Term
| name key differences between systemic and pulmonary circulation. |
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Definition
- systemic circulation:
- vessels deliver blood everywhere EXCEPT to the lungs
- higher pressure
- pulmonary circulation:
- delivers (de)oxygenated blood tolungs
- lower pressure
- exclusive to gas exchange functions, unable to handle high pressure
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Term
| what are several of the main functions of the CV system? |
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Definition
- meet metabolic needs of body, under ALL conditions (O2 delivery, waste removal)
- blood flow to vital organs (BRAIN, HEART) at ALL times
- blood pressure to drive renal filtration
- nutrient/immune cell/hormone distribution
- core temperature regulation
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Term
| Two main principles govern CVS function. What are they? |
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Definition
1. Maintain pressure in arterial system (M.A.P.) 2. Provide adequate total flow (C.O.) |
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Term
| what role do arterioles play in circulation? |
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Definition
they function as "stopcock or resistance" vessels; control flow distribution to tissues
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Term
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Definition
Pi -Po = Q x R or ΔP = Q x R P= pressure (force/area) Q=fluid flow (volume/time) R=hydraulic resistance -frictional resistance to fluid movement w/in the tube; pressure drop occurs as a result |
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Term
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Definition
RATE at which fluid moves. Units of velocity (distance/time) |
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Term
| why is blood pressure SO crucial? |
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Definition
Since the flow,Q, is directly proportional to pressure (equal to ΔP/R), the higher the pressure the higher the flow. Pressure is necessary to drive flow through a tube because the tube has hydraulic resistance. Due to this resistance, the pressure decreases/drops in the direction of flow, Q. P=F/A --> the pressure in a liquid flows by force in a tube
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Term
| what are some of the sources of pressure on blood? |
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Definition
- force of heart's muscular contraction (arterial blood pressure)
- hydrostatic pressure (P=ρ*g*h)
- skeletal muscles squeezing on blood vessels
- respiratory forces
- external forces
*** P = FORCE / AREA *** |
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Term
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Definition
total flow of blood out of the left ventricle; also out of the right ventricle in the normal steady state condition CO = HR x SV (L/m = beats/m x L/beat) CO = (MAP-MRAP) / TPR *since Q = ΔP/R *
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Term
what effect does the resistance level of the large arteries have on pressure changes?
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Definition
Resistance of the large arteries is low and so there is very little pressure drop throughout the arterial system The pressure produced upon blood ejection from the left ventricle to the aorta is well-sustained throughout systemic circulation. Q relatively constant because P is relatively constant (due to low R)
Q= P/R
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Term
| Mean Arterial Pressure (MAP) |
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Definition
MEAN ARTERIAL PRESSURE= 1/3 (PULSE PRESSURE) + DIASTOLIC PRESSURE pulse pressure= systolic pressure - diastolic pressure
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Term
| what determines pulse pressure? |
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Definition
- rate of ejection into arterial system
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Term
| Mean Right Atrial Pressure (MRAP) |
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Definition
Pressure in large veins, inferior and superior vena cava, right atrium are VERY similar Little pressure drop as blood travels towards heart due to presence of low resistance The average pressure in the venous system is the mean right atrial pressure (MRAP, or central venous pressure, CVP)
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Term
| total peripheral resistance (TPR) |
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Definition
total hydraulic resistance in all blood vessels between left ventricle and right atrium the big vessels don't have a lot of pressure and so the main source of this TPR is the highly resistive small arteries, arterioles, and pre-capillary sphincters
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Term
How do you calculate total flow (Qt) in networks of tubes with different resistances?
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Definition
First: Q total = ΔP / R total = (Pi-Po)/ R total Resistance in series (pressure is dropped at each resistance; flow across each resistance is the same): R total = R1 + R2 + R3 + ... Q1 = Q2 = Q3 = .... Q1= ΔP1/R1 = (Pi-P1)/R1 Resistance in parallel (flow divides at each resistance; pressure dropped across each resistance is the same): R total = 1/R1 + 1/R2 + 1/R3 +... Q total = Q1 + Q2 + Q3 +... Q1 = ΔP/R1 = (Pi-Po)/R1
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Term
| Total Pulmonary Artery Flow (CO) |
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Definition
(MPAP - MLAP) / TPulmR MPAP: mean pulmonary artery pressure MLAP: mean left atrial pressure TPulmR: total pulmonary resistance |
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Term
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Definition
ΔVolume/ ΔPressure determines how much work the heart must perform to provide a certain flow; veins much more compliant than arteries, which are more compliant that aged aorta. Highly compliant venous compartment in systemic circulation contains most of the total blood volume (over 60% total blood in the veins) Combination of low pressure and high volume creates high compliance
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Term
| What is the relationship between TPR and MAP? |
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Definition
regulation of TPR is ONE of the key mechanisms to control MAP CO = MAP/TPR, and so CO x TPR = MAP TPR is regulated through changes in hydraulic resistance of small arteries, arterioles and pre-capillary sphincters Hydraulic resistance in these vessels is regulated mostly via changing their radius
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Term
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Definition
[image][image][image] Q = (Pi - Po)*∏*r^4 ______________ 8*∩*l R= (8*∩*l) / (∏*r^4) ∩= viscosity of fluid l = length r= radius of vessel moral of the story: resistance is commonly controlled via the radius of arterioles |
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Term
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Definition
decrease in radius (contraction) causes MASSIVE (inverse 4th power) increase in resistance lumen shrinks a lot more in response to contraction than the outside layers of the vessel
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Term
| flow versus flow velocity |
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Definition
Q, flow: vol/time (ie, mL/s) v, flow velocity: distance/time (ie, cm/s) velocity = Q/A A= r^2 ∏ Flow velocity depends on cross-sectional area of the tube in which flow is occuring; decrease in area makes an increase in velocity
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Term
| what type of flow obeys Poiseuille's equation? |
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Definition
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Term
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Definition
in most cases in Cv system, flow is laminar laminar flow is silent parabolic distribution of flow velocity across the tube velocity is not constant throughout the tube velocity is greatest at the center of tube, but decreases as you move outward (dragging against the wall of artery, pressure dissipates)
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Term
| what creates turbulent flow? |
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Definition
- high velocity laminar flow breaks up
- flow from narrow tube to a larger tube
- constrictions in artery
turbulent flow is NOISY (can be heard with stethoscope), and its velocity distribution is chaotic |
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