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ctb > CTB4 - Blood Pressure and Flow > Flashcards

CTB4 - Blood Pressure and Flow Flashcards

1
Q

Define compliance.

A

Ability of an organ to swell in response to applied pressure.

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2
Q

Define resistance.

A

Ability of an organ to resist a change e.g. in blood flow which is referred to as vascular resistance.

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3
Q

Define capacitance.

A

Ability of a blood vessel to store blood - e.g. act as a reservoir storing the blood volume.

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4
Q

Is there a link between structure and function of a blood vessel?

A

Yes. The function of the blood vessel is closely linked to its structure - particular what makes up the vessel wall.

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5
Q

Use one word to describe the functions of each of the following blood vessels - aorta, arterioles, capillaries and veins.

A

Aorta - distribution
Arterioles - resistance
Capillaries - exchange
Veins - capacitance

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6
Q

Discuss the pulse dampening effect and which blood vessels exhibit this. How are these vessels adapted to have this function?

A

Pulse dampening refers to the reduction in pressure within the vessel. Larger elastic arteries have a pulse dampening effect. Large elastic content within vessel wall.

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7
Q

How are arterioles adapted in their structure to suit their resistance function?

A

Extensive wall of smooth vascular muscle within the vessel wall. Allows regulation of blood vessel diameter. Controls blood flow within the vessel.

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8
Q

How are capillaries aided in their exchange function?

A

Walls are mainly just one layer of endothelial cells, providing thin diffusion distance. Many capillaries present at each tissue provide large surface area for exchange.

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9
Q

How are veins suited to their reservoir function?

A

Contain valves to stop bad flow of blood and are compliant meaning that they can move the blood volume along, and back to the heart.

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10
Q

Which vasculature has the greatest mean blood pressure? What is this value?

A

Aorta - approx 90 mmHg.

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11
Q

Between which arteries is the largest drop in blood pressure?

A

Between smaller elastic arteries and the arterioles.

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12
Q

What is the approx mean blood pressure in the capillaries?

A

Approx 25-30 mmHg.

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13
Q

Why does pressure decrease as you go downstream circulation?

A

Due to increases in friction.

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14
Q

Which circulatory system (systemic or pulmonary) has the greater pressure?

A

Systemic circulation.

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15
Q

Define systolic and diastolic blood pressure.

A

Systolic blood pressure - maximum pressure within arterial walls following full ventricular contraction.

Diastolic blood pressure - minimum pressure within arterial walls following ventricular relaxation.

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16
Q

What factor about pressure, allows blood to flow within the circulatory system?

A

Pressure differences. Blood flows from areas of higher pressure to areas of lower pressure. The absolute pressure does not have an effect.

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17
Q

What is pulse pressure?

A

The oscillation of pressure within a blood vessel.

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18
Q

What happens to pressure if there is a large increase in resistance? Where in the circulatory system is this observed?

A

Large increase in resistance means large decrease in pressure. Seen between the small arteries and the arterioles.

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19
Q

Why does arterial blood pressure not reach zero?

A

Arteries have elastic recoil ability meaning that they can maintain blood pressure within the vessel. Ensures continuous blood flow around circulation, in accordance to the windkessel effect.

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20
Q

Discuss the reduction in the following two pressures during ventricular relaxation - ventricular pressure and arterial pressure.

A

Ventricular pressure - rapidly decreases

Arterial pressure - slow decrease due to elastic recoil

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21
Q

What parts of the cardiac cycle are associated with the following regions of an ECG - P wave, QRS complex and T wave?

A

P wave - firing of SA node
QRS complex - ventricular depolarisation.
T wave - ventricular repolarisation

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22
Q

What limitations are there to Hales’ use of tubes inserted into arteries to measure blood pressure?

A

Long tubes with constant diameter - blood vessels are not long continuous structures and can change diameter
Tube wall composition - blood vessels have differing amounts of elastin and muscle in their wall which contributes to differences in pressure within the vessel

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23
Q

Discuss brief overview of the movement of blood around the circulatory system.

A

Oxygen enters blood at lungs. Oxygenated blood pumped through pulmonary vein into the left atrium of the heart. Pumped into left ventricle and then to tissues via aorta. Returned to right atrium via vena cava. Pumped to right ventricle. Pumped to lung via pulmonary artery.

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24
Q

What are the two types of blood flow? Describe each and where you might find that blood flow.

A

Laminar - all fluid moves in linear direction - found in most blood vessels.

Turbulent - fluid contains whirlpool regions that do not move linearly - found at branching points or occluded blood vessels.

25
Q

Discuss vascular occlusion and one thing which may cause it.

A

Refers to blockage of the blood vessels e.g. blood clot within the vessel or atherosclerosis on vessel wall.

26
Q

What are the two haemodynamic forces that affect vascular endothelial cells? Describe each.

A

Cyclical strain - refers to the pressure across the vessel wall that means that the vessel stretches to accommodate the pressure
Shear stress - force between blood and surface of blood vessel

27
Q

How do you calculate shear stress?

A

Shear rate multiplied by fluid viscosity

28
Q

Define shear rate.

A

The rate at which fluid layers move past one another within a tube.

29
Q

Which type of blood vessel has the great relative cross sectional area of all vessels?

A

Capillaries

30
Q

Which blood vessels have the great volume of blood contained within the vessels?

A

Venues and veins

31
Q

Which blood vessels have the lowest volume of blood contained within the vessels?

A

Capillaries

32
Q

What two factors about blood are controlled by the compliance of the vessel?

