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Phys: Cardio > Circulation > Flashcards

Circulation Flashcards

1
Q

Where is the greatest volume of blood at any one time located?

A

Veins (50-60%)

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2
Q

What vessels contribute the most to vascular resistance?

A

Small arteries and arterioles

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3
Q

How much of the blood volume is located in capillaries?

A

5% of blood volume

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4
Q

Define Poiseuille’s law

A
  1. the radius of tube/vessel is most important factor affetcing blood flow through a tube
  2. Flow is directly proportional to the 4th power of the radius of the tube/vessel
    A. Double the radius, 16-fold increase in flow, if other factors are constant
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5
Q

What is the relationship between resistance and length?

A

Direct

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6
Q

What is the relationship between resistance and blood viscosity?

A

Direct

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7
Q

What is the relationship between resistance and radius?

A

Resistance is inversely proportional to the fourth power of the radius of the tube

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8
Q

Define laminar flow

A
  1. Greatest velocity of flow in center of vessel

2. Lowest velocity of flow near the vascular wall

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9
Q

Define turbulent flow

A
  1. Irreg. flow patterns, such as vortices, eddies
  2. Vascular disease (i.e. plaques) asst w/ sites of turbulence
  3. Turbulence in blood vessels cause the audible murmurs/bruits heard on PE
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10
Q

How is blood flow regulated?

A

Blood flow is regulated by constriction and dilation of smooth muscle of arterioles, metarterioles, and precapillary sphincters. Symp nerves extend to arterioles, metarterioles, and venules in microcirculation

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11
Q

Define shear stress

A

Flowing blood creates a force on the endothelium that is parallel to the long axis of the vessel

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12
Q

What ions does the endothelium of blood vessels secrete?

A

Nitric oxide and PGI2 in response to shear stress, ACh, and bradykinin.

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13
Q

What does nitric oxide mediate?

A

Vasodilation

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14
Q

What does endothelin mediate?

A

Vasoconstriction

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15
Q

Define tunica intima

A
  1. Inner lining of arteries & veins composed of endothelium

2. Continuous with endothelium of heart

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16
Q

Define tunica media

A
  1. Middle layer of arteries & veins
  2. Composed of elastic tissue & smooth muscle
  3. Smooth muscle layer much thinner in veins compared with arteries
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17
Q

Define tunica adventitia

A
  1. Outer layer of arteries & veins

2. Composed mainly of connective tissue

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18
Q

What causes blood flow through arteries?

A
  1. Pressure within the arteries

2. Contraction of smooth muscle in tunica media

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19
Q

What causes blood flow through veins?

A
  1. Skeletal muscle contraction

2. Veins have valves

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20
Q

Define capillary exchange

A
  1. Exchange of nutrients, gases, wastes btw blood & cells essential for survival of the tissues
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21
Q

What is the structure of a capillary wall?

A

One cell thick: contain tunica intima layer only

22
Q

Why does blood move slowly through capillary beds?

A

Capillaries are short, but blood moves slowly b/c total cross-sectional area of the capillary bed is large

23
Q

How much does blood flow increase during exercise?

A

Blood flow through skeletal muscles increases 15-25 fold during exercise

24
Q

How does blood flow increase during exercise?

A

increase in blood flow results from vasodilation of skeletal muscle arterioles

25
Q

How does peripheral vasodilation occur?

A
  1. Reduction of O2 in skeletal muscles

2. K+ ions, lactic acid and CO2 build-up

26
Q

What effects does the symp ns have on the circulatory system during exercise?

A

inc heart rate
inc contractility
Thus, inc CO

27
Q

What arterioles in the periphery do not constrict during exercise?

A

Most of arterioles in peripheral circulation contract EXCEPT:

  1. Arterioles in active muscles
  2. Coronary system
  3. Cerebral arterioles
28
Q

How does pressure change during exercise?

A
  1. inc systemic filling pressure

2. inc in arterial pressure

29
Q

How does blood flow to the skin change during exercise?

