Parasympathetic NS Flashcards
Parasympathetic NS =
REST & DIGEST!
What are reflex arcs?
Feedb. control mechanisms!
- unmyelinated AFFERENT SENSORY FIBRES from visceral R’s monitor body status; the info. is integrated in BRAINSTEM & HYPOTHALAMUS
- Descending info. flow is adjusted to compensate
What signaling does the Parasympathetic NS specialise in?
Organised for DISCRETE & LOCALISED SIGNALING
(long pregang. fibre with postgang. fibre located close(r) to target organ)
What are some of the Parasymp. NS main goals?
Conservation of energy
Maintence of organ funtions at rest
What do cranial nerves innervate?
Where do the originate from?
- Originate in BRAINSTEM!
- Innervate ganglia in heart, lung, digestive syst organs, eyes, glands
e. g. VAGUS NERVE
–carries AFFERENT - visceral sensory info.
–carries EFFERENT - parasymp. regulation of heart and other organs
What do spinal nerves innervate?
Where do they orginate from?
- Originate from SACRAL REGION!
- Innervate ganglia is intestine, bladder & reproductive organs
What are some unique characteristics of the Parasymp. NS?
Parasymp. syst. shows LITTLE DIVERGENCE
PRECISE LOCAL CONTROL of target organs
Each pregang. neuron controls only 1-3 POSTGANG. NEURONS (in contrast to high divergence of symp. syst.)
What neurotransmitter is used in the parasymp. NS?
Neurotransmitter = ACh
[pre- and postgang. neurons]
What are the 2 types of ACh receptors involved in the parasymp. NS?
Nicotinic
Muscarinic (=GPCR)
What type of R is the postgang. neuron R?
nACHR
What type of R is the target organ R?
mAChR (=GPCR)
mACHR’s are GPCR.
THUS how many subtypes exist? Show whether these sutypes are excitatory or inhibitory. What do these specialisations depend on?
5 subtypes!
M1 –> M5
[M1 & M3 = EXCITATORY]
[M2 = INHIBITORY]
Specialiation of responses depends on the GPCR COUPLING MECHANISM! (i.e. which intracellular signaling pathways are activated)
Discuss M1 and M3 mAChR’s.
EXCITATORY RESPONSE
Phospholipase C causes release of intracellular Ca2+ (promoting contraction)!
Discuss M2 mAChR’s.
INHIBITORY RESPONSE
Muscle relaxation caused by an increased Kir conductance, or by inhibiting adenylate cyclase
(Go GPCR)
OR
(Gi GPCR)
What are mAChR’s inhibited by?
ATROPINE
(opposes normal parasymp. actions, THUS promoting a “sympathetic-like” effect)!
