Intro to ANS Flashcards
what are the 3 branches to the CNS?
- ANS
- somatic NS
- neuroendocrine system
what does the ANS act on?
- exocrine glands
- smooth muscle
- cardiac muscle
- metabolism
- in host defence
what are some targets of the ANS?
- pupillary constriction: constriction mediated by PNS via oculomotor nerve
- cephalic and gastric phases of digestion: vagal nerve PNS mediation
- basal HR: PNS dominant at rest
what targets only receive one branch of the ANS?
blood vessels
only SNS innervation
what NT do all pre-ganglionic fibres release?
ACh
describe the features of the PNS
- long pre-ganglionic
- short post-ganglionic
- all transmitters ACh
- discrete (1:1)
describe the features of the SNS
- short pre-ganglionic
- long post
- releases mainly A and NA
- mass discharge
describe the sensory neurones in the enteric nervous system
- sensory neurons are connected to mucosal chemoreceptors and stretch receptors
- they detect chemical substances in gut lumen or tension in gut wall caused by food
- info relayed to submucosal and myenteric plexus by interneurones
describe the motor neurones of the enteric NS
- motor neurones release ACh or Substance P
- contract SM, vasoactive intestinal peptide or NO to relax SM
describe the somatic NS
long neurones with eventual ACh release
what are nicotonic receptors?
- found at ALL autonomic ganglia
- stimulated by nicotine/ ACh
- type 1 - ionotropic
what are muscarinic receptors?
- found at effector organs innervated by PNS post-ganglionic fibres
- stimulated by muscarine/ACh
- type 2: G-protein coupled
what effect would blockade of nicotinic ACh receptors have on HR at rest and then in exercise?
Rest: PNS dominant so inc. in HR if PNS blocked
Exercise: SNS dominant so dec. in HR if SNS blocked
what are the subtypes of muscarinic receptors?
M1: neural e.g. forebrain (learning and memory) - Gq
M2: cardiac e.g. inhibitory autoreceptors - Gi
M3: exocrine and smooth muscle e.g. hypothalamus - Gq
M4: periphery e.g. prejunctional nerve endings
M5: striatal dopamine release
where are adrenoreceptors found?
- found at all effector organs innervated by post-ganglionic SNS fibres
- not sweat gland
- stimulated by NA/A
- type 2