Unit 2: Circulation Pt1 Flashcards
What is the main function of the systemic circulation?
to deliver adequate oxygen nutrients to systemic tissues and remove CO2 and other waste products form the systemic tissue
T/F. Systemic circulation can act as a conduit for transport of hormones, and other substances and allows these substances to potentially act at a distant site from their production.
True
What are systemic arteries designed to do?
to carry oxygenated blood under high pressure out to tissue beds
What are the 5 functional parts of the circulation system?
- systemic arteries
- arterioles and pre capillary sphincters
- capillaries
- venules
- systemic veins
What collects blood from capillaries?
venules
What is the functional unit of circulation and is one cell layer thick and is where exchange b/w tissues (cells) and blood occurs?
capilaries
What act as control valves to regulate local flow?
arterioles and pre capillary sphincters
What are the three things included in micro-circulation?
- arterioles and pre capillary sphincters
- capillaries
- venules
What percentage of blood is on the venous sides at any give time?
65%
What returns the blood to heart/dynamic storage?
systemic veins
superior vena cava, inf. vena cava, coronary sinus
What is blood flow proportional to?
metabolic flow
What controls cardiac output?
local systemic tissue flow (venous return)
T/F. Arterial pressure fluctuates drastically.
False– it is kept relatively CONSTANT
What is arterial pressure independent of? What is arterial pressure control based on?
local flow or cardiac output
Based on:
- neural control (brain)
- volume control (kidney)
Characteristically wise, what does the wall of a capillary consist of?
only endothelium
Characteristically wise, what does the wall of the aorta consist of?
Elastic tissue > Fibrous tissue > smooth muscle
What is the one layers in vessel walls that exists in ALL vessels?
endothelium
Characteristically wise, what does the wall of a typical artery consist of?
Smooth muscle > elastic tissue > fibrous tissue
Characteristically wise, what does the wall of a vein consist of?
elastic tissue = smooth muscle = fibrous tissue
–equal amounts of all
What is Ohm’s Law?
V = IR
analogous to change in P = FR —–or—– F = (change in P)/R
What is the volume of blood that passes a certain point per unit of time?
Flow (F); eg. ml/min
“Q” – can also = Flow
What are two equations for Flow?
F = velocity X cross sectional area
F = Pressure gradient/ R
At a given Flow, the velocity is ______ proportional to the total cross sectional area.
inversely
Flow is directly proportional to ____ and inversely proportional to _____.
Directly–> to pressure gradient (change in P)
Inversely–> (R) resistance
What is the driving force of blood and is the difference in pressure b/w two points?
Pressure gradient
What is the pressure gradient proportional to?
Flow (F)
Where does the greatest resistance to flow occur?*
in the pre-capillary resistance vessels:
- arterioles
- metarterioles
- precapillary sphincters
At a give F (flow rate) the greater the drop in P in a segment or compartment will cause what?*
greater the resistance to flow
In a parallel circuit how do you get the Total Resistance?
find lowest number in resistance and go below it
Total resistance < smallest ind. R
In a series circuit, how do you find the Total Resistance?
= sum of ind. R’s
What type of circuit is the systemic circulation, predominantly?*
parallel circuit
What are some advantages to parallel circuitry?
- independence of local flow control
- minimizes TPR (total peripheral resistance)
- oxygen rich blood supply to every tissue
In parallel circuitry, how is local flow controlled?
independently–> increase/decrease flow to tissues independently
What type of circuit is the pulmonic and systemic circulations in? How would one calculate the Total Vascular Resistance (TVR)?
series; TVR = sum of total pulmonic resistance + the total peripheral resistance (TPR)
What is the internal friction of a fluid associated with the intermolecular attraction?
viscosity
What is the viscosity of blood? Plasma? Water?
