13.5 Synapses Flashcards
What is a synapse
The junction between 2 nuerones
What are the parts of a synapse
Synaptic cleft Presynpatic neurone Postsynaptic nuerone Synaptic knob Synaptic vesicles Nuerotransmitter receptors
What is the synaptic cleft
Gap that separates axon of 1 nuerone to the dendrite of another
What is the difference between presynspatic and postsynaptic neurone
Presynpatic is nuerone that impulse arrived on
Postsynaptic is neurone that receivers neurotransmitters
What is the synaptic knob
Swollen end of presynpatic nuerone that contains lots of mitochondria and endoplasim reticulum to enable manufacture of neurotransmitters
What are the synaptic vesicles
Vesicles containing neurotransmitters
They release contents into the synaptic cleft
What are the types of neurotransmitters abs what is the difference between them
Excitatory - result in depolarisation of neurone - triggering an action potential
Inhibitory - results in hyperpolarisation of neurone - preventing an action potential
What happens at the start of the transmission of an impulse across synapses
The action potential reaches the end of the presynpatic neurone and depolarisation of it causes calcium channel ions to open
What happens when calcium ions fuse into the presynpatic knob in the transmission of impulses across synapses
The synaptic vesicles containing the neurotransmitters will then fuse with the presynpatic membrane and release the neurotransmitters into the synaptic cleft by exocytosis
Neurotransmitter diffuses across the cleft abs binds with specific receptor molecules on the post synaptic membrane
What happens when neurotransmitter bind to specific receptors on postsynaptic membrane in impulse transmission across synapses
The sodium ion channels are triggered to open and sodium ions diffuse into the postsynaptic membrane this triggers an action potential and the impulse is propagated along the postsynaptic neurone
What neurotransmitters are used in cholinergic synapses
What happens to them
Acetylcholine
Once the action potential is triggered acetylcholine is hydrolysed to give chlorine and ethanol acid which are then taken back to the knob to turn into acetylcholine
What are the main roles of synapses
Ensure impulses are unidirectional
They allow an impulse from one neurone to be transmitted to a number of neurones at multiple synapses
A number of neurones may feed into the same synapse with a single postsynaptic neurone
What are the two types of summation
Spatial summation
Temporal summation
What is spatial summation
When a number of presynaptic neurones connect to 1 postsynaptic neurone and each release a neurotransmitter which builds up to a high enough level to tigger an action potential in post synaptic neurone
What is temporal summation
When a single presynpatic neurone releases an neurotransmitter several times over a short period which causes a build up in the synapse until the quantity is sufficient enough to trigger an action potential
