Physiology 3120 Lecture Notes - Lecture 9: Long-Term Potentiation, Skeletal Muscle, Atropa Belladonna
9 May 2018
School
Department
Course
Professor
Physiology 3120
Dr. Hore
Lecture 17
ANS II
Otto Loewi
- 100 years ago they did not know how a synaptic junction
worked, they thought it was either via a chemical or
electrical
- so this man otto loewi ask is the transmission chemical or electrical?
- Have a heart in some sort of fluid
- Stimulate the vagus nerve – causing the HR to slow (bc it sht PSYN nerve to the heart)
- He then removed some of the fluid, now with some of the transmitter in it and added some of it
to the recipient heart
- The recipient heart also slowed down
- At the time, they realized that was a evidence that is CHEMICAL transmission
Receptor
Agonist
Antagonist
Action
Mechanism
Nicotinic
Skeletal
Muscle
(NM)
ACh
Nicotine
(from tobacco)
d-Tubocurarine
(South American
Indian Poison)
α-Bungarotoxin
(Snake poison)
Ligand Gated
Opens Na+ and K+ and
Ca2+ Channel
Fast EPSP
Nicotinic
ANS Ganglion
(NN)
ACh
Nicotine
(Tobacco)
Hexamethonium
Ligand Gated
Opens Na+ and K+
Channel
Fast EPSP
Muscarinic
At the ANS Ganglia,
At the
Parasympathetic
Organs
(there are 5 subtypes)
ACh
Muscarine
(Toadstool
poison)
Atropine
(Deadly nightshade)
G Protein
Coupled
Modify K+ , Ca++
Channel
Conductances
Slow EPSP (bc they
are G protein
coupled)
Slow IPSP
Adrenergic
Alpha
(4 subtypes)
NE has a greater
effect on
adrenergic alpha
than Epinephrine
Phentolamine
G Protein
Coupled
Slow EPSP
Slow IPSP
Adrenergic
Beta
(3 subtypes)
Epi has a greater
effect on
adrenergice beta
receptors than NE
Propanolol
G Protein
Coupled
Slow EPSP
Slow IPSP
find more resources at oneclass.com
find more resources at oneclass.com
- Nicotinic receptor at ANS ganglion has different structure to that at NMJ
- Nicotinic receptor at ANS ganglion, like that at skeletal muscle NMJ, is ionotropic with fast EPSP
- Muscarinic receptors (G protein, slow EPSP) also occur at ANS ganglia
o Therefore at ANS ganglia, ACh acts on 2 different postsynaptic receptor types
- Muscarinic and Adrenergic alpha, beta receptors are metabotropic (acting through G proteins)
- Different sub-types: Muscarinic (5), Adrenergic alpha (4), Adrenergic beta (3)
- There is co-transmission
o You could have either very slow or very fast changes in electrical potential at the
postsynaptic side
o For ex at ANS ganglia
▪ Nicotinic receptor Fast EPSP (10-50ms)Initiates Action Potential
▪ Muscarinic Slow EPSP ’s msIncreases Excitability
▪ Peptidergic Very Slow (minutes) Increases Excitability
• There is a release of peptides at the same time that there is the release
of Ach which can then produce very slow electrical potentials to
increase excitability
▪ So you have the possibility of a bunch of diff things happening at the ganglion in
terms of potentiating - you can have a very long term potentiation, or a medium
one or a very instant electrical potential to produce and AP
▪ Metabotropic: Like LTP (Long Term Potentiation)
• This is somewhat like long term potentiation in NMDA receptors
• In the gut, LTP For ion channels can occur by: Increase
Sensitivity(opening them up in some way to allow ions to come
through), Insertion into membrane, Alter gene expression
o Co-transmission also in enteric nervous system
▪ Most postganlionic axons have varicosities (bulbous enlargements)
▪ Adrenergic Varicosities Decrease activity in the gut (smooth muscle, blood
flow, glands)
▪ Cholinergic Varicosities in the gutpostganglionic axons will Increase activity
(smooth muscle, blood flow, glands)
▪ Purinergic ReceptorsATP is the excitatory transmitter (WEIRDDDDDD)
- Here is a post ganglionic neuron coming down and having a lot of end branches
- Each of the bulbous things is a varicosity
- This could be either in the postganglionic axon in the SYN or PSYN
- Within each varicosity, there are vesicles with transmitter in them
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Have a heart in some sort of fluid. He then removed some of the fluid, now with some of the transmitter in it and added some of it. Stimulate the vagus nerve causing the hr to slow (bc it sht psyn nerve to the heart) to the recipient heart. At the time, they realized that was a evidence that is chemical transmission. Ne has a greater effect on adrenergic alpha than epinephrine. Epi has a greater effect on adrenergice beta receptors than ne. Slow epsp (bc they are g protein coupled) Nicotinic receptor at ans ganglion has different structure to that at nmj. Nicotinic receptor at ans ganglion, like that at skeletal muscle nmj, is ionotropic with fast epsp. Muscarinic receptors (g protein, slow epsp) also occur at ans ganglia: therefore at ans ganglia, ach acts on 2 different postsynaptic receptor types. Muscarinic and adrenergic alpha, beta receptors are metabotropic (acting through g proteins)
