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160 Cards in this Set

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Which is more powerful for the resistance of blood flow; blood viscosity or radius/diameter of the vessel?
Radius/diameter of the vessel
If vessel one has a diameter half the size of vessel 2, what factor is the resistance to flow for vessel 1?
Vessel one has a greater resistance by an amount of 16 times!!! Factor of 4
What is the equation for flow rate through a vessel?
F =ΔP/R
Flow rate = pressure gradient / resistance of blood vessel
What are main 2 properties that resist blood flow?
-Blood viscosity (hematocrit)
-Radius/diameter of the vessel.
what is the main strategy used by the body to regulate blood flow?
Changing vessel radius and diameter size
What property of the blood can the body NOT regulate to reduce resistance?
Blood viscosity
Describe arteries.
large, highly muscular, highly elastic and have thick walls that resist stretch
What are the 2 functions of arteries?
1. Fast transport from the heart to the tissues

2. Store pressure and provide driving force for flow when heart is resting (elastic walls)
What comprises the outermost layer of the arteries?
Layer of strong connective tissue
What lies under the outmost layer of the arteries?
A thick layer of smooth muscle
Are the arteries innervated? if so, where?
Yes!!

Neuronal innervations lies between the outermost and smooth muscle layer
What does innervation in the arteries do?
provides for a rapid way to stimulate smooth muscles to contract or relax
What lies under the smooth muscle layer of the artery?
connective tissue of collagen or elastin
What is the innermost layer of the arteries?
Layer of endothelia cells
What role does the endothelial cells of the arteries play?
-Not just structural
-Play a vital role in regulating the flow through a vessel
-can react to the composition and have local control of smooth muscle tone.
How do the vessels (aorta) control pressure?
-During ventricular contraction, the force is transferred into stretch in the aorta
-During diastole, the rebound of the stretch is generating the perfusion pressure and allowing it to drive perfusion dow the arterial tree
define BP?
the force exerted by the blood against the walls of the vessels
What 2 factors does BP depend on>?
Vessel compliance and distensibility
What is distensibility?
Ability of the vessel to be stretched
What is compliance of the vessel?
How easy it is to get the stretch (distended)
Are are veins and arteries both distensible?
YES!
Do veins and arteries have the same compliance?
NO!
- Arteries have LOW compliance
- Veins are HIGHLY compliant
What combination of dispensability and compliance enables the drive of perfusion?
Normal dispensability and low compliance on the part of the arteries?
Athero and artereosclerosis are characteristic of what level of compliance?
The occur when compliance levels get too low and the heart has to work too hard to eject blood.
Other than artero and atherosclerosis, what other physiological occurrence takes place when compliance gets too low?
Dichrotic notch that reverberates throughout the arterial tree when the aortic valve shuts.
What is the Mean Arterial Pressure?
The pressure that is stable and drives perfusion whether the heart is resting or contracting.

**it is the stable, average pressure that drives perfusion no matter what phase the heart is in!**
How do you calculate MAP?
MAP = diastolic pressure + 1/3 (systolic pressure - diastolic pressure)

-aka 1/3 of pulse pressure
Describe the invasive method for getting BP.
Actually puncture artery wall and insert a pressure transducer.
What device is used to measure BP non-invasively?
Sphygmomanometer
Read over notes on how to take BP the "right" way.
Read over notes on how to take BP the "right" way.
Why do we use the antecubital most often to take BP?
Because brachial artery comes closest to the skin in that region.
What determines the diastolic BP?
-Blood volume
-elasticity of arterial wall
-compliance of the arterial wall
How can you describe the differences between arteries and arterioles?
It is like taking off excess clothing
- shedding of the wall
Which vessels have the most changeable diameters?
Arterioles
What layers do arterioles have?
A layer of endothelium and a small smooth muscle covering over the endothelium.
What are the 2 functions of arterioles?
1. Variably distribute cardiace output based on current demands of that current organ

2. Regulate arterial blood pressure
When do arteries form arterioles?
Right before the vessel enters the organ!
In order to perfuse an organ, where does blood have to pass through?
Arterioles
What do the phases of ventricular contraction and relaxation have on the arterial tree?
The 2 phases cause a change in the pressure of the arterial tree. Arterial tree has 2 different pressures
What happens if the arteries were more compliant?
They would not be able to rebound. No recoil
How do you know if a patient has adequate perfusion?
If their Mean Arterial Pressure si stable.
When compliance is normal, what do you expect the diastolic pressure to be?
about 60-80
If compliance gets too low, what happens to BP?
the DIASTOLIC Pressure goes DOWN! (Systolic pressure goes up!)
Can be a sign of atherosclerosis
Where does baseline arteriole tone come from?
1. The elastic properties of the smooth muscle that surrounds the arteriole (distensibility and recoil ability

2. baseline sympathetic tone (presser input to that arteriole)
What do are baseline cortisol levels contribute to?
Our baseline arterial tone.

