Synaptic transmission - L19 Flashcards
What kind of channels on the cell body terminals?
Chemically gated to receive info through neurotransmitters
What is released at a nerve terminal?
Neurotransmitter
What does the neurotransmitter do in the next cell?
Results in an excitatory or inhibitory postsynaptic potential which travels to the next cell
Synpatic vesicles
carries neurotransmitters at the nere terminal
What can a graded potential lead to?
If big enough, leads to an AP that travels down the axon to terminals at other cells
How many synapses on one cell body?
100s - 1000s
Key features of a synapse
presynaptic neuron –> synaptic cleft which is a gap –> postsynaptic neuron
What is on the postsynaptic cell?
Chemically gated ion channels to detect the neurotransmitters
What is on the presynaptic cell?
Voltage gated Calcium channels, affected by the APs
*Has mitochondria and vesicles (made of membrane that pre is made of) inside
Synapse that uses Acetylcholine (made and packaged in the vesicles)
Colinergic synapse
What inactivates the neurotransmitters?
Actetlycholine - acetylcholiesterase
Why is Ca2+ removed from the cell
To stop ACh from being released into synapse
Why do reflexes have very few synaptic connections
To prevent overall culminative delay (usual delay is 0.5ms)
What happens when the APs passes through pre
Ca2+ passes from outside into the presyn cell through voltage gated Ca2+ channels (channels change shape to allow Ca2+ to move)
Intracellular calcium levels are:
Very low to control interaction and signalling inside and high outside
What does Ca2+ do?
Causes the vesicles to join w the nerve terminal and release neurotransmitters into the synaptic cleft due to mosaic model (exocytosis)
What does the neurotransmitter do?
Joins to the chemically gates channels (most cases Acetylcholine gated Na+ channels), allows Na+ to enter cell down the gradient
What does GABA do?
Attatched to GABA gated Cl- channels that make the inside of cell more negative –> inhibitory
How are Ca2+ levels maintained?
*Sequestered back into cell membrane such as ER
* Binds to Ca2+ binding proteins
*Pumps it out
What happens after the neurotransmitter binds to channel?
Affinity decreases so it unbinds, so it changes back into chanpe and closes (stops flow of Na+)
neurotrans can bind if still in the syn cleft
How is action of neutrans terminated?
Enzyme such as Acetylecholinesterase cuts Acetylcholine into Choline and Acetate
*Acetate diffuses away from syn cleft
*Choline is taken back into cell through transporter protein and bound to by products of AcetylCoA to make more Acetylcholine
What are electrical synapses?
Where pre and post cells sit close together and are joined by gap junctions (transmembrane channels)
* Depol of presyn directly passes to post
*Relatively rare and dont allow signal modulation
eg retina
Excitatory neurotrans
ACh, Glutamate
Inhibitory Nuerotrans
IPSP , GABA
Why is there folding in postsyn cells?
Increase SA for Acetylcholine receptors
Nerve-Nerve synapse
*Synapses are tiny
*1000S of synapses on postsyn cell
*AP of individuals neurons rarely brings next cell to threshold
*Excitatory/Inhibitory
