Autonomics 3 Flashcards
What type of receptor do preganglionic parasympathetic fibers synapse on?
nicotinic
What type of receptor do postgangilonic parasympathetic fibers synapse on?
muscarinic receptors
Two Types of Cholinergic Receptors
- Nicotinic
- Muscarinic
Describe the path of ACh in the synapse.
- Aceytlcholine made in presynaptic neuron from choline and acetyl CoA
- Released from a vesicle into the synapse
- Some ACh will bind to receptors, other will be broken down by acetylcholinesterase
- Choline transported back into axon terminal to make more ACh
Are nicotinic receptors always excitatory?
yes
What type of receptor is a nicotinic receptor?
ligand-gated ion channel (ACh binds and causes channel to open, Na+ rushes in and membrane depolarizes)
What type of receptor will you find in neuromuscular junctions?
nicotinic
Nicotine
mimics ACh at nicotinic receptors
How many types of muscarinic receptors are there?
five (5)
Muscarine
mimics ACh at muscarinic receptors; water-soluble toxin derived from a mushroom
Are muscarinic receptors always excitatory?
NO, they can be excitatory or inhibitory, depending on type and where it binds
What are muscarinic receptors bound to?
G-proteins, and second messenger systems (therefore slower acting and more local)
Gq
excitatory G protein
Gi
inhibitory G protein
Which muscarinic receptors are excitatory?
M1, M3, and M5