Autonomic nervous system Flashcards by Midnight Hallows

what is the autonomic nervous system

the efferent division if the nervous system which regulates automatic, involuntary events (usually those that involve smooth/cardiac muscle)

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what are the 2 subdivisions of the ANS

sympathetic; parasympathetic

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3 functions of the ANS

fight or flight (symp)
simple involuntary reflexes e.g. pupillary light, salivation etc. (parasymp)
maintain negative feedback

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what is the enteric nervous system

a plexus of nerves around the gut that control its actions (usually still controlled by para/symp)

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where is the distribution of sympathetic nerves found in the body

T1 - L2 (thoracolumbar outflow)

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pre vs post ganglionic nerve fibre length - sympathetic

pre ganglionic - short
post ganglionic - long

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pre vs post ganglionic nerve fibre length - parasympathetic

pre ganglioninc - long
post ganglionic - short

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where is the distribution of parasympathetic nerves found in the body

cranium + sacrum (separate sections) -> craniosacral distribution

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where are the preganglioninc cell bodies of the sympathetic fibres found

in the intermediolateral grey column of the SC or in the homologous nuclei of the brain (cranial nerves)

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what type of nerve fibres are the preganglionic sympathetic fibres

myelinated slow type B fibres

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what type of nerve fibres are the post-ganglionic sympathetic fibres

usulay unmyelinated type C

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where are the pre ganglionic cell bodies (ganglia) found in the parasympathetic system found

near/within the target organ

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what type of nerve fibres are the preganglionic parasympathetic fibres

so myelinated type B fibres

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what ANS division is the edinger-westphal nucleus part of

paraasympathetic

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what is the nucleus tractus solitarus

a major sensory nucleus in the dorsal medulla that receives cardiovascular, visceral, respiratory, gustatory, and orotactile information

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parasymp innervation of the eye

CN III -> ciliary ganglion -> pupillary constriction

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parasymp innervation of the lacrimal/salivary glands

CN VII/IX -> stimulation of salivary secretion

parasymp innervation of the heart

CN X -> reduction in heart rate

parasymp innervation of the the bronchial tree

CN X -> bronchocontriction and stimulation of secretions

parasymp innervation of the upper GI tract

CN X -> increase in peristaltic rate, relaxation of the sphincters, stimulation of secretions

parasymp innervation of the lower bowel, bladder, reproductive organs

S2-4 sacral plexus -> contraction of smooth muscle of lower bowel, bladder and relaxation of internal urethra sphincter

sympathetic innervation of the eye

T1-2 -> superior cervical ganglion -> pupillary dilaition + retraction of the eyelid

sympathetic innervation of the lacrimal/salivary glands

T1-2 -> inhibition of secretion

sympathetic innervation of the heart

T1-6 -> increase HR and force of contraction

sympathetic innervation of the bronchial tree

T3-T6 -> bronchodilation + secretion inhibition

sympathetic innervation of the upper GI

T5-T12 -> coeliac ganglion -> inhibits peristaltic rate and secretions, sphincter contractions

sympathetic innervation of the adrenal gland

T6-T11 -> no post ganglionic fibres -> releases adrenaline

sympathetic innervation of the skin + peripheral vasculature

T8-T11 -> vasoconstriction of skin vasculature, dilation of vessels in muscle, piloerection, sweat secretion

sympathetic innervation of the lower bowel, bladder and reproductive organs

T9-L2 -> superior + inferior mesenteric ganglion -> inhibits peristalsis

how can the CNS control the ANS (4)

1. via the hypothalamus (ventromedial hypothalamus affects sympathetic stimulation); 2. lateral hypothalamic area (affects parasymp); 3. Peri Aqueductal Grey (direct/indirect effect); 4. lower nuclei in brainstem (rostro-ventralmedulla can cause increases sympathetic stimulation to cardio system)

what sensory input does not send signals to the nucleus tractus solitarus

nociception

3 cortical effects on the ANS

1. fear -> fight or flight; 2. emotional stress/painful stimuli -> vasovagal syncope; 3. seizures/cardiac death (massive symp. output)

what NT is released by preganglionic neurons

Ach

what receptor type do preganglionic neurons synapse onto

nictoinic (ligon gated ion channels) -> N1 in skeletal muscle, N2 in ANS

what receptor type do postganglionic parasymp neurons synapse onto (and their subtypes)

muscarinic (G-protein coupled) -> there are 5 subtypes: M1/3/5 (PLC mediated), M2/4 (adenyl cyclase mediated)

what receptor type do postganglionic sympathetic neurons synapse onto (and their subtypes)

adrenergic: 1. alpha 1 (PLC), alpha 2 (adenyl cyclase); 2. beta 1/2/3 (adenyl cyclase)

what is the main post ganglionic sympathetic NT

noradrenaline

what drug activates beta-adrenergic receptors and can be used to treat bradycardia

Isoproterenol

what ANS systems mediate the pupillary light reflex

both 1. parasympathetic -> excitation of the ciliary + sphincter muscles 2. sympathetic -> radial fibers of the iris (dilation)

where do the sympathetic fibers of the pupil arise from

the thoracic aspect

what is the blink and dazzle reflex

blink -> relaxaton of the levator palpebrae superialsis (CN III) -> contraction of orbicularis oculi (CN VII) dazzle ->bright light causes eyelid closure due to afferent nerves from the retina passing to the oculomotor nuclei

what nerve is involved in the corneal irritation reflex

CN V