-Without cortisol, we would be starting off with a lower arteriole tone and the binding of NE wouldn't produce enough vasoconstriction to adequately regulate BP.
What 2 main factors control diameter of vessels?
-Intrinsic Factors: when the conditions of the organ change the arteioles will sense the change

-extrinsic factors: come from the nervous system or circulating hormones
What is myogenic activity?
Elastic property of the muscle tissue
What is the local environment for the arterioles?
The ORGAN! because arterioles penetrate the organ.
What two factors can be local?
Chemical and physical
What are some physical factors to local control of the arterioles?
-An abrupt change in blood flow to the area will cause SM to resist the stretch

-Temperature: Heat relaxes SM, cold constricts SM
What are some chemical factors to local control of the arterioles?
-Local metabolic changes

-Histamine release
-an inflammatory mediator
--is a potent vasodilator
What function does histamine have on the arterioles?
It is a POTENT Vasodilator!
What happens to arterioles if an organ is metabolically active?
Arteriole dilation, which will cause an increase in blood perfusion
What do we monitor to sense a change in metabolic demand?
-PO2
-PCO2
-acidity (low pH)
-High adenosine (from the breakdown of ATP,
IS a POTENT VASODILATOR!
What cells sense metabolic changes in the arterioles
the endothelial cells
What happens when endothelial cells sense a change in metabolic factors of the organ?
They release a vasoactive mediator (dilator or constrictor)
What vasodilator do the endothelial cells release in a metabolically active organ?
Nitric Oxide (g) aka EDRF, (endothelial derived relaxing factor)
What do the endothelial cells release in an organ with low metabolic activity?
Vasoconstrictor called ENDOTHELIN: limits blood flow to the organ.
What factor of extrinsic control is the MOST important for arterioles?
The effect of the SYMPATHETIC nervous system
Is there any parasympathetic innervation in the arterial vasculature?
NO, only sympathetic!
What does Vasoactive mean?
It has effects on the vasculature
Where does sympathetic innervation go specifically in arterial vasculature?
To the superficial arteriolar smooth muscle
Where is sympathetic activity not as responsive in the body?
The brain! It wants what it wants all the time.
What happens when NE binds to B2 receptors on arteriole system?
It causes vasodilation!

-B2s on arterioles are ones that are perfusing SKELETAL MUSCLE!!!
For most arteriolar smooth muscle, what happens when NE binds to alpha receptors?
Causes vasoconstriction
Where are the greatest amount of B2 receptors located on arteriolar smooth muscle?
On the arterioles that perfuse SKELETAL MUSCLE!
What do you see if you look at the net effect across the vasculature of generalized sympathetic stimulation?
You see vasoconstriciton.
What is Total Peripheral Resistance TRP?
The total resistance of blood flow across the arterial tree
In terms of TPR, what is cardiac output analogous to?
Flow Rate
What is MAP analogous to?
Change in Pressure
What is TPR analogous to?
Resistance!!!
Give the equation for MAP.
MAP = CO x TPR
What is TPR most influenced by?
Arteriolar resistance!

-Determined by viscosity, but MOST influenced by overall diameter of the ARTERIOLES!!! Far more than other parts of the arterial tree because they are much more changeable in diameter.
What happens to TPR when sympathetic stimulation is high?
The net arteriolar diameter has reduced, which increases TPR and increases MAP
When symp stimulation goes down, what happens to TPR and MAP?
TPR and MAP goes down.
Which vessels determine the volume of blood entering the tissues?
The arterioles!!
Is the distribution of cardiac output fixed?
NO!
-we have a resting
-and a stress related changes
What happens to CO and % of blood perfused to tissues during exercise?
-CO drastically increases because we go from 5 liters/min to 12.5liters/min

-% of blood changes drastically (except for the brain, it remains constant)
Which muscles have the greatest increase in blood perfusing during exercise?
-The heart (pumping harder)
-The skin (sweat to regulate temperature)
-The Skeletal Muscle (driving the exercise)
Why do you we get an increase perfusion to skeletal muscle and the heart due to increase sympathetic stimulation?
-We are constricting blood flow to the viscera and increasing (dilating) it to the skeletal muscle and the heart

-We also have LOCAL CONTROL increasing dilation (heart and skeletal are most metabolically active) So we have a build up of metabolites that are sensed by the endothelium and get a release of nitric oxide!
What action does vasopressin have on the vasculature?
It is a potent vasoconstrictor
What action does ANGIOTENSIN II have on the vasculature?
It contributes to arteriolar tone

-It a potent vasoconstrictor
What receptor does epinephrine have a higher affinity for?
B2
What is the site for exchange of all material between blood and tissue?
At the CAPILLARIES in passive forces
How does the bulk of the exchange between blood and fluid occur?
Through passive forces: simple diffusion!.
Every cell in our body is close to what?
A capillary to allow for transport of all material.
What is the thickness of the capillaries that allows for optimal diffusion?
It is basically naked endothelium

-Very small sheets of endothelium
What happens to the velocity of blood flow in the capillaries? What does this speed do to diffusion?
-It slows down tremendously!

