Factors Affecting Blood Flow Flashcards
What does an increased haematocrit indicate?
dehydration
What does an decreased haematocrit indicate?
anemia
What is the Buffy coat?
thin pale layer contains platelets (thrombocytes) and WBCs (leucocytes)
What is blood flow dependant on?
metabolic demands of each organ system
What does skeletal muscle requirement during exercise?
more oxygen therefore greater blood flow
What does the GI system require after a meal?
more oxygen therefore greater blood flow
Where in the body does blood flow align with cardiac output?
pulmonary system as all blood must pass through lungs for removal of CO2 and addition of oxygen
the lungs require a high blood flow rate to ensure that a large volume of blood is exposed to the alveoli for gas exchange. The cardiac output is the amount of blood pumped by the heart per minute and it must be equal to the blood flow to the lungs to ensure efficient gas exchange. This ensures that sufficient oxygen is delivered to the body tissues to meet metabolic demands and that excess carbon dioxide is removed from the body.
What are the two mechanisms that regulate blood flow?
local (intrinsic)
neural/hormonal (extrinsic)
What are specific needs of the tissue that blood flow provides?
delivery of oxygen and nutrients (glucose, amino acids, fatty acids)
removal of carbon dioxide and hydrogen ions
maintenance of ion concentrations
transport of hormones
Describe in what three ways can local (intrinsic) control occur?
Autoregulation
Maintenance of constant blood flow while arterial pressure changes
If coronary arterial pressure decreases, immediate compensatory vasodilatation of coronary arterioles to decrease coronary vasculature resistance, will attempt to maintain constant blood flow in this coronary artery.
Active Hyperemia
Blood flow to tissues is proportional to its metabolic activity
Increased blood flow when metabolic activity increases (exercising skeletal muscle increased O2 consumption / ATP demand)
Increased arteriolar dilation
Reactive Hyperemia
Increase in blood flow in response to a prior period of decreased blood flow.
E.g. following period of arterial occlusion, an O2 dept accumulates – longer the arterial occlusion, greater O2 debt, greater the increase in blood flow (above pre-occlusion levels) until the O2 dept reversed.
What layer of the vessel is responsible for vasoconstriction and vasodilation?
tunica media
What are the factors that determine resistance to blood flow?
vessel diameter
vessel length
viscosity of blood
How can blood become more viscous?
dehydration
What disease occurs when blood flow is reduced?
deep vein thrombosis
What is vessel resistance directly proportional to?
length of vessel
viscosity of blood
What is vessel resistance inversely proportional to?
diameter (radius)
What is the equation of flow?
flow(Q) = change in pressure/resistance
What is poiseulles equation?
flow is directly proportional to
(radius^4) X (change in pressure)
/
(viscosity of blood N) X (length of vessel L)
What does poiseulle’s equation tell us?
the flow (Q) of fluid is related to a number of factors: the viscosity (n) of the fluid, the pressure gradient across the tubing (P), and the length (L) and diameter(r) of the tubing.
What does poiseulles equation assume?
flow is through a straight tube
flow is non-fluctuating
flow is smooth
What aids venous return?
skeletal muscles compressing the veins
What is venous return aided by during exercise?
inter-thoracic pressure becoming more negative
What can become a problem in coronary heart disease (angina) and heart failure?
if preload increases (heart will have to work harder)
Where does blood supply to the heart derive from?
left and right corona arteries
