Introduction to the Autonomic Nervous System Flashcards
Which limb of the autonomic nervous system has more of an effect on the Liver?
Sympathetic – causes hepatic gluconeogenesis and glycogenolysis
Which limb of the autonomic nervous system dominates the lungs and the eyes at rest?
Parasympathetic
Lungs – causes partial bronchoconstriction
Eyes – allows near vision
Describe the relationship between baroreceptor firing and parasympathetic discharge.
Baroreceptors are stimulatory to the parasympathetic nerves i.e. an increase in baroreceptor firing stimulates an increase in parasympathetic firing
- ie increased barareceptor firing activates parasympathetic fibres to heart, inhibitory and slows heart rate
Describe the differences between sympathetic responses and parasympathetic responses.
Sympathetic – coordinated and divergent
Parasympathetic – discrete and localised
What type of receptor are nicotinic receptors?
Type 1 – ionotropic receptors
They are VERY fast
What type of receptor are muscarinic receptors?
Type 2 – G-protein coupled receptors
Slower than Type 1 receptors
Describe the difference in the transmission through nicotinic and muscarinic receptors.
Nicotinic is much faster
What effect does parasympathetic dominance at rest have on the: lungs, gut, bladder and eyes?
Lungs – partial bronchoconstriction
Gut – increased gut motility
Bladder – increased urinary frequency
Eyes – short-sightedness
Why would giving a ganglion blocker at rest cause constipation?
At rest the parasympathetic nervous system is dominant, which increases gastric motility. This means that a ganglion blocker will knock out this effect and cause constipation.
Where are the 5 (three MAIN) types of muscarinic receptor found?
M1 – neural tissue (forbrain, learning and memory)
M2 – heart cardiac (slow HR) Brain (inhibitory autoreceptors)
M3 – exocrine and smooth muscle (contraction) hypothalamus (food intake)
M4 - periphery, pre-junctional nerve endings (inhib)
M5- striatal dopaminergic release
Which adrenergic receptors are responsible for the sympathetic control of vasculature?
Alpha 1 – constriction
Beta 2 – dilation
What type of receptor are all adrenergic receptors?
G-protein coupled
Describe the synthesis of acetylcholine. and action
It is formed from acetyl CoA and choline by choline acetyltransferase
It is broken down by acetyl cholinesterase
- ach + coA causes Ca2+ in and Ach out, binds to receptor in effector cell and then broken down by acetylcholine esterase)
Describe the synthesis of Noradrenaline and its release
Tyrosine -> DOPA (enzyme: tyrosine hydroxylase)
DOPA -> dopamine (enzyme: DOPA decarboxylase)
Dopamine -> Noradrenaline (enzyme: dopamine beta-hydroxylase)
This last step takes place in a vesicle
Released by Ca2+ triggered by action pot
What are the two uptake and breakdown mechanisms of noradrenaline?
Uptake 1 – neuronal tissue – mainly Monoamine Oxidase breakdown (MAO)
Uptake 2 – extraneuronal tissue – mainly Catechol-O-Methyl Transferase (COMT)
general location for adrenoceptors and type
predom at end of sympa nervous system
all GPCR than stim by NA + A
what stimulates and blocks nicotinic receptors and where are they found
location: transmit pre to post ganglionic (release Ach)
stim: nicotine
inhib: hexamthonium
nicotinic receptor method of action
ach binds, causes channel open and Na/Ca influx and allows signal transmission
muscarinic receptor location, method of action, stim and inhibited by?
location: in all tissues innervated by post ganglionic parasympathetic fibres (and sweat glands have muscarinic receptors releasing Ach
- type 2 g protien coupled
- stim: Ach/Muscarine
- inhib: atropine
- slower than nicotinic
what happens at rest if you block muscarinic receptors
increased heart rate and decreased sweat production
muscarinic effect in heart and vasculature?
M2 in heart (in AV and SA node and atria)
- binding stimulates decreased cAMP production, decreased HR, CO, and Ca entry, and increased K+ efflux
On vasulature:
- most blood vessels dont have direct parasympathetic innervation but have muscarinic receptors that can be stimulated
- Ach acts on enothelial cells and stimualtes NO release, causes muscle relaxation and decrease in TPR
THESE ALL CAUSE DECREASE IN BLOOD PRESSURE
muscarinic effects on non-vascular smooth muscle and endocrine glands
lungs: bronchoconstiriction, gut: increased motility, bladder: increased emptying
endo glands: increased bronchial and GI secretions (inc HCL) and increased sweating
