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Physiology > Overview of Circulation > Flashcards

Overview of Circulation Flashcards

1
Q

Blood flow resistance is indirectly proportional to what?

A

vessel diameter

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2
Q

Reynolds number is a measure of what parameters?

A

tendency for turbulence

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3
Q

What is the viscosity of blood with a hematocrit of 38-42?

A

3.0

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4
Q

Velocity of Blood Flow equation

A

velocity of blood flow (v) = Volume of blood flow (F)/vascular cross-sectional area (A)

V = F/A

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5
Q

What are the functional principles of the circulatory system?

A
  1. Rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need (demand style system)
  2. the cardiac output is controlled mainly by the sum of all the local tissue flows
  3. arterial pressure regulation is generally independent of either local blood flow control or cardiac output control
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6
Q

What are the factors determining blood flow?

A
  • pressure difference between the two ends of a vessel (pressure gradient)
  • impediment to blood flow through the vessel (resistance)
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7
Q

Blood flow equation

A

Flow in mL/min (F)= pressure difference (P1-P2)/ resistance between P1 and P2

F= (P1-P2)/R

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8
Q

What is laminar blood flow?

A
  1. blood flows at a steady rate
  2. blood vessel is long and smooth
  3. blood flows in streamlines (layers)
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9
Q

What is turbulent flow?

A
  • nonlayered flow that creates murmurs and produces more resistance than laminar flow
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10
Q

When does Turbulent flow occur? (4 listed)

A
  1. when flow is too great
  2. when blood passes an obstruction within the vessel
  3. when blood has to make a sharp turn
  4. when blood passes over a rough surface
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11
Q

Tendency for turbulence equation

A

Reynolds number (Re) = (mean velocity of blood flow in cm/sec (v) * vessel diameter in cm (d) * density (p))/ viscosity in poise (n)

Re= (Vdp)/ n

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12
Q

What does Reynolds number have to be above for turbulence to occur in a straight vessel?

A

2000

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13
Q

What does reynolds number have to be above for turbulent flow to occur in some regions of a vessel?

A

200-400

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14
Q

What are the three major variables that determine resistance?

A
  1. vessel radius
  2. Blood viscosity
  3. vessel length
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15
Q

Resistance equation

A

Resistance (R) = (8* viscosity of blood (n) * length of vessel (l))/ (pi * radius of the blood vessel to the 4th power (r^4))

R = 8nl/ pi*r^4

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16
Q

What is pulse pressure?

A

the difference between systolic and diastolic pressures

17
Q

What is conductance?

A

the measure of blood flow through a vessel for a given pressure difference

18
Q

How does conductance compare to resistance?

A

conductance = 1/resistance

19
Q

What is conductance directly proportional to?

A

the diameter of the vessel to the 4th power

20
Q

Poiseuille’s Law: equation for conductance

A

Rate of blood blow (F) = (pressure difference between ends of the vessel (delta P) * pi * radius of vessel to the forth power ( r^4))/ (8 * blood viscosity (n) * vessel length (l))

F = (pi * delta P * r^4)/(8 * n * l)

21
Q

What does anemia do to viscosity and what does polycythemia do to viscosity?

A 
anemia = decreases
polycythemia = increases
22
Q

84% of the blood volume is in the systemic circulation. Of this 64% is found where?

A

veins

23
Q

Why does blood continue to move through the arterial system during relaxation?

A

It is due to the elasticity of the arterial system

24
Q

Why is pulmonary artery pressure so much lower than systemic artery pressure?

A

It doesn’t take much pressure to send blood from the heart to the lungs and back to the heart because of the short distances needed to travel

25
Q

Why would the velocity of blood flow be slower in capillaries at rest comparded to the aorta at rest?

A

Because in the capillaries in order to get the maximum exchange in the tissues the blood needs to move slower

26
Q

What are the functional principles of the circulatory system?

A
  • rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need
  • the cardiac output is controlled mainly by the sum of all the local tissue flows
  • arterial pressure regulation is generally independent of either local blood flow control or cardiac output control
27
Q

What happens if arterial pressure falls below 100 mm Hg, the nervous reflexes?

A
  • Increase force of heart pumping
  • constrict large venous reservoirs
  • generally constrict most of the arterioles throughout the body (increases arterial pressure)
  • kidneys may later play important role in pressure control
28
Q

What are eddy currents?

A

occur when blood flows crosswise in the vessel and along the vessel, usually forming whorls in the blood. simillar to whirlpools

29
Q

How does eddy currents effect the resistance of blood flows?

A

Blood will flow with greater resistance

30
Q

What is blood pressure physiologically?

A

the force exerted by the blood against any unit area of the vessel wall

31
Q

If resistance is increased what doest that mean for the blood flow, upstream pressure, and downstream pressure?

A

Blood flow: decreases
Upstream pressure: increases
downstream pressure: decreases

32
Q

Why is there a low pressure drop across major arteries?

A

Because they have low resistance

33
Q

Where is the largest pressure drop and why?

A

in the arterioles because they have the highest resistance

34
Q

What is resistances relationship to blood pressure?

A

they are inversely proportional to each other

35
Q

What is pulse pressure?

A

the difference between systolic and diastolic pressure

36
Q

How will the amputation of a limb or removal of a kidney which removes a parallel circuit affect circulation?

A
  • reduces total vascular conductance
  • reduces total blood flow
  • increases total peripheral vascular resistance
37
Q

What is the prime determinant of blood viscosity?

A

the hematocrit of blood

38
Q

What is blood flow autoregulation?

A

the ability of each tissue to adjust its vascular resistance and to maintain normal blood flow through changes in arterial pressure between approximately 70 and 175 mm Hg

39
Q

What happens if you get beyond 70 and 175 mm Hg for arterial pressure?

A

autoregulation will fail

Physiology (6 decks)

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