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CV Week 3 > Regional Circulations > Flashcards

Regional Circulations Flashcards

0
Q

Explain blood flow from the pulmonary to regional circulations.

A

Right heart pumps its entire output into the pulmonary circulation-left heart receives the entire CO pumped through the pulmonary circulation-The left heart pumps it out through aorta-from which flow is divided up b/n regional circulations.

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1
Q

Why is control of CV function is needed?

A

1) Insure that brain and heart get the perfusion required to maintain normal function.
2) Match perfusion of every tissue and organ to its perspective metabolism.
3) Maintain BP so CO can be apportioned by varying resistance.
4) All of the above require the control of CO, blood vessel size (resistance) and the blood volume regulation.

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2
Q

Draw the chart for the blood flow from the pulmonary to regional circulation.

A

pp. 196 of week 3 notes.

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3
Q

How are the pulmonary circulation related to the right heart and the regional circulations to the left heart and right heart?

A
  • Pulmonary circulation in series with the right heart and receives entire CO.
  • Regional circulations are in parallel b/n left and right heart.
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4
Q

What are the 2 types of mechanisms of vascular control which determine blood b/n regional circulatory beds?

A

1) Central (exogenous)-signals generated centrally
2) Local (endogenous)-signals generated at a local tissue level
NOTE: some signals are neural and others are humoral/chemical

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5
Q

The endogenous (local) regulation of blood vessel diameter include:______, ________, and _________.

A

1) Basal tone
2) Local tissue chemical (metabolic) modifiers
3) Autoregulation of blood flow

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6
Q

What are the 2 types of local regulation of blood flow by metabolic modifiers?

A

1) Active hyperemia

2) Reactive hyperemia

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7
Q

Define hyperemia.

A

increased blood flow.

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8
Q

Define active hyperemia.

A

-increased flow that takes place simply in response to increased demand. Ex: Exercise-tissues increase the release of metabolites-causes vasodilation and increased flow.

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9
Q

Define reactive hyperemia.

A

-increased flow due to all of the metabolites that built up while the blockage was still there. Ex: Block an artery, metabolites build up in front of blockage (b/c flow to these tissues is interrupted)-vasodilation-relieve blockage and get a massive increase in flow with out increase in blood.

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10
Q

What does exogenous regulation of arterioles include?

A

1) Neural: ANS innervation and actions which include both sympathetic (NE, Epi) and cholinergic responses (cholinergic responses are rare and when present relate to primary function of organ).

2) Other vasoactive materials: Humoral-Epi, NEpi, vasopressin,
Local: pCO2, pO2, pH, [K], Temp
FIGURE 3.2 pp198.

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11
Q

What is weight and surface area of a normal human heart?

A

70kg, surface area=1.7m^2

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12
Q

FIGURE 3.3 (pp. 200) show the estimated distribution of the CO and O2 consumption in a normal human subject. What does each column mean?

A

Blood Flow:
ml/min-amount of blood flow through the tissue in ml per min
ml/100g/min-amount of blood flow per 100gm of tissue per min
%CO-what % of CO travels to the tissue
Oxygen Uptake
ml/min-how much O2 in ml/min is consumed (taken) by the tissue
ml/100g/min-amount of O2 which 100g of each tissue would consume
% total-what % of the total O2 is consumed by the tissue
(a-V)O2 Diff.-difference in O2 content b/n arterial blood going into the tissue and venous blood coming out of the tissue. the amount of O2 extraction (high difference greater extraction, lower difference lower extraction)

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13
Q

T/F The O2 consumption varies greatly among different tissues.

A

T.

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14
Q

Compare the heart, kidney and skin activity.

A

Heart and Kidney have very active cells with many energy consuming processes such as ion transport, and active contraction.

Skin relatively low rate b/c not much is going there.

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15
Q

Why does the splanchnic bed use more O2 at rest compared to the kidneys, which are more active?

A

It is because the splanchnic bed weighs more.

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16
Q

What percentage of the total O2 does the splanchnic bed get?

A

There is a total of 234ml O2/min being consumed by all of the circulator beds. The splanchnic gets 58ml O2/min (25%)

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17
Q

Generally speaking the CO should match the metabolic needs of the tissue. However the skin and kidney get much higher percentages than what they consume, why is that?

A

Because the perfusion in these cases are not related to the tissue metabolism but their function.
Kidneys filter blood and make urine.
Skin involved in thermoregulation.

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18
Q

Define over-perfused organs.

A 
Excess perfusion (CO) of organs which is more than what they need for tissue metabolism.
Ex: Kidney, skin
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19
Q

Define under-perfused organs

A

the organs have high metabolic rates but flow to these organs is well regulated to supply their metabolism in times of need.
Ex: Heart: well regulated supply so if it does not get the supply that it does not need.

NOTE: this does not mean they don’t get enough blood.

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20
Q

How is under-perfusion and over-perfusion related to O2 extraction?

A

Under perfused tissues have very good extraction of O2 and nutrients from blood (thus the (a-V)O2 or the volume % O2 difference is high)

Over perfused tissues extract just the O2 they need (have a low volume O2 difference).

