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PHYSIOLOGY II > WEEK VII (Blood vessels & Blood pressure) > Flashcards

WEEK VII (Blood vessels & Blood pressure) Flashcards

1
Q

What is the function of blood vessels?

A

Blood vessels transport and distribute blood pumped through them baby the heart to meet the body’s needs for O2 and nutrient delivery, waste removal and hormonal signalling

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2
Q

What is the function of arteries?

A

Arteries transport blood from the heart to the organs and serve as a pressure reservoir to continue driving blood forward when the heart is relaxing and filling

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3
Q

What does the amount of blood that flows through a given organ depend on?

A

The CALIBER/INTERNAL DIAMETER of the highly muscular ARTERIOLES that supply the organ

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4
Q

What are capillaries?

A

The site of exchange between blood and surrounding tissue cells

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5
Q

What is the function of Veins?

A

Return blood from the organs to the heart and serve as a blood reservoir

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6
Q

What is closely regulated to ensure adequate blood delivery to the organs?

A

Mean arterial blood pressure

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7
Q

Blood flow to other organs can be adjusted according to metabolic needs except which organ?

A

The brain

[The brain can least tolerate disrupted supply therefore always needs blood supply otherwise brain death can occur in 4 mins]

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8
Q

Describe the flow rate of blood through a vessel

A

The flow rate is DIRECTLY proportional to the PRESSURE GRADIENT (as the pressure gradient increases, flow rate increases) and INVERSELY proportional to the VASCULAR RESISTANCE (as resistance increases, flow rate decreases)

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9
Q

What is the equation to calculate blood flow?

A

F = ΔP/R

F = flow rate of blood through a vessel
ΔP = Pressure gradient
R = Resistance of blood vessels

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10
Q

What is the Pressure gradient?

A

The pressure difference between the beginning and end of a vessel

[blood flows from area of higher pressure to area of lower pressure]

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11
Q

What is resistance?

A

A measure of opposition of blood flow through a vessel which depends on blood viscosity, vessel length and vessel radius

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12
Q

What are the properties of Blood flow?

A
  • The vessel’s radius determines resistance
  • Slight change in radius produces significant change in blood flow
  • R is proportional to 1/r^4
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13
Q

What is the main driving force for flow through a vessel?

A

Contraction of the heart imparting pressure to the blood

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14
Q

What happens when resistance to flow increases?

A

It is more difficult for blood to pass through the vessel -> Flow rate decreases -> Pressure gradient must increase correspondingly to maintain the same flow rate -> Heart must work harder to maintain adequate circulation

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15
Q

What are the properties of Resistance to blood flow?

A
  • Directly proportional to viscosity of the blood
  • Directly proportional to vessel length
  • Inversely proportional to vessel radius
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16
Q

What is Poiseuille’s equation?

A

Poiseuille’s equation gives factors that change the resistance of blood vessels

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16
Q

What is Poiseuille’s equation?

A

Poiseuille’s equation gives factors that change the resistance of blood vessels

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17
Q

What is parallel resistance?

A

In Parallel resistance each organ is supplied by an artery that branches off the aorta and the total resistance of this parallel arrangement is a compilation of the different resistances in other circulations 1/Rtotal=1/Ra+1/Rb+1/Rc

[illustrated by systemic circulation]

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18
Q

What are the properties of Parallel resistance?

A
  • Each artery in parallel receives a fraction of the total blood flow
  • The total resistance is less than the resistance of any of the individual arteries
  • When an artery is ADDED in parallel, the total resistance DECREASES
  • In each parallel artery, the pressure is the same
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19
Q

What is Series resistance?

A

Series resistance

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19
Q

What is Series resistance?

A

Series resistance is illustrated by the arrangement of blood vessels within a given organ. Each organ is supplied by a large artery, smaller arteries, arterioles, capillaries and veins arranged in series. The total resistance is the sum of the individual resistances Rtotal=Rartery+Rarterioles+Rcapillaries

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20
Q

What are the properties of Series resistance?

