L9: Drugs affecting the PNS Flashcards
What is the autonomic NS involved in?
Constant involuntary control of essential organs & functions
Subdivisions of the autonomic NS
1) Sympathetic NS
2) Parasympathetic NS
Function of sympathetic NS
Flight or fright
Function of parasympathetic NS
Activated at rest
Define ganglion
“Swelling” which contains a chemical synapse
Function of efferent nerves of parasympathetic NS
Leave the spinal cord in the medullary & sacral regions and carried by a system of pre-ganglionic & post-ganglionic nerve
Where does chemical synaptic transmission occur?
Ganglia & the “neuro-effector junction”
Define “neuro-effector junction”
Synpase between post ganglionic nerve & organ being controlled
Key neurotransmitter in the parasympathetic NS
Acetylcholine (ACh)
How does ACh play a role as neurotransmitter in the ganglia & neuroeffector junctions?
Released from both pre- & post-ganglionic nerves
What does ACh act on in the ganglia?
On nictotinic receptors found on post-ganglionic nerves
What does ACh act on in the neuroeffector junction?
On muscarinic receptors found on cells of target organ
Function of efferent nerves of the sympathetic NS
Leaves the spinal cord in the thoracic & lumbar regions
Compare pre-ganglionic nerve fibres between SNS & PSNS
SNS pre-ganglionic nerve fibres are shorter than post-ganglionic nerve, but PSNS is the opposite way around
Key neurotransmitters in the sympathetic NS
ACh & noradrenaline
2 receptors found in PSNS
1) Nicotinic (ganglia)
2) Muscarinic (NEJ)
Receptors in the SNS
1) Nicotinic (ganglia)
2) Muscarinic (sweat glands)
2 types of ACh receptors
1) Nicotinic
2) Musarinic
Where is “ganglionic” nicotinic ACh receptors found?
In the ganglia of both PSNS & SNS
Where is muscarinic ACh receptors found?
At the neuroeffector junctions of the parasympathetic NS
Action of inhibitors of acetylcholinesterase
Enhance the effects of ACh by preventing its destruction
3 types of inhibitors of acetylcholinesterase
1) Edrophonium
2) Neostigmine
3) Irreversible, organophosphates
