SYNAPSES
TYPES OF NEUROTRANSMITTERS
Excitatory- Theses neurotransmitters result in the depolarisation of the postsynaptic neurone
If the threshold is reached in the postsynaptic membrane an action potential is triggered
An example is acetylcholine
Inhibitory- These neurotransmitters result in the hyperpolarisation of the postsynaptic membrane.
This prevents an action potential being triggered.
Gamma-aminobutyric acid is an example.
Transmission across cholinergic synapse
They use the transmitter acetylcholine
Common in the CNS
and at neuromuscular junctions where a motor neurone and a muscle cell meet.
(1) Acetylcholine is realised from the vesicles in the presynaptic knob
(2) It then diffuses across the synaptic cleft where it binds to specific receptors in the postsynaptic membrane
(3) This triggers an action potential in the postsynaptic neurone or muscle cells
(4) Ones the action potential has been triggered acetylcholine is hydrolysed
summation and control
Spatial summation
Temporal summation
Occurs when a number of presynaptic neurones connect to one postsynaptic neurone
Where two ore more nerve impulses arrive in quick succession from the same presynaptic neurone
This makes an action potential more likely as more neurotransmitters are released into the synaptic cleft