Flashcards in Test 2 week 4 Deck (145)
Tissue ____ blood in proportion to its need
What are the tissue needs?
- Delivery of o2 to tissues
- delivery of nutrients --> glucose, amino acids
- removal of CO2, hydorgen, and other metabolites from the tissues
- Maintenance of proper ionic concentrations in tissues
- transport various hormones and other substances to different tissues
Flow of blood is closely related(proportional) to _______
metabolic rate of tissues
What is the difference between flow and perfusion?
Flow is volume over time, while perfusion is volume over time over an amount of tissue
Because we do not have the ability to constantly pump the max amount to all organs at the same time...
Some organs receive constant amount of blood flow regardless of other organs (the brain), other organs change the amount they receive depending if they are active or inactive depending on the need
Possible regulators of acute control of local blood flow: metabolic control
- O2 demand theory
- Vasodilatory theory: as metabolism increases, certain substance conc. also increases around the tissue. These metabolisms have different effects on SMC & on endothelium that causes vasodilation
Oxygen demand theory
regardless if there is a decrease in O2 or increase in tissue metabolism, there will be a decrease in tissue O2 levels. This leads to relaxation, which leads to vasodilation, which leads to an increase in blood flow
Decrease in O2, is sensed by...
precapillary sphincters, which causes then to relax and vasodilate
As oxygyen saturation increases, _____decreases
No decrease in O2 levels leads to...
sphincter contraction, and decreased blood flow. Blood is then shunted to other areas that needs it
What is reactive hyperemia?
The blocking of blood supply for a period of time causes build-up of waste product metabolites that have vasodilatory properties.
Increase in blood flow will be proportional to time of ischemia & how strong it is.
What is active hyperemia?
An increase in local metabolism causes rapid diminishing of nutrients and increased release of vasodilatory substances
What does the increased release of vasodilatory substances do?
it stimulates endothelium & SMC to vasodilate, hence increasing blood flow
As activity levels increase, so does _____
blood flow. Once activity returns to normal, so will blood flow
What are the two components of metabolic autoregulation?
Intrinsic and extrinsic components
Intrinsic factors that increase the activity of the muscle produces...
vasodilator metabolites that will act on microcirculation to produce vasodilation.
Where is the most resistance found?
In the arterioles and microcirculation
What does flow-induced dilation in the extrinsic component do?
It increases blood flow & will further increase dilation upstream
Flow- mediation dilation is a good indicator of...?
Arterial & endothelial health
How is flow mediation dilation does
Use a probe to find the brachial artery, get a baseline video & use it to get the average diameter of the artery, wrap a cuff around it & inflate it to around 200mmHg & leave it for 5 mins, let g of the cuff, resulting in great increase of blood flow & the dilation of the arteries
What type of hyperemia is flow mediation dilation?
What does the pressure curves in flow mediation dilation tell?
How fast the blood is flowing and how much blood is flowing. This tells us the function and state of the microcirculaton.
Multiple signaling pathways that determines vascular tone
When blood flow increases, it causes shear stress pulling on the endothelium.
What does shear stress and pulling of the endothelium do?
1. stimulates the endothelial cells to open K channels. (hyperpolarizes the cell membrane) At the same time, muscle contraction also stimulates K channels on the SMC to hyperpolarize the SMC membrane, because of metabolites released from muscle & gap junction.
2. Hyperpolarization transfers to neighboring SMC & endothelial cells via gap junctions.
3. Hyperpolarization inhibits Ca channels, decrease Ca intracellular conc. in SMC. Contraction depends on Ca.
4. shear stress on endothelial, stimulates vasodilators (NO), stimulates muscle to relax further.
Exercise wants to vasoconstrict, but the ____ process negotiates this & stronger signals
shear stress and pulling of the endothelium
Phosphorylation _____ Ca
What is the role of endothelial cells?
- Vasoconstrictor: norepinephrine increases muscle tone in muscles, and the addition of acetylcholine decreases it
- A destroyed endothelium occurs when acetylcholine is added
What is the role of NO
it is an endothelial relaxing factor.
Endothelial dysfunction is a precursor to...