Autonomic Pharmacology Flashcards
peripheral nervous system subdivisions
afferent (sensory) and efferent (motor)
- efferent divided into somatic nervous system (under conscious control) and autonomic nervous system (automatic)
dominant tone
either SNS or PSNS is more dominant in an organ system - sympathetic dugs may be more effective in a certain organ
terms used to indicate PSNS
- cholinergic (acetylcholine)
- muscarinic (muscarinic receptors)
terms used to indicate SNS
adrenergic (adrenaline)
PS nerves originate from
craniosacral
- originate from the top (cranio) and bottom (sacral) regions of the spinal cord
SNS nerves originate from
thoracolumbar
- middle (thoracic and lumbar) regions of the spinal cord
PS usually have ____ preganglionic and ____ postganglionic fibers
longer; shorter
why dont we see more ganglionic blocking drugs
because we want more selectivity - wanna affect either the sympathetic or parasympathetic nervous system - not both - wanna go downstream right to the target organ
- instead, we target postganglionic receptors on target organs because it gives us more selectivity
____ is the neurotransmitter released at the ganglia in both PS and SNS
acetylcholine
receptors at the ganglia
nicotinic receptors
acetylcholine is synthesized from
Acetyl CoA and Choline
- stored in synaptic vesicles
adrenal medulla
- part of the sympathetic nervous system
- releases epinephrine (80%) and norepinephrine (20%)
catecholamines
dopamine, epinephrine, norepinephrine, serotonin
- made from tyrosine
- tyrosine –> dopa –> dopamine –> norepinephrine –> epinephrine
2 types of cholinergic receptors
- NICOTINIC [Nm (muscle) and Nn (neurologic - ganglia)]
- MUSCARINIC (M1… M5)
Adrenergic receptor division
- alpha 1 (1a, 1b, 1d) and 2 (2a, 2b, 2c)
- beta 1,2,3
receptors in the PSNS are referred to as
Muscarinic
M1, M3, M5 receptors
- usually causing contraction
- G-protein coupled (Gq - stimulatory)
- G-protein (Gq) –> phospholipase C –> IP3 –> DAG –> Ca2+ –> smooth muscle contraction
M2, M4
- inhibitory
- G-protein coupled (Gi)
- Gi –> reduced adenylate cyclase –> reduced cAMP –> reduced calcium channels –> reduced heart rate
effects of a muscarinic agonist
- decreased HR, contraction
- bronchoconstriction
- relaxed sphincters of GI and bladder
- contracted walls of GI (to move food along)
- increased secretion (salivary, respiratory, tears)
example of coordinated action
bladder and urination
- M3 in bladder wall contracts
- M3 in sphincter relaxes
anti-cholinergic drugs
blocking cholinergic receptors
- side effect: M receptors important in the CNS (imp. in cognitive function) - so blocking cholinergic receptors in the brain can affect cognitive function
ways to stimulate M receptors
- direct: using an agonist
- indirect: acetycholinesterase inhibitors (increase the concentration of ACh) - revrsible/irreversible
3 types of chemical rxn that can occur when cholinesterase is bound (acetylcholinesterase inhibitors)
- acetylation: rapid recovery of enzyme (physiological modulation of acetylcholine breakdown)
- carbamylation: slower recovery of enzyme (reversible acetylcholinesterase inhibitors - neostigmine)
- phosphorylation: no recovery of enzyme (covalent reaction - irreversible inhibition - nerve gases)
excessive cholinergic response
- increased secretions (drooling, tearing, clogged airways)
- bronchoconstriction (difficulty breathing)
- reduced heart rate (decreased endurance)
- increased GI motility (nausea, vomiting, diarrhea)
- contraction of bladder, relaxation of sphincters (urination)
