Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
19 Cards in this Set
- Front
- Back
|
arterioles
|
- control BF on arterial side
- relatively thickest muscular wall - change diameter within wide range - Poiseuille's law: diameter changes have strong effect on resistance and therefore BF |
|
|
veins gen
|
- at rest, hold about 2/3 total BV: most in small vv and venules
- change in V only has a minor effect on venous BP |
|
|
velocity of BF on arterial side
|
- diameter and velocity decrease:
- increasing number of vessels at each level increases the total cross-sectional area, decreasing flow velocity -lowest velocity at capillaries |
|
|
laminar flow
|
concentric layers of the same velocity:
- smooth flow - low friction against walls because of low velocity of outer layers - less E required than turbulent - eg aorta, vena cavae |
|
|
turbulent flow
|
no layers, but same velocity
- chaotic movements in and along the vessel - high friction against the wall - more energy required - eg valves |
|
|
bolus flow in capillaries
|
- small capillaries:
1. RBCs become bell-shaped allowing them to fit through vessels smaller than their own flat diameter 2. aggregate and move in single files, reducing viscosity of blood 3. stay away from wall: reduced flow resistance 4. turbulent flow of surrounding plasma facilitates metabolic exchanges with cells of neighboring tissue |
|
|
stroke volume
|
- BV ejected by one ventricle during systole
- difference between end diastolic and end systolic P |
|
|
cardiac output
|
- BV ejected/ min by one ventricle
- stroke v x HR - rest: < 50% of enddiastolic ejected - exercise: up to 90% ejected |
|
|
Factors that determine stroke volume
|
1. preload
2. afterload 3. contractility - 70-140mL in man |
|
|
Cardiac reserve
|
= COmax/ COrest
- rest: man 5, cow 30 - max: man 25 therefore CR= 5 in man |
|
|
perfusion (delta) P
|
=inlet P- outlet P
- driving force of flow - independent of vessel diameter - |
|
|
resistance gen
|
- depends strongly on diameter
- flow deterimine by resistance and perfusion P |
|
|
Ohm's Law
|
flow = delta P/ resistance
|
|
|
factors that determine resistance
|
1. fluid viscosity
2. length 3. diameter |
|
|
Pouiseuille's Law
|
R = (8*n*l)/(pi*r^4)
R= resistance n= viscosity l= length r= radius |
|
|
Total peripheral resistance
|
= (mean aortic P- vena caval P)/ CO
= systemic perfusion P/ CO - total resistance to blood flow of all vessels of systemic circulation |
|
|
Factors determining TPR
|
1. radius of vessel
2. number of vessels 3. blood viscosity 4. length (minor influence) |
|
|
hematocrit and viscosity
|
- higher hematocrit increases friction between cells, plasma and walls
|
|
|
blood viscosity and friction in small vessels
|
1. viscosity is lower than in large: blood vessels file up, stay in the center of the flow and don't touch the wall so there is less friction
2. viscosity increases when velocity decreases: formation of larger aggregates increases viscosity and may result in intravasal blood clotting |
