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Unit 4 Physiology > principles of blood flow > Flashcards

principles of blood flow Flashcards

1
Q

what is the trend of blood pressure as an individual ages?

A

sharp increase during early growth and subsequent rise after age 45

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2
Q

what are the mean pressures in the large arteries, arterioles, capillaries, venules and veins?

A

large arteries 95, arterioles 60, capillaries 35-15, venules 15, veins 15-3

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3
Q

is blood a newtonian fluid?

A

no

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4
Q

what is the main change of blood pressure in the body?

A

cyclic periodic beating of the heart

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5
Q

from what is the energy in the blood composed of?

A

static pressure, gravitational force and motion

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6
Q

how to blood vessels accommodate pressure changes?

A

they change shape (elastic)

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7
Q

describe flow through a series of tubes with different diameters? what property does this support?

A

constant flow throughout the tubes

conservation of mass- same amount of blood flows in as blood flows out in a given time

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8
Q

define blood flow (Q).

A

the quantity of blood passing in a particular observation point in a given time interval

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9
Q

describe blood flow in a parallel circuit.

A

volume flow is additive (Qt=Q1+Q2)

flow across any total cross sectional area is constant

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10
Q

what two major vessels can be compared in the vascular system as being in series and having the same blood flow?

A

the aorta and the pulmonary artery

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11
Q

describe a parallel circuit in the body and how it relates to flow in other vessels.

A

capillaries can be thought of as parallel circuits and their total blood flow is the same as the blood flow in the aorta

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12
Q

what controls the rate of blood flow to a tissue? how is this accomplished?

A

the tissue need

accomplished by he adjustment of resistances located prior to the capillary beds

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13
Q

what mainly controls cardiac output?

A

the sum of all local tissue flows

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14
Q

id the arterial pressure regulated by local blood flow or cardiac output control?

A

no, arterial pressure has other means of regulation

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15
Q

what is the main overall arrangement of vasculature? what are some exceptions?

A

overall arrangement is primarily a parallel circuit
splenic and mesenteric capillaries are in series with hepatic circulation and renal glomerular and tubular circulations are in series with each other

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16
Q

how is hypoxia avoided in tissues?

A

flow of oxygen in the arteries to the tissues must be equal to or greater than the rate of oxygen consumption by the tissues

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17
Q

what is mobilized during exercise to accomplish the necessary added profusion of tissues? Where does the added flow go?

A

venous reserve

the flow goes to the skin, muscles and heart while maintaining flow to the brain

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18
Q

what is the flow of oxygen in arteries?

A

flow of O2=cardiac output x arterial O2 content

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19
Q

define the velocity of a fluid. how is it different from flow?

A

the rate of displacement of a particle of fluid with respect to time. flow is the rate of displacement of a volume of fluid (distance per hour instead of volume per hour)

20
Q

what is the equation for volume in a cylindrical tube. under what conditions is the flow past successive cross sections equal?

A

Q=A (cross sectional area) x v (velocity)

the fluid must be incompressible and the tube must be rigid

21
Q

what is the equation for cross sectional area of a cylinder?

A

A=pi x r^2

22
Q

what is the velocity of a particle?

A

v=change in distance/change in time

v=Q/A

23
Q

if the flow of a fluid is constant and v=Q/A, then what must be true of two different cross sectional areas in the same circuit?

A

v1 x A1=v2 x A2

24
Q

how does linear velocity relate to cross sectional area?

A

velocity is inversely related to cross sectional area

25
Q

what is the Q of the aorta?

A

5L/min

26
Q

what is the ratio of velocity of the aorta to the velocity in the capillaries?

A

510:1

27
Q

what is the equation for transit time of a blood cell between two points in the system?

A

t=l/v (length/velocity)

t-V/Q (volume/flow)

28
Q

how long does it take for a red blood cell to travel through a capillary bed?

A

1 second

29
Q

what is the total circulation time for one bass through the systemic and pulmonary circulation?

A

one minute

30
Q

when is the approximation for circulating blood in a steady flow of incompressible fluids in rigid, straight cylindrical tubes acceptable?

A

for all but the smaller vessels

31
Q

what assumptions are not always true of flow when talking about blood?

A

that the flow is laminar with no slippage at the wall and that the viscosity is constant across the diameter of the vessel

32
Q

define viscosity. when does it effect fluid flow?

A

how much a fluid resists shear forces

affects flow when there are changes in velocity

33
Q

what is a at the vessel surfaces in contact with blood?

A

a boundary layer.

34
Q

what is another equation for flow using pressure and resistance? where does resistance to flow come from?

A

Q= pressure difference/resistance

resistance comes from the walls of the vessel and the viscosity of the blood

35
Q

why is pressure from the heart propagated throughout the circulatory system?

A

because the blood is incompressible and continuous

36
Q

blood viscosity and resistance from vessel walls are what type of forces?

A

frictional forces

37
Q

what variables of flow does Poiseuille’s law relate?

A

pressure difference, radius of the vessel, viscosity and length of the tube

38
Q

how is resistance related to radius and area?

A

resistance is inversely related to the radius to the fourth power
resistance is inversely related to the square of the cross sectional area

39
Q

what vessels mainly determine the resistance to the flow of the blood?

A

the arterioles

40
Q

how does the sympathetic nervous system control blood flow?

A

receptors are stimulated that cause vasoconstriction of vascular smooth muscle. This increases the flow greatly

41
Q

besides vessel radius, what affects resistance to flow? what variable has an inverse relationship to this variable?

A

viscosity
temperature is inversely related to viscosity
(colder temperatures increase blood viscosity and decrease blood flow)

42
Q

what equation can help you measure pressure drop along a length of blood vessel? what conditions increase pressure drop in blood vessels?

A

Poiseuille’s law

decreased radius, increased viscosity and increased lenth of the vessels

43
Q

where in the vasculature is blood pressure decreased more slowly and where more rapidly?

A

slowly: large arteries and veins
rapidly: small arterioles and capillaries

44
Q

what is the total resistance for blood vessels in series?

A

Rt=R1+R2+R3…

45
Q

what is the total resistance for blood vessels in parallel?

A

1/Rt=1/R1+1/R2+1/R3…

46
Q

how are branches in a parallel network correlated to the total resistance? what is the implication of this for capillaries?

A

more branches in a parallel network decreases the total resistance
the overall resistance for a capillary bed may be very low even though the resistance in each capillary is relatively high

Unit 4 Physiology (31 decks)

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