PSYC1011 Lecture Notes - Lecture 4: Nernst Equation, Axon Hillock, Reuptake
Action potentials and synapses
• Synapse
o Point of communication between cells
o
• Graded potentials
o Signals travelling down the dendrite and cell body
o Change in voltage between the cell
o
• Action potential or nerve impulse
o Signals down the axon
o
Synapse
• Electrical synapse
o Gap junctions
o Faster form of communication
o Less common
o Requires smaller distance for the signal to be transmitted
o
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o
• Chemical synapse
o Slower
o Complex connection
o Common
o
Synaptic communication
• Nerve impulse arrives at the axon terminal
▪ Initiates the synaptic communication
▪
Voltage gated calcium channels open
o Calcium floods into the cell
o
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• Increased positive charge activates synaptic vesicles
o Vesicles contain neurotransmitters
o Activation of the vesicles leads to release of neurotransmitters into the synaptic cleft
o
• Neurotransmitter in the synaptic cleft is free to bind to receptors on the postsynaptic
neuron
o Has a specific receptor point where specific neurotransmitters can bind, opening the
channel
o Allows specific ions to enter
o
• When a neurotransmitter binds to a receptor, in the example shown, a ligand-gated ion
channel opens
o This example allows sodium to enter a cell (excitation)
• More likely to fire
o Other neurotransmitter /receptor combinations open chloride channels (inhibition)
• Negatively charged ion - reduces action potential
• The excitation or inhibition of a cell is known a postsynaptic potential (graded potential)
o
Neurotransmitter reuptake
• Neurotransmitters are generally actively returned to the presynaptic cell
o Neurotransmitters (e.g. serotonin) are received by serotonin receptors
o After signal is received, serotonin is actively returned to the transmitted neuron via
serotonin reuptake transporter
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Document Summary
Synapse: point of communication between cells, graded potentials, signals travelling down the dendrite and cell body, change in voltage between the cell, action potential or nerve impulse, signals down the axon. Synapse: electrical synapse, gap junctions, faster form of communication, less common, requires smaller distance for the signal to be transmitted, chemical synapse, slower, complex connection, common. Synaptic communication: nerve impulse arrives at the axon terminal. Voltage gated calcium channels open: calcium floods into the cell. Neurotransmitter reuptake: neurotransmitters are generally actively returned to the presynaptic cell, neurotransmitters (e. g. serotonin) are received by serotonin receptors, after signal is received, serotonin is actively returned to the transmitted neuron via serotonin reuptake transporter. Forms of synaptic communication: axodendritic, dendrite of receiving neuron receives the signal from the axon of transmitting neuron, axosomatic, soma of receiving neuron to axon of transmitting neuron, axoaxonic, synapse to axon of another transmitting neuron.
