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 (constricts pupil)
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 + divergent, 1:20
Parasympathetic: discrete + localised, 1:1
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 3 types of muscarinic cholinoceptor found?
M1 – neural tissue
M2 – cardiac
M3 – exocrine and smooth muscle
Where are adrenoceptors found, what are they stimulated by and what type are they?
At (nearly) all effector organs innervated by post ganglionic sympathetic fibres
Stimulated by noradrenaline + adrenaline
Type 2 – G-protein coupled
Describe the synthesis and breakdown of ACh
It is formed from acetyl CoA and choline by choline acetyltransferase
It is broken down by acetyl cholinesterase
Describe the synthesis of Noradrenaline.
Tyrosine -> DOPA (enzyme: tyrosine hydroxylase)
DOPA -> dopamine (enzyme: DOPA decarboxylase)
Dopamine -> Noradrenaline (enzyme: dopamine beta-hydroxylase)
Last step takes place in a vesicle
What are the 2 uptake mechanisms of noradrenaline?
Uptake 1: neuronal tissue – Monoamine Oxidase A (MAO-A)
Uptake 2: extraneuronal tissue – Catechol-O-Methyl Transferase (COMT)
Main targets for autonomic nervous system
exocrine glands
smooth muscle
cardiac muscle
metabolism
host defence
Main targets for Somatic nervous system
Skeletal muscle
inc. Diaphragm + respiratory muscle
Main targets for neuroendocrine system
Growth, metabolism, reproduction, development,
Salt & water balance,
Host defence
State the 2 divisions of the autonomic nervous system
Sympathetic
Parasympathetic
Describe the autonomic response to drop in blood pressure
Arterial baroreceptor firing rate drops
Lose inhibition of the sympathetic system
Increases HR + BP
Describe the effects of sympathetic innervation on: eyes, salivary glands, trachea and bronchioles
Eyes: Pupil dilation
Salivary glands: Thick viscous secretions
Trachea: Dilates
Describe the effects of parasympathetic innervation on: eyes, salivary glands, trachea and bronchioles
Eyes: Pupillary constriction + ciliary muscle contraction
Salivary glands: Copious, watery secretion
Trachea: Constriction
Describe the effects of sympathetic innervation on: skin, liver, kidney and adipose
Skin: Piloerection
Liver: Glycogenolysis + Gluconeogenesis
Kidney: Increased renin secretion
Adipose: Lipolysis
Describe the effects of sympathetic innervation on: blood vessels to skeletal muscles and skin, mucous membranes and splanchnic area
Skeletal muscles: Dilation
Skin: Constriction
Describe the effects of sympathetic innervation on: heart, GI system, ureters and bladder
Heart: Increase rate + contractility
GI: Decrease motility + tone, sphincter contraction
U+B: Relaxes detrusor, constriction of trigone + sphincter
Describe the effects of parasympathetic innervation on: heart, GI system, ureters and bladder
Heart: Decrease rate and contractility
GI: Increase motility + tone, increase secretions
U+B: Contraction of detrusor, relaxation of trigone + sphincter
Describe the cholinergic sympathetic response of skin
Increased sweating
Which nervous system releases NA from post-ganglionic neurones?
Sympathetic
Which neurotransmitter is used by the parasympathetic nervous system?
ACh
What neurotransmitter is used by pre-ganglionic sympathetic neurones?
ACh
Can ACh be released by sympathetic post-ganglionic neurones?
Yes
E.g. On sweat glands
Describe the journey of signalling in the enteric nervous system
Sensory neurone connected to mucosal chemoreceptors + stretch receptors
Info relayed to submucosal + myenteric plexus via interneurones
Motor neurones release ACh or substance P to contract smooth muscle
Or
Vasoactive intestinal peptide or NO to relax smooth muscle
Which neurotransmitter is used by the somatic nervous system?
ACh
Where are nicotinic receptors found, what are they stimulated by, what type are they and what is their speed?
At all autonomic ganglia
Stimulated by nicotine + ACh
Type 1 - Ionotropic
Very fast
Where are muscarinic receptors found, what are they stimulated by, what type are they and what is their speed?
At all effector organs innervated by post-ganglionic parasympathetic fibres
Stimulated by muscarine + ACh
Type 2 - G Protein coupled
Slower
What effect would blockade of nicotinic acetylcholine receptors have on heart rate at rest and during exercise?
Rest: Parasymp in control, keeps heart rate suppressed. If blocked, HR will increase
Exercise: Symp. Becomes dominant, drives increased HR and BP. If blocked, there would be less of an increase
List 4 adrenoceptors
Alpha 1
Alpha 2
Beta 1
Beta 2
For ACh, when considering effects on the gut
What and where is the drug target? What is the end result of the interaction?
- Muscarinic receptor (M3) as parasympathetic
- Gastric smooth muscle, acid producing cells of stomach, endocrine cells that produce gastrin in stomach
- Contraction, increased acid production, increased gastrin secretion
For Noradrenaline, when considering effects on heart rate
What and where is the drug target? What is the end result of the interaction?
- Adrenoceptors (B1)
- Nodal tissue in heart that controls rate
- Increase in HR
Blockade of what target would cause the most significant rise in synaptic noradrenaline concentrations?
Uptake 1 transport protein
as interferes with NA ability to leave synpase, so NA accumulates in synapse