Parasympathetic Nervous System Receptor Mechanisms Flashcards
what are the 2 cholinergic receptors?
nicotinic and muscarinic receptors
what are the 2 types of nicotinic receptors?
N1/NN: present on SKM
N2/NM: present on all autonomic ganglia and CNS
what are the different types of muscarinic receptors?
- M1: present int he CNS, peripheral neurones and gastric parietal cells
- M2: on the atria, AVN and SAN
- M3:on visceral SM, secretory glands and endothelial cells
- M4: on the CNS
- M5: on the CNS
what are nicotinic receptors an example of?
ligand gated ion channels
what are muscarinic receptors an example of?
g protein coupled receptors
what do M1, M3 and M5 receptors interact with?
phospholipase C
what do M2 and M4 receptors interacts with
adenylate cyclase
how are the M2AchR activated in the SAN and AVN?
- the αi subunit of the G protein interacts with adenylate cyclase
- this decreases the amount of cAMP so less PKA is activated
- that means less Ca2+ is released thus decreasing force of contraction and slows HR
- βγ subunit of G protein interacts w K+ channel so cell is hyper polarised and that limits activation of the cell
describe the activation of the M3 receptors found on SM
- α11 subunit binds to PLC which causes Ca2+ to be released
- this causes the SM to contract
how does the activation of M3AchR indirectly relax arteries?
- endothelial layer of arteries activates NO synthase
- NO binds to gunnel cyclase which causes the relaxation of SM cell
what are the main PS effects and what are the receptors involved?
- M2 receptors: decrease in cardiac activity
- M3 receptors: increases secretion, genital erection, eye accommodation, contraction of the SM
how was does the activation of M3 cause penile erection?
- penile arteries + corpus cavernosum fills w blood and relaxes
- caused by small amounts of cholinergic neurones that bind to M3 receptors on the endothelial cells which release NO but mainly by NANC neurones
- NANCE releases NO which binds to gunnel cyclase which causes the rapid relaxation of SM
