Download Module 725 1. [6 marks] a Briefly define an autoreceptor Receptor

Module 725
1. [6 marks] a Briefly define an autoreceptor
Receptor on presynaptic cell for its own transmitter
b Give two proposed functions of autoreceptors
i
regulation of transmitter release
ii
control of LTP (long term potentiation
2. a With the aid of diagram(s) describe the uptake of amines at a synapse [4 marks]
12 span protein, co-transport using Na gradient
Diagram to follow
b Distinguish the actions of Prozac and cocaine on uptake. [2 marks]
Prozac is selective for serotonin (SSRI) cocaine is not specific for serotonin
3. a Explain the cause of Parkinson’s disease [2 marks]
loss of dopaminergic cells in substantia nigra
b. Give 4 treatments and suggest a disadvantage of each [8 marks]
i.
L-DOPA effective for a while – (less effective as time goes on)
ii.
MAO inhibitors e.g. selegiline (interesting range of side effects)
iii.
cell replacement (rejection, fetal issues, xenografts)
iv.
deep brain/thalamus stimulation (expensive, experimental)
4. Briefly describe FOUR functions that astrocytes perform in the CNS. [8 marks]
a,
spatial buffering – uptake of K+ at nodes/synapses and release near blood vessels
b,
maintain the blood-CNS barrier to create safe environment in CNS
c.
help with neurotransmitter uptake at synapses especially of glutamate. recycle it to
neurones as glutamine
d.
help in energy supply to neurones-take up glucose at blood vessels, export it as
lactate to neurones. Or derived from glycogen
5. Metabotropic receptors in the CNS largely signal through heterotrimeric G proteins.
Briefly describe FIVE downstream results which may result from their activation. [10
marks]
a, G s activates andenylylcyclase to generate cAMP. This can activate cAMP-sensitive
ion channels.
b, cAMP generated as in a above activates PKA which phosphorylates CREB leading to
increased transcription of relevant genes
c, PKA activated by cAMP and associated with AKAP scaffolds phosphorylates specific
channels to alter their function, eg AMPA/L-type Ca2+ and K+ channels
d, G q activates PI-phospholipase C leading to hydrolysis fo PIPs, formation of
DAG and IP3 second messengers. DAG activates PKC which phosphorylates channels.
IP3 triggers Ca2+ release from e/r stores activating calmodulin leading to activation of
CaCaM which influences ion channel activity.
e,
subunits from heterotrimeric G proteins activated at the muscarinic ACh receptor in
heart tissue cause opening of a K+ channel hyperpolarising the membrane.
Essay title:
Either
Describe the evolution of voltage-activated ion channels
or
Discuss how oligodendrocytes develop and myelinate axons in the CNS.