autonomic nervous system - general Flashcards
ANS Disorders ?
Primary autonomic disorders rare
May be secondary autonomic disorders from neuropathies or damage or epiliepsy ect.
ANS DRUGS/PHARMACOLOGY
Nicotine effect on the ANS
It increases the release of adrenaline from the adrenal glands.
Think about where nicotine receptors are within the brain.
Pupillary response to SNS and PNS systsem.
Parasympathetic nervous system controls the sphincter muscle via the M3 receptors causing it to go smaller - MIOSIS
Sympathetic
Radial muscle
α1 – constriction - DILATES THE EYES (MYDRIASIS)
Blurred vision is a potential side effect of antimuscarinics and alpha-adrenoceptor drugs
Cocaine – SNS enhancer (mydriasis) INCREASES THE SYMPATHETIC NERVOUS SYSTEM BY EFFECTING THE ALPHA 1 CAUSING DILATION.
Opioids – SNS suppressants (“pinpoint pupils”) BY EFFECTING THE M3 causing them to go smal.
PNS AND SNS Drugs on the lungs
Parasympathetic
Smooth muscle
M3 – contraction
Sympathetic
Smooth muscle
β2 receptors – relaxation
Where does the parasympathetic nervous system act on in the heart ?
ONLY THE NODES
Where does the sympathetic nervous system act on in the heart ?
BOTH THE NODES AND THE MYOCYTES
Increased Ca2+ entry to increased force of contraction
This increases the rate and contraction.
Antimuscarinics – tachycardia
Beta-blockers – bradycardia
Where do the receptors of the SNS and PNS sit on the receptors ?
Sympathetic
Vascular smooth muscle
β2 receptors – relaxation
Sympathetic
Vascular smooth muscle
α1 receptors – contraction
Parasympathetic
Vascular epithelium (viscera)
M3 receptors – NO release
NO relaxation of smooth muscle. THESE ARE ON THE EPITHELIAL CELLS. THIS CAN CAUSE NITRIC OXIDE RELEASE CASUSING VASOLDILATION THE WAY THAT GTN WORKS.
Saliva
Saliva secretion is mostly controlled by parasympathetic – tends to fluid release. Parasympathetic
M1/3 – secretion (fluid)
Sympathetic innervation more complex. Partially inhibitory but also can increase some saliva production (α1). Sympathetic
α1 & β receptors (protein & thick secretion)
Dry mouth very common with antimuscarinics, occasional with alpha-blockers. Sympathetic
GI motility & secretions
Parasympathetic
Complex!
Mostly M3 receptors → stimulate myenteric plexus → contraction
Sympathetic
Complex!
Mainly α2 receptors → inhibit plexuses → relaxation
ANS and Kidney & Adrenal Gland
There is no significant parasympathetic innervation of the kidneys or adrenal gland
- Other than when you think about blood supply.
However adrenal gland releases ACH to NACHR.
There is B1 receptors in the kidney that increase risk release of renin.
Bladder
Urinary retention may be a side effect of antimuscarinics
Rarer with adrenergic drugs
Alpha-blockers for prostate growth !!!!
Genitals
Side effects complex
ANS drugs that affect blood pressure (up or down) may adversely affect erectile function
Alpha-adrenoceptor antagonists may suppress ejaculation/orgasm
HOWEVER Sympathetic
Pelvic floor muscle
α1 receptors – contraction
Ejaculation/orgasm
THEREFORE PEOPLE TAKING ALPHA-1 BLOCKERS SOMETIMES CAN’T EJACULATE.
Anticholinergic side effects
Lack of selectivity and widespread distribution of receptors (especially M3) mean side effects can be a major issue (*CNS)
Many other drugs also antagonise mAChRs – e.g. antipsychotics, antidepressants, antihistamines
More severe in the elderly
Dry mouth
Constipation
Blurred vision
*Loss of co-ordination
Tachycardia & arrhythmias
*Hyperpyrexia
Sedation
Increased intraocular pressure
*Confusion
*Hallucinations / delirium
Urinary retention
Acetylcholinesterase Inhibitors
Clinical uses:
Neostigmine, pyridostigmine: myasthenia gravis (NMJ)
recovery from general anaesthesia
Donepezil, galantamine: Alzheimers Disease (CNS)
Side effects
Usually mild – enhance cholinergic activity