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21
Q

What supplies the nutritive supply to the lungs?

A

Bronchial circulation

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22
Q

What distinguishes the pulmonary circulation from the regional circulations?

A

It is connected in series to the right heart (gets all the CO) but the regional circulations are connected in parallel to the heart since they receive a fraction of the CO.

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23
Q

Explain what is meant by the “pulmonary region is a low pressure (13mmHg mean pulmonary artery to 5mmHg in left atrium), low resistance circulation.”

A

The pulmonary artery and its branches have thinner walls, contain less elastin, and smooth mm than the thick-walled, highly muscular systemic arterioles. Less ability to constrict.
The tissue hydrostatic pressure is also low in the lungs. The walls of the membrane separating the alveolus from the capillary are also extremely thin. If the hydrostatic pressure was as high as the it is in the systemic circulation, massive amounts of filtration and fluid accumulation.
NOTE: capillary is very thin and have high resistance but when you have millions of them present they can increase their surface area to volume ration to greatly decrease the resistance.

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24
Q

Study Figure 3.4: Regional circulation…

A

pp.202

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25
Q

What affects the distribution of flow to the lungs because of the pulmonary blood vessels low pressure and high compliance?

A

Gravity

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26
Q

Referring to Figure 3.6 pp 204. In zone C the arterial and venous pressure are 25 and 15mmHg which is 10mmHg higher than their value at B 15 and 5mmHg. Why is that?

A

At the C the vessels are situated below the pulmonary artery and vein with the blood above pushing down on the region.
NOTE: this same situation happens in the systemic circulation below the heart (say in the legs and feet).

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27
Q

Define the transmural pressure.

A

the difference in hydrostatic pressure b/n the lumen of the vessels and the tissue.

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28
Q

In Zone C, the transmural pressure is increased because of the higher hydrostatic pressure in the vessels. What happens as a result of this?

A

The higher pressure stretches the walls in the highly compliant pulmonary circulation-diameter of the lumen increases-resistance falls-flow is higher in the base of the lung
NOTE: Increased hydrostatic pressure in this region makes increased filtration and edema more likely here.

29
Q

In the erect individual, compare transmural pressure, diameter, vascular resistance at points A, B and C?

A

From apex to base: the transmural pressure increases, the diameter increases, vascular resistance decreases and flow increases. Thus, flow is higher in the erect individual in Zone C (Base).

30
Q

What happens to the pulmonary circulation with fall in alveolar O2?

A

Hypoxic vasoconstriction: the vessels will not dilate if there is lack of alveolar O2

NOTE: the opposite phenomenon happens in the systemic circulation if an area is hypoxic the vessels dilate to allow enough O2 to reach the region.

31
Q

How should the exchange surface area and barrier change to allow nutrient exchange?

A
  • Large exchange surface area

- Thin exchange barrier

32
Q

T/F The pulmonary circulation is really sensitive to neural control.

A

F. It is relatively insensitive to neural control (i.e. plays no role in the baroreceptor reflex).

33
Q

T/F. Cardiac O2 consumption is proportional to cardiac work and that demand is very high under conditions when CO is high.

A

T.BUT Heart has high metabolic relate relative to its blood flow-underperfused.

34
Q

What does the “the heart has limited anaerobic capability” mean?

A

It can’t function (anerobically) well if its O2 supply is cut down or insufficient in times of high demand.

35
Q

Look at the Summary

A

pp 206 and 210

36
Q

What is the principal determinant of coronary resistance in the coronary circulation?

A

Metabolic control of the coronary circulation. This means that the heart is goo at increasing flow with increased demand.

37
Q

What is a capillary reserve (collateral vessel development)?

A

When the lumen of a coronary artery is narrowed, these collateral vessels will develop and transport and blood around the obstruction.

38
Q

How does neural control play a role in controlling blood flow in the heart?

A

Neural control is weaker than the local control (collateral vessels).
Flow increases with sympathetic stimulation: alpha (constrictor) and beta (dilator) are present in Smm. Increase in flow-stronger contraction-tachycardia=> effect is limited b/c the vessels are compressed.

39
Q

Where does the flow peak in other tissues?

A

The flow peaks during ejection (i.e. during systole).

40
Q

When is flow in the left coronary artery maximum?

A

During diastole.

NOTE: This is the opposite of when it happens in the right coronary artery or other tissues (happens during systole).

41
Q

Compare the blood flow and (a-v)O2 difference of the skin compared to its metabolism?

A

High blood flow and low O2 difference. Skin is over perfused and blood flow is used for thermoregulation in addition to supply of nutrients to the tissue.

REFER to Summary pp. 214.

42
Q

Where are the thermoregulatory centers?

A

They originate in the hypothalamus and via the ANS determine the resistance in the cutaneous bed.

43
Q

What is counter-current flow?

A

Counter-current flow in the limbs-the end result of venules and arterioles being close to each-other. Arrangement limits heat loss through the skin when it is cold and maximize it when the body gets hot. Skin has fewer capillaries (doesn’t need that many to meet its metabolic function).

