1. Intro to ANS Flashcards
what autonomic system controls pupillary constriction?
parasympathetic system
what autonomic system controls cephalic (secretions) and gastric (motility/secretions) phases of gastric secretion and via which nerve?
parasympathetic system via the vagus nerve
what autonomic system is the heart mainly controlled by?
parasympathetic (vagal) system
what happens to baroreceptor firing if BP falls?
baroreceptor firing goes down, decreasing the stimulation of the parasympathetic system and decreasing the inhibition of the sympathetic system so BP rises
which autonomic system is involved in the liver and which processes occur as a result of stimulation?
sympathetic nervous system stimulating an increase in gycogenolysis and gluconeogenesis
in the parasympathetic system which ganglionic fibre is shorter and which is longer?
pre-ganglionic fibre is longer and post-ganglionic fibre is shorter
where do parasympathetic pre-ganglionic fibres originate?
brain (cranal) and spine (sacral)
where do sympathetic pre-ganglionic fibres originate?
spinal cord (thoracolumbar)
describe the nature of the parasympathetic pathway
discrete/localised with little divergence (1:1 pre vs post ganglionic fibres)
describe the nature of the sympathetic pathway
coordinated response that is very divergent (up to 1:20 pre vs post ganglionic fibres)
what are sensory neurones in the enteral nervous system connected to?
mucosal chemoreceptors and stretch receptors
what do mucosal chemoreceptors and stretch receptors detect?
chemical substances in the gut lumen
tension in the gut wall caused by food
where is information from the enteral nervous system relayed to?
submucosal (Meissner’s) and myenteric (Auerbach’s) plexuses via interneurons
what do motor neurones in the enteral nervous system release?
ACh or substance P to contract smooth muscle
vasoactive intestinal peptide or NO to relax smooth muscle
how is the somatic nervous system different from the autonomic nervous system?
it involves one motor neurone projecting from the spinal cord to skeletal muscle where ACh is released which stimulates skeletal muscle contraction
where are nicotinic receptors found and what are they stimulated by?
at all autonomic ganglia between pre and post ganglionic fibres
stimulated by nicotine/ACh
what type of receptors are nicotinic receptors and what is their speed?
ionotropic receptors that are linked to ion channels
fast
where are muscarinic receptors found and what are they stimulated by?
at all effector organs innervated by parasympathetic post-ganglionic fibres or when the effector organ is a sweat gland
stimulated by muscarine/ACh
what type of receptors are muscarinic receptors and what is their speed?
G-protein coupled receptors
slow
what are the subtypes of muscarinic cholinoceptors?
*M1 - neural
*M2 - cardiac
*M3 - exocrine and smooth muscle
M4 - periphery
M5 - striatal dopamine release
where are adrenoreceptors found and what are they stimulated by?
at all effector organs innervated by sympathetic post-ganglionic fibres
stimulated by NA/Adrenaline
what type of receptors are adrenoreceptors and how do these receptors work?
G-protein coupled
an agonist binds to the receptor causing G-protein activation. A 2nd messenger is generated which activates cell signalling
list the steps involved in the synthesis of neurotransmitters
- NT produced by precursor via enzymatic conversion
- NT packaged into vesicles
- an action potential causes calcium influx that promotes the exocytosis of the NT
- vesicle fusion - NT is released into the synapse
- the NT reacts with the receptor
- the receptor transduces the response
- degradation of NT
- reuptake
what are the precursors of ACh and what enzyme converts them to ACh?
Acetyl-CoA (from glucose metabolism) and choline (from diet)
enzymatic conversion by choline acetyl transferase (byproduct is CoA)
