2.5 & 2.6

Question 1

I. Organization of the circulatory system
1. How the the circulatory system organize?

Answer 1

Compromised of 3 systems that work together:
1. Heart (cardiovascular)
2. Pulmonary circulation: propels blood to the lungs for exchange of O2 and CO2
3. Systemic circulation: carries O2, nutrients and hormones to peripheral tissues and removes waste products (CO2)

Question 2

I. Organization of the circulatory system
2. What are other functions of the circulatory system?

Answer 2

• Nutrient/waste transport
• Thermoregulation
• Hormone transport
• Immune function

Question 3

II. Hemodynamic functions of different vessels
1. What are Hemodynamic functions of Aorta, large arteries?

Answer 3

• Windkessel effect of the large elastic arteries convert intermittent, pulsatile blood flow resulting from heartbeat into a steady flow

a) During the systole, high elastic content of the wall of the aorta allows it to store a great amount of blood
-> elastic potential energy stored during systole

b) In the diastole, previously stored elastic potential energy pushes the stored blood to the periphery as the aorta returns to its original shape

Question 4

II. Hemodynamic functions of different vessels
2. What are Hemodynamic functions of Middle and small arteries?

Answer 4

• Transport blood into arterioles
• Pulse pressure↓, but still present, which can be palpated in some regions

Question 5

II. Hemodynamic functions of different vessels
3. What are Hemodynamic functions of Arterioles?

Answer 5

• Provides the largest degree of resistance in the systemic circulation
• Their SMCs are single unit
• Pacemaker cells provide continuous vasoconstriction
• Resting tone:
  +) Myogenic tone from smooth muscle
  +) Sympathetic tone from sympathetic innervation

Question 6

II. Hemodynamic functions of different vessels
4. What are Hemodynamic functions of Veins?

Answer 6

• Much higher capacitance due to lower elastic tissue content in walls
• Contain ~65% of total blood volume, so major hemodynamic functions can be considered storage

Question 7

III. Relationship of pressure and flow
1. What are the 2 type of blood vessels in human (not anatomically)

Answer 7

1) Lung-type vessels (contains elastic fiber)
2) Kidney-type vessels (contains smooth muscle)

Question 8

III. Relationship of pressure and flow
2. How does Lung-type vessels (contains elastic fiber) work?

Answer 8

• Works under passive mechanism
• Lung-type vessels are very compliant, so the volume increases proportionally as the pressure increases
• As the pressure (gradient) increases, the resistance within the vessel constantly decreases
  -> Results from the increase in diameter/radius of the vessel due to the elastic fibers int these vessels (passive mechanism)
  -> Resistance equation: when d/r increases, resistance decreases

Question 9

III. Relationship of pressure and flow
3. How does Kidney-type vessels (contains smooth muscle) work?

Answer 9

• Works under active mechanism
• Kidney-type vessels maintain a constant blood flow within a certain range of blood pressure via autoregulation
• As the pressure increases, the resistance will also increase
  -> Results from the increased tension in the vessel wall, which contains SM
  1. Smooth muscle contains ‘’stretch-activated non-specific cation channels’’
  2. When these channels are activated -> depolarization
  3. Depolarization activates VGCC -> influx of Ca2+ -> vasoconstriction
  4. Vasoconstriction will decrease the diameter / radius -> resistance equation

Question 10

III. Relationship of pressure and flow
4. What are the characteristics of active reaction in blood vessels?

Answer 10

• Requires active reaction response of SMCs
• Bayliss effect (autoregulation): certain range of
  pressure, where blood flow is constant

Question 11

IV. Biophysical basis of blood flow
1A. What does Continuity equation state?

Answer 11

In stationary flow of blood , the volumetric flow rate (IV) at any point along the tube is constant

Question 12

IV. Biophysical basis of blood flow
1B. How to use continuity equation?

Answer 12

• Formula: 𝐼𝑉 = 𝐴1 ∗ 𝑣1 = 𝐴2 ∗ 𝑣2 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡
• Total cross-sectional area (CSA) of the vessels are inversely proportional to the volumetric flow
  => CSA is the greatest in the capillaries, hence,
  the volumetric flow rate is the lowest there