44
Q

What are the 2 type of resistance vessels in the skin?

A

1) arterioles

2) arteriovenous (AV) anastomoses (“shunt”)

45
Q

Define AV anastomoses.

A

shunt blood from arterioles to venules and bypass the capillary bed.
NOTE: almost exclusively sympathetic (which constricts them).

46
Q

What happens the AV anastomoses and heat transfer when the environment is cold or hot?

A

1) Cold environment: vasoconstriction-reduce blood flow to skin. Heat transferred from arterial blood-venous blood-warmer blood returned and heat loss minimized
2) Hot environment: vasodilation-increase blood flow to skin. Heat transferred from venous blood-arterial blood-cooler blood is returned.

47
Q

Understand Figure 3.11

A

pp. 216

48
Q

What is the splanchnic circulation compose of?

A

1) Gastric
2) Small Intestine
3) Colonic
4) Pancreatic
5) Hepatic
6) Splenic circulation

49
Q

What functions do the GI tract circulations support?

A

1) motility (propulsion of food)

2) absorption of digested products

50
Q

What is the capillary hydrostatic pressure to favor absorption of H2O and other nutrients?

A

The pressure is relatively low.

51
Q

Generally speaking, is the GI blood flow high or low?

A

High and increases during absorption of digested food. This is a classic example of active hyperemia.

52
Q

What are the neural controls in the splanchnic bed?

A

Predominantly sympathetic and play a role in the baroreceptor reflex and in response to exercise-under these conditions vasoconstriction shunts blood to skeletal and cardiac mm.

53
Q

Since splanchnic bed is a major blood “reservoir” it participates in reflex control of _______and ______

A

Blood Pressure

Blood Volume

54
Q

What is the role of countercurrent mechanism in the GI?

A

The villae of intestines maximize surface area to volume ration to increase absorption but this also maximizes O2 loss. Thus countercurrent exchange of O2 from the arterial to the venous blood minimizes this loss.

55
Q

Define portal circulation.

A

connects 2 capillary beds in series.

56
Q

What is a classic example of a portal circulation?

A

Hepatic portal circulation-blood drains from the intestines to the liver through the hepatic portal vein.

57
Q

How does the liver get O2?

A

The portal vein is mixed with that of the hepatic artery and it is this vessel that supplies the needed O2 to the liver.

NOTE: Low hydrostatic pressure in the portal vein (about 10mmHg) with a relatively low O2 content. Very permeant to protein, small oncotic difference. FIGURE 3.13 pp 218

58
Q

What happens in the case of heart failure (HF)?

A

HF-portal hypertension-ascites (fluid accumulation in the abdomen)

59
Q

REVIEW Summary of the physiology of circulation of the LIVER and the Kidneys.

A

pp. 220

60
Q

Describe the renal circulation

A

Kidney overperfused. Anatomically this is another portal system connecting glomerulus (which filters blood) with the vasa recta (which wraps around the renal tubules to allow for reabsorption and further secretion of substances). Figure 3.16 pp.222
2 capillary system connected by efferent arteriole

61
Q

T/F The vasa recta is another example of countercurrent exchange system.

A

T. This countercurrent prevents major Na loss.

62
Q

What percentage of the body weight does SK mm make up?

A

40%

63
Q

Describe SK mm metabolism.

A

Has a low resting metabolism but requires very large increase in perfusion with increased tissue activity (contraction).

Has a large capillary mediated by capillary recruitment. This is the result of opening capillaries through dilation of precapillary sphincters (Figure 3.18) pp. 224 NOTE: large number of capillaries in SK mm as compared to the relatively inactive cutaneous tissue.

64
Q

REFER to SUMMARY of circulation in the SK mm.

A

pp 223.

65
Q

What is the primary purpose of the skeletal muscle pump?

A

To increase venous return during exercise. Anatomically this process has its root in the fact that the veins have one way valves.

66
Q

How do the valves function in the muscle pump in SK mm?

A

allow blood only to flow towards the heart.
SK mm contracts-vessels are compressed by surrounding mm-pressure increase-pressure behind the upper valve is higher than pressure in front of it-valve opens-blood goes to the heart
ON the other hand, higher pressure in this segment exceeds pressure behind the lower valve-thus closing the valve. (Blood prevented from flowing the other way).

67
Q

T/F. CNS has almost no anaerobic capacity.

A

T. Must receive an uninterrupted supply of O2. Underperfused organ and the flow to brain is highly regulated.

68
Q

What is the effect of an increase in the tissue volume in the cranium?

A

Since the brain is contained in a rigid container (skull) and increase in tissue volume will affect the extramural pressure on all blood vessels.

69
Q

What is the role of neural controls on cerebral circulation?

A

Role of neural controls is small and plays no role in reflex maintenance of blood pressure.
NOTE: strong metabolic controls on the circulation with increased CO2 acting as a potent vasodilator.

CV Week 3 (8 decks)

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