What are synapses?
The point where activity transmitted from
One nerve cell to other.
Motor neuron to muscle cell.
Two types
Chemical synapses - release neurotransmitter at synapses.
Electrical synapses – potential spread directly from one cell to other.
Electrical synapses
Gap junction between presynaptic and postsynaptic cells.
Ions pass in a bridge.
Shorter latency than chemical synapses.
Only few synapses are electrical synapses.
Structure of chemical synapses
Presynaptic cell – contain terminal buttons
Postsynaptic cell
Neurotransmitter (Only in chemical synapses)
Types of Synapses
Axodendritic
Axo-axonal
Axosomatic
Neurotransmitter release
Voltage gate Ca2+ channels open when action potential come to the presysptic terminal.
Result Ca2+ influx.
Release neurotransmitter from synaptic vesicle.
Convergence & Divergence
Convergence – Input from different presynaptic neurons.
Divergence - presynaptic neurons divide into many branches and end in many postsynaptic neurons.
Excitatory Postsynaptic Potentials
All stimuli reach the end of presynaptic terminal doesn’t make action potential in postsynaptic neurons.
Some stimuli produce only transient depolarization in the postsynaptic membrane.
Call Excitatory Postsynaptic Potentials - EPSP.
Open Na+ and Ca2+ ion channels and inwards flow.