Catecholamines (cont) and Adrenergic receptors Flashcards
The flight or flight response is mediated by
Norepinephrine
produce and released by neurons
No fight or flight response if we see the
HPA Axis
because it needs time (but fight or flight response is a quick response)
The fight or flight response is not a response to cortisol
it is a response to stress
- cortisol stimulates EP synthesis and release and works to improve response
Norepinephrine functions primarily as a neurotransmitter for
cardiac effects
Both norepinephrine and epinephrine influence the
vascular tone
(vasoconstriction and dilation)
epinephrine affects
metabolic processes such as carbohydrate metabolism
stress hormone (happen quick)
- heart rate increases
- blood sugar levels increase
- blood pressure in arteries increase
- pupils dilate
- intestinal muscles relax
- breathing rate increase
- blood flow to skeletal muscles increase
Actions of catecholamine
Norepinephrine
- increase heart rate and blood pressure and peripheral vasoconstriction
Epinephrine
- increase heart rate, blood pressure, peripheral vasoconstriction, increase lipid breakdown, coronary dilation, bronchial dilation, glycogen to glucose
catecholamines are initiated through interaction with two different types of specific cell membrane receptors
alpha-adrenergic
- alpha 1
- alpha 2
Beta- adrenergic
- beta 1
- beta 2
- beta 3
these receptors have different affinities for norepinephrine and epinephrine and can cause opposing physiological effects depending on …
location and concentration of the hormone
at low plasma concentration, EP predominantly stimulates
beta- adrenergic receptors (causing vasodilation)
at higher plasma concentration, EP stimulates
alpha receptors sufficiently to override vasodilation and cause vasoconstriction
alpha 1
more affinity to NE
Gq»_space;PKC»_space; increase IP3, DAG, and Ca2+ (related to vasoconstriction)
alpha 2
more affinity to NE
Gi»_space; Adenylyl cyclase is inhibited = decrease cAMP
beta 1
equal affinity to EP and NE
Gs»_space; Adenylyl cyclase»_space; increase cAMP
beta 2
more affinity to EP
Gs»_space; Adenylyl cyclase»_space; increase cAMP
beta 3
more affinity to NE
Gs»_space; Adenylyl cyclase»_space; increase cAMP
effects of circulating epinephrine
- increased heart rate & inotropy (beta1) *depending on concentration alpha1
- vasoconstriction in most systemic arteries and veins (alpha 1)
- vasodilation in muscle and liver vasculatures at low concentrations (B2)
- vasoconstriction at high concentration (alpha1)
- cardiovascular response to low -to moderate circulating concentration of epinephrine includes increase cardiac output and redistribution of the cardiac output to muscular and liver circulations with only a small change in mean arterial pressure (not altered by levels of EP circulating)
- although cardiac output is increase, arterial pressure does not change because the systemic vascular resistance falls due to beta2 activations
- at high plasma concentration, EP increase arterial pressure b/c ninf to alpha 1 on blood vessels which offset B2
although EPI and NE can bind to alpha and beta receptors, these are 2 main things that dictate the response
- affinity for the receptor
- concentration of the hormone in circulation
- location of the receptors
