Section 2. Signal Transmission Between the Neurons
Section 2: Signal Transmission Between the Neurons
Neurotransmission 1. Chemical synapse(Classical Synapse) Predominates in the vertebrate nervous system 2.Non-synaptic chemical transmission 3. Electrical synapse Via specialized gap junctions Does occur. but rare in vertebrate NS Astrocytes can communicate via gap junctions
Neurotransmission 1.Chemical synapse (Classical Synapse) – Predominates in the vertebrate nervous system 2.Non-synaptic chemical transmission 3.Electrical synapse – Via specialized gap junctions – Does occur, but rare in vertebrate NS – Astrocytes can communicate via gap junctions
Chemical synapse Copyright O The MeGraw-Hit Companies, Inc, Permission required for reproduction or display. Terminal bouton is Action Axon separated from Ca2+ potentials Action Ca potential postsynaptic cell by Ca2+ Ca haptic cleft Protein kinase activates. Protein kinase Inactive Calmodulin Synaptic (inactive) vesicles phosphorylates Ⅴ esicles fuse with synapsin Docking proteins axon membrane and Synaptic cleft Fusion and nt released by Ca exocytosis" Ca2+ Neurotransmitter.. exocytosis released Ca2+ amount of nts released depends upon frequency of AP
Chemical Synapse • Terminal bouton is separated from postsynaptic cell by synaptic cleft. • Vesicles fuse with axon membrane and NT released by exocytosis. • Amount of NTs released depends upon frequency of AP
Non-synaptic chemical transmission Vesicle The postganglionic neurons innervate the ⊙ smooth muscles Smooth muscle ⊙ no recognizable endplates Intervaricose Axon segment or other postsynaptic Varicosity specializations, Mitochondrion The multiple branches are beaded with enlargements (varicosities) that are not Varicosity covered by Schwann cells and contain synaptic vesicles Terminal Fig. Ending of postganglionic autonomic neurons on smooth muscle
Non-synaptic chemical transmission The postganglionic neurons innervate the smooth muscles. • No recognizable endplates or other postsynaptic specializations; • The multiple branches are beaded with enlargements (varicosities) that are not covered by Schwann cells and contain synaptic vesicles; Fig. : Ending of postganglionic autonomic neurons on smooth muscle
Non-synaptic chemical transmission continued In noradrenergic neurons, the varicosities are about ⊙ 5μm, with up to20,000 Smooth muscle varicosities per neuron ⊙o Intervaricose Axon segment Transmitter is apparently Varicosity released at each varicosity, Mitochondrion at many locations along each axon ● One neuron innervate Varicosity many effector cells 了 Termina Fig. Ending of postganglionic autonomic neurons on smooth muscle
• In noradrenergic neurons, the varicosities are about 5m, with up to 20,000 varicosities per neuron; • Transmitter is apparently released at each varicosity, at many locations along each axon; • One neuron innervate many effector cells. Fig. : Ending of postganglionic autonomic neurons on smooth muscle Non-synaptic chemical transmission continued