Week 8: Local and hormonal regulation Flashcards
What is the O2 content of arterial blood?
200 ml/l
What is the O2 content of venous blood?
150 ml/l
What is the arteriovenous O2 difference (AVDO2)
50 ml/l
What are the three types of local control?
- Bayliss-effect autoregulation
- Metabolic Regulation
- Endothelium Mediated Regulation
Describe the Bayliss-effect
- works through endothelium
- small arteries, arterioles
- smooth muscle
Describe the graph showing the relationship between pressure and flow
P↓ ⇒ r↑ ⇒ R↓ Q is maintained
P↑ ⇒ r↓ ⇒ R↑ Q is maintained
What happens when pressure is increased in regards to the Baylis-effect?
P↑ ⇒ T↑
mechanosensitive ion channels open
↓
depolarization
↓
L type Ca2+ channels
↓
Ca2+ ↑
↓
constriction of vessels
Describe metabolic regulation
self regulating
- precapillary sphincters
- smooth muscle of terminal- and meta- arterioles
- no sympathetic regulation
How does the metabolic regulation work?
↑ function of tissue cells ⇒ ↑ metabolism
in general all the molecules have vasodilation effect on the smooth muscle (local flow ↑)
What changes in the environment will lead to relaxation (dilation) of smooth muscle and hence ↑ flow
PO2 ↓
PCO2 ↑
lactic acid, pH ↓
adenosine
[K+] ↑
What happens when there is an ↑ in [metabolites] and ↑ Q
functional hyperemia
reactive hyperemia
What are the two types of endothelium mediated regulation?
- metablism ↑
- histamine and seratonin
What are the vasodilators of endothelium mediated regulation?
PGl2 → activates Gs receptors → cAMP↑ → PKA → relaxation of SM
NO → cGMP → PKG → relaxation of SM
Endothelium mediated regulation: What happens when metabolism is increased?
* retrograde vasodilation *
[metabolites] ↑
↓
R↓
↓
Q↑
↓
shear stress ↑
↓
endothelial cells
↓
NO production ↑
↓
vasodilation
Endothelium mediated regulation: What does histamine and seratonine do?
activated endothelial cells
↓
vasodilation
What does angiotensin II provoke?
vasoconstriction
What is another option for regulation?
hormonal, humoral regulation (slow)
has direct effect on smooth muscle
What are the vasoconstrictors that aid in hormonal regulation?
- Norepinephrine
- Angiotenstin II
- Vasopressin (ADH)
- Histamine, seratonine
Describe Norepinephrine
Sources: sympathetic system
adrenal gland
alpha adrenergic receptor → activates Gq → [Ca2+]↑ → vasoconstriction
Describe Angiotensin II
Angiotensin II is a peptide
composed of: angiotensin I
angiotensinogen
renin production → AT1R → Gq
Describe Vasopressin (ADH)
V2R → Gs → kidney function; water reabsorption
V1R → Gq → kidney function; water reabsorption
What G protein is associated with Histamine, seratonine?
Gq
What are vasodilators in regards to hormonal regulation?
- Epinephrine
- ANP
- PGl2
Describe epinephrine
Source: adrenal gland
binds to beta 2 receptor w/ higher affinity
[Epinephrine] ↓
↓
activates Gs
↓
relaxation
vise versa if [E] ↑ more alpha 1 activated → vasoconstriction