-Allows for increase opportunity for exchange

-Slows down because the cross sectional area is increasing
What is the equation for velocity of flow at any given level?
Velocity of flow = flow rate/ cross-sectional area
What happens to the overall blood flow rate in the capillaries?
It actually stays stable because the cross sectional area increases.
What is located in between the endothelial cells?
Pores: that allow the movement of water or soluble substance to get through

-Don't allow plasma proteins or cells to get out.
Why do the RBCs squeeze through the capillaries?
To make no space between them diffusion space!
What happens to the capillaries when the pt have chronic hypertension?
The capillaries begin to fall apart because of increase in pressure
How do larger proteins get out of the capillary?
Through vesicular transport. Exocytosis
Can plasma proteins get out of capillaries?
Give some examples
NO

-albumin
-coagulations factors
How does the majority of exchange between Blood and tissue cell happen?
By Diffusion
Where do capillary beds sit?
Between arterioles and venules
What are metarterioles?
"fast freeways between country-side roads"

-if blood flows through these the flow will be more rapid but will have less opportunity for exchange
What are pre-capillary sphincters?
-Bands of smooth muscle that regulate if the blood will flow through the capillary or through the metarteriole
What is the importance of pre-capillary sphincters?
They are another level of local REGULATION of blood distribution within the tissue itself
How are pre-capillary sphincters controlled?
-Receive NO external innervation or extrinsic regulation

-CONTROLLED by the level of HEAT and METABOLIC Mediators (O2, CO2, temp, acidity)

Completely controlled through local control!
What is a second means of exchange in the capillaries?
BULK FLOW
What is the main purpose of bulk flow?
-Regulate distribution of ECF between caps and interstitial space (plasma and interstitial fluid)

-Primarily for fluid exchange
What is ultrafiltration?
-Fluid moving out of the capillary
What is reabsorption?
Fluid moving back into the capillary
What are the osmotic forces promoting ultrafiltration and reabsorption?
1. Hydrostatic Pressure: Pushing presure

2. Oncotic Pressure: Pulling Pressure (osmotic pressure exerted by plasma proteins)
Describe Hydrostatic Pressure.
-Pushing pressure that comes from the fluid just containing any particular space.
What is Oncotic Pressure?
Pulling pressure.

-The osmotic pressure exerted by plasma proteins
What is Capillary Blood Pressure Pc?

Is it significant? If so, to what
-Pressure coming from inside the capillary, pushing pressure promotes ultrafiltration!

-Yes it is significant to ultrafiltration. Can be relatively high or relatively low
What is the determining factor for capillary blood pressure?
the precapillary sphincter tone *it allows blood to flow into the capillary or not)
What is the Plasma Colloid Osmotic Pressure np?
-Capillary oncotic pressure coming from the plasma protein in the capillary
How is plasma colloid osmotic pressure significant and why is it
It promotes reabsorption

-But it does not change (albumin level)
What is interstitial fluid hydrostatic pressure? (Pif)
-Comes from the volume of interstitial fluid just exerting its own pressure.

-Exerting reabsorption!

-This and capillary oncotic pressure help determine reabsorption

-Significant, but does not change!
What is a key concept of Bulk Flow?
The distribution of fluid is done completely by passive forces!
What is interstitial Fluid- Colloid Osmotic Pressure (Nif)
-Sometimes a theoretical pressure

-Coming from plasma proteins that may have gotten out of the capillaries and are now occupying some of the interstitial space.
What ways can plasma proteins get our of the capillaries and increase Interstital fluid osmotic pressure?
-There can be a break in the capillary wall
-Can happen on purpose in inflammatory response
What kind of force is Interstitial Fluid- Oncotic Pressure promoting?
-ultrafiltration, but DOES NOT MATTER!!!
When does reabsorption occur?
When the capillary blood pressure is low
When does ultrafiltration occur?
When capillary blood pressure is high
What are the Forces of ultrafiltration and reabsorption also know as?
Starling Forces
What type of force will result in the capillary following a hemorrhage?
We have 20% loss of blood volume, Pressure is low, including in the capillary, we have NET REABSORPTION
What compensatory mechanism do capillaries have for dealing with large blood loss?
They are capable of buffering 2-5% of the blood loss by increasing net reabsorption.
In reality, how many pressures are promoting reabsorption and ultrafiltration?
We have 1 promoting ultrafiltration and 2 promoting reabsorption (which stay relatively constant)
What happens to the capillary's rate of reabsorption/ultrafiltration when a pt is fluid overloaded?
-The capillaries blood pressure is too high, so we want ultrafiltration that will be pushed into the interstitial space causing EDEMA!!!
What can occur with a pt with liver dysfunction?
They cannot make ALBUMIN and you end up getting a lot of edema
-Occurs b/c you have a decrease in capillary oncotic pressure causing an increase in ultrafiltration (fluid flows osmotically out of the cell because "solute concentration" of protein in the capillary has gone down)
What runs alongside all of our capillaries?
Lymphatic vessels
What area do lymphatic vessels occupy?
The space outside of the vasculature
What role to lymphatic vessels have?
They are designed to drain some of the interstitial fluid that has leaked out of the capillaries due to baseline slight ultrafiltration
What is the fluid called in the lymph nodes?
Lymph fluid
Where does the fluid in the lymph nodes go?
Drain to the IVC and SVC and back into the circulatory system
What does it mean when we have edema?
We have maxed out the rate of lymphatic drainage!

