Intro to ANS Flashcards
Which limb of the ANS has more of an effect on the liver?
Sympathetic
Causes hepatic gluconeogenesis and glycogenolysis
Which adrenergic receptors are responsible for the sympathetic control of vasculature?
Alpha 1 – constriction
Beta 2 – dilation
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
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)
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.
How is noradrenaline synthesised?
Tyrosine -> DOPA (enzyme: tyrosine hydroxylase)
DOPA -> dopamine (enzyme: DOPA decarboxylase)
Dopamine -> Noradrenaline (enzyme: dopamine beta-hydroxylase)
This last step takes place in a vesicle
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
Describe the differences between sympathetic responses and parasympathetic responses
Sympathetic – coordinated and divergent
Parasympathetic – discrete and localised
How is acetylcholine synthesised?
From acetyl CoA and choline
Enzyme: choline acetyltransferase
How is acetylcholine broken down?
By acetyl cholinesterase in the synapse
Where are the three types of muscarinic receptor found?
M1 - neural tissue
M2 - heart
M3 - exocrine and smooth muscle
What type of receptor are nicotinic receptors?
Type 1 – ionotropic receptors
VERY fast
What type of receptor are muscarinic receptors?
Type 2 - G-protein coupled
Slower than type 1 ionotropic
What type of receptor are all adrenergic receptors?
G-protein coupled
Describe the difference in the transmission through nicotinic and muscarinic receptors
Nicotinic is much faster
Which limb of the autonomic nervous system dominates the lungs and the eyes at rest?
Parasympathetic
Lungs – causes partial bronchoconstriction so can constrict further and dilate
Eyes – smooth muscle needs to be partially constricted so can change in both directions - allows near vision
What are the two main branches of the autonomic nervous system?
Sympathethic
Parasympathetic
What is the enteric nervous system?
Nervous system of the GIT
Responds to various types of stimuli within GIT
ANS does project onto ENS though
What are the principal target organs of the sympathetic NS?
- GIT
- Heart
- Vasculature
- Bladder
- Uterus
- Eye
- Skin - sweat, lacrimal, salivary, pilomotor glands
- Kidney
- Liver
- Adipose tissue
- Pancreatic islets
What are the principal target organs of the parasympathetic NS?
- GIT
- Heart
- Bronchi
- Eye
- Male sex organs
- Vasculature of erectile tissue + salivary glands
- Uterus
- Salivary and lacrimal glands
How is the sympathetic NS organised?
Sympathetic trunk just outside spinal cord
Short pre-ganglionic fibres
Long post-ganglionic fibres
How is the parasympathetic NS organised?
Long pre-ganglionic fibres
Short post-ganglionic fibres
Ganglion near effector organ
How does the somatic nervous system differ from the ANS
In somatic NS, one motor neurone innervates a muscle and releases ACh - no ganglion
What transmitter is released from pre-ganglionic fibres in the sympathetic NS?
ACh
What transmitter is released from post-ganglionic fibres in the sympathetic NS?
NA
A/NA from adrenal medulla
ACh in sweat gland
What transmitter is released from pre-ganglionic fibres in the parasympathetic NS?
ACh
What transmitter is released from post-ganglionic fibres in the parasympathetic NS?
ACh
Where else is acetylcholine used as a transmitter?
Somatic nervous system
Brain
Where are adrenaline and noradrenaline also used?
As transmitters in brain
What are the potential targets for pharmacological manipulation of cholinergic transmission?
- Acetylcholinesterase
- Choline acetyl transferase?
- Muscarinic and nicotinic ACh receptors
What are the potential targets for pharmacological manipulation of A/NA transmission?
- Uptake 1 transport protein (CG dependent)
- Tyrosine hydroxylase
- DOPA decarboxylase
- Monoamine oxidase
- Catechol-O-methyl transferase
- Adrenoceptors
- AChRs
What are the principal efferent paths of communication between the CNS and the periphery?
Parasympathetic NS
Sympathetic NS
Somatic NS
