神经递质医学ppt课件.pptVIP

* Neurotransmitters Properties of neurotransmitters: 1) synthesized in the presynaptic neuron 2) Localized to vesicles in the presynaptic neuron 3) Released from the presynaptic neuron under physiological conditions 4) Rabidly removed from the synaptic cleft by uptake or degradation 5) Presence of receptor on the post-synaptic neuron. 6) Binding to the receptor elicits a biological response * * Neurotransmitters found in the nervous system EXCITATORY Acetylcholine Aspartate Dopamine Histamine Norepinephrine Epinephrine Glutamate Serotonin INHIBITORY GABA Glycine * Acetylcholine synthesis: In the cholinergic neurons acetylcholine is synthesized from choline. This reaction is activated by cholineacetyltransferase As soon as acetylcholine is synthesized, it is stored within synaptic vesicles. * Release of acetylcholine from presynaptic neurons: 1)When the nerve impulse (Action potential) moves down the presynaptic axon to the terminal bulb the change in the membrane action potential causes the opening of voltage gated calcium channels open allowing Ca+2 ions to pass from the synaptic cleft into the axon bulb. 2)??Within the bulb the increase in Ca+2 concentration causes the synaptic vesicles that contain acetylcholine to fuse with the axonal membrane and open spilling their contents into the synaptic cleft. * Binding of acetylcholine to the postsynaptic receptors: The postsynaptic membrane of the receptor dendrite has specific cholinergic receptors toward which the neurotransmitter diffuses. Binding of acetylcholine trigger the opening of ion channels in the postsynaptic membrane initiating action potential that can pass in the next axon. Acetylcholine receptors: Acetylcholine receptors are ion channels receptors made of many subunits arranged in the form [(α2)(β)(γ)(δ)]. When Acetylcholine is not bounded to the receptors, the bulky hydrophobic leu side close the central channels preventing the diffusion of any ion