Blood –> 3
Plasma –> 1.5
Water–> 1
T/F. Water has 3x viscosity than blood. (is thicker)
False– blood is 3x more thicker than water
Blood –> 3
Water–> 1
What is the relationship b/w viscosity and velocity in blood?
viscosity is inversely proportional to velocity (speed)
- -blood moving slower = thicker
- blood moving fast = thinner
At micro-circulation, as velocity decreases what happens to viscosity? Why?
viscosity increases; due to elements in blood sticking together
What effect does fibrinogen have on RBC’s? How does age correlate?
increase flexibility of RBC’s
–increase age may decrease flexibility of RBC’s and therefore may be why older inds have decreased circulation
T/F. In small vessels cells line up which decreases viscosity and offsets the fact that velocity decrease will increases viscosity.
True (thank you Fahaeus-Lindquist)
What is the percent of packed cell volume? What is the normal range? What if it is below normal range?
Hematocrit (primarily is RBCs)
Normal Range = 38%-45%
Below–> means decrease in RBCs– maybe they are anemic
What type of flow pattern is considered normal?
Laminar
What type of flow pattern is most efficient?
laminar
What type of flow patterns is silent and streamline?
laminar
What type of flow pattern has cross mixing and vibrational noise?
turbulent flow (least efficient)
What type of flow pattern is frequently ass. with vessel disease (bruit)?
turbulent flow
What is the probability statement for turbulent flow? If this number is higher, what does that mean for turbulence?
Reynold’s number; greater the R number, the greater the probability for turbulence
If Reynold’s Number < 2000 flow is usually _______.
If Reynold’s Number > 3000 flow is usually ____.
laminar
turbulent
**notice it says USUALLY—> it is NOT definitely
What is the equation for Reynold’s number?
Reynold’s number = (velocity x tube diameter x density) / viscosity
What is the ultrasound used to determine velocity of flow? How does it work?
Doppler Ultrasonic Flow-meter
RBC’s moving toward transmitter, compress sound waves, increase frequency of returning waves
A broad band Doppler reading is indicative of what type of flow?
turbulent flow
A narrow band Doppler reading is indicative of what type of flow?
laminar flow
What two things can be used to determine Cardiac Output?
- Fick Principal
2. Indicator dilution
What two tings can be used for Determination or Flow?
- Determination of Cardiac Output
2. Determination of Vessel flow
What does the Fick Principal measure?
blood flow to a tissue/organ
What are the three necessary components to calculate the Fick Principal and measure the blood flow to a tissue/organ? Ex: measuring oxygen
- input blood conc. of oxygen
- output blood conc. of oxygen
- addition/removal of oxygen from tissue (uptake of O2)
What it comes to the Fick Principal, what is Flow equal to?
= amount of substance per min / Artery-Vein difference
(Fick Principal)
What does the Pulmonary Blood Flow (PBF) equal?
= O2 uptake / AV O2 difference
PBF = CO
What is the relationship b/w Pulmonary Blood Flow (PBF) and Cardiac Output (CO)?
they are equal
PBF = CO
(Fick Principal) Ex:
if VO2 = 160 ml/L and AO2 = 200 ml/L and the O2 uptake is 200 ml/min. What is the Pulmonary Blood Flow (PBF)?
PBF = = O2 uptake / AV O2 difference
PBF = 200 ml/min // (200ml/L - 160ml/L)
PBF = 200 ml/min // 40ml/L
PBF = 5 L/min
What is the gold standard of flow determination? What is it based on?
Indicator Dilution; based on conservation of mass
CO is inversely proportional to average duration of the curve (dye concentration)
If the Indicator dilution curve average duration increased, what happens to CO?
CO will decrease
(they are inversely proportional)–
What is the ability of a vessel to stretch?
distensibility
What is the ability of a vessel to stretch and hold volume?
conpliance
What is the equation for distensibility?
= change in volume / (change in pressure x initial vol.)
What is the equation for compliance?
= change in volume / change in pressure
= Distensibility x initial vol.
What is the relationship b/w volume and pressure?
