Introduction to the ANS Flashcards
What are the three branches to the CNS
ANS, somatic nervous system and neuroendocrine system
What are the two basic responses of the ANS?
SNS - fight and flight
PNS - rest and digest
Give some examples of targets of the ANS
Pupillary constriction - constriction mediated by PNS CN3
Cephallic and gastric phases of digestion - vagal nerve PNS mediation
Basal heart rate - PNS is dominant at rest (SNS dominant in increasing HR)
Does the SNS or ANS innervate blood vessels
Only SNS
What neurotransmitter do all pre-ganglionic fibres release, regardless of type?
ACh
How long are the pre and post ganglionic fibres in the parasympathetic NS
Long pre-ganglionic
Short post-ganglionic
How long are the pre and post ganglionic fibres in the sympathetic NS
Short pre-ganglionic
Long post-ganglionic
What neurotransmitters are released in the parasympathetic nervous system?
All transmitters are ACh
What neurotransmitters are released in the sympathetic nervous system?
Releases mainly Adrenaline and Noradrenaline
How many pre-ganglionic fibres join to how many post-ganglionic fibres in parasympathetic nervous system?
1:1 pre vs post
Is discrete
How many pre-ganglionic fibres join to how many post-ganglionic fibres in sympathetic nervous system?
1:20 pre vs post
Is divergent
Where are the sensory receptors in the enteric nervous system found?
In the mucosal chemoreceptors and stretch receptors detect chemical substances in the gut lumen or tension in the gut wall caused by food
How is sensory information relayed in the enteric nervous system? What plexus do they go into?
By interneurones to submucosal and myenteric plexus
What neurotransmitter do motor neurones in the enteric nervous system release? What do these NTs do?
ACh or SubstanceP to contract SM
Vasoactive intestinal peptide or NO to relax smooth muscle
What neurotransmitters do the somatic nervous system release?
ACh
Where are nicotinic receptors found?
At all autonomic ganglia
What neurotransmitters/chemicals stimulate nicotinic receptors?
Nicotine/ACh
What type of protein receptor do nicotinic receptors have?
Type 1 - ionotropic ie ligand bind, gate opens
Where are muscarinic receptors found?
At the effector organs innervated by PNS and rarely SNS post ganglionic fibres
What neurotransmitters/chemicals stimulate muscarinic receptors?
Muscarine
ACh
What type of protein receptor do muscarinic receptors have?
Type 2 - G protein coupled (SLOWER than type 1)
Which of the following effects would be observed after blockade of nicotine ACh receptors in an individual at rest?
- Bronchoconstriction
- Increased sweat production
- Constipation
- Increased urinary freq.
- Short sightedness
- Constipation due to blockage of PNS - decreased gut motility
What effect would a blockade of nicotinic acetylcholine receptors have on heart rate at rest?
PNS is normally dominant at rest so an increase in HR if PNS blocked
What effect would a blockade of nicotinic acetylcholine receptors have on heart rate during exercise?
SNS is dominant so decrease in HR if SNS blocked
What are the types of muscarinic receptors?
M1 – Neural – e.g. forebrain (learning and memory)
M2 – Cardiac – e.g. inhibitory autoreceptors
M3 – Exocrine & smooth muscles – e.g. hypothalamus
M4 – Periphery – e.g. prejunctional nerve endings (inhibitory).
M5 – Striatal dopamine release.
What type of G protein coupled receptor do M1, M2 and M3 use?
M1 - Gq
M2 - Gi
M3 - Gq
Where are adrenoceptors found?
At all effector organs innervated by post-ganglionic SNS glands (but not sweat glands)
What type of protein receptor are G protein receptors
Type 2 G protein coupled
What enzyme is involved in acetylcholine production?
Choline acetyl transferase
What enzyme is involved in acetylcholine degradation?
Acetylcholinesterase
What is the formula for acetylcholine production?
Acetyl CoA + Choline -> ACh + CoA
How is Dopamine made?
Tyrosine -> DOPA with tyrosine hydroxylase
DOPA -> Dopamine with DOPA decarboxylase
How is Noradrenaline made?
Make dopamine and then Dopamine -> NA with dopamine beta hydroxylase
How is Adrenaline made
Dopamine -> NA -> A via PNMT
What are the two uptake channels for adrenaline/noradrenaline?
Uptake 1. Monoamine oxidase A - MAO-A
Uptake 2. Cathecol-O-Methyl Transferase - COMT
