PNS Flashcards
myenteric plexus
increases tonic and rhythmic contractions
submucosal plexus
increases secretory activity and absorption
adrenal medulla
releases NA and A
sympathetic
short and long, Ach and NA, T1-L2
parasympathetic
postganglionic neuron close to target, only ACh, (nic, then musc), cranial and S2-4
LHRH or GnRH
Luteinizing hormone-releasing hormone or Gonadotrophin releasing hormone
Muscarinic 2 autoreceptor
inhibits synaptic transmission
Muscarinic 2 R
vagus nerve acts on them, found in heart, slow down hear rate by slowing the speed of depolarisation
Muscarinic 3 R
stimulates, found in exocrine glands
Muscarinic 1 R
stimulates, in gut tract and bladder
Alpha 1
stimulates, in blood vessels, gut, bladder
Alpha 2 R
inhibits,as autoreceptor decreases the release of NA, or in vascular smooth muscle , also in CNA - where it can produce analgesia
Beta 1
stimulates, only in heart, increases heart rate (chronotropic) and force (ionotropic)
Endothelium derived relaxation factor is…
Nitric oxide, causes relaxation of smooth muscle and platelet inhibition
At sympathetic ganglion there is co-transmission:
Nicotinic ACh Rs mediate fast depolarisation , LHRH causes slow depol, M2 muscarinic and opioid Rs mediate slow hyperpolarisation
adrenal gland is composed of..
cortex and medulla- catecholamines cause vasoconstriction and tachycardia
Muscarinic receptors in the heart are located in atria and conduction system
are innervated by vagus nerve, mostly the sino-atrial and atrio-ventricular nodes and the atria. cause slowing of conduction
M receptor activation slows heart rate by slowing the spontaneous depolarisation of pacemaker cells
not force as this is ventricular!
The eye: muscarinic receptors control pupil size and accommodation
ciliary muscle contracts, releasing the lens, which relaxes into a “fat” shape, good for near vision (accommodation)
Cabachol is a muscarinic agonist
for both nic and musc , is resistant to choline esterases
Pilocarpine
is a muscarinic agonist, resistant to choline esterases
Therapeutic use of muscarinic agonists
Glaucoma- pilocarpine eye drops
In glaucoma an increased intraocular pressure leads to retinal damage. Muscarinic agonist are helpful because pinpoint pupils (miosis) and ciliary spasm improve the drainage of aqueous humour.
Relieve dry mouth (xerostomia; pilocarpine)
Atropine causes..
- CNS: antiemetic (motion sickness); less tremor in Parkinson’s; excitation (toxic doses); cognitive impairment in elderly
- Eye: pupil dilatation (mydriasis); paralysis of accommodation, intraocular pressure may rise- glaucoma
- Secretions reduced: saliva, tears, sweat, bronchi, GI
- Smooth muscle relaxed (bronchi, GI tract)
- Heart: may increase heart rate; no effect on blood vessels
- Urinary retention
Many common drugs (antipsychotics, antidepressants, antihistamines)
can block muscarinic receptors
Therapeutic uses of muscarinic antagonists
Anaesthesia: Hyoscine- Scopolamine: pre-medication (sedation, less secretions) or to reduce effects of ChE inhibitors and vagus stimulation induced by surgery of visceral organs and against Motion sickness
- Urinary urgency & incontinence =oxybutynin
- Tropicamide= eye drops to induce mydriasis and ciliary muscle paralysis for retinal examination
Noradrenaline in the brain..
Thalamus, hypthalamus, septum, amygdala, cerebelum, pituitary
Dopamine Beta hydroxylase
catalyses dopamine-> noradrenaline
inhibited by disulfiram
Disulfiram is used to treat cocaine treatment, because excess dopamine causes anxiety and increased bp- unpleasant
Disulfiram is also used to treat alcoholism- bc is also inhibits acetyl-dehydrogenase- gives a hangover feeling
L- Dopa to Dopamine
Dopa- decarboxylase
- inhibited by carbidopa
Carbidopa is given to Parkinson’s patients- allows more L-Dopa to cross BBB, because catabolism in the periphery is reduced, doesnt cross BBB itsself
Pheochromocytoma is a neuroendocrinetumor of the medulla of the adrenal gland
It results in an over-production of catecholamines.
Alpha- methyl - p- tyrosine is used to treat it. It inhibits tyrodine hydroxylase whic is the enzyme that converts tyrosine to L-dopa
