Exam II Circ Flashcards by Corey Allen

In most tissue beds, blood flow is regulated in proportion to what?

Local metabolism

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Consider the resistance in the following tissue beds: 
Coronary= .40 mmHg/ml/min
Brain= .13 mmHg/ml/min
Liver= .08 mmHg/ml/min
Kidneys= .10 mmHg/ml/min

What is the total peripheral resistance?

Less than .08

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Using the data from the previous question, which tissue bed would have the greatest flow (lowest resistance)?

Liver

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In the following vessels, the flow rate is identical, which vessel is offering the greatest resistance to flow?
A. P1=50 P2=25
B. P1=70 P2=60
C. P1=80 P2=65

A. P1=50 P2=25

The greatest change in pressure = the greatest resistance (occurs in arterioles)

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A broad band Doppler reading is indicative of what type of flow?

Turbulent

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If a vessel with a length of 100cm has a cross-sectional area of .5cm2, and velocity of flow of 10cm/sec, and the pressure drop across that length is 10mmHg, what is the flow in that vessel?

300ml/min

.5cm2 x 10cm/sec = 5ml/sec x 60= 300ml/min

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The vascular compartment with the greatest total cross-sectional area is what?

Capillaries

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What are characteristics of parallel circuitry?

Independent of flow control, maximizes oxygen delivery to tissues, and decreases work load on the heart, minimizes TPR

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A small change in volume producing a large change in pressure is characteristic of which vascular compartment?

Systemic arteries

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Acetylcholine binding to the vascular endothelium has what effect?

Vasodilatation by causing nitric oxide release

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What is the effect of sympathetic nervous stimulation on most vascular smooth muscle?

Vasoconstriction mediated by alpha receptors

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During widespread sympathetic nervous system stimulation, which tissue bed would show the least increase in vascular resistance?

Lung

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As a tissue becomes more active, how is blood flow to that tissue increased?

Tissue releases local vasodilators

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At a given mean circulatory filling pressure what happens to venous return as central venous pressure increases?

Venous return decreases

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If cardiac output is stopped, arterial pressure will be expected to fall until it equals what?

Critical closing pressure

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In a healthy young adult comment about tissue flow during diastole.

Maintained by recoil of the arteries

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If blood flow to a tissue doubles from 200ml/min to 400ml/min, and the AV O2 difference falls from .05ml O2/ml to .025ml O2/ml, comment on the increase in flow.

It is likely due to shunting (through the capillary beds)

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What increases the plasma colloid osmotic effect by about 50%?

Negative changes on protein attracting and holding positive ions like sodium

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What effects are attributed to slow breathing?

Increased resting oxygen saturation, decreased chemoreflex activation, decreased mean arterial blood pressure

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What effect does decreasing velocity have on blood viscosity?

Increases

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How does fibrinogen decrease blood viscosity?

Makes RBC’s more flexible

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Use the following graph to answer the following questions.

              \
                 \
VR                 \
                            \
                                 \
		0	5	10	CVP
Considering vascular function as central venous pressure increases, what happens to venous return?

What is the mean circulatory filling pressure equal to?

Decreases; 10mmHg

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The chronic use of anti-inflammatory drugs could be expected to inhibit what process?

Angiogenesis

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Consider the following data:

average capillary hydrostatic P = 17 mmHg
average capillary colloid osmotic P = 28 mmHg
average interstitial hydrostatic P = -2 mmHg
average interstitial colloid osmotic P = 9 mmHg

a. filtration > reabsorption
b. filtration

C. Filtration = reabsorption

Net filtration = (17- -2) - (28-9) = 0

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Which brainstem area is tonically active and is associated with a tonic SNS outflow?

Neurons anterolateral in the upper medulla and pons

Which substances are associated with local vasodilatation?

Adenosine, CO2, K+, histamine and lactic acid

What high-resistance microvessels control local blood flow by integrating multiple input which determines lumen diameter?

Arterioles

Compare the distensibility of the following vessels. Vessel one: Vessel two: Orig vol. = 20 ml Orig vol. = 10 ml /_\ vol = 1 ml /_\ vol = 1 ml /_\ pressure = 2 mmHg /_\ pressure = 2 mmHg a. vessel one is more distensible than vessel two b. vessel two is more distensible than vessel one c. vessel one and vessel two are equally distensible

B. Vessel 2 is more distensible than vessel 1 V1: 1ml/(2mmHg*20ml) = 1/40 V2: 1ml/(2mmHg*10ml) = 1/20 (higher)

What may act at the level of the CNS in the development of hypotension?

NO and serotonin

In the kidney, how dos SNS stimulation increase angiotensin formation?

