1 - introduction to the ANS 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? What effects does this cause from the lungs/eyes?
Parasympathetic
Lungs – causes partial bronchoconstriction - so it can further constricted and dilated
Eyes – allows near vision - partially constricted so it can be both constricted and dilated
What nerve is the major parasympathetic nerve?
vagus
In the baroreceptor reflex, what structures do the sympathetic and the parasympathetic separately act on?
parasympathetic - heart
(there is no parasympathetic innervation of arterioles)
sympathetic - heart and vessels (arterioles and veins)
What is the relationship between the baroreceptors and parasympathetic and sympathetic nerves?
- positively coupled to parasympathetic nerves (stimulatory)
- negatively coupled to sympathetic nerves (inhibitory)
Draw out diagram showing the different branches of the ANS ganglion neurones and what neurotransmitter is used at synapses
(one Note)
Where do all sympathetic post-ganglionic neurones project out from?
What does this indicate about the sympathetic response?
the sympathetic trunk
sympathetic responses are coordinated and divergent
Describe the differences between sympathetic responses and parasympathetic responses.
Sympathetic – coordinated and divergent
Parasympathetic – discrete and localised
Name the two plexi of the enteric nervous system
submucosal and myenteric
Describe the pathway and role of neurones in the enteric nervous system
- sensory neurone connected to mucosal receptors and stretch receptors detect chemical substances in the gut wall caused by food
- interneurones relay information to the myenteric and submucosal plexi
- motor neurones release ACh or substance P to contract smooth muscle or vasoactive intestinal peptide or NO to relax smooth muscle
How is the somatic nervous system different to the autonomic in terms of efferent nerves?
it has just ONE motor neurone innervating a muscle and releasing ACh (no pre- and post-ganglionic neurones)
Where are nicotinic and muscarinic receptors found in the autonomic NS?
nicotinic - on ALL post-ganglionic membranes
muscarinic - on any tissue innervated by a parasympathetic post ganglionic fibres (and on sympathetic sweat glands)
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 would the effect of blockage of the nicotinic ACh receptors by on the heart?
(nicotinic - on ALL post-ganglionic membranes)
therefore, both sympathetic and parasympathetic arms would be affected
at rest, parasympathetic is dominant - blockade would result in a increase in heart rate
during exercise, sympathetic dominate - blockade would result in an decrease in heart rate
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
Describe what would happen is the parasympathetic NS was blocked (lungs, sweat gland, gut, bladder and eyes)
o Bronchodilation o Reduced sweat production o CONSTIPATION - reduced gut motility o Decreased urinary frequency o Long-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 three types of muscarinic receptor found?
M1 – neural tissue
M2 – heart
M3 – exocrine and smooth muscle
What are adrenoreceptors generally found?
receptors at the end of efferent sympathetic pathway
Explain how the SNS can control vasculature by itself?
Which adrenergic receptors are responsible for the sympathetic control of vasculature?
This is because of the nature of adrenoreceptors - mainly alpha 1 and beta 2
Alpha 1 – constriction
Beta 2 – dilation
What type of receptors are adrenoreceptors?
g-protein coupled receptors
Describe the synthesis and metabolism of acetylcholine.
It is formed from acetyl CoA and choline by choline acetyltransferase
It is broken down by acetyl cholinesterase into choline and acetate
Describe the synthesis of Noradrenaline.
- Tyrosine -> DOPA
(enzyme: tyrosine hydroxylase) - DOPA -> dopamine
(enzyme: DOPA decarboxylase) - Dopamine -> Noradrenaline
(enzyme: dopamine β-hydroxylase)
This last step takes place in a vesicle
What are the two uptake and breakdown mechanisms of noradrenaline?
NOTE: breakdown does not occur in the synapse, but only once uptake has occurred
Uptake 1 – neuronal tissue – mainly Monoamine Oxidase breakdown (MAO)
Uptake 2 – extraneuronal tissue – mainly Catechol-O-Methyl Transferase (COMT)
What is basal heart rate?
50-70 bpm
Only one arm of the ANS effects the lens of the eye (i.e. the ciliary muscle)? Which arm is this?
parasympathetic arm of the ANS - causes contraction of the ciliary muscle
What is unusual about the ANS innervation of the lungs?
there are no sympathetic nerves present int he lungs - dilation is stimulated through adrenaline from the adrenal medulla
What is unusual about the ANS innervation of the liver?
the liver ONLY has sympathetic control
What is unusual about the ANS innervation of blood vessels?
sympathetic nerve carry out all the effects - can have opposing effects on different blood vessels
