Canonical Question

ANS Physiology

V5 H3.i Historical V4 M1.i 1 appearance

Master answer

Sympathetic nervous systemParasympathetic nervous system
IntroductionThe sympathetic nervous system (SNS) is one of two main divisions of the autonomic nervous system (ANS).

Its general action is to mobilize the body’s fight-or-flight response.
The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system (ANS).

Its general function is to control homeostasis and the body’s rest-and-digest response.
FunctionControl the body’s response during perceived threat. Diffuse physiological acceleratorControl the body’s response while at rest. Acts as local brake
Activates response ofFight-or-flightRest and digest
Neuron PathwaysVery short neurons, faster systemLonger pathways, slower system
SuppliesViscera and skinOnly viscera

Sympathetic nervous systemParasympathetic nervous system
   
Originates inThoracic and lumbar regions of spinal cordSacral region of spinal cord, medulla, cranial nerves 3, 7, 9, and 10
Pre-Ganglionic fibresCholinergicCholinergic
GanglionSympathetic ganglion – Synapse between
Short pre-ganglionic fibre
Long post-ganglionic fibre		PNS Ganglion sit close to target organ.
Long pre-ganglionic fibre
Short post ganglionic fibre
Post-ganglionicRelease Norad Ach at Adrenal medulla & Sweat glandsAll release Ach
Target organ receptorsAdrenoreceptors
(Alpha 1&2, Beta 1&2)
G protein coupled		Ach receptors:
Muscarinic M1-5: G protein couples
Nicotinic: Ion channel

Sympathetic nervous systemParasympathetic nervous system
General Body ResponseBody speeds up, tenses up, becomes more alert.
Functions not critical to survival shut down.		Counterbalance;
restores body to state of calm.
Cardiovascular System (heart rate)↑↑↑ inotropy
↑↑↑ Chronotropy
↑↑↑ lusitropy
↑↑ dromotropy		↓ inotropy (Atria > Vent)
↓↓↓ Chronotropy
↓ lusitropy (Atria > Vent)
↓↓↓ dromotropy
VasculatureConstriction 
Pulmonary System (lungs)Bronchial tubes dilateBronchoconstriction
increased mucous production
Musculoskeletal SystemSweating, contraction, lipolysisMuscles relax
PupilsDilateConstrict, lacrimation
Gastrointestinal SystemDecreased salivation and GIT motility,
increased sphincter tone,
gluconeogenesis		Increases stomach movement and secretions,
decreased sphincter tone
Salivary GlandsSaliva production decreasesSaliva production increases
EndocrineAdrenaline and noradrenaline releaseNo involvement
GUDetrusor relaxation, sphincter contraction,
↑ uterine tone		Detrusor contraction, erection

JC 2019

Answer by JC

Exam appearances

ExamExact wordingRelationshipSuccess
2017B Q07 Compare and contrast the sympathetic and parasympathetic nervous systems historical_member —