Physiology 3120 Lecture Notes - Lecture 29: Otto Loewi, Vagus Nerve, Adrenergic Receptor
2 May 2018
School
Department
Course
Professor
Human Physiology Lecture 29
Autonomic Nervous System 2
November 22 2017
Otto Loewi
- Transmission: chemical or electrical?
- Idea came from a dream
- Heart in fluid + stimulate the vagus nerve
o Causes the HR to slow down (vagus nerve to heart decreases HR)
o Took fluid out of it (with the transmitter in it) and added it to the recipient heart
o Recipient heart slowed
- Evidence for CHEMICAL transmission
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find more resources at oneclass.com
POINTS TO KNOW:
i) Nicotinic receptor at ANS ganglion has different structure to that at NMJ (blocked by different
antagonists)
ii) Nicotinic receptor at ANS ganglion, like that at skeletal muscle NMJ, is ionotropic with fast EPSP
iii) Muscarinic receptors (G protein, slow EPSP) also occur at ANS ganglia. Therefore, at ANS ganglia
ACh acts on two different postsynaptic receptor types (nicotinic, muscarinic)
o There are also muscarinic receptors at ANS ganglia
o Slow effects because it is G coupled
iv) Muscarinic and Adrenergic alpha, beta receptors are metabotropic (G proteins with slow
signalling cascades)
o Slow effects because it is G coupled
o Eg., at ANS ganglia ACh produces a slow EPSP by closing a K+ channel, which results in less
outward K+, and depolarization
v) Different sub-types: Muscarinic (5), Adrenergic alpha (4), Adrenergic beta (3)
Receptor
Agonist
Antagonist
Action
Mechanism
Nicotinic Skeletal
Muscle (NM)
Ach
Nicotine (Tobacco)
d-Tubocurarine
(South American Indian
Poison)
alpha-
Bungarotoxin
(Snake poison)
Ligand gated
Opens Na+/K+
channel
Fast EPSP
Nicotinic ANS
Ganglion (NN)
ACh
Nicotine (Tobacco)
Hexamethonium
Ligand gated
Opens Na+/K+
channel
Fast EPSP
Muscarinic
ANS Ganglia,
Parasympathetic
Organs (5 subtypes
of muscarinic
receptors)
ACh
Muscarine
(Toadstool poison)
Atropine (deadly
nightshade)
G protein Coupled
Modify K+. Ca++
Channel
Conductance
Slow EPSP (G)
Slow IPSP
Adrenergic Alpha
(4 subtypes)
NorE > Epi
Phentolamine
G protein Coupled
Slow EPSP
Slow IPSP
Adrenergic Beta (3
subtypes)
Epi > NorE
Propanolol
G protein Coupled
Slow EPSP
Slow IPSP
- Muscarinic receptors in post ganglionic neuron in ANS, parasympathetic division will go to gland,
smooth muscle, or cardiac muscle
o Receptor on those organs are muscarinic
- Note: muscarinic receptors also occur at the ANS ganglion
- If G protein coupled – leads to slow effects
- On the sympathetic nervous system, on the post ganglionic to end organ, there are adrenergic
receptors
o Two types – Alpha + Beta
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Nicotinic receptor at ans ganglion has different structure to that at nmj (blocked by different antagonists) 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. Ach acts on two different postsynaptic receptor types (nicotinic, muscarinic: there are also muscarinic receptors at ans ganglia, slow effects because it is g coupled. Different sub-types: muscarinic (5), adrenergic alpha (4), adrenergic beta (3) Muscarinic receptors in post ganglionic neuron in ans, parasympathetic division will go to gland, smooth muscle, or cardiac muscle. On the sympathetic nervous system, on the post ganglionic to end organ, there are adrenergic: receptor on those organs are muscarinic. Note: muscarinic receptors also occur at the ans ganglion. If g protein coupled leads to slow effects: two types alpha + beta receptors.
