Lect 2 - neuro excitation/inhibition/modulation

Question 1

differentiate between excitatory, inhibitory, and modulatory

Answer 1

excitatory - increase excitability of the cell

inhibitory - makes resting membrane less likely to depolarise

modulatory - indirectly change excitability of the pre or postsynaptic membrane without having direct effects

Question 2

what is reversal potential, what’s its relationship to the quilibrium potential, does it differ between excite and inhib reps

Answer 2

reversal potential is the membrane potential at which there is no net movement of ions across the membrane

it is the same as the equilibrium potential

lower Erev mean that the membrane is capped at that voltage therefore if threshold is higher than it, the postsynaptic response is more likely to be an IPSP

Question 3

which one is bigger, ESPS or EPP? what consequences does this have on ESPS

Answer 3

EPSP is much smaller, so EPSP must always be summed for it to have an effect. EPP are much larger and is fail-safe in that it will always have an excitory postsynpatic response

Question 4

what is an example of excitatory NT

Answer 4

gluatmatergic, e.g. glutamate or aspartate

Question 5

what is an example of modulatory NT

Answer 5

norepinephrine

Question 6

how is modulatory synapse different to the other two

Answer 6

modulatory synapse doesn’t have direct effect on synapse, but makes them more or less sensitive

Question 7

describe the typical characteristic of modualtory synapse, why do we need them

Answer 7

generally mediated by slower metatropic receptors (G-protein coupled receptors)

hence they are slower and last longer, they will undergo signal amplification.

there is also more potential and flexibility to vary excitability

Question 8

what happens when K channels are closed

Answer 8

cells harder to depolarise, leading to greater excitablity

Question 9

compare what happen in excitation vs inhibition in terms of ion channels openning

Answer 9

excitation: we dont want K to go, we dont want Cl to come in

Question 10

what is the presynaptic effect

Answer 10

reduced NT release or production

Question 11

list some types of NTs, what are some differences between them

Answer 11

gases, amino acids, monamines, catcholamines, purines, lipid metabolites, peptides

amino acids and biogenic amines are small and fast acting

peptides are slower acting but have long term change

Question 12

what are the 3 ways by which NT signals achieve its effect

Answer 12

1. ligand-gated (fastest, 1 bound receptor = 1 open channel)
2. amplification by membrane pathway aka G-protein
3. amplification by signally cascade, longer term change
   (e. g. bound receptor -> alpha-subunits -> make many cAMPs -> protein -> protein kinase opens heaps of channels)

Question 13

what are examples of inotropic receptors

Answer 13

a

Question 14

differentiate between ionotropic and metatropic

Answer 14

a

Question 15

describe the glutamate cycle

Answer 15

a

Question 16

what are the 3 main ionotropic glutamate receptors

Answer 16

a

Question 17

why is there a delay in repolarization with NMDA receptors

Answer 17

a

Question 18

what are the types of metabotropic glutamate receptors

Answer 18

a

Question 19

describe the typical exitatory synpase

Answer 19

most of them use glutamatergic

opens non-selective Na/K ion channels (fast)

increase excitabiliyt of membrane

Question 20

describe the typical inhibitory synpase

Answer 20

most use GABAergic or glycinergic, e.g. GABA or glycine

also mediated by fast ionotropic receptors

IPSP by opening Cl channels - negative keeps the cell polarised, they keep membrane voltage away from potential threshold

in reality, the excitability of most neurons is determined by the balance of excitory and inhibitory

Question 21

what are the two types of excitatory synapses?

Answer 21

glutamatergic - glutamate

cholinergic - ACh

Question 22

why is glutamate controlled, and how is it controlled

Answer 22

highly toxic, controlled via uptake, using e.g. astrocytes

EAAT transports glutamate to either glial cells, where it is made into glutamine, or back into the presynaptic terminal for reuse

Question 23

what are the 3 ionotropic glutamate receptors, and what are their characteristics

Answer 23

1. AMPA - for fast stuff
2. NMDA - synaptic plasticity (therefore need to be slow)
3. Kainate - regulates release of GABA

Question 24

compare AMPA with NMDA

Answer 24

AMPA - nice and fast, open even with negative membrane potential

NMDA - slower acting, opens when Vm is more positive (because of Mg plug). this brings in Ca which signals long term change

NMDA is like a coincidence detector, important for plasticity and developent

Question 25

how are metabotropic glutamate receptors different

Answer 25

metatropic means signal requires second messenger.

Glu meta receptors function in the perisynaptic membrane

there are different subtypes, one of which is autoreceptor

Question 26

difference between nicotinic and muscarinic, where are they found

Answer 26

nicotinic - ionotropic ACh receptor
found in NMJ CNS

muscarinic - metabotropic ACh receptor
efferents innervating the heart

Question 27

what are the 2 types of inhibitory synapses

Answer 27

GABA

Glycine

Question 28

what are interneurons

Answer 28

neurons that are within the same nuclei

Question 29

how is GABAa and GABAb different, where are they located

Answer 29

GABAa is ionotropic
GABAb is metabotropic

GABAa is fast in CNS
GABAb is slow in CNS

Question 30

what are the 5 type of modulatory synapses

Answer 30

1. gasses
2. biogenic amines
3. purines
4. peptides
5. lipid

Question 31

what are some examples of biogenic amines

Answer 31

dopamine
noradrenaline
serotonin
histamine

Question 32

what are the roles of these basic amines

Answer 32

setting global states such as arousal, attention, mood

Question 33

what is an example of modulatory purine

Answer 33

ATP, which is coreleased with NT

ATP modifies the action of other transmitters such as NA, DA, Glu, GABA

Question 34

how does cannibis affect the brain

Answer 34

through G-protein coupled receptors

reduce the opening of Ca channels, this leading to reduce in Glu or GABA