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MED 101- PHYSICS I > 16. PHYSICS OF THE CIRCULATION SYSTEM (PART 1) > Flashcards

16. PHYSICS OF THE CIRCULATION SYSTEM (PART 1) Flashcards

1
Q
  1. What are the three components of the Cardiovascular system?
A
  1. Blood is the vehicle for transport
  2. The circulatory system is the distribution system
    - it consists of a series of branches blood vessels
    - blood represents about 7% of our body mass
  3. The heart is a four-chambered pump
    - it is composed mostly of cardiac muscles
    - these enable the circulatory flow
    - each section of the heart pumps about 80 mL with
    each contraction
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2
Q
  1. In Newtonian terms, what kind of fluid is blood?
A
  • it is a Non-Newtonian fluid
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3
Q
  1. What does the blood solution consist of?
A
  • plasma
  • red blood cells
  • white blood cells
  • platelets
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4
Q
  1. What does Blood Viscosity increase with?
A
  • it increases with hematocrits

HEMATOCRITS= the volume percentage of red blood cells in blood

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5
Q
  1. What is the Rate of Deformation of a Newtonian Fluid?
A
  • it is the velocity gradient
  • it is proportional to the shear stress

VISCOSITY:
- the constant of proportionality

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6
Q
  1. What can be said about the shear stress in solid substances?
A
  • it is proportional to the deformation rate
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7
Q
  1. What variation exists with regards to Newtonian and Non-Newtonian fluids?
A
  • a variation in the shear stress with the rate of deformation

VISCOSITY:
- the slope of a curve at a point
- this is the apparent viscosity at that point

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8
Q
  1. Blood is a Non-Newtonian fluid, however, we regards it as a Newtonian fluid within this section of studies.
    Why is that?
A
  • Blood behaves with an extreme similarity to a Newtonian Material
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9
Q
  1. What is a Newtonian Fluid?
A

IT IS A FLUID WITH:
- a constant viscosity
- zero shear rate at zero shear stress
- the shear rate being directly proportional to the
shear stress

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10
Q
  1. What is Blood Pressure?
A
  • it is the pressure needed to push blood flow
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11
Q
  1. What is the Oscillating pressure of blood as it leaves the aorta?
A
  • it has pressures of between 80 mmHg and 120 mmHg
  • this is reflected by the Oscillations in blood pressure
    along the major arteries in systemic circulation
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12
Q
  1. How long does systole last in one cycle?
A
  • it lasts about ⅓ of the cycle

SYSTOLE = a phase of the heartbeat
= when the heart muscle contracts and pumps
blood from the chambers into the arteries

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13
Q
  1. How do we calculate the weighted sum of blood pressure?
A
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14
Q
  1. What is P pulse?
A
  • this is the arterial pulse pressure
  • it is the difference in pressure between systole and
    diastole
  • this pressure difference is 40mmHg

DIASTOLE= a phase of the heartbeat
= this is when the heart muscle relaxes
= this allows the chambers to fill with blood

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15
Q
  1. Where does much of the pressure drop within the arterial system?
A
  • it drops within the arterioles
    (the small arteries)
  • the capillaries
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16
Q
  1. What can be said about the blood pressure in the veins?
A
  • it is very low
17
Q
  1. What does the Pulmonary System mirror?
A
  • systemic circulation

EXCEPT:
- all the pressures are lower

18
Q
  1. What happens when you stand upright?
    (with regards to pressure)
A
  • there is an additional pressure
  • p.g.h
  • h = the height relative to the heart
19
Q
  1. What is the approximate height in the upper arm where the blood measurements are made?
A