By stimulation of the JG cells to release renin

In response to a fall in systemic arterial blood pressure, what changes would be counterproductive in offsetting that fall?

Increase in ANP release

In the face of rising arterial blood pressure, what response would autoregulate both renal blood flow and glomerular filtration?

Constriction of the afferent arterioles

What effect does stimulation of baroreceptors have on sympathetic outflow?

Decreases

During systole, what is happening to baroreceptor activity?

Increasing

In the fetus, the ductus arteriosis shunts blood from the pulmonary artery to the aorta returning primarily from what vessel?

Superior vena cava

What is the function of the ductus venosus in the fetus?

Shunt blood from the umbilical vein into the inferior vena cava (bypasses liver)

In which tissue bed does SNS stimulation cause a metabolically-induced local increase in blood flow?

Heart

During exercise, what normally decreases?

VO2 and TPR

During exercise, most of the increase in cardiac output is due to which of the following?

Increase in heart rate

What is the main function of systemic circulation?

To deliver adequate oxygen and nutrients and remove CO2 and other waste from systemic tissues

True/False: Blood flow is proportional to metabolic demand.

True

What are the 4 components that make up vessels?

Endothelium, elastic tissue, smooth muscle, fibrous tissue

The aorta contains more _____, a typical artery contains more _____, while capillaries contain _____.

Elastic tissue; smooth muscle; endothelium only

What is the equation for Ohm's Law?

V = IR V is voltage I is current flow R is resistance

Ohm's law is analogous to?

/_\ P = FR P is pressure gradient F is flow R is resistance

Flow is equal to:

Velocity x Cross-sectional area

Where does the greatest resistance to flow occur?

Pre-capillary resistance vessels (arterioles, metarterioles, precapillary sphincters)

Resistance is equal to:

8nl/Pir4 n is viscosity l is length of vessel r is radius

Systemic circulation is predominantly a _____ circuit.

Parallel

What is the normal range of hematocrit?

38-45%

A narrow band Doppler reading indicates what type of flow?

Laminar flow

Reynold's number describes:

The probability statement for turbulent flow (the greater the number, the greater the probability of turbulence)

If Reynold's number (R#) is

Laminar

If R# is >3000, flow is usually:

Turbulent

Fick's Principal describes:

Blood flow to a tissue/organ

What is distensibility?

Ability of a vessel to stretch/distend

What is compliance?

Ability of a vessel to stretch and hold volume

True/False: Systemic arteries are more compliant than veins.

False, veins are 24x more compliant

True/False: Veins are more distensible than systemic arteries.

True (8x more)

During chronic exercise, most of the increase in cardiac output is due to:

Increase in stroke volume

In the face of falling arterial blood pressure, which response would autoregulate both renal blood flow and glomerular filtration?

Dilation of the afferent arterioles

What causes the release of VEGF?

Hypoxia

What are the mechanical triggers for angiogenesis?

Hemodynamic and shear stress

What are the chemical triggers for angiogenesis?

Hypoxia and NO

What are the molecular triggers for angiogenesis?

Decreased glucose, inflammation and angiogenic growth factors

The vasoactive role of endothelium includes releasing what?

Prostacyclin, NO, and endothelin

Oxygen uptake is determined by what calculation?

O2 uptake = F x (A-V O2 difference)

What is the most common plasma protein in circulation?

Albumin

The reflection coefficient expresses:

How readily protein can cross the capillary wall

If the reflection coefficient is 0:

All colloid proteins freely cross the capillary wall

If the reflection coefficient is 1:

All colloid proteins are reflected, none cross the capillary wall

What is responsible for draining excess fluid from interstitial spaces?

Lymph capillaries

2/3 of all lymph comes from:

Liver and intestines

If cardiac output is stopped, what effects will be observed?

Arterial pressure will fall and venous pressure will rise

The equalibration pressure where arterial BP is equal to venous BP is called:

Mean circulatory filling pressure

Which brainstem area has vasodilatory effects and decreases cardiac activity?

Neurons anterolateral in the lower M.O.

Neurons in the posterolateral portions of the pons and medulla are associated with what area?

Sensory area (A2)

The sensory area of the vasomotor center receives input primarily from what cranial nerves?

CN IX and X

Baroreceptors are especially abundant in:

Carotid sinus and arch of aorta

True/False: Baroreceptors are more sensitive to changing pressure than static pressure.

True

What are specialized peritubular capillaries associated with juxtamedullary neurons?

Vasa recti

What hormones decrease renal blood flow?

Norepinephrine, epinephrine and angiotensin II

What hormones increase renal blood flow?

