6: Synaptic Transmission Flashcards
(15 cards)
What is the gap between cells at a synapse called?
The synaptic cleft
What is the end of the presynaptic neurone called?
The synaptic knob
What does the synaptic knob contain?
Vesicles filled with neurotransmitters
What causes impulses to be unidirectional?
Receptors are only on the postsynaptic membrane
What are synapses that use acetylcholine called?
Cholinergic synapses
What happens when an action potential reaches the synaptic knob on the presynaptic neurone?
Voltage-gated calcium ion channels open, calcium ions diffuse into the synaptic knob, causes the synaptic vesicles to fuse with the membrane and release the neurotransmitters into the synaptic cleft - Exocytosis
What happens when acetylcholine binds to cholinergic receptors on the postsynaptic membrane?
Sodium ion channels open, depolarisation
How is acetylcholine removed from the synaptic cleft?
Broken down by acetylcholinesterase (AChE), products re-absorbed by the presynaptic neurone
How do inhibitory neurotransmitters work?
Hyperpolarise the postsynaptic membrane, preventing it from firing an action potential
How do excitatory neurotransmitters work?
Depolarise the postsynaptic membrane
What is an inhibitory synapse?
a synapse where inhibitory neurotransmitters are released from the postsynaptic membrane following an action potential
What is spatial summation?
Two or more presynaptic neurones release their neurotransmitters at the same time onto the same postsynaptic neurone
What is temporal summation?
Two or more nerve impulses arrive in quick succession from the same presynaptic neurone
What are receptors at a neuromuscular junction called?
Nicotinic cholinergic receptors
What does a neuromuscular junction have that a cholinergic synapse doesn’t?
The postsynaptic membrane has folds that form clefts that store acetylcholinesterase
Postsynaptic membrane has more receptors
ACh is always excitatory