p = 1 060 kg/m³
g = 9.8 m/s²
h = 1m
P (pressure) = 10 400 Pa
= 79 mmHg

20
Q
  1. What can be said about the driving pressure difference from the arteries to the veins AT ANY GIVEN HEIGHT?
A
  • it is unchanged
21
Q
  1. Why is it not important to consider the pressure change between the arteries and the veins WHEN looking at the pressure changes between the inside and the outside of a vessel?
A
  • the p.g.h is added to both the inside and the outside of the vessel
  • the effect of gravity is significant
22
Q
  1. How high does the blood pressure at the aorta have to be?
A
  • it has to be high enough to pump the blood to the top of the brain
  • this has a height of 40cm
  • the pressure drop is about 30mmHg
23
Q
  1. What manifestation shows the effect of gravity?
A
  • the potential of fainting when you stand
  • the negative effects of standing on your head for long
    periods of time
  • the veins in your head are not designed to pump blood
    back to the heart
  • your feet would also stop receiving blood
  • it is also why varicose veins are worse when you stand
    upright
  • this is because blood needs to be pumped up
24
Q
  1. What happens when you stand up?
A
  • the volume of blood in the veins in your legs increases
  • the pressure in the veins decreases
    (these veins pump blood back to the heart from the leg)
  • this decreases the cardiac output
  • this decreases the flow of blood to the brain

HOWEVER:
- the reflex constriction of the leg veins makes sure that
the above mentioned rarely happens

25
Q
  1. What is the effect of the reflex arteriolar constriction of the veins in the legs?
A
  • it limits the blood pool
  • it increases the blood flow resistance
  • this lessens the decrease in arterial blood pressure
26
Q
  1. What are the two types of conditions that the mechanical properties of blood vessels can be measured under?
A
  1. THE LENGTH OF THE GIVEN VESSEL IS KEPT
    CONSTANT
    • the diameter is measured
    • this is a result of the distending pressure
  2. THE DIAMETER OF THE GIVEN VESSEL IS KEPT
    CONSTANT
    • the length is measured
    • this is because it is stretched longitudinally
27
Q
  1. What affects the flow of blood in the arteries?
A
  • the changes in the rate of the heart beat
  • the volume of blood pumped per beat
    (stroke volume)
  • changes in the arteries themselves
  • they control their diameters
  • they do this through chemical and neural mechanisms
28
Q
  1. Are blood vessels elastic or inelastic?
A
  • they are elastic
  • these tubes can change their diameter and area
  • this is based on the pressure and the temperature they
    are exposed to
29
Q
  1. What are the two physical attributes of blood vessels in a steady state?
A
  1. THEY HAVE A RESISTANCE TO BLOOD FLOW
    • they need a pressure difference along the length of
      the vessel
    • this will drive the blood flow
  2. THEY HAVE A COMPLIANCE
    - this is in response to a distending pressure
    - DISTENDING = swelling caused by pressure from the
    inside

NB: without pressure fluid or tilting of the vessel
- no fluid will flow within the vessel

30
Q
  1. What is a Rigid Vessel?
A
  • a rigid vessel has a constant volume (V)
  • this is called a Resistance Vessel
  • it has only friction present
  • there is no compliance
  • the flow rate of this vessel is affected by the pressure
    drop inside the vessel
31
Q
  1. What is an Elastic Vessel?
A
  • a vessel that has no noticeable resistance
  • this is called a Compliance Vessel
  • the volume of this vessel is affected by the pressure
    difference between the inside and the outside of the
    vessel
32
Q
  1. What can be said about real blood vessels?
A
  • they have attributes of both Resistance and Compliance Vessels
33
Q
  1. What are three examples of vessels that are similar to Compliance Vessels?
A
  1. the Aorta
  2. Large Arteries
  3. Large Veins
  • the pressure drops along these vessels are relatively
    small
34
Q
  1. What are three examples of vessels that are similar to Resistance Vessels?
A
  1. Arterioles
  2. Capillaries
  3. Venules
35
Q
  1. Which vessel is the main site for pressure drops?
A
  • arterioles
  • this is why the heart needs to pump blood at such high pressures
36
Q
  1. How would we mathematically explain the relationship between the pressure inside and outside the blood vessel walls?
A

▵P = P - Pext

  • the pressure inside the blood vessels walls (P)
    is GREATER than the pressure outside (Pext)
37
Q
  1. What is the Law of Laplace for hallow cylinders?
A

T = ▵P x R

T = tension
▵P = change in pressure
R = the radius of curvature

MED 101- PHYSICS I (28 decks)

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