Fx of SNS
“Fight or Flight”
Is continually active to some degree (maintains tone of vascular beds)
- incr HR (tachy) & BP
- mobilizes E
- blood vessel constriction @ skin, mucus mem, & splanchnic area)
- blood vessel dilation @ skeletal & heart
- bronchodilation
- pupil dilation (mydriasis)
- CB relaxation (dist vision)
- decr urination
- stimulates ejaculation
Fx of PNS
“Rest or Digest”
Maintains essential bodily fxs. Required for life.
- decr HR (Brady) & BP
- stores E
- blood vessel dilation @ skin, mucus mem, & splanchnic area)
- blood vessel constriction @ skeletal & heart
- bronchoconstriction
- pupil contriction (miosis)
- CB contraction (near vision)
- incr urination
- stimulates erection
Actions of Muscarinic agonist
Parasympathetic-like
Actions of Muscarinic Antagonist
Sympathetic-like
Organs only receiving sympathetic inn.:
Blood vessels
Adrenal medulla
Pilomotor muscles
Sweat glands
Important NTs in ANS
Acetylcholine (ACh)
Norepinephrine (NE)
Epinephrine (Epi)
Neurons which release ACh
Cholinergic
Mediates transmission of nerve impulses across ganglia in both SNS & PNS
ACh
NT at adrenal medulla
ACh
Transmits signal from autonomic postgang nerves to effector organ in PSN
ACh
Transmitter at neuromuscular junction in somatic nervous system
ACh
Neurons releasing NE or Epi are termed
Adrenergic
Mediate the transmission of nerve impulses from autonomic postgang to effector organs
NE
Released from adrenal medulla into blood, binds to and activates adrenergic receptors
Epi
Rate limiting step in ACh synthesis is
Choline
3 fates of ACh
- diffuse across synaptic cleft and bind with postsynaptic receptor (N or M)
- metabolized (choline part is recycled by ACh esterase)
- bind back w/ presynaptic receptor (usually M2)
ACh estates rapidly or slowly metabolizes ACh?
Rapid —> reason ACh has such a short t(1/2)
Drugs the effect ACh
- Muscarinic agonist
- ACh esterase inhibitors (incr t(1/2))
- Botox (inhibits ACh release, thus muscle can’t contract, stops sweating)
- spider venom (massive ACh release, constant muscle contraction)
M3 found primarily where?
GI, urinary tract, blood vessels (physiologically unable to be activated, but can be activated by drugs)
M2 are found primarily where?
Heart
Muscarinic Agonist Drugs to know
BethaneCHOL, carbaCHOL, metaCHOLine,
Pilocarpine,
Cevimeline
BethaneCHOL
- Muscarinic agonist
- stim GI & bladder
- gastric atony
CarbaCHOL
- Muscarinic agonist
- decr IOP in glaucoma
- rarely used b/c of nicotinic effects on autonomic ganglia
MethaCHOLine (inhaler)
- stim bronchoconstriction
- used to dx bronchial airway hyperreactivity in non-apparent asthma pts (methacholine challenge test)
- asthma pts will be more sensitive to this test
