PSL300H1 Chapter 5: Ionotropic Receptors
Document Summary
Neuron communication is a chemical processes, involving release of specific neurotransmitter agent. when action potential reaches bouton, presynaptic membrane increases its permeability to ca++ (sequestered at high concentrations in synaptic cleft). Ca++ enters bouton via voltage-gated ca++ channels and triggers fusion of vesicles to presynaptic membrane. Once vesicle contents released into synaptic cleft, transmitter agent rapidly diffuses across and binds to specific receptor sites on postsynaptic membrane. Vesicle release is quantitatively proportional to degree of membrane depolarization or the amount of ca++ that enters bouton. When transmitter binds, undergo steric configurational changes, which causes opening of ion pores (ionotropic receptors) Post-synaptic potential is depolarizing, excitatory, called excitatory post-synaptic. Other receptor proteins may sterically induce permeability increase to k+ or cl-, generating inhibitory post-synaptic potential (ipsp). Effect of transmitter depends on post-synaptic receptor protein, not the transmitter itself. Most excitatory synaptic connections onto dendritic trees of neurons. Impulse initiation occurs at the axon initial segment.
