BIOD27H3 Lecture 5: BGYB30H3 Lecture 5 Notes Chemical Synapse 1-Sep 24
11 Aug 2010
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BGYB30H3 Lecture 5 Notes
-graded potentials occur in the cell body and dendrites
-action potentials occur in the axon (particularly the axon hillock)
-chemical neurotransmission occur in the synapse of the neuron
-neurotransmission is the conversion of the action potential into a chemical signal, which induces a
response in the target
-chemical signal could be a neurotransmitter
-pre-synaptic bouton is located near the post-synaptic junction (synaptic cleft in between)
-post-synaptic junction contains voltage gated channels of sodium and potassium
-pre-synaptic bouton contains calcium channels
-before a synapse, the action potential depolarizes the axon terminal by opening calcium channels and
calcium enters the bouton
-calcium triggers exocytosis of synaptic vesicles that release neurotransmitter
-neurotransmitter binds with receptor on post-Çv]oovZdownstream response[oo
signal transduction
-neurotransmitter remains outside the post-synaptic cell
-signaling cascades are activated by different types of receptors which are ionotropic receptors and G-
protein coupled receptors
-ionotropic receptors (ligand gated) are coupled to an ion channel
-ionotropic receptors cause movement of ions across membrane through ion channel when
neurotransmitter binds to them (creates a fast response)
-in G-protein coupled receptors, neurotransmitter causes activation of receptor, which activates G-
protein (creates a slow response)
-signal is amplified once receptor is activated because G-protein signals amplifying enzymes that signal
secondary messengers
-secondary messengers are the initiators of responses in the cell
-ionotropic and G-protein coupled receptors alter the open state of voltage gated channels by closing
the channel to alter membrane potential
-less sodium inside the cell causes IPSP, less potassium outside the cell causes an EPSP
-secondary messengers modify existing proteins and synthesize new proteins, which are referred to as
co-ordinated cellular responses
-after synapsis, neurotransmitters are transported back to presynaptic cell where they are packed into
vesicles again and transported to a reserve pool of synaptic vesicles
-the active zone is the region where the exocytosis of neurotransmitters occurs
-calcium binds to calcium sensitive proteins on vesicles before exocytosis occursn
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Document Summary
Graded potentials occur in the cell body and dendrites. Action potentials occur in the axon (particularly the axon hillock) Chemical neurotransmission occur in the synapse of the neuron. Neurotransmission is the conversion of the action potential into a chemical signal, which induces a response in the target. Pre-synaptic bouton is located near the post-synaptic junction (synaptic cleft in between) Post-synaptic junction contains voltage gated channels of sodium and potassium. Before a synapse, the action potential depolarizes the axon terminal by opening calcium channels and calcium enters the bouton. Calcium triggers exocytosis of synaptic vesicles that release neurotransmitter. Signaling cascades are activated by different types of receptors which are ionotropic receptors and g- protein coupled receptors. Ionotropic receptors (ligand gated) are coupled to an ion channel. Ionotropic receptors cause movement of ions across membrane through ion channel when neurotransmitter binds to them (creates a fast response)
