Module 3: Synaptic transmission

Question 1

what is temporal summation?

Answer 1

when 2 EPSPs from the same presynaptic neuron occur close in time to depolarise the membrane to threshold

Question 2

what is spatial summation?

Answer 2

2 EPSP from different presynaptic neurons occur close in time to depolarise the membrane threshold

Question 3

what’s the difference between temporal and spatial summation?

Answer 3

temporal: EPSP from same presynaptic neuron
Spatial: EPSP from 2 different presynaptic neurons

Question 4

where does a synapse occur?

Answer 4

At the end of the axon - presynaptic neuron/axon terminal - and post synaptic neuron (attached to other neuron area)

Question 5

where can synapses form on a neuron?

Answer 5

cell body: axosomatic
dendrite:axodendritic
hillock:axoaxonal synapse

Question 6

which neuron to neuron synapse is most common?

Answer 6

axon-dendrite (axodendritic)

Question 7

what is the name for the chemicals in the vesicles of the presynaptic neuron/axon terminal?

Answer 7

neurotransmitters

Question 8

are neurotransmitter chemical or electrical?

Answer 8

chemical

Question 9

what is the name of the gap between the presynaptic terminal and postsynaptic terminal?

Answer 9

the synaptic cleft

Question 10

how do the receptor proteins work in the postsynaptic terminal?

Answer 10

the neurotransmitters chemically bond to the protein receptors, opening them

Question 11

how do the electrical signals from the axon terminal convert into a chemical signal?

Answer 11

the voltage from the action potential triggers the +Ca2 voltage gated protein to open, flooding the presynaptic terminal and causing the vesciles to exocytosis to the membrane wall.

Question 12

what happens when the neurotransmitters are in the synapse cleft?

Answer 12

the neurotransmitters bond to the ligand or g couple protein gates and cause them to open, allowing Na+,K+ and Cl- to flow bidirectionally across the postsynaptic membrane generating a local or graded potential

Question 13

why is it useful to have many electrical transmitters happening?

Answer 13

allows to modification of the signal

Question 14

what is a ligand gated ion channel?

Answer 14

a channel that is activated by chemicals (neurotransmitters) which allow ions to flow through and cause a direct change in the EPSP or IPSP

Question 15

what does the ligand gate do?

Answer 15

creates a small and direct change in the voltage to create a local or graded potential

Question 16

how is synaptic transmission terminated?

Answer 16

1. breakdown by enzymes in the cleft
2. diffusion away from the cleft and break down elsewhere
3. reuptake into the presynaptic axon terminal or dealth with by the astrocytes

Question 17

are synapses excitatory or inhibitory

Answer 17

both

Question 18

what does it mean to have an excitatory postsynaptic potential (EPSP)?

Answer 18

it allows more positive ions into the cell, like Na+ and some positive out (K+) causing the cell the depolarise and becomes closer to triggering an action potential

Question 19

what does it mean to have an inhibitory postsynaptic potential (IPSP)?

Answer 19

it allows more negative ions into the cell, like Cl- and some positive out (K+) causing the cell the hyperpolarise and becomes further away to triggering an action potential

Question 20

why don’t local/graded potentials create action potentials on their own?

Answer 20

1. they don’t have a strong enough voltage to cause one
2. there’s not enough voltage gated Na+ channels in the areas to create a postivie feedback loop.

Question 21

how do local/graded potentials create an action potential?

Answer 21

1. temporal summation: same neuron firing twice
2. spatial summation: 2 neurons firing twice

Question 22

what does summation mean?

Answer 22

to stack

Question 23

what are the 9 characteristics of graded potentials?

Answer 23

1. local event in: dendrite, cell body or hillock
2. peter out
3. have different sizes of voltage
4. no positive feedback loop due to lack of Na+ channels
5. repolarisation occurs due to peetering out of stimulus
6. can summate (stack)
7. underlied by a chemical/ligand channel
8. can be excitatory or inhibiory
9. chemical stimulus/trigger

Question 24

what are the 9 characteristics of an action potential?

Answer 24

1. triggered by an accumulation of graded potentials in the hillock only
2. can travel long distances due to voltage gated channels in the axon
3. always the same size ( all or nothing) +30mV and doesn’t decay
4. has a voltage stimulus.trigger
5. has a positive feedback loop
6. repolarisation is voltage dependent and mediated by K+ channels
7. can’t summate due to refactory periods
8. only excitatory
9. underlied by voltage gated ion channels

Question 25

what are the 3 dependents of the effect or synaptic transmission?

Answer 25

1. type of cell it terminates on e.g. neuron, heart, skeletal muscle 2. type of neurotransmitter the neuron releases e.g. excitatory or inhibitory (created during foetal development) 3. types of neurotranmittor receptors on the postsynaptic membrane e.g. ligand gate

Question 26

what is a synaptic transmission?

Answer 26

when a neuron axon attached to any cell

Question 27

what is a neurotransmittor?

Answer 27

when a neuron axon attaches to another neuron

Question 28

what are the 2 main types of neurotransmitters present in the synapses in neurons?

Answer 28

1. ligand gated ion channels: fast and direct because neurotransmitters bind to channel and allow neurons to directly flow through 2. G protein coupled receptor: slow and indirect because the activation doesn't directly affect the neurons, but affects the neuron flow by changing width of opening in channel

Question 29

excitatory neurotransmitters examples

Answer 29

glutamate and acetylcholine

Question 30

inhibitory neurotransmitters examples

Answer 30

GABA and glycine

Question 31

g protein receptor example

Answer 31

dopamine

Question 32

do neurotransmittors have specicific channels they can bind to?

Answer 32

no, most of them can bind to both types of channels

Question 33

what decides the effect of the neurotransmitter?

Answer 33

the receptors expressed by the postsynaptic cell