A

Blood flow and blood pressure

33
Q

Do arteries or veins have a great compliance and by how much?

A

Veins are more compliant, by approx 10-20X more.

34
Q

What happens to venous compliance as vascular smooth muscle contraction within it is increased?

A

Compliance decreases.

35
Q

Discuss high and low compliance in terms of blood vessels and their changes to blood pressure and volume.

A

High compliance - deform more readily to pressure and volume changes
Low compliance - deform less readily to pressure and volume changes

36
Q

What parameters affect blood flow resistance and do they change? What equation can be used to calculate resistance?

A

Poiseuille’s equation. Involves using fluid viscosity, tube length, inner tube radius. Fluid viscosity and tube length is considered constant.

37
Q

Why does Poiseuille’s equation have its limitations?

A

Assumes that blood is behaving as a Newtonian fluid - which it is not. Also assumes long straight tube structure for blood vessels, which they are not.

38
Q

What is the main takeaway from Poiseuille’s equation?

A

A small decrease in loop vessel radius causes a large increase in resistance which causes a large decrease to blood flow.

39
Q

How do you calculate mean blood pressure?

A

Multiply cardiac output by peripheral vascular resistance.

40
Q

How do you calculate cardiac output?

A

Multiply stroke volume by heart rate.

41
Q

How do you calculate stroke volume? What is stroke volume?

A

Stroke volume is the amount of blood ejected from the heart per beat. Can be calculated by subtracting end systolic volume from end diastolic volume.

42
Q

What are five factors affecting the regulation of vascular resistance/blood pressure?

A

Myotonic theory
Vascular injury - vascular tone regulation
Vasoactive mediators - vascular tone regulation
Systemic regulation
Autonomic nervous system - parasympathetic and sympathetic branches

43
Q

Discuss the myogenic theory in blood pressure regulation.

A

Pressure changes within the vessel cause vascular smooth muscle to either contract or relax causing vasoconstriction or vasodilation, respectively. Controlled by stretch sensitive ion channels.

44
Q

Discuss the role of vascular injury in blood flow regulation.

A

Upon damage to vascular wall, platelets and other inflammatory mediators are signalled to the site of damage. Includes serotonin which is a vasoconstrictor. Vasoconstriction of blood vessel reduces lumen size reducing blood flow to this area.

45
Q

Discuss the role of vasoactive mediators in regulating vascular tone.

A

Various endothelium derived or non endothelium derived vasorelaxants and vasoconstrictors are released continuously to maintain vascular tone. If imbalance is present, either vasoconstriction or vasorelaxation will occur.

46
Q

Discuss the role of systemic regulation in blood pressure/flow regulation.

A

Various circulating hormones can act as vasoactive mediators, controlling vascular tone of blood vessels.

47
Q

Discuss the role of both branches of the autonomic nervous system in blood flow and pressure regulation.

A

Parasympathetic - rest and digest - acts to decrease heart rate, cardiac output and blood pressure.
Sympathetic - fight or flight - acts to increase heart rate, cardiac output and blood pressure. Vasoconstriction of blood vessels that feed non essential organs allowing blood flow to be directed to essential organs.

48
Q

What are baroreceptors and why are they necessary? Name the two typos baroreceptors.

A

Baroreceptors are receptors that identify pressure changes - ensures that blood pressure is maintained. Types include either high pressure or low pressure baroreceptors.

49
Q

What are the two main locations for baroreceptors, and what is the benefit to their being located there? How/where do they send information to?

A

Located in the carotid sinus and aortic arch - found where they are able to extend or distend the vessel allowing for pressure regulation, Send information to the cardiovascular centre.

50
Q

Which nerves do the carotid sinus and aortic arch baroreceptors respectively, use to send information To the cardiovascular control centres? What exactly is the cardiovascular control centre?

A

Carotid sinus baroreceptors - glossopharyngeal nerve.
Aortic arch baroreceptors - vagus nerve.

Sends to the vasomotor centre in medulla oblongata

51
Q

Where are low pressure baroreceptors located, and what is their role?

A

Located in vena cava and right atrium. Respond to changes in blood volume. Allowing signalling of cardiovascular system or renal system (I.e. renin angiotensin system).

52
Q

What is the normal blood pressure value?

A

120/80mmHg.

53
Q

How can blood pressure be measured? Discuss the general overview of the process.

A

Measured using a sphygmomanometer. Pressure applied to brachial artery to stop blood flow. Pressure slowly released. At first point of release, largest pressure within arterial indicates systolic blood pressure. As pressure is released to the finish (I.e no pressure being applied), lowest pressure is recorded as diastolic blood pressure.

54
Q

What are korotkoff sounds?

A

Sounds heard within an artery when measuring blood pressure. Five distinct sounds can be heard but only two are required for systolic and diastolic blood pressure measurement

55
Q

How do you calculate pulse pressure?

A

Systolic blood pressure minus diastolic blood pressure

56
Q

What calculation can be used to approximate mean blood pressure?

A

Diastolic blood pressure plus third of pulse pressure

57
Q

Discuss the windkessel effect and why it is apparent. Discuss its importance.

A

Refers to reduction in blood pressure fluctuation, allowing pressure to be maintained within arteries. Apparent due to elastic recoil ability of arteries. Important as it ensures that blood is always flowing in the circulatory system.

58
Q

What factors cause windkessel effect to reduce? What is the effect on pulse pressure?

A

Reduction in arterial compliance which can be caused by age - arteries become more stiff with age. Pulse pressure would increase

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