Synaptic transmission - L19

Question 1

What kind of channels on the cell body terminals?

Answer 1

Chemically gated to receive info through neurotransmitters

Question 2

What is released at a nerve terminal?

Answer 2

Neurotransmitter

Question 3

What does the neurotransmitter do in the next cell?

Answer 3

Results in an excitatory or inhibitory postsynaptic potential which travels to the next cell

Question 4

Synpatic vesicles

Answer 4

carries neurotransmitters at the nere terminal

Question 5

What can a graded potential lead to?

Answer 5

If big enough, leads to an AP that travels down the axon to terminals at other cells

Question 6

How many synapses on one cell body?

Answer 6

100s - 1000s

Question 7

Key features of a synapse

Answer 7

presynaptic neuron –> synaptic cleft which is a gap –> postsynaptic neuron

Question 8

What is on the postsynaptic cell?

Answer 8

Chemically gated ion channels to detect the neurotransmitters

Question 9

What is on the presynaptic cell?

Answer 9

Voltage gated Calcium channels, affected by the APs

*Has mitochondria and vesicles (made of membrane that pre is made of) inside

Question 10

Synapse that uses Acetylcholine (made and packaged in the vesicles)

Answer 10

Colinergic synapse

Question 11

What inactivates the neurotransmitters?

Answer 11

Actetlycholine - acetylcholiesterase

Question 12

Why is Ca2+ removed from the cell

Answer 12

To stop ACh from being released into synapse

Question 13

Why do reflexes have very few synaptic connections

Answer 13

To prevent overall culminative delay (usual delay is 0.5ms)

Question 14

What happens when the APs passes through pre

Answer 14

Ca2+ passes from outside into the presyn cell through voltage gated Ca2+ channels (channels change shape to allow Ca2+ to move)

Question 15

Intracellular calcium levels are:

Answer 15

Very low to control interaction and signalling inside and high outside

Question 16

What does Ca2+ do?

Answer 16

Causes the vesicles to join w the nerve terminal and release neurotransmitters into the synaptic cleft due to mosaic model (exocytosis)

Question 17

What does the neurotransmitter do?

Answer 17

Joins to the chemically gates channels (most cases Acetylcholine gated Na+ channels), allows Na+ to enter cell down the gradient

Question 18

What does GABA do?

Answer 18

Attatched to GABA gated Cl- channels that make the inside of cell more negative –> inhibitory

Question 19

How are Ca2+ levels maintained?

Answer 19

*Sequestered back into cell membrane such as ER
* Binds to Ca2+ binding proteins
*Pumps it out

Question 20

What happens after the neurotransmitter binds to channel?

Answer 20

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

Question 21

How is action of neutrans terminated?

Answer 21

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

Question 22

What are electrical synapses?

Answer 22

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

Question 23

Excitatory neurotrans

Answer 23

ACh, Glutamate

Question 24

Inhibitory Nuerotrans

Answer 24

IPSP , GABA

Question 25

Why is there folding in postsyn cells?

Answer 25

Increase SA for Acetylcholine receptors

Question 26

Nerve-Nerve synapse

Answer 26

*Synapses are tiny
*1000S of synapses on postsyn cell
*AP of individuals neurons rarely brings next cell to threshold
*Excitatory/Inhibitory