Lecture 18: Blood distribution and control of local circulation Flashcards
(28 cards)
The max HR is approximated at what?
220-age
Is the percentage of the CO going to various organs/regions equal?
No it is not and it can change from minute to minute depending on conditions
What is CO at rest?
5 L/min
What is CO while exercising?
25 L/min
True or false? Blood flow to the tissue is matched to the needs of the tissue.
true
Active tissue can require up to ______ increase in blood flow.
20x
Even though active tissue can require up to 20x increase in blood flow, CO only increases 6x, so what must happen?
Changes in microcirculation must take place to increase blood flow to the active tissue even more
If blood flow exceeds the need of the tissue, what happens?
regulatory mechanisms will decrease blood flow
Does the SNS innervate blood vessels?
yes
The PNS doesn’t innervate the majority of blood vessels but does regulate what?
dilation of some blood vessels in specific areas of the body (genitals)
What is the primary controller of coronary and cerebral blood flow?
Local metabolism and release of vasodilator substances
Epinephrine binds to B2 receptors and so these receptors are said to be stimulated. What do these stimulated receptors cause?
Vasodilation (lactate can also cause vasodilation)
What are some factors that are released from metabolically active or hypoxic tissues that cause relaxation of smooth muscle and vasodilation of small arteries and arterioles?
adenosine, CO2, H+, K+
Endothelial cells release nitric oxide in response to what?
sheer stress from blood flow
The nitric oxide that’s released from the endothelial cells will diffuse into smooth muscle in local area and cause what?
smooth muscle relaxation (vasodilation)
What does Endothelin cause?
vasoconstriction
What 3 autocrine/paracrine peptides cause arteriole dilation and capillary permeability?
Bradykinin, prostaglandins, and histamine
What is a form of long term regulation of blood flow?
angiogenesis
Tissues release angiogenic factors (VEGF, FGF) in response to what?
chronic ischemia
What happens to the oxygen demand in muscles during exercise?
increases & blood flow to those tissues increase as well
What happens to the oxygen consumption (VO2) in skeletal muscle during exercise?
increases
What happens to the arteriovenous oxygen difference (a-vO2 difference) in skeletal muscle during exercise?
increases
What is the A-VO2 difference?
the difference in the PO2 between the arterial blood and the venous blood
If the A-VO2 increases, what does it represent?
an increase in oxygen uptake by that tissue
