Autonomic nervous system Flashcards
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)
what are the 2 subdivisions of the ANS
sympathetic; parasympathetic
3 functions of the ANS
- fight or flight (symp)
- simple involuntary reflexes e.g. pupillary light, salivation etc. (parasymp)
- maintain negative feedback
what is the enteric nervous system
a plexus of nerves around the gut that control its actions (usually still controlled by para/symp)
where is the distribution of sympathetic nerves found in the body
T1 - L2 (thoracolumbar outflow)
pre vs post ganglionic nerve fibre length - sympathetic
pre ganglionic - short
post ganglionic - long
pre vs post ganglionic nerve fibre length - parasympathetic
pre ganglioninc - long
post ganglionic - short
where is the distribution of parasympathetic nerves found in the body
cranium + sacrum (separate sections) -> craniosacral distribution
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)
what type of nerve fibres are the preganglionic sympathetic fibres
myelinated slow type B fibres
what type of nerve fibres are the post-ganglionic sympathetic fibres
usulay unmyelinated type C
where are the pre ganglionic cell bodies (ganglia) found in the parasympathetic system found
near/within the target organ
what type of nerve fibres are the preganglionic parasympathetic fibres
so myelinated type B fibres
what ANS division is the edinger-westphal nucleus part of
paraasympathetic
what is the nucleus tractus solitarus
a major sensory nucleus in the dorsal medulla that receives cardiovascular, visceral, respiratory, gustatory, and orotactile information
parasymp innervation of the eye
CN III -> ciliary ganglion -> pupillary constriction
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)
- via the hypothalamus (ventromedial hypothalamus affects sympathetic stimulation);
- lateral hypothalamic area (affects parasymp);
- Peri Aqueductal Grey (direct/indirect effect);
- 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
- fear -> fight or flight;
- emotional stress/painful stimuli -> vasovagal syncope;
- 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
