Vasoconstrictors Flashcards
Adrenergic/Cholinergic receptor associated with SNS?
Adrenergic is associated with the SNS and cholinergic is associcated with the PNS
What happens when an SNS neuron is stimulated?
Stimulation travels the length of the neuron. Once it reaches the presynaptic region, NE is released and is it attaches itself to the postsynaptic receptor (Beta or Alpha).
Where do the SNS nerves originate from?
Thoracolumbar origin (T1-L2).
What substance enters the synaptic vessel?
Dopamine
What converts Dopamine to Norepinephrine?
Dopamine Beta Hydroxylase
T/F: 99% of norepinephrine is metabolized in the body?
False; 2/3rds is reuptaken into the presynaptic cleft again.
What are the two enzymes that rapidly inactivate catecholamines?
- Monoamine oxidase (MAO).
2. Catechol-o-transferase (COMT).
What three ways is norepinephrine’s signal terminated?
- Reuptake
- Dilution by diffusion
- Metabolism (MAO/COMT).
What are four main adrenergic receptors?
Alpha 1
Alpha 2
Beta 1
Beta 2
Which adrenergic receptor is located primarily in the heart?
Beta 1
Which adrenergic receptor is located primarily centrally: alpha 1 or alpha 2?
Alpha 2
Which adrenergic receptors are G Proteins?
Beta 1 and 2
Which enzyme is responsible for converting ATP into cAMP?
(AC) Adenylyl cyclase
What is phosphodiesterase’s role in contractility?
Phosphodiesterase breaks down cAMP and stops the action of contraction
Which enzyme (instead if cAMP) does do Alpha receptors use to stimulate contraction in smooth muscle?
Inositol triphosphate
What 8 things occur with Alpha 1 Postsynaptic receptor activation?
- Increased intracellular calcium
- Smooth muscle contraction
- Peripheral vasocontriction
- Bronchoconstriction
- Inhibits insulin secretion
- Stimulates glycogenolysis and gluconeogensis
- Mydriasis
- GI relaxation
Which adrenergic receptor system uses a negative feedback system?
Alpha 2
What are the effects of Alpha 2 receptors presynaptically?
- Decreases entry of calcium into the cell
2. Limits the release of norepinephrine
What are the effects of Alpha 2 receptors post-synaptically?
- Sedation
- Decreased sympathetic outflow
- Decreased BP
- Platelet aggregation
3 Effects of Beta-1 postsynaptic receptor agonism?
- Increased HR
- Increased conduction velocity
- Increased myocardial contractility
7 effects of Beta-2 postsynaptic agonism?
- Smooth muscle relaxation
- Peripheral vasodilation
- Decreased BP
- Bronchodilation
- Increased insulin secretion
- increased glycogenolysis and gluconeogenesis
- Decreased GI mobility
What are the main differences between Alpha 1 and Beta 2 stimulation?
Alpha 1 is more fight/flight and will decrease insulin and cause bronchoconstriction and vasocontriction.
Beta 2 increases insulin and causes bronchodilation and vasodilation
Where does the parasympathetic nervous system originate?
Craniosacral origin (III,V,VII,X).
Is the preganglia of the PNS near the organ or near the origin ?
Near the organ that it innnervates.
What is secreted by the postganglia with PNS stimulation?
Acetylcholine
Which electrolytes mediates the action potential of acetylcholine in the ANS?
Calcium
What deactivates acetylcholine?
Acetylcholinesterase
What are the two different types of cholinergic receptors?
- Nicotinic
2. Muscarinic
SNS or PNS cause gallbladder relaxation and urinary bladder muscle relaxation/sphincter contraction
SNS
What does extended exposure to agonists do to the body?
Reduces the number, but not their response. The result is tachyphylaxis/down regulation
What is up regulation?
Chronic depletion of catecholamines or use of antagonists increases the number of receptors, but noth their sensitivity. May accoutn for withdrawal syndrome with beta blockers.
What is sequestration of cell receptors?
Movement of receptors from the cell surface to intracellular compartments
T/F: Vasoconstrictors we use are all catecholamines, but not all of them are sympathomimetics?
False; all are sympathomimetics, but not all have catecholamine structure
What is different about the chemical structure of a NON-catecholamine sympathomimetic?
The hydroxyl groups are not present in both the 3 and 4 positions of the benzene ring.
Can a sympathomimetic be an indirect-acting catecholamine?
No; indirect acting sympathomimetics are synthetic non-catecholamines
What are the three different types of sympathomimetics?
- Naturally occurring catecholamines
- Synthetic catecholamines
- Synthetic non-catecholamines
a. Indirect
b. Direct