The release of noradrenaline from a presynaptic neuron stimulated postsynaptic a
ID: 277740 • Letter: T
Question
The release of noradrenaline from a presynaptic neuron stimulated postsynaptic a-adrenoceptors. This caused an influx of Ca2+ ions and stimulated the postsynaptic neuron.
The scenario in the background is an example of
a. Direct synaptic transmission
b. Hyperpolarization
c. An amino acid acting as a neurotransmitter
d. Ca2+ acting as a second messenger
e. A response mediated by ligand-gated sodium channels
I believe the answer is D but was hoping someone could give some context and reasoning just to confirm my thoughts! Thanks
Explanation / Answer
The answer is 'A' which is direct synaptic transmission.
Stimulation of post synaptic adrenoreceptors leads to influx of Ca2+ and stimulation of postsynaptic neuron.
Explanation:
All adrenoreceptors are G-protein coupled receptors (GPCRs), Most of these GPCRs follows three pathways i.e Adenylyl cyclase/cAMP pathway, Phospholipase-C/IP3 /DAG pathway and activation ion channels (particularly Ca2+and K+ channels) pathway.
Activation of Adenylyl cyclase converts ATP into cyclic AMP(cAMP) which in turn activates cAMP dependent protein kinases. Activation of cAMP dependent protein kinases increases the activity of voltage-gated calcium channels which leads leads to influx of Ca2+.
Activation of phospholipase C converts phosphatidylinositol (4,5) bisphosphate (PIP2), to diacylglycerol
(DAG) and inositol (1,4,5) trisphosphate(IP3). (IP3) binds to IP3receptor-which is a ligand-gated calcium channel which which increases the release of Ca2+ from intracellular stores.