lecture 4 - claudia racca

Question 1

what are the two types of receptors

Answer 1

ionotropic and metabotropic

Question 2

what are receptors distinguished by

Answer 2

the NT that they bind to

Question 3

what are the types of receptors that bind to ACh

Answer 3

muscarinic and nicotinic

Question 4

what are the types of receptors that bind to glutamate

Answer 4

NMDA
non-NMDA (AMPA and kainate)

Question 5

what are the types of the receptors that bind to GABA

Answer 5

GABAa
GABAb
etc

Question 6

what is the main excitatory NT

Answer 6

glutamate

Question 7

are glutamate receptors (AMPA, NMDA and kainate) ionotropic or metabotropic

Answer 7

ionotropic receptors

Question 8

How does the NMDA receptor function

Answer 8

At resting membrane potential (~65mV) the receptor is blocked by Mg2+ molecule in the pore.
when the membrane depolarises the Mg2+ moves out of the pore.
The NMDA receptor also requires glycine as well as glutamate to open.
Then calcium and sodium can move in and potassium out.

Question 9

examples of ionotropic receptors

Answer 9

• ACh nicotinic
• Glutamate (AMPA, NMDA and kainate)
• GABAa
• Glycine receptor

Question 10

examples of metabotropic receptors

Answer 10

• ACh muscarinic
• Glutamate metabotropic
• GABAb
• 5HT receptor
• Dopamine receptor
• NE receptor

Question 11

what is an autoreceptor

Answer 11

receptors on the presynaptic membrane

Question 12

what do autoreceptors do

Answer 12

regulate neurotransmitter synthesis and release

Question 13

excitatory receptors cause

Answer 13

depolarisation of the post synaptic membrane by sodium moving across the membrane

Question 14

inhibitory receptors cause

Answer 14

hyperpolarisation of the post synaptic membrane by chloride ions moving across the membrane

Question 15

how do metabotropic receptors work

Answer 15

they are G protein coupled

Question 16

how many membrane spanning domains do metabotropic receptors have

Answer 16

7

Question 17

G protein can also be inhibitory or excitatory

Answer 17

Gs - stimulates effector protein
Gi - inhibits effector protein

Question 18

two metabotropic effector systems

Answer 18

shortcut (GABAb, mACh)
2nd messenger cascade (NE)

Question 19

G protein shortcut pathway

Answer 19

ACh binds to the muscarinic receptor and activates the G protein and the alpha subunit which is bound to GTP phosphorylates the potassium channel which will then open.

Question 20

G protein 2nd messenger cascade pathway

Answer 20

activation of the G protein causes phosphorylation of an enzyme and this causes a signalling cascade
takes longer but creates a stronger response (more channels open)

Question 21

a single neuron receives thousand of synapses and the inputs may be…

Answer 21

excitatory and inhibitory

Question 22

these inputs interact to produce a…

Answer 22

synaptic potential
if above threshold the cell will fire an action potential

Question 23

what are the different types of synapses

Answer 23

axodendritic
axosomatic
axoaxonic

Question 24

EPSP spatial summation

Answer 24

multiple excitatory synapses coming in to the same dendrite at the same time
causes a large increase in membrane potential

Question 25

EPSP temporal summation

Answer 25

one synapse on a dendrite but there are multiple APs coming in from the same axon within 1-15ms of each other the individual EPSEs generated at the same synapse add together.

Question 26

whether or not an EPSE contributes to the generation of an AP depends on

Answer 26

- number of coactive synapses - distance of the synapse from the spike initiation zone in the axon - properties of dendritic membrane - nature of the synapses (excitatory vs inhibitory)

Question 27

current is injected into the dendrite and the depolarisation is recorded. as this current spreads down the dendrite, much of it dissipates across the membrane. therefore the depolarisation (EPSP) measured at a distance from the site of current injection is...

Answer 27

smaller than that measured at the site of injection

Question 28

voltage gated channels are present on dendrites and can...

Answer 28

amplify small EPSPs

Question 29

inhibitory synapse causes the depolarising current from the excitatory synapse to leak out before it reaches the soma. this is called...

Answer 29

shunting

Question 30

the effect of NE binding to NE beta receptors

Answer 30

- NE binding to beta receptors activated G protein - G protein activates the enzyme adenylyl cyclase - adenylyl cyclase converts ATP --> cAMP - cAMP activated a protein kinase - kinase phosphorylates a potassium channel in the dendrite - phosphorylation causes potassium channel to close - closure of potassium channels insulates the dendrite, excitable signals spread to soma more easily