11. structure of ANS Flashcards
sympathetic fight of flight actions
heart inotropy and chronotropy (contraction force and rate)
vasoconstriction in gut
vasodilation in skeletal muscle
sensory awareness – eg vision
sweat secretion
sympathetic ganglionic pre and post length
parasympathic
SNS: short pre, long post
PNS: long pre,short post
SNS where do preganglionic fibres emerge from
T- L2 of spinal cord
innervate prevertebral or paravertebral
sympathetic outflow from spinal cord I
sympathetic outflow from spinal cord II
sympathetic outflow from spinal cord III
pre synapses at several segments upwards
sympathetic outflow from spinal cord IV
pre moves through paravertebral chain and synapse at splanchnic nerve
PNS characteristics and nerves
cranio-sacral outflow: two exits for pre-ganglionic fibres beginning and base of spinal cord
Cranial nerves III (occulomotor), VII (facial), IX (glossopharyngeal), X (vagus)
sacral: bladder, lower GI, genitalia
tissues with only sympathetic innervation
adrenal medulla
piloerector muscles
sweat glands
spleen
many blood vessels
tissues with only parasympathetic innervation
ciliary muscle (eye)- contracts thickens lens for close and focused vision
constrictor pupillae (eye)
radial are supplied with SNS
what happens when radial muscles contract
increase pupil diameter
what happens when circular muscles contract
decrease pupil diameter (PNS)
direct and consensual pupil reflex
parasympathomimetics
Agonists of parasympathetic systems
pilocarpine (mACh agonist),
physostigmine (indirect action - increasing Ach by preventing breakdown)
miosis (constriction of the pupil),
decrease in near point (able to focus on near objects),
decrease in intraocular pressure (IOP)
parasympatholytics
Blockers of parasympathetic systems
e.g. muscarinic receptor antagonists - tropicamide
mydriasis (dilation of pupil),
cycloplegia (loss of accommodation),
increased IOP
Sympathomimetics
Agonists of sympathetic systems
eg adrenaline (agonist),
amphetamine (indirect action – increase NA)
Effects
mydriasis (excessive dilation of pupil),
increased IOP
Sympatholytics
Blockers of sympathetic systems
ie adrenoceptor antagonists eg phentolamine
Effect
= miosis (constriction of pupil).
