Autonomic nervous system Flashcards
Where are alpha 1 receptors found?
peripherally
- in a variety of tissues (vascular smooth muscle, glands)
- innervated by sympathetic postganglionic neurons
Where are alpha 2 receptors found?
-
Pre-synaptic receptors
- CNS - brainstem (inhibits outflow of the SNS)
- Medulla - decreases SNS tone
- Vagus Nerve - increases SNS tone
- Locus ceruleus - sedation and hypnosis
- Dorsal horn of spinal cord - analgesia
- PNS peripherally (inhibits NE synthesis and release–> negative feedback system)
- CNS - brainstem (inhibits outflow of the SNS)
- Post-synaptic - smooth muscle and peripheral tissue
- Platelets (non-synaptic)
Where are beta 1 receptors found?
heart, kidney, adipose tissue
Where are beta 2 receptors found?
smooth muscle and glandular tissue
physiologic response to alpha 1 receptor activation
- pupils dilate (mydriasis “OH MYdriasis”)
- vasoconstriction of arteries (increased SVR)
- vasoconstriction of veins (increased preload)
- release of RBCs from the spleen
- decrease renin release
- relax stomach and intestines
- decrease insulin secretion and increase glucagon secretion
- contract the uterus
Phyosiologic response to alpha 2 receptor activation?
- decrease insulin secretion
- inhibit NE synthesis and release (negative feedback) in presynaptic nerve terminals of sympathetic postganglionic neurons -in brainstem, inhibit outflow of SNS
- in substantia gelatinosa, promote analgesia
physiologic response to beta 1 receptor activation?
- increased HR (chrono)
- increased conduction speed (dromo)
- increased contractility (inotropy)
- increased renin release
- iypolysis (breakdown of fats)
What response is seen when beta 2 receptors are activated?
- vasodilation in skeletal muscle vessels (decreased SVR)
- bronchodilation
- increased secretions
- glycogenolysis and gluconeogenesis (increased glucose)
- relax gallbladder
- relax urinary bladder wall
- increase insulin secretion
- relax uterus
- stimulate Na-K pump (decrease plasma K+; 3 Na Out, 1 K+ in)
______ stimulation promotes hyperglycemia (secondary to glycogenolysis and gluconeogenesis).
beta 2
______ stimulation promotes hypokalemia.
beta 2 (stimulation of Na-K pump)
Side effects of _____ receptor stimulator, _________, include hyperglycemia, hypokalemia, and tachycardia (d\t some beta 1 receptor activity)
beta 2 receptor; ritodrine (yutopar)
Relaxes the uterus?
beta 2
Increased chronotropy, dromotropy, and inotropy?
beta 1
Vasoconstriction of arterial systemic vessels and veins?
alpha 1
Bronchodilation and increased secretions?
beta 2
Glycogenolysis and Gluconeogenesis?
beta 2
Mydriasis?
alpha 1
Stimulate Na-K pump?
beta 2
Why should you alpha block before you beta block?
alpha blockade produces arterial dilation, a decrease in SVR, and a decrease in afterload—> this makes it easier for the heart to eject blood after being beta blocked If beta blockade happened first, then heart failure may ensue b\c the beta blockade prevents increased contractility or ejection of an adequate SV when the SVR and afterload become elevated as a result of increases in circulating EPI and NE
What is phosphodiesterase III?
Enzyme that converts cAMP to AMP - essentially terminating its downstream effects
(thus PDEIII inhibitors such as milirinone keep cAMP in the cell increaseing free Ca++ in myocardail cells - increased contractility and leusitropy, and vascualr smooth muscle vasodialtion AKA increases inotropy wile decreasing afterload)
Where is Norepinephrine synthesized to Epinephrine and via what enzyme?
Norepi is converted to Epinephrine in the adreanal medulla via Phenylethylamine N-methyltransferase.
(the adrenal medulla releases 80% epinephrine and 20% NE)
