Lec 34 Drugs acting on the ANS Flashcards
What is the 1 synapse vs 2 synapse organization of our nervous system?
somatic uses 1 synapse
autonomic system uses 2 synapses = have preganglionic and postganglionic fiber
What are the 3 branches of the ANS?
- parasympathetic
- sympathetic
- enteric
What is the action of enteric nervous system?
- complex network of neruons in gut wall
mostly independent of CNS
does extensive intrinsic gut activity including peristalsis
Where are preganglion cell bodies located for sympathetic vs parasympathetic?
SNS: thoracic and lumbar levels of spinal cord
PNS: medulla, sacral levels of spinal cord
Which nerves cary preganglionic axons for SNS vs PNS
SNS: thoracolumbar = thoracic + lumbar
PSN: craniosacral = cranial and sacral
Where are ganglia located for SNS vs PNS?
SNS: near spinal cord in paravertebral or prevertebral ganglia
PNS: near or in wall of innervated organ
In what tissues do the SNS and PNS exert complementary/similar effects?
male sex organs
uterus during labor
What tissues are only innervated by one branch [PNS or SNS]?
vasculature = only SNS
liver = only SNS
sweat glands = only SNS
generally when something is innervated by only one branch its going to be sympathetic!
What types of ANS synapses release ACh?
- all preganglionic neurons
- all postganglionic PNS neurons
- a few post-G SNS neurons = sweat glands
What types of ANS synapses release NE?
most sympathetic postganglionic neurons
What types of ANS synapses release dopamine?
sympathetic fibers that innervate the renal vasculature and some other vessel beds
What types of ANS synapses realease epinephrine?
not synaptic! its a hormone released by adrenal medulla
How can you tell wich is the predominant tone of a titssue?
usually its the branch of ANS that makes the organ or tissue contract/movie
ex. PNS increases GI motility so is dominant tone
exception: hearts predominant tone is PNS but PNS slows HR
How is ACh action terminated at synapse?
- acetylcholinesterase [AChE] on postsynaptic membrane hydrolyzes
What is action of physotstigmine?
inhibits AChE –> more ACh around –> more PNS
How is action of catecholamines [NE, Epi, Dopamine] terminated at synapse?
mainly by reuptake of transmitter
What type of receptor is cholinergic nicotinic receptor? cholinergic muscarinic receptor?
nicotinic = ionotropic = voltage gated muscarinic = GPCR
How does nAChR of ANS ganglia differ from one at NMJ?
Nn = ganglionic type
Nm = NMJ type
different morphologies –> drugs can be selective for one type or the other
What are the different types of muscarinic ACh receptors? What G proteins are they coupled to?
M1/M3/M5 = couple to Gq
- activate phospholipase C, increase Ca, stimulate protein kinase C; mostly M3 in ANS
M2/M4 = couple to Gi and Go
- inhibit adenylyl cyclase and hyperpolarize membrane via GIRKs [inward rectifying K channels]; mainly M2 in ANS; activate G
What type of receptors are a receptors vs B receptors
a = GPCRs B = GPCRs