Prostaglandins (E & I)

The RAA system is stimulated by:

Decreased perfusion pressure, SNS stimulation, decreased NaCl delivery and hormones (thyroid & growth)

Renin is an enzyme that catalyzes the formation of _____ from _____.

Angiotensin I from angiotensinogen

The conversion of angiotensin I to angiotensin II occurs primarily in the:

Lung

What is the effect of tying off one renal artery?

Development of systemic hypertension

What is the effect of tying off a renal artery and removing a kidney?

No development of HTN or uremia

What is the effect of tying off a renal artery and removing both kidneys?

Development of both HTN and uremia

Hypertension generated by tying off a renal artery is called:

Goldblatt hypertensive model

What allows blood to bypass the lungs?

Ductus arteriosis and foramen ovale

What allows umbilical and portal blood to bypass the liver?

Ductus venosus

Blood from which source in the fetus is most saturated with oxygen?

Umbilical vein (80%)

Which tissues escape SNS vasoconstriction?

Heart, brain and lungs

Which CV endpoint decreases with exercise?

Total peripheral resistance

Extra O2 is used to:

Restore metabolite levels and metabolize lactate generated by glycolysis

True/False: Arterial pressure control is independent of both local flow and cardiac output.

True

In which vessel would velocity of flow be slowest?

Inferior vena cava

Blood flow to most tissues or organs is regulated in proportion to:

Metabolic demand

If the flow in a vessel is 20cm/sec and the cross-sectional area is .1cm2, what is the flow rate?

120ml/min

Which groups of vessels regulate blood flow to an organ?

Arterioles

What effect does fibrinogen have on the viscosity of blood?

Decreases viscosity

A broad band Doppler reading is obtained over the right carotid artery. What is the significance of this finding?

Partial occlusion

Angiogenesis can be impaired by:

Anti-inflammatory drugs

In cardiac failure, what happens to central venous pressure?

Increases

All else being equal, what effect would a decrease in TPR have on diastolic BP?

Decreased

When would venous return be stopped?

If CVP is equal to MCFP

A vessel has an original volume of 20ml. As volume is increased 5ml, pressure is increased to 2mmHg. Calculate the distensibiility.

.125 Distensibility = change in vol/change in pressure x original vol D = 5/(2 x 20) = .125

As a tissue becomes more active, what is the primary way local blood flow increases?

Release of local vasodilators

What receptor mediates the SNS vasoconstrictor response?

Alpha

How does circulating Ach cause local dilation of vascular smooth muscle in a tissue bed?

Binds to endothelium causing release of NO

During ejection of blood, comment on baroreceptor activity.

Increasing

If blood flow to a tissue doubles, but AV O2 difference falls by 1/2, what happened?

It is likely due to shunting

If blood flow to a tissue is 400ml/min, the AO2 is .2ml O2/ml and VO2 is .1ml O2/ml, what is the O2 uptake?

40ml/min F = 400 x (.2 - .1)

Using indicator dilution to determine cardiac output, as the duration of the curve increases, what is happening to the cardiac output?

Decreases

In the brain, how is excess plasma filtrate returned to the vascular system?

Via the arachnoid villi

What is "hydraulic filtering?"

Stretch and recoil of the arterial tree during the cardiac cycle

If one renal artery was stenotic, what would be expected?

Development of HTN and elvated angiotensin II levels

What is the mechanism by which SNS stimulation to the heart cause local vasodilation of coronary vascular smooth muscle?

Norepinephrine stimulation of cardiac cells which release adenosine

Which area of the vasomotor center is tonically active and provides basal stimulation of the SNS?

Pressor center

In response to a rise in extracellular fluid levels, which change would be counterproductive in keeping BP from rising?

Decreased arterial naturectic peptide release

In the fetus, what is the function of the ductus venosus?

Allows blood returning from placenta to bypass the liver and flow into the inferior vena cava

In the fetus, the blood that shunts through the ductus arteriosis is returning from which location?

Head

Slow breathing has been shown to decrease both systolic and diastolic BP due to:

Decreasing sympathetic activity

What will not increase venous return during exercise?

Increased central venous pressure

As total cross-sectional area decreases, what happens to the velocity of flow?

Increases

Under strong widespread SNS stimulation, which tissue bed would show the greatest increase in blood flow?

Heart

A large increase in local tissue flow due to an increase in metabolic activity is usually associated with what changes?

Vasodilation of pre-capillary resistance vessels

Which change is associated with a decrease in the viscosity of the blood?

Fahreus-Lindquist effect

True/False: Total peripheral resistance is always less than total coronary resistance.

True