Autonomic Function and Disfunction - Hexamethonium Man PDF

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Summary

Case based lecture to demonstrate the function of the ANS - given by Dr Alison Cooper...

Description

HEXAMETHONIUM MAN What is the mechanism of action of hexamethonium - Nicotinic cholinergic receptor antagonist in the ANS -- non depolarising ganglionic blocker in the ganglions of both the parasympathetic and sympathetic system - These receptors are ligand gated ionotropic receptors (ligand gated ion channels) - It is neuronal nicotinic- does not affect skeletal muscle -- neuronal nicotinic receptors - Note -- Neuronal and muscle nicotinic receptors are different; they bind different substances, one of these substances being hexamethonium Which divisions of the autonomic nervous system will it affect - Hexamethonium causes overall paralysis of the autonomic nervous system because it does not distinguish between sympathetic and parasympathetic ganglia and therefore is not specific in its action (widespread effect). - Has effects on adrenal medulla cells as it has nicotinic receptors Can you explain how each of the symptoms described above is produced - Pink complexion → blockage of the SNS means less sympathetic innervation of the smooth muscle of the blood vessels in the skin, which leads to vasodilation; change in vascular tone in his skin (innervated by SNS) - Vasomotor tone is important when thinking about the impact of drugs - Smooth muscle of blood vessels in the skin have sympathetic innervation only - Pale and faint upon standing for a long time → body wide vasodilation due to reduced sympathetic innervation results in blood accumulating in the feet/legs, and reduced blood flow to the brain as constriction of blood vessels doesn’t occur to push blood upwards towards the brain - Benefits of a corset - applying pressure to the abdomen keeps the fluid inside the blood vessels rather than in the periphery - Hands are warm and dry → warm due to vasodilation in the skin (SNS block), dry due to reduced sweat gland activity (SNS block) - No chilblains → change in vascular function as vasoconstriction cannot occur due to reduced sympathetic innervation so less likely to get chilblains - Clean and sweet feet, clean collars → reduced sweat gland activity (SNS block) - Cannot cry → no activity of lacrimal glands (PNS block) - Can’t blush nor become pale → neither vasodilation (PNS block) nor vasoconstriction (SNS block) of blood vessels in the face- Already pink due to vasodilation. - Dry mouth and throat → reduced activity of sublingual, submandibular and parotid glands (SNS block) - Long sightedness → reduced parasympathetic innervation to/control of ciliary muscles that control accommodation in the lens of the eye (PNS block in ciliary ganglia); - Ciliary muscles (control lens shape) have single innervation - only parasympathetic - Easily blinded by bright light → reduced parasympathetic innervation to/control of the circular muscles of the iris that control pupil constriction (PNS block in ciliary ganglia); loss of parasympathetic mediated constriction - Iris has dual innervation but the parasympathetic innervation is dominant, so the loss of dominant input is what would be seen if both are blocked

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- Pupil- Para. dominates Increased heart rate at rest → parasympathetic (dominant during rest) block causes increase in heart rate Red eyes- no tears due to lack of innervation to lacrimal glands Belching and hiccups → …. Feels cold → vasodilation (SNS block) so cannot conserve heat Modest appetite → reduced parasympathetic innervation of the stomach and small intestine (PNS block) - GIT is controlled by the SNS, PNS and ENS No peptic ulcers → reduced enteric innervation to the acid secreting glands of the stomach Constipation → reduced innervation to the colon (PNS block) + less secretions to lubricate the movement of the faeces through the tract Retention of urine → reduced innervation to the smooth muscle of bladder (SNS and PNS block) Impotence?

Can you think of any other symptoms that hexamethonium man might experience What additional symptoms might hexamethonium woman experience - A woman may be additionally affected because smooth muscle in the female reproductive organs will be less active...