ANS cont'd Flashcards
Phospholipase C system in heart
- Agonist activates alpha 1 and M3 receptors in smooth muscle
- Leads to activation of phospholipase C
3.Activates Ca release
- Activates Protein kinase
Adenylyl cyclase system in heart
1.Agonist activates either beta receptors OR alpha 2 and M2 receptors
(Alpha 2 and M2 inhibit; beta excites pathway)
- Leads to activation of adenylyl cyclase
3.Activates cAMP which then activates protein kinase
- REsults in further activation of enzymes leading to increased contraction in heart (beta 1) and bronchodilation (beta 2)
What deactivates cAMP?
Phosphodiesterase (PDE3)
-will convert cAMP to AMP which is the inactive form
M3 of vascular endothelium
- Activated M3 on vascular endothelium, results in Ca Calmodolin release which acts on NO synthase to produce NO
- NO activates Guanylyl cyclase. Increasing cGMP causing relaxation
**deactivated by Phosphodiesterase converting cGMP into GMP
M3 of vascular smooth muscle activation
M3 receptor activation leads to Ca released in muscle, resulting in contraction
Viagra (sildenafil) as a phosphodiesterase inhibitor
-Works on vascular smooth muscle leading to the vasodilation of pulmonary arteries in pulmonary hypertension
Black widow spider venom
-Causes an increase in Ach release due to increased leakiness of vesicles into synapse
-will cause mild SLUD, and muscle twitching
*not usually deadly…usually from an allergy
Botulinum toxin
-Blocks exocytosis (release) of Ach vesicles= anticholinergic effect
**no systemic application! Many side effects!
Acetylcholinesterase
Acetylcholinesterase= OFF SIGNAL
-Cholinesterase inhibitors prevent off signal from occurring. Results in high levels of Ach present in the synapse= Cholinergic receptors are heavily acitivated
What occurs with high levels of Ach that cannot be removed due to acetylcholinesterase?
- SLUD
salivation, lacrimation, urination, defecation - Blue- extremely low heart rate
- Twitching
Cholinergic receptor agonists or antagonists
Either increase or decrease cholinergic receptors
Adrenergic Neurotransmission
Associated with NE release into synapse which will bind to alpha and beta receptors
Metyrosine
Prevents the synthesis of NE
Amphetamine
Causes NE to leak out of nerve terminals
Results in excitation/stimulation (proadrenergic or indirect adrenergic agonist)
Bretylium
Prevents NE release
Cocaine
Blocks NE reuptake into the pre-synaptic neuron, resulting in accumulation of NE into the synaptic cleft
Increase HR, vasoconstriction, activated fight or flight response
Adrenergic receptor agonists or antagonists
-Either increase or decrease adrenergic alpha or beta receptors
Monoamine oxidase
Enzyme used to convert NE into metabolites
-antidepressants used to prevent it because increase serotonin production BUT will also result in higher levels of NE resulting in side effects
Neuromuscular junctions
Ach acts on Na channels
-Off signal=acetylcholinesterase
Acetylcholinesterase inhibitors
- Irreversible= insecticides
2.Reversible
- edrophonium
Tubocurarine or Pancuronium
Competitive antagonists for Ach at junction, preventing Ach effects on receptors
-Used when need flaccid paralysis (eg. orthopaedic procedures)