Synaptic transmission
The action potential is the information unit of the brain. Connecting neurons -> Synaptic
transmission: the communication of electrical signals between cells.
➔ Different synapses
➔ Different neurotransmitters
➔ Release mechanism of neurotransmitter is the same
➔ Neurotransmitter receptors
➔ Summation to a new action potential
The contact point between two neurons = the synapse. Neuron sending out information =
presynaptic cell. Neuron receives input = postsynaptic cell. Two types of synapses:
• Electrical synapse: direct exchange of ions and small molecules by passive flow between the
pre= and postsynaptic cell. Channels make direct contact between the cells: channels; pre
and postsynaptic side.
• Chemical synapse: in the brain most used, but this synapse is more unreliable: indirect
transmission of electrical signals through chemical signalling molecules (neurotransmitters).
On postsynapse you have the receptors.
Electrical synapse Chemical synapse
Extremely fast Fast
Bi-directional Mostly one-directional
One-to-one transmission, presynaptic action Tuneable transmission, enhance and lower the
potential huge chance for postsynaptic action chance for action potential. Allow us to have
potential synaptic plasticity.
Exchange of small molecules Variety of neurotransmitters
Use: synchronisation of cells in a network fast Use: regulated activity plasticity (learning,
responses. Needed in e.g. heart, cause need memory)
simultaneous contraction.
The power of electrical synapse, pre and postsynaptic cell almost simultaneously depolarize only very
short delay, reliable one-to-one action potential transmission. Need it for synchronisation. Important
for fast and automated behaviour.
The chemical synapse: action potential depolarization of pre-synaptic brain open calcium channels,
then release neurotransmitters and bind to receptors on postsynaptic cell. Two neurotransmitter
receptors:
➔ G-protein-coupled receptor (metabotropic receptor)
➔ Ligand-gated ion channels (ionotropic)
What properties should a neurotransmitter have?
• Recycling / breakdown neurotransmitters -> end to present of neurotransmitter/information
conduction (stop). Should only be temporally present outside the cell, the signal must be
stopped.
• Water soluble most of them are, but there are a few exception but these are unconventional
• Can be charged but doesn’t have to
The action potential is the information unit of the brain. Connecting neurons -> Synaptic
transmission: the communication of electrical signals between cells.
➔ Different synapses
➔ Different neurotransmitters
➔ Release mechanism of neurotransmitter is the same
➔ Neurotransmitter receptors
➔ Summation to a new action potential
The contact point between two neurons = the synapse. Neuron sending out information =
presynaptic cell. Neuron receives input = postsynaptic cell. Two types of synapses:
• Electrical synapse: direct exchange of ions and small molecules by passive flow between the
pre= and postsynaptic cell. Channels make direct contact between the cells: channels; pre
and postsynaptic side.
• Chemical synapse: in the brain most used, but this synapse is more unreliable: indirect
transmission of electrical signals through chemical signalling molecules (neurotransmitters).
On postsynapse you have the receptors.
Electrical synapse Chemical synapse
Extremely fast Fast
Bi-directional Mostly one-directional
One-to-one transmission, presynaptic action Tuneable transmission, enhance and lower the
potential huge chance for postsynaptic action chance for action potential. Allow us to have
potential synaptic plasticity.
Exchange of small molecules Variety of neurotransmitters
Use: synchronisation of cells in a network fast Use: regulated activity plasticity (learning,
responses. Needed in e.g. heart, cause need memory)
simultaneous contraction.
The power of electrical synapse, pre and postsynaptic cell almost simultaneously depolarize only very
short delay, reliable one-to-one action potential transmission. Need it for synchronisation. Important
for fast and automated behaviour.
The chemical synapse: action potential depolarization of pre-synaptic brain open calcium channels,
then release neurotransmitters and bind to receptors on postsynaptic cell. Two neurotransmitter
receptors:
➔ G-protein-coupled receptor (metabotropic receptor)
➔ Ligand-gated ion channels (ionotropic)
What properties should a neurotransmitter have?
• Recycling / breakdown neurotransmitters -> end to present of neurotransmitter/information
conduction (stop). Should only be temporally present outside the cell, the signal must be
stopped.
• Water soluble most of them are, but there are a few exception but these are unconventional
• Can be charged but doesn’t have to
