Autonomic Nervous System

Question 0

The ans transmits all cns info to peripheral parts of the body. Except

Answer 0

Motor innervation of skeletal muscle -somatic system

Question 1

What is the central source of the ans

Answer 1

Hypothalamus

Question 2

What are the two divisions of the ANS. And their neuro transmitters:

Answer 2

Sympathetic- Noradrelanine

Parasympathetic - acetylcholine

Question 3

What’s the parasympathetic pathway

Answer 3

Through edinger Westphal nucleus
Relays in ciliary ganglion
Transmits to the neuro effector junction
Communicates via acetylcholine
After acting on muscarinic reveptors
Hydrolysed to acetic acid and choline by acetylcholinesterase

Question 4

What do parasympothemrtics do:

Answer 4

mimic the effects of parasympathetic nerve stimulation
simulate the action of ACh at cholinergic neuro-effector junctions
competitive agonists for muscarinic receptors-drugs whose molecules combine directly with receptors which are normally for ACh molecules.
simulate a direct muscarinic effect of ACh on the muscle cell membrane.
miosis and spasm of accommodation.
two classes of parasympathomimetics:
cholinomimetic esters
cholinomimetic alkaloids- pilocarpine- naturally occurring liquid alkaloid from the pilocarpus species and is used in general medicine for xerostomia following irradiation for head and neck cancer as well as dry mouth and dry eyes in Sjögren’s syndrome.

Question 5

what are the different pharmacological groups

Answer 5

1. Parasympathomimetics
2. Anticholinesterases
3. Antimuscarinics
4. Sympathomimetics
5. Adrenergic blockers

Question 6

what do anticholinesterases do?

Answer 6

inhibit the enzyme acetylcholinesterase from hydrolyzing ACh into choline and acetic acid,
allowing ACh to accumulate at the receptor site.
acetylcholinesterase not destroyed- inhibited.
sustain indirectly cholinergic nerve stimulation
miosis and spasm of accommodation (when an accommodative facility is present).
two classes of anticholinesterases:
reversible- Physostigmine is a reversible anticholinesterase that has been used in the past in optometry as a miotic but is no longer used.
irreversible

Question 7

what are antimuscarinics used for

Answer 7

majority
block the muscarinic action of ACh.
cycloplegia and mydriasis. T
combine with muscarinic receptors - block the muscarinic action of ACh by competition with ACh for these receptors. 
competitive antagonists for acetylcholine.
anticholinergics or parasympatholytics- these terms are not normally used.
don’t react with ACh nor do they affect synthesis or release or rate of hydrolysis of ACh. 
Antimuscarinics drugs have marked affinity for receptor sites but not efficacy, i.e. the site is 
blocked in that selective ionic permeability changes are not initiated in the muscle cell 
membrane.
as affinity for muscarinic receptors (but not efficacy) members of this drug group generally- possess some elements of the (CH3)3N+ in their structure - i.e. they fit the muscarinic receptor but jam the ‘lock’.
less commonly nowadays for symptomatic relief of gastro-intestinal disorders
smooth muscle spasm and as premedicants to reduce bronchial and salivary secretions
two classes of antimuscarinic drugs:
natural
atropine is derived from the roots and leaves of the atropa belladonna (or Deadly Nightshade).
Hospital Eye Service for orthoptics treatment of convergent strabismus or in the treatment of uveitis.
synthetic.
cyclopentolate, tropicamide and homatropine all have clinical use as cycloplegic and mydriatic agents

Question 8

ADRENERGIC BLOCKING DRUGS

Answer 8

prevent, inhibit, reduce or reverse the responses observed after sympathetic nerve stimulation.
two classes of adrenergic blockers:
adrenergic receptor blocking drugs (sometimes referred to as sympatholytics)- prevent action of noradrenaline on receptors at the receptor site;
Thymoxamine is a competitive antagonist of noradrenaline for alpha 1 receptors.
miosis due to unopposed parasympathetic constrictor tone in the sphincter muscle (nb both the dilator and sphincter muscles work synergistically to produce a given pupil diameter).
Accommodation is affected minimally as there very few alpha 1 receptors in the cilliary muscle.
Dapiprazole has a very similar action to thymoxamine (i.e. an alpha 1 antagonist) and is used as a miotic in the USA.
thymoxamine- treatment of peripheral vascular disorders such as cerebral vascular insufficiency and for the short-term treatment of primary Raynaud’s syndrome.
adrenergic neurone blocking drugs- alter the storage, release, uptake or metabolism of noradrenaline.
Both categories will have the ocular effects of miosis, ptosis and conjunctival reddening.

Question 9

SYMPATHOMIMETICS

Answer 9

adrenergic analogy of parasympathomimetics.
mimic the effects of stimulation of the sympathetic nervous system
mydriasis
some P preparations they are combined with antihistamine for vasoconstriction of the conjunctival blood vessels.
Accommodation and pupil responses may be affected slightly- not clinically sig
two classes of sympathomimetics drugs:
catecholamines
non- catecholamines.
Phenylephrine (P medicine): is principally an alpha-1 receptor stimulating agent (i.e. an alpha-1 agonist) used as a mydriatic and, in lower concentrations, as a conjunctival decongestant
Naphazoline and xylometazoline (both P): are alpha receptor stimulators and are used as conjunctival decongestants a vasoconstrictors )and are often combined with an antihistamine drug, e.g. antazoline.