A

Blood flow to skin initially reduced but soon rises to promote heat loss

30
Q

How does the venous return rate change during exercise? How is this facilitated?

A
  1. inc venous return to match increased CO

A. Driven in part by the alternating contraction and relaxation of the exercising limbs and by venoconstriction

31
Q

What factors affect bp?

A
  1. Cardiac output (CO)
    A. Amount of blood pumped out by the ventricles in a given period of time
    B. CO (mL/min) = HR (bpm) x SV (mL/beat) = approx 5L/min
  2. Peripheral vascular resistance
    A. Reflects change in radius of arterioles and viscosity of blood
32
Q

What is the equation for Mean Arterial pressure?

A

MAP = CO x TPR

33
Q

What is the pulmonary bp?

A

25/10

34
Q

Define SBP

A

peak arterial pressure reached during ejection of blood by the heart
120/80

35
Q

Define DBP

A

lowest arterial pressure reached during diastole (not ejecting blood, heart relaxed)

36
Q

What factors or conditions have an effect on CO?

A
  1. Meds
  2. Temperature
  3. Anxiety
  4. breathing
  5. Heart disease/failure
  6. Vagal stimulation
  7. Sleeping
37
Q

How is bp raised acutely through the autonomic ns?

A

High-pressure baroreceptors in the aortic arch and carotid sinus are extremely important in acute regulation of blood pressure

38
Q

What part of the kidneys help regulate raise bp?

A
  1. Afferent arterioles in the renal juxtaglomerular apparatus also contain high-pressure baroreceptors
  2. Involved in regulation of renin release, and consequently, regulation of sodium and water balance, important in long-term regulation of blood pressure.
39
Q

How is bp lowered acutely through the autonomic ns?

A
  1. Low-pressure baroreceptors in the heart and pulmonary circulation respond to changes in blood volume and modulate sympathetic activity and vasopressin release.
  2. The cardiac atria also release atrial natriuretic peptide (ANP) in response to elevated blood volume.
40
Q

When is blood flow to the coronary arteries interrupted in the cardiac cycle?

A

Systole

41
Q

What is the most important mechanism in controlling blood flow through coronary arteries?

A

Local metabolic factors

42
Q

How is long term control of blood flow regulated?

A

development of collateral circulation

43
Q

How is short term autoregulation of blood flow controlled?

A

Intact endothelium of small arteries and arterioles releases NO that causes relaxation of vascular smooth muscle (vasodilation)

44
Q

Define Reactive hyperemia

A

An increase in local blood flow following a brief period of ischemia

45
Q

What stimulates the release of nitric oxide?

A
  1. Shear stress

2. Acetylcholine, bradykinin,histamine

46
Q

What are the functions of NO other than vasodilation?

A
  1. NO protects against vasoconstriction and thrombosis (inactivates plts adhesion and aggregation)
  2. NO inhibits leukocyte adhesion and migration
    A. Acts as a mediator of inflammatory response
47
Q

What are the 3 actions of Nitric oxide?

A
  1. A. flow-induced vasodilatation (shear stress)
  2. Poststenotic vasodilation
  3. Negative feedback control of plt aggregation
48
Q

What vasoconstrictive substances does the endothelium release?

A
  1. Endothelin
  2. Angiotensin II
  3. Prostaglandins (inflammatory mediators)
  4. Serotonin
  5. Thromboxane A2
49
Q

Vasoconstrictors stimulate the release of what?

A

Many vasoconstrictors (as well as vasodilators) stimulate the release of NO from the endothelium

50
Q

Define angiogenesis

A

Physical reconstruction of tissue vasculature to meet the metabolic needs of the tissue

51
Q

Define collateral circulation

A

Anastomotic channels allow perfusion of an area by more than one artery. When one artery is occluded, these channels  in size, allowing blood from open artery to perfuse the area supplied by the occluded vessel. These collateral vessels assume the major role in supplying blood/O2 to that region of myocardium. This collateral circulation is most efficient when obstruction to flow is gradual rather than sudden

Phys: Cardio (6 decks)

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