Integration of synaptic potentials

Question 1

action potential characteristic, pros, cons

Answer 1

Characteristic: highly coordinated activity of Na+ and K+ ion channels, all or nothing, brief
Pros: signal size maintained over distance, versatility of information coding (freq encoding, pattern encoding)
Cons: membrane must be hyperpolarised to start, system must be reprimed after use (refractory period)

Question 2

sketch a graph of the synaptic potential as the neurotransmitter passes through the synaptic cleft

Answer 2

ref. notes

Question 3

How do synaptic potentials decay

Answer 3

unbinding, diffusion, uptake
Glutamate acts at AMPA Rs->decline of EPSP thought to be ddue to AMPA R desensitization
destruction of ACh by cholinesterase in cholinergic synaapses

Question 4

What are EPSP amplitude and decay ussually dependent on

Answer 4

Amplitude:
1. Amount of neurotransmitter released
2. Number of receptors
3. state of receptors
Decay: 
1. Dissociation of ligand
2. Diffusion and uptake
(3. Desnsitisation AMPA-glutamate receptors
4. Enzymatic destruction e.g. ACh)

Question 5

What happens at the axon hillock

Answer 5

synaptic potentials contributing to somatic depolarisation leading to generation of action potential summates here

Question 6

EPSP characteristics, pros, cons

Answer 6

Characteristics: not all or nothing, usually fast, fast EPSP usually due to activation of ligand-gated non specific cation channels
Pros: diff transmitters can act on same post synaptic cell using diff receptors, diff receptor/channels can be regulated independently independent post synaptic and presynaptic control of synaptic strength
cons: metabolically expensive, vulnerable to chemical attacks

Question 7

Sketch a graph for the inhibitory post synaptic potential

Answer 7

ref. notes

Question 8

What does IPSP do

Answer 8

prevent somatic depolarisation and generation of an AP at the axon hillock

Question 9

IPSP characteristics, pros, cons

Answer 9

Characteristics: not all or nothing,, usually fast, fast
Pros: diff transmitters can act on same post synaptic cell using diff receptors, diff receptor/channels can be regulated independently independent post synaptic and presynaptic control of synaptic strength
cons: metabolically expensive, vulnerable to chemical attacks

Question 10

In convergence, what determines whether post synaptic neurone will fire

Answer 10

whether the EPSP and IPSP add together to cause sufficient depolarisation of axon hillock

Question 11

Sketch a graph for convergence

Answer 11

ref. notes

Question 12

Why can acuity of sensation be compromised at higher levels in the neuronal network and how can it be restored

Answer 12

compromised due to divergence of sensory signal at higher levels in the network
Can be restored due to ‘surround’ inhibition by negative feedback mediated by inhibitory interneurones

Question 13

What are the three types if inhibtion by intterneurones and what do they involve

Answer 13

feed forward, feedback, recurrent ref. notes