A
  • The largest proportion of resistance is contributed by ARTERIOLES
  • Each blood vessel receives the same total blood flow
  • As blood flows through the series of blood vessels, PRESSURE DECREASES
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21
Q

What is the difference between Laminar flow and Turbulent flow?

A

Laminar flow = Streamlined
Turbulent flow = Not streamlined

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22
Q

What is Reynold’s number?

A

Reynold’s number predicts whether blood flow is LAMINAR or TURBULENT

Reynold’s number is INCREASED -> Greater tendency for TURBULENCE -> Causes audible vibrations called BRUITS

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23
Q

What is Reynold’s number increased by?

A
  • Decrease in blood viscosity
  • Increase is blood velocity
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24
Q

What is viscosity?

A

Viscosity refers to the friction between fluid molecules during flow

[thicker liquids have higher viscosity and greater resistance to flow]

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25
Q

What is Blood viscosity and Resistance to flow determined by?

A

Blood viscosity = number of circulating red blood cells
Resistance to flow = vessel’s radius

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26
Q

Why does blood flow more easily through larger vessels?

A

Because a given volume of blood contacts less surface area compared to smaller vessels resulting in lower resistance

27
Q

How do changes in vessel radius have a significant impact on flow?

A

Resistance is inversely proportional to the fourth power of the radius

28
Q

The factors that affect flow rate through a vessel are integrated in __________________

A

Poiseuille’s law

29
Q

How can the volume of blood flowing through an organ be adjusted by?

A

Regulating the CALIBER (internal diameter) of the organ’s arterioles

30
Q

Where do all exchanges with surrounding cells occur?

A

Capillaries

31
Q

What is the ‘microcirculation’ and where is it located?

A

Microcirculation are the arterioles, capillaries and venules
and it is located within the organs

32
Q

What composes the vascular tree?

A
  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins
33
Q

What are the properties of Arteries?

A

NUMBER: Several hundred
SPECIAL FEATURES: Thick, highly elastic walls, large radii
FUNCTIONS: Passageway from the heart to organs & pressure reservoir
STRUCTURE: Endothelium, Elastic fibers, smooth muscle & collagen fibers

34
Q

What are the properties of Arterioles?

A

NUMBER: Half a million
SPECIAL FEATURES: Highly muscular, well-innervated walls & small radii
FUNCTIONS: Primary resistance vessels & determine distribution of cardiac output
STRUCTURE: Endothelium, Smooth muscle & Collagen fibers

35
Q

What are the properties of Capillaries?

A

NUMBER: 10 billion
SPECIAL FEATURES: Very thin walled, large total cross-sectional area
FUNCTIONS: Site of exchange, determine distribution of extracellular fluid between plasma and interstitial fluid
STRUCTURE: Endothelium

36
Q

What are the properties of Veins?

A

NUMBER: Several hundred
SPECIAL FEATURES: Thin walled compared to arteries, highly distensible & large radii
FUNCTIONS: Passageway to the heart from organs & blood reservoir
STRUCTURE: Endothelium, Elastin fibers, Smooth muscle & Collagen fibers

37
Q

What is the blood volume contained in arteries called?

A

Stressed volume

38
Q

Where is the site of highest resistance in the cardiovascular system?

A

Arterioles

39
Q

What is Arteriolar resistance regulated by?

A

The autonomic nervous system

40
Q

Where are α1 Adrenergic receptors found?

A
  • Arterioles of the skin
  • Splanchnic and renal circulations
41
Q

Where are β2 Adrenergic receptors found?

A

On the arterioles of skeletal muscle

42
Q

What has the largest total cross-sectional and surface area?

A

Capillaries

43
Q

___________ are formed from merged capillaries

A

Venules

44
Q

What is the blood volume contained in the veins called?

A

Unstressed volume

45
Q

Do veins have α1-adrenergic receptors?

A

YES

46
Q

What is the function of arteries?

A
  • To serve as a RAPID-TRANSIT PASSAGE for blood from the heart to the organs
    [large radius -> offer little resistance to blood flow]
  • To act as a PRESSURE RESERVOIR to provide the driving force for blood when the heart is relaxing
47
Q

Large arteries near the heart contain more elastin and are called _______________

A

Elastic arteries

48