Chapter 30 General Principles of the Neuron Activities
Chapter 30 General Principles of the Neuron Activities
Contents ● Neurotransmission o Neurotransmitter and Receptor ● Synaptic Plasticity o Properties of the Synaptic Neurotransmission
Contents ⚫ Neurotransmission ⚫ Neurotransmitter and Receptor ⚫ Synaptic Plasticity ⚫ Properties of the Synaptic Neurotransmission
Part I NEUROTRANSMISSION
NEUROTRANSMISSION Part I
I Synapse 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
I Synapse 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
1. Chemical Synapse Terminal bouton is separated from Copyright O The uo.H Companies, c. Permission required for reproduction or display Action A Xon postsynaptic cell by Cactpotentials Action Caz+ otential synaptic cleft Ca2+ Ⅴ esicles fuse with Protein kinase activates. Protein kinase inactive Calmodulin Synaptic (inactive axon membrane and vesicles phosphorylates synapsin Ntreleased b Docking proteins Synaptic cleft exocytosis Fusion and exocytosis Ca Amount of nts Neurotransmitter oo released released depends upon Cas+ frequency of
1. 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
2. Non-synaptic chemical transmission ° Sympathetic Nerve The postganglionic °2 Smooth neurons innervate the muscle smooth muscles Intervaricose Axon segment No recognizable endplates Varicosity Mitochondrion or other postsynaptIc specializations The multiple branches are beaded with enlargements Varicosity (varicosities) that are not covered by schwann cells Terminal o and contain synaptic Fig. Ending of postganglionic vesicles autonomic neurons on smooth muscle
2. Non-synaptic chemical transmission • Sympathetic Nerve • 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 Smooth muscle 5um, with upto20,000 ⊙o Intervaricose segment varicosities per neuron Varicosity Mitochondrion Transmitter is released at each varicosity One neuron innervate many effector cells Varicosity 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 released at each varicosity • One neuron innervate many effector cells. Fig. : Ending of postganglionic autonomic neurons on smooth muscle Non-synaptic chemical transmission continued
Innervation of adrenal medulla spinal cord 有手 adrenal sympathetic medulla preganglionic neuron epinephrine, norepinephrine (to circulation)
Innervation of Adrenal Medulla
3. Electrical Synapse Impulses can be regenerated without interruption in adjacent cells Cytoplasm Gap junctions Plasma Adjacent cells electrically membrane of one cell coupled through a channel Plasma Each gap junction is Two cells, membrane inter of adjacent connected ce composed of 12 connexin by gap unctions Connexin proteins proteins Examples Cytoplasm forming qal unctions Smooth and cardiac muscles brain, and glial cells
3. Electrical Synapse • Impulses can be regenerated without interruption in adjacent cells. • Gap junctions: – Adjacent cells electrically coupled through a channel. – Each gap junction is composed of 12 connexin proteins. • Examples: – Smooth and cardiac muscles, brain, and glial cells
Electrical Synapses 1. Communication takes place by flow of electric current directly from one neuron to the other cell2 2. No synaptic cleft or crop vesicles cell membranes in direct contact 3. Communication not polarized-electric current can flow between cells in cytoplasm Iong and Charnel forned either direction ena.1 noleculemby pores in
1. Communication takes place by flow of electric current directly from one neuron to the other 2. No synaptic cleft or vesicles cell membranes in direct contact 3. Communication not polarized- electric current can flow between cells in either direction Electrical Synapses