Sympathetic System Flashcards
Sympathomimetics
effects of sympathetic stimulation are mediated by NE.
NE and epi
NE is released from nerve terminals.
Epi is released into blood from adrenal medulla (adrenaline)
Receptor types of sympathomimetic drugs
Adrenergic:
Alpha 1 and Alpha 2
Beta 1 and Beta 2
*All are GPCR. Slow on/slow off. Desensitization can occur.
Main diff of all of these are location
*many agonists have selectivity for one of the major subtypes of receptors, but not specificity!
Selectivity vs specificity
Selectivity: Has diff affinities for many receptor types. Will be non- selective at high concentration. More selective at lower doses.
Specificity: No matter the concentration, will always bind 1 type of receptor.
Alpha 1 adrenoceptor
Vasoconstriction Increased peripheral resistance Increased blood pressure Mydriasis Increased closure of internal sphincter of bladder (hold in urine)
Alpha 2 adrenoceptor
Inhibition of NE, Ach, and insulin release
Beta 1 adrenoceptor
Increased HR- Tachycardia
Increased lipolysis
Increased myocardial contractility
Increased release of renin
Beta 2 adrenoceptor
Vasodilation
Decreased peripheral resistance
Decreased blood pressure
Bronchodilation
Increased muscle and liver glycogenolysis (more glucose)
Increased release of glucagon
Relaxed uterine smooth muscles (have to pee)
Drugs that cause vasoconstriction. What is the reflex??
Reflex decreased HR
Drugs that cause vasodilation. What is the reflex?
Reflex increased HR
The net effect of any sympathomimetic will be a combo of
Its direct effect on a receptor and a counteraction by compensatory mechanisms. The bodys goal is to maintain homeostasis.
Cardiovascular system and Alpha 1 activation
Arterial and venous vasoconstriction–> leads to increased peripheral tolerance, which increases BP.
As reflex, will get a decrease in HR.
Cardiovascular system and Alpha 2 activation
Decrease transmission of NE (sympathetic info) resulting in a decrease in BP. Prob due to vasodilation (from parasympathetic becoming more dominant)
Cardiovascular system and Beta 1 activation
Increased HR (tachycardia) and increased contractility. Leads to an increase in CO and blood pressure.
Cardiovascular system and Beta 2 activation
Vasodilation –> Decreased peripheral tolerance –> decrease in blood pressure –> reflex of increased HR.
A non selective beta agonist will have a net effect of?
Decreasing blood pressure through B2 activation.
B1 increases BP and B2 decreased BP but B2 wins.
Respiratory system activation of Beta 2
Bronchodilation.
Eye and alpha 1 activation
Mydriasis (contraction of pupillary dilator muscle)
Good dilation drop
Eye and alpha 2 activation
Acts on iris and ciliary body to decrease IOP.
Decrease aqueous production
Increase uveoscleral outflow.
Eye and beta 2 activation
Relaxation of ciliary muscle- dilation but not significantly. Would not be a good drop.
Production of aqueous- increases IOP.