15. DSA Circulation and Hemodynamics Flashcards
What contains a stressed volume of blood?
Arteries
What is the site of the highest resistance and largest drops in pressure. Will also have Alpha1 adrenergic receptors which contract smooth muscle and increase resistance to flow?
Arterioles
Which vessels contain unstressed volume of blood and have the largest percent of blood at any given time? Innervated by sympathetic alpha1 adrenergic
Veins and venules
What is the equation for velocity of blood flow (v)?
v (velocity in cm/s) = Q (flow mL/s (volume almost) ) / A (cross sectional area cm2)
While velocity is low in capillaries, velocity is greater near?
The ends (aorta, SVC/IVC)
Blood flow (Q) is determined by?
Q= Change in Pressure (P) / R (resistance)
The resistance to blood flow equation is R= 8nL/pi r^4
What does this mean?
A small decrease in radius will increase resistance by 16 fold
Increase in R will decrease blood flow
Laminar flow means streamlined. Turbulent flow occurs when laminar flow is disrupted and takes more energy to drive turbulent flow forward. So laminar flow is?
more efficient
Turbulent flow can be heard!
Reynolds number is used to predict whether flow will be turbulent or laminar, where less than 2000 predicts laminar flow. How is the Nr (reynolds number) calculated?
Nr= (p d v) / n p density of blood d is diameter of BV v is velocity of blood flow n is blood viscosity
Shear occurs because velocity is not the same along the vessel wall as it is in the center. Where is shear great and lowest at?
greatest along the vessel wall and lowest in the center
Compliance is the amount of stretchability in veins and arteries and is inverse of elasticity or recoil. Vein compliance is ______ compared to artery. What happens if the compliance decreases in a vein?
Vein compliance is greater than arteries
If compliance in vein decreases, the blood will be redistributed from unstressed volume to the stressed volume
How is the pulse pressure calculated? What does it represent
Systolic blood pressure (SBP) minus the diastolic blood pressure (DBP)
Represents volume of blood ejected from left ventricle in a single beat
Mean arterial pressure (MAP) is determined by?
MAP= 2/3 DBP + 1/3 SBP
Microcirculation refers to capillaries and capillary beds which branch from?
metaarterioles
What exchange of substances occur across the capillary wall?
Simple diffusion
Lipid and water soluble things
Proteins do not cross
What are the starling forces that influence fluid exchange across the capillaries?
Hydrostatic tissue
Hydrostatice capillary
Oncotic capillary only force to bring fluid out from alveoli to cap
Oncotic tissue
An Increase in filtration by the lympathic capillaries around the capillaries can be caused by what? (2)
- decrease in oncotic capillary pressure from reduced plasma protein concentration
- Increase in hydrostatic capillary pressure from increased VENOUS/arterial pressure
What is one mechanism for control over regional flow by the maintenance of a constant blood flow in face of changing arterial pressure. This takes place in kidneys, brain, and heart
autoregulation
What is a mechanism of control over regional flow in which blood flow to an organ is proportional to its metabolic activity?
Activer hyperemia
What is a mechanism of control over regional flow in which increase in blood flow in response to a period of decreased blood flow?
Reactive hyperemia
What does the myogenic hypothesis state?
If there is a stretch in the wall of arteries, the smooth muscle will constrict to increase resistanceand maintain flow
Shear stress will also contribute similar to stretch, in that greater shear stress will be synonymous with greater pressure
Active hyperemia uses a process in which oxygen delivery is matched to oxygen consumption. What hypothesis is this know as?
Metabolic hypothesis
What are some vasoactive substances along with the sympathetic NS for neuronal and hormonal control of the circulation?
Histamine Bradykinin Serotonin Prostaglandins Angiotensin II Vasopressin ANP
What does histamine result in?
Dilation of arterioles and contriction of venules = increased hydrostatice pressure = edema
In coronary, cerebral, pulmonary, and renal circulation- local metabolic control is most important while…?
sympathetic control is least important
In skin and skeletal muscle (at rest) circulation, local metabolic control is least important while?
sympathetic control is most important using Alpha 1 adrenergic receptors for vasoconstriction and B2 for vasodialation