Question 13

IV. Biophysical basis of blood flow
2. What does Bernoulli’s Law state? How to calculate it?

Answer 13

• An increase in the speed of blood flow (dynamic pressure) occurs simultaneously with a decrease in hydrostatic pressure (side pressure) -> when the flow speed increases, side pressure decreases
• The blockage of a major vessel will increase the speed of blood flow, and it results in the side pressure supplying the branching vessels

Question 14

IV. Biophysical basis of blood flow
3. What does Hagen-Poiseuille Law state?

Answer 14

The largest volumetric flow rate (IV) is achieved at the section in a circulatory system where the diameter of a vessel is the largest
=> Volumetric flow rate is proportional to the 4th power of the radius of the blood vessel

Question 15

IV. Biophysical basis of blood flow - Resistance equation
4A. What are the 2 factors that determine the blood flow?

Answer 15

1. Pressure gradient between 2 ends of the blood vessels
2. Resistance provided by the vessels (to the blood flow)

Question 16

IV. Biophysical basis of blood flow - Resistance equation
4B. What is the mechanism of changing blood flow?

Answer 16

It is changing the resistance

Question 17

IV. Biophysical basis of blood flow - Resistance equation
4C. How to calculate by using resistance equation?

Answer 17

1. Ohm’s law: pressure gradient is the voltage (U), volumetric flow rate is the current (I)
   => U=I*R -> Δp = Q * R -> Q= 1/R * Δp
2. Combination of the Ohm’s law and H-P-Law gives us the resistance equation:
3. Most important: resistance is inversely proportional to the 4th power of the radius

Question 18

IV. Biophysical basis of blood flow - Serial/ parallel resistances
5A. Characteristics of serial resistance?

Answer 18

• To calculate the total resistance of vessels connected continuously in series, you add up the individual resistances
• Formula: 𝑅𝑇𝑜𝑡𝑎𝑙 = 𝑅1 + 𝑅2 + 𝑅3

Question 19

IV. Biophysical basis of blood flow - Serial/ parallel resistances
5B. Characteristics of Parallel resistance?

Answer 19

• To calculate the total resistance of vessels flowing through different organ systems, you can add up the reciprocal of the individual resistances

Question 20

IV. Biophysical basis of blood flow - Serial/ parallel resistances
5C. Characteristics of Total peripheral resistance?

Answer 20

Total resistance that must be overcome to push the blood through the circulatory system and create flow

Question 21

IV. Biophysical basis of blood flow
6A. What does Reynold’s Number determine?

Answer 21

Determines the tendency of a flow to be laminar (smooth flow, vectors not crossing each other) or turbulent (vectors cross each other, mechanical stimulus on wall)
- <2000 – probably laminar
- >3000 – probably turbulent

Question 22

IV. Biophysical basis of blood flow
6B. How to use Reynold’s Number?

Answer 22

Important: high diameter, high velocity or low viscosity (decreased hematocrit in blood) can cause turbulence

Question 23

IV. Biophysical basis of blood flow
6C. What are the diseases you can observe by using Reynold’s Number?

Answer 23

• Anemia: decreased hematocrit = turbulent flow
• Stenosis: small diameter of the vessel = turbulent flow
• Aneurysm: weakness of wallincreases the diameter = turbulent flow

Question 24

IV. Biophysical basis of blood flow
7A. What is the definition and formula of Laplace’s Law?

Answer 24

• The tension within the wall of a sphere filled with a particular pressure depends on the thickness of the blood vessel wall

Question 25

IV. Biophysical basis of blood flow 7B. Describe a disease you can observe by using Laplace’s Law?

Answer 25

Aneurysm -> Bulging of blood vessel/GI-tract wall causes an increased lumen radius and decreased wall thickness, causing a great increase in wall tension, which may result in rupture