When volume increases what happens to pressure?
change in Vol and change in pressure are proportional
pressure increases too
A small change in volume that is associated with a large change in pressure is characteristic of what vascular compartment?
systemic arteries
A large change in volume that is associated with a small change in pressure is characteristic of what vascular component?
systemic veins
Wall tone is _______ related to compliance and distensibility.
inversely related to
Veins are about _____ times more distensible and _____ times more compliant than systemic arteries.
8x
24x
T/F. Systemic arteries hold less blood under higher pressure, while systemic veins hold more blood under lower pressure.
True (therefore why veins are more compliant)
How is local blood flow regulated?
in proportion to metabolic demand in most tissues
What is involved in short term control of blood flow to a tissue?
vasodilation, vasoconstriction of pre-capillary resistant vessels (aterioles, metarterioles, pre-capillary sphincters)
What is involved in long term control of blood flow to tissues?
involves changes in tissue vascularity
- formation (angiogenesis) or dissolution of vessels
- vascular endothelial growth factor and angiogenin peptides
What will vasoconstrict an arteriole vessel?
SNS releasing NE onto an alpha- receptor that is on vessel wall
Vasodilation will do what to Resistance and Flow?
Vasoconstriction will do what to Resistance and Flow?
Vasodilation–> decrease R; and increase F
Vasoconstriction –> increase R; and decrease F
What is the Local vasodilatior theory?
active tissue release local vasodilator (metabolites) which relax vascular smooth muscle
(**newer theory)
What is the Oxygen demand theory?
as tissue uses up oxygen, vascular smooth muscle cannot maintain constriction
(older theory)
What are some local vasodilators?
- Adenosine
- CO2
- adenosine phosphate compounds
- histamine
- K+ and H+
- PGE and PGI series prostaglandins
- CO and NO
Why is autoregulation important for blood vessels?
- ability to keep blood flow (F) constant in face of changing arterial BP
- most tissues show some degree of autoregulation (RoA = Range of Autoregulation)
- flow is proportional to metabolic demand
What is autoregulated in the kidney?
renal flow and glomerular filtration rate (GFR)
What is production of new micro-vessels called?
angiogenesis
What is the shear stress caused by enhanced blood flow velocity associated with partial occlusion?
arteriogenesis
What are small peptides that stimulate growth of new vessels? What is an example?
Angiogenic factors
Ex: VEGF (vascular endothelial growth factor) –> first isolated from tumors
What does stress activated endothelium up-regulate expression of?
MCP-1 (moncyte chemo attractant protein-1)
- monocytes invade arterioles–> inflam. occurs
What does Hypoxia causes release of? Which stimulates what?
VEGF–> stimulates capillary proliferation and maybe collateral arterial vessels
- partial mediated by adenosine
T/F. NPY from SNS is angiogenic.
True
What are three mechanisms for Neovascularization (= new vessels)?
- Vasculogenesis
- Angiogenesis
- Arteriogenesis
What type of neovascularization is mesenchymal cell differentiate into endothelial cells (de novo development of new blood vessels)?
Vasculogenesis
What type of neovascularization is formation of new blood vessels by sprouting from pre existing small vessels (usually lacking developed tunica media)?
angiogenesis
What type of neovascularization is rapid proliferation of pre-existing collateral vessels with fully developed tunica media?
arteriogenesis
What are three angiogenesis triggers?
- Mechanical (hemodynamic and shear stress)
- Chemical (hypoxia and NO)
- Molecular (decrease glucoise leads to increase VEGF); inflam.; angiogenic growth factors
What are four Angiogenic growth factors?
- fibroblast growth factor
- VEGF (VEGF receptors)
- placenta growth factor (PLGF)
- angiopoietin
What are three methods of Therapeutic angiogenesis?
- Protein therapy (use of GF proteins)
- gene therapy (manipulate gene expression for angiogenic peptides)
- cellular therapy (cells that produce angiogenic factors are introduced into ischemic tissues)
What is clinical enhancement/promotion of collateral blood vessels/flow in ischemic tissues?
Therapeutic angiogenesis
