Physiology/pharmacology of the Autonomic Nervous System Flashcards
Branches of the nervous system
Function of ANS
-Involuntary control
-Autonomic functions (E.g. cardiac function, respiration, digestion)
-Maintains homeostasis
What are the 3 branches of the ANS
-Sympathetic (noradrenaline at adrenergic receptor)
-Parasympathetic (acetylcholine at muscarinic receptor)
-Enteric (second brain, can act independent of CNS, active in gut)
What spinal section does sympathetic nervous system span?
T1-L2
-Presynaptic neurone shorter
-Post synaptic neurone longer
What spinal section does parasympathetic nervous system span?
-Come out from cranial nerves and sacral nerves
-Presynaptic neurone is longer
-Postsynaptic neurone is shorter
Parasympathetic nervous system example
Sympathetic nervous system example
Exception sympathetic neurone
-Sympathetic neurone that innervates adrenal gland doesn’t have postsynaptic neurone
-Because it releases adrenaline into blood that affects target tissues
Parasympathetic effect on organs
-Pupil constricts
-Lacrimal glands produce tears
-Salivary glands produce saliva
-Decreased heart rate
-Bronchoconstriction
-Increased stomach/small/large intestine motility
-Bladder contracts
-Erection
Sympathetic effect on organs
-Pupil dilates
-Blood vessels constrict
-Increased heart rate
-Bronchodilation
-Decreased stomach/small/large intestine motility
-Increased liver metabolism
-Bladder relaxation
-Ejaculation
Signalling in Sympathetic, Parasympathetic, Somatic nervous systems
What are the 2 cholinergic receptors in parasympathetic signalling?
-Nicotinic receptor
-Muscarinic receptor
How does parasympathetic signalling slow down heart rate?
-ACh binds to M2 muscaranic receptor in heart (coupled to Gi inhibitory protein)
-Alpha subunit of Gi stops adenylyl cyclase producing cAMP
-cAMP is needed to activate HCN channel
-Decreased activity of HCN channel in SAN
-Increased potassium current decreases cell excitability (hyperpolarisation)
