Synapses Axodendritic—between the axon of one neuron and the dendrite of another Axosomatic—between the axon of one neuron and the soma of another Less common types: Axoaxonic (axon to axon) Dendrodendritic (dendrite to dendrite) Dendrosomatic (dendrite to soma) Figure Dendrites Cell body Axon Axodendritic synapses Axosomatic synapses Cell body (soma) of postsynaptic neuron Axon (b) Axoaxonic synapses Axosomatic synapses (a) Electrical Synapses Less common than chemical synapses Neurons are electrically coupled (joined by gap junctions) Communication is very rapid, and may be unidirectional or bidirectional Are important in: Embryonic nervous tissue Some brain regions Chemical Synapses Specialized for the release and reception of neurotransmitters Typically composed of two parts Axon terminal of the presynaptic neuron, which contains synaptic vesicles Receptor region on the postsynaptic neuron Synaptic Cleft Fluid-filled space separating the presynaptic and postsynaptic neurons Prevents nerve impulses from directly passing from one neuron to the next PLAY Animation: Neurotransmitters Synaptic Cleft Transmission across the synaptic cleft: Is a chemical event (as opposed to an electrical one) Involves release, diffusion, and binding of neurotransmitters Ensures unidirectional communication between neurons Information Transfer AP arrives at axon terminal of the presynaptic neuron and opens voltage-gated Ca2+ channels Synaptotagmin protein binds Ca2+ and promotes fusion of synaptic vesicles with axon membrane Exocytosis of neurotransmitter occurs Information Transfer Neurotransmitter diffuses and binds to receptors (often . | 11 Fundamentals of the Nervous System and Nervous Tissue: Part C The Synapse A junction that mediates information transfer from one neuron: To another neuron, or To an effector cell The Synapse Presynaptic neuron—conducts impulses toward the synapse Postsynaptic neuron—transmits impulses away from the synapse PLAY Animation: Synapses Types of Synapses Axodendritic—between the axon of one neuron and the dendrite of another Axosomatic—between the axon of one neuron and the soma of another Less common types: Axoaxonic (axon to axon) Dendrodendritic (dendrite to dendrite) Dendrosomatic (dendrite to soma) Figure Dendrites Cell body Axon Axodendritic synapses Axosomatic synapses Cell body (soma) of postsynaptic neuron Axon (b) Axoaxonic synapses Axosomatic synapses (a) Electrical Synapses Less common than chemical synapses Neurons are electrically coupled (joined by gap junctions) Communication is very rapid, and may be unidirectional or bidirectional Are important in: Embryonic .