-The fluid is accumulating faster than the lymphatic system can drain, so it builds up in the interstitial spaces.
Which vessels are highly compliant?
Systemic Veins
Which vessels are high capacitance vessels and what does that mean?
The veins

-They serve as a reservoir for blood
At any given time, where is the majority of our blood?
In the veins, about 64%!
What effect does the Symp NS have on our Veins?
It causes vasoconstriction and REDUCES the compliance of the veins.

-Forces the blood back to the heart!
What is it called when we vasoconstrictor the veins forcing blood flow back to the heart?
Increase in effective circulating blood volume!
What are the 5 factors that influence venous return?
1. Sympathetically induced venous vasoconstriction
2. Skeletal Muscle Activity
3. Effect of Venous Valves on Venous Return
4. Effect of respiratory activity on venous return
5. Effects of Cardiac suction on Venous return.
What effect does skeletal muscle activity have on venous return?
-Contracting helps promote movement because veins run through skeletal muscle (milks the blood though)
-
What can happen in reference to venous return for someone standing for a long time, without skeletal muscle contraction?
-Drop in venous return, drop in CO, drop in MAP and drop in BP (may cause syncope)
What effect do valves have on venous return?
-Without in valves the blood would move in both directions away from a muscle contraction

-Valves allow all of the force of the skeletal muscle to push blood upwards
Respiratory activity has what effect on venous return?
-as blood comes back to the thoracic cavity, the drop in intrapleural pressure aides the blood in getting back to the heart

-aka the RESPIRATORY PUMP
Cardiac Suction does what for venous return?
-the expansion of the atria during systole causing a slight drop in pressure allow blood to be sucked into the R atria!
What happens to perfusion if MAP is low
-Inadequate perfusion
If the MAP is too high, what happens to the workload on the heart?
-Increase in workload due to damage capillary beds.
What is the main driving force for perfusion?

Why is it important?
MAP

-stable pressure that drives perfusion during systole AND diastole
What is our total blood volume controlled by?
The Kidneys mainly (long term control)

-but also the bulk flow fluid shifts
what are some of the control routes that keep MAP under control?
1. Short-term control: Baroreceptor reflex

2. Long-term: done by the renal system
What are Baroreceptors?
Pressure receptors

-nerve endings that wrap themselves around the large vessels and measure the degree of stretch in the arch and the sinus!
Where are Baroreceptors located?
-Aortic Arch
-Carotid Sinus
What center in the medulla gets constant information from the baroreceptor?
Cardiovascular control center
what is the carotid sinus baroreceptor tell?
Status of BP perfusing the brain
What is the aortic arch baroreceptors tell?
The status of pressure perfusing the brain
What happens to the firing rate to the brain when you hold down both carotid arteries?
Signal of low blood pressure to the brain from the carotid.

Signal of high blood pressure to the body.

Will cause blood pressure to shoot up because the brain will win.
What happens if you have a change in BP that lasts longer than 2 mins?
The baroreceptors adapt to the change.
What type of BP are baroreceptors designed to monitor?
Moment-to-moment changes and not good at remembering what BP was before 2 mins prior
What happens to the firing rate of baroreceptors if the BP stays high for more than 2 mins>?
The firing rate will drop back down because they have adapted
Give an example of an output used by baroreceptors to bring BP down?
Autonomic control: Control of parasympathetic control

-Vagus Nerve on Heart
Decrease HR --> Decrease CO --> Decrease MAP
What adjustment is often enough to regulate BP?
A change in HR, especially when it comes to positional changes
What happens if parasympathetic stimulation is not enough to drop BP?
-You need a full response, which means the addition of a decrease in sympathetic stimulation
What happens if an increase in parasym and a decrease in symp does not bring BP down?
-The baroreceptors will end up adapting
-The kidneys take over (corrects for long term changes by adjusting blood volume)