Lecture 11 - Blood flow control & Kidneys Flashcards
Describe the mechanism of acute control of blood flow
Vasoconstriction/dilation by means of changes to SNS tone
Describe the mechanism behind long-term blood flow control
Tissue remodeling (any others???)
Describe the theory of vasodilation in acute blood flow control.
Increased metabolic activity -> decreased [oxygen] -> formation of vasodilators
Describe the theory of oxygen/nutrient lack in acute blood flow control.
Decr. [oxygen] causes a decrease in SNS tone -> blood vessel relaxation -> vasodilation
Cyclical opening and closing of precapillary sphincters is known as ______.
vasomotion
Why can pre-capillary sphincters remain contracted for only short times with decreased [oxygen]?
Long term contraction requires oxygen (oxydative phosphorylation to reconstitute ATP)
Describe reactive hyperemia.
Due to blocked blood flow, tissues “react” when the blockage is removed; this increased blood flow 4-7x more than normal
Describe active hyperemia
Increased metabolic activity in a tissue causes an increase in blood flow. This is to increased nutrient transport/removal of waste.
Blood flow autoregulation show and increased blood flow and (an increase/a decrease) in BP.
decrease
In autoregulation, blood pressure (is/is not) returned to normal.
Is not; autoregulation of flow has NOTHING to do with control of blood pressure
What are the two theories of autoregulation of blood flow?
Metabolic:
increased metabolism -> increased blood flow -> too much O2/nutrients -> “wash out” of vasodilators
Myogenic:
Increased blood flow -> blood vessel dilation -> reactive vasoconstriction
Myogenic autoregulation can occur without the presence of ______.
Vasosconstrictors (appears to be mediated by smooth m.)
Monitors [NaCl] in the juxtaglomerular apparatus.
macula densa (part of DCT)
Secretes renin
Juxtaglomerular cells
Healthy endothelium secretes _____, which helps with maintaining vessel tone.
Nitric oxide (NO)
Nitric oxide assists in the reaction of __ to ___.
cGTP to cGMP
cGMP is important in the activation of _______, which promote vasodilation.
protein kinases
cGTP is found in ______
vascular smooth muscle cells
Damaged cells (either through HTN or trauma) secrete _____, which promotes vasoconstriction.
endothelin
Damage to endothelium may cause hypertension by what mechanism?
Lack of NO production. This causes decreased [endothelin] -> [Nitric oxide] -> vasoconstriction; (+) feed back; essentially, the lack of nitric oxide from damaged endothelium produces HTN
Circulation control is also mediated by humoral factors. What vasoconstriction mediators are present?
- NE
- Epi
- ANG II
- Vasopressin
Released from SNS neurons, is a vasoconstrictor
norepinephrine
Released from the adrenal glands, is a vasoconstrictor
epinephrine
This hormone, also known as “ADH,” acts on the vessels to increase peripheral resistance
vasopressin
Acts as a vasoconstrictor, controls body fluid volume; also prevents water loss
vasopressin (“vaso”-vessel; “-pressin” - increases pressure); AKA “ADH”
Acts as a vasodilator by increasing capillary permeability
bradykinin