Synaptic Transmission

Front 1

How can a signal be transferred?

Back 1

1. Synapse (neuron to neuron)
2. Neuromuscular junction (neurone-muscle)
3.Neuroglandular junction (neuron - gland)

Front 2

What are the two types of synapse?

Back 2

Chemical (most common in vertebrates) and electrical

Front 3

What is an agonist?

Back 3

drugs that mimic that action of natural transmitter

Front 4

What is an antagonist?

Back 4

drugs that block the actions of neurotransmitters (bind to receptor but do not activate)

Front 5

What was the first established neurotransmitter?

Back 5

Acetylcholine

Front 6

Name an agonist..

Back 6

Nicotine (operates through nicotinic acetylcholine receptors)

Front 7

What does curare do?

Back 7

prevents transmission at nicotinic receptors (antagonist) causing paralysis

Front 8

In what way is curare competitive?

Back 8

it competes, against acetylcholine, for binding sites on the nicotinic receptor

Front 9

How would you reverse the action of curare?

Back 9

Use Eserine to inactivate acetylcholine esterase so that acetylcholine is no longer degraded. Enough acetylcholine can now build up to knock curare from the binding sites.

Front 10

Chemical synapses have two actions, what are these?

Back 10

Excitation or inhibition

Front 11

What does an excitatory neurotransmitter cause?

Back 11

depolarisation of postsynaptic membrane (less negative) ==> An EPSP (Excitatory Post synaptic Potential)

Front 12

What is required to reach action potential?

Back 12

Summation of several EPSPs (either by temporal or spatial summation)

Front 13

What does an inhibitory transmitter cause?

Back 13

hyperpolarisation of the post synaptic membrane- IPSP (inhibitory post synaptic potential)- reduces chance of neuron reaching action potential

Front 14

Where are excitatory synapses usually located?

Back 14

dendritic tree

Front 15

Where are inhibitory synapses usually located?

Back 15

cell body and axon hillock

Front 16

What is presynaptic inhibition?

Back 16

axo-axonic synapse reduces the amount of transmitter released by the axon terminal

Front 17

How do you tell if a synapse is electrical?

Back 17

there is no synaptic delay

Front 18

What does an electrical synapse have?

Back 18

A gap junction

Front 19

What is responsible for communication at electrical synapses?

Back 19

connexions

Front 20

Why are electrical synapses useful?

Back 20

escape mechanism, synchronising neuronal activity

Front 21

How do you tell the difference between a neurotransmitter and neuromodulator?

Back 21

the first acts quickly creating transient EPSPs and IPSPs, while the second acts slowly which creates EPSPs and IPSPs that last for longer

Front 22

Name the 5 stages that must be met to identify a neurotransmitter..

Back 22

Synthesis, Presence, Release, Action, Inactivation

Front 23

Where are transmitters stored?

Back 23

In vesicles at the presynaptic axon terminal

Front 24

Small molecules transmitters are thought of differently to large molecule transmitters, why is this?

Back 24

small molecule transmitters are synthesised at axon terminals while large molecule transmitters are synthesised in the cell body and then transported to nerve terminals by axonal transport

Front 25

What is essential for transmitter release?

Back 25

Calcium ions (depolarisation of pre synaptic membrane allows Ca in to initiate release of transmitter)

Front 26

What can block release?

Back 26

Magnesium ions

Front 27

Release of transmitter is quantal. What does this mean?

Back 27

transmitters are released in uniform packets (single vesicle = quantum)

Front 28

What do auto-receptors do?

Back 28

regulate presynaptic activity

Front 29

There are two classes of postsynaptic receptor, what are these?

Back 29

Ionotropic and Metabotropic

Front 30

What receptors are associated with fast transmission?

Back 30

Ionotropic receptors ( e.g. nicotinic)

Front 31

What receptors are associated with slow action?

Back 31

Metabotropic receptors

Front 32

Metabotropic receptors are special why?

Back 32

They use second messengers which can also trigger cascades with are important for longterm changes such as acquiring new information- learning

Front 33

In what three ways may a transmitter be inactivated?

Back 33

1. Ezymatic breakdown (acetyl choline esterase breaks down acetylcholine)
2. specific uptake (monoamines)
3. diffusion (peptides)