9 - ANS Flashcards
What is the anatomical structure of the parasympathetic nervous system?
S2 to S4
What is the anatomical structure of the sympathetic nervous system?
What neurotransmitters and receptors are involved in each synapse?
What is the main difference between nAchR and mAchR?
nAChR = LGIC
mChR = GPCR
What neurotransmitter is released from sympathetic post-ganglionic neurones?
- Mainly noradrenaline
- In sweat glands and hair follicles it is ACh
Are there other neurotransmitters to NA and ACh?
What could be classified as the third divsion of the autonomic nervous system?
Enteric in GI tract
Thousands of neurones in microcircuit
What is the hormonal part of the sympathetic nervous system?
- Post-ganglionic neurones are chromaffin cells in adrenal medulla that synthesise adrenaline
- Whole cell depolarised by pre-ganglionic neurone, vesicles contain A fuse with membrane and release adrenaline into blood stream to act on adrenoreceptors
Summarise the neurotransmitters in the somatic and autonomic nervous system.
Why are beta 2 receptors classed as part of the sympathetic nervous system?
Dilate airways allowing more air and therefore more oxygen for respiration into the body
Where does NO generation occuring and what is it used to stimulate?
Locally
Causes penile erection, iris sphincter and cilliary muscles
What is dysauntomia?
Umbrella term for malfunctions of the ANS. Can be primary or occur secondarily to another condition (e.g to Parkinson’s)
What is NCS, POTS and MSA?
- Neurocardiogenic Synope - Fainting spells
- Postural Orthostatic Tachycardia Syndrome - Lightheaded, tachycardia, fainting, chest pains, temperature sensitivity. Mainly in young women who look healthy
- Multiple System Atrophy - Fatal dysautonomia in adults over 40. Neurodegenerative disease with similarities to Parkinson’s. Bed ridden after 2 years of diagnosis and dead in 5-10 years. Very rare
What are the clinical abnormalities in asthma?
- Bronchospasms
- Excess production of secretions
What are the basic steps of neurotransmission and highlight the steps that can be targeted by drugs?
How is acetylcholine synthesised and degraded?
What drugs can target AChR?
- Targets skeletal muscle and pre-ganglionic neurones
- Trimethapan (ganglion blocking drug) used in hypertensive emergencies and controlled hypotension in surgery. Nicotinic antagonist
What is the issue with developing drugs to act on the parasympathetic nervous system?
5 Muscarinic ACh receptors and hard to make drugs that are selective so drug will bind to all receptors, causing unwanted side effects
What is sludge syndrome?
Pathological effects of overstimulation of muscarinic AChR’s in the parasympathetic nervous system.
Usually caused by:
- Drug overdose
- Organophospphorous insecticides (parathion) and nerve gases (sarin)
- Ingestion of magic mushrooms
What is the treatment for SLUDGE syndrome?
- Agents covalently bind to AChE to irreversibly deactive enzyme and raise ACh levels
- Need drugs that either block muscarinic receptors or reverse covalent modification of AChE
- Atrophine and Pralidoxime
What are some muscarinic agonists and antagonists?
Administered locally not systemically
Agonists:
- Pilocarpine (glaucoma)
- Bethanechol (stimulate bladder emptying)
Antagonists:
- Ipratropium (asthma but only certain causes)
- Tiotropium (COPD)
- Tolterodine, Darifenacin and Oxybutynin (overeactive bladder)
What are sympathetic post-ganglionic neurones like?
- Noradrenaline release
- One neurone has lots of varicosities that are specialised for Ca2+ dependent noradrenaline release
- Allows coordinate control over a large area
How is noradrenaline and adrenaline synthesised?
What happens to Noradrenaline/Adrenaline once it has been released?
1. Reuptake by noradrenaline transport proteins (NET)
- Uptake 1: Uptake back into pre-synaptic neurone via a Na dependent high affinity transporter
- Uptake 2: Low affinity transporter
2. Metabolism (10%)
- Monoamine Oxidase (MAO)
- Catechol-O-methlytransferase (COMT)
Can produce drugs that inhibit these enzymes so NA not broken down
What receptors does NA interact with?
- Pre-synaptic adrenoreceptors: To feedback and regulate processes in nerve terminal like NA release
- Post-synaptic adrenoreceptors: Pass on message and then rapidly removed by NET
Why is salbutamol such a good asthma treatment?
Relieves asthma no matter what has caused it
Why would you use selective adrenoreceptor agonists?
To limit side effects, like cardiovascular side effects, as non-selective will act on both beta adrenoreceptors
What are two drugs used to treat hypertension and other cardiovascular disorders?
Atenolol: B1 antagonist
Doxazosin: A1 antagonist
Bisprolol Fumarate: B1 antagonist
What is thyrotoxicosis and how is it treated?
- Excess of thyroid hormone in the body causing lots of symptoms
- Beta agonists used to combat some of the symptoms, e.g high b.p.
- Propanolol, Attenolol, Nadaolol
- Methimazole and Propylthiouracil stop thyroid overproducing hormone