Question 26

IV. Biophysical basis of blood flow 8A. What is Distensibility?

Answer 26

Ability to distend and increase its volume according to increasing transmural pressure

Question 27

IV. Biophysical basis of blood flow 8B. How to measure distensibility?

Answer 27

- Measured in % volume change per mmHg (V0 = original volume) - Distensibility of veins is 8x greater than distensibility of arteries

Question 28

IV. Biophysical basis of blood flow 8C. Compare the Distensibility between the vein and the artery

Answer 28

- Distensibility of veins is 8x greater than distensibility of arteries

Question 29

IV. Biophysical basis of blood flow 8D. What is Compliance?

Answer 29

- The slope of the tangent of any point along the pressure-volume curve - Measure of the distensibility

Question 30

IV. Biophysical basis of blood flow 8E. What are the characteristics of Compliance

Answer 30

- The higher the compliance of a vessel is, the more volume it can hold at a given pressure - Arteries have a rather stable resistance despite changes in transmural pressure, therefore, they are referred to as resistance vessels - High compliance of veins allow them to accommodate large volumes of blood with less buildup of pressure, therefore, they are referred to as capacitance vessels (C = ∆V/ ∆p)

Question 31

IV. Biophysical basis of blood flow 8F. Compare the compliance between the vein and artery

Answer 31

Compliance of veins is 25x greater than compliance of arteries

Question 32

IV. Biophysical basis of blood flow - Shear / Viscosity (Fåhræus-Lindqvist effect) 9A. Characteristics of shear

Answer 32

1. Shear is due to the fact that blood travels at different speeds in the blood vessel in different parts of the vessel. - E.g, near the vessel wall, there is a layer of unmoving blood and next to it, the blood is moving – the difference in velocities is the shear. 2. Shear is highest near the wall of the vessel and lowest at the center of the vessel since the blood is moving at the same velocity at the center

Question 33

IV. Biophysical basis of blood flow - Shear / Viscosity (Fåhræus-Lindqvist effect) 9B. Application of shear IN BLOOD VESSELS

Answer 33

- Near the wall, there is a layer of slow-moving blood - In the center of the lumen, blood flows the fastest (RBC) - The difference in velocities is the shear (shear is highest near the wall and lowest at the center) - According to the bridge analogy. The relative amount of faster particles will decrease, and since RBC is the fastest -> hematocrit will decrease

Question 34

V. Interpret this graph

Answer 34

1. The pressure starts off high and towards the end, the pressure is about 4mmHg. 2. In the aorta, the pressure is high due to the low compliance of the wall and the pressure caused by the CO. 3. Little energy is lost in the large arteries, but then there is a huge decrease in pressure in the small arteries – due to the high resistance. 4. Since pressure + resistance are inversely related, the pressure goes down as resistance goes up. 5. In capillaries the pressure decreases even further until the blood gets to the right atrium which is a pressure of 2 – 0mmHg

Question 35

VI. Measurement of arterial blood pressure 1. How is blood pressure measured?

Answer 35

The BP measured in the upper arm represents the pressure within the brachial artery (Differs from pressure in the aorta)

Question 36

VI. Measurement of arterial blood pressure 2. What are the characteristics of Invasive measurement of BP – insertion of catheter?

Answer 36

- In the brachial artery, the P sys is increased while the P dia is decreased, therefore P pulse↑

Question 37

VI. Measurement of arterial blood pressure 3. What are the characteristics of Non-invasive measurement of BP - sphygmomanometry?

