APK 2105C Lecture Notes - Lecture 28: Cyclic Adenosine Monophosphate, Gs Alpha Subunit, Gi Alpha Subunit
5 Jun 2018
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Chapter 8, Lecture 1
Synaptic Transmission
• Synapses in the nervous system
o Electrical synapses
▪ Gap junctions
▪ Electrical coupling of cells with similar function
▪ Less common
o Chemical synapses
▪ Neurotransmitters to communicate with
• Neurons
• Muscles
• Glands
▪ Most common
▪ Parts of synapse are acting together to create site of communication
• Presynaptic neuron contains mitochondria
o Mitochondria needed to exocytose neurotransmitters
• Synaptic cleft = space between pre and postsynaptic neurons
o Very small
o Neurotransmitters cross this and then bind to ligand gated
receptors on the postsynaptic neurons
• Postsynaptic neuron
• Functional anatomy of chemical synapses
o Presynaptic neuron
o Postsynaptic neuron
o Most common with multipolar neurons
o Synaptic cleft
▪ Full of interstitial fluid
o Axo-dendritic synapse
o Axo-somatic synapse
o Axo-axonic synapse
▪ Usually closer to end of axon on postsynaptic neuron
• Synaptic transmission
o The more Ca allowed into the axon terminal the more neurotransmitter is
released
▪ How can we get more Ca in?
• Higher firing frequency of APs
• Ca channel stays open for a longer period of time
▪ More neurotransmitter = more response from target cell
o Steps
▪ AP comes down
▪ Ca is absorbed through voltage gated Ca channels
• Voltage change from AP coming down
▪ Initiates exocytosis
▪ Neurotransmitter binds to receptor site on postsynaptic neuron
▪ Degretory enzymes on membrane of pre and post synaptic neurons
• Break down ligands so they can be reused
• Reuptake enzymes on presynaptic neurons
o Helps recycle ligands
o May break down and only some parts are recycled
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