Answer 37

- During sphygmomanometry, a clinician inflates the cuff to a pressure that is greater than the Psys and then slowly releases the pressure in the cuff  Systolic pressure corresponds to the first tapping sound (usually 120mmHg)  Diastolic pressure corresponds to the muffling (dampening) of the sounds (usually 80mmHg)

Question 38

VI. Measurement of arterial blood pressure 4. What is the value of systolic pressure?

Answer 38

- Systolic pressure = the highest arterial pressure in cardiac cycle and is the pressure in the arteries after blood has been ejected from LV during systole. - Systolic pressure = 120mmHg (Psys)

Question 39

VI. Measurement of arterial blood pressure 5. What is the value of Diastolic pressure?

Answer 39

- Diastolic pressure = the lowest arterial pressure in cardiac cycle and is the pressure in the arteries during ventricular relaxation (no ejection from LV) - Diastolic pressure = 80mmHg (Pdiastolic)

Question 40

VI. Measurement of arterial blood pressure 6. What is the value of Pulse pressure?

Answer 40

- Pulse pressure = the difference between systolic pressure and diastolic pressure. - Pulse pressure = 40mmHg (Ppulse)

Question 41

VI. Measurement of arterial blood pressure 7. What is the value of the mean arterial pressure?

Answer 41

- Mean arterial pressure is the average pressure in a complete cardiac cycle - Mean arterial pressure = 93 mmHg => If the heart rate increases, both diastole and systole time length decrease but it is more effective for diastole. - E.g., if the HR is 120 bpm, time length of diastole and systole are roughly equal to each other thus increases the mean arterial pressure.

Question 42

VII. Factors influencing arterial blood pressure 1. What are the Factors influencing arterial blood pressure?

Answer 42

- Physical parameters 1) Blood volume: the greater the blood volume, the higher the blood pressure -> Greater SV results in an increased CO 2) Compliance (V/P): high compliance associated to a low pressure, as the blood vessel expands upon receiving of a great volume of blood and vice versa - Physiological parameters 1) Cardiac output (SV*HR): volume which enters the system 2) TPR: how blood can leave the arterial system

Question 43

VII. Factors influencing arterial blood pressure 2. How can blood volume influence blood pressure?

Answer 43

- Changing blood volume changes SV and thus CO -> effects on BP

Question 44

VII. Factors influencing arterial blood pressure 3. How can Compliance (V/P) influence blood pressure?

Answer 44

Aging results in loss of elastic fibers in the vascular walls -> compliance decreases -> affecting pressure Psys increases, Pdia decreases = high Ppulse

Question 45

VII. Factors influencing arterial blood pressure 4. How can Increasing Cardiac output (SV*HR) influence blood pressure?

Answer 45

An increase in CO results in an overall pressure increase, but a larger increase in Psys than Pdia -> Ppulse also changes (increases)

Question 46

VII. Factors influencing arterial blood pressure 5. How can increasing total peripheral resistance (TPR) influence blood pressure?

Answer 46

Changes Psys and Pdia equally, so no change in Ppulse. In older people, ΔPsys > ΔPdia

Question 47

VII. Factors influencing arterial blood pressure 6. How can increasing VISCOSITY influence blood pressure?

Answer 47

- Hematocrit (% of RBCs)↑ -> viscosity ↑ -> R↑ -> TPR↑ -> no change in Ppulse

Question 48

VII. Factors influencing arterial blood pressure 7. How can GRAVITATION influence blood pressure?

Answer 48

- Affects BP depending on body position - 1cmH2O = 0,7mmHg - Standing: pressure is higher in lower limbs when standing - Lying down: both arteries and veins affected equally, pressure difference between them is unchanged

Question 49

VII. Factors influencing arterial blood pressure 8. How can GENDER influence blood pressure?

Answer 49

- Hormones can affect BP - Estrogen = vasodilator -> decrease TPR -> low BP - Testosterone = vasoconstrictor -> increase TPR -> high BP

Question 50

VII. Factors influencing arterial blood pressure 9. How can climate influence blood pressure?

Answer 50

- Warmth induces arteriolar vasodilation in skin -> decreases TPR -> low BP

Question 51

I. Factors influencing arterial blood pressure 10. How can Physical exercise influence blood pressure?

Answer 51

- CO increases and TPR decreases (due to vasodilation for increased blood flow)

Question 52

I. Factors influencing arterial blood pressure 11. Can SLEEP & EMOTIONS influence blood pressure?

Answer 52

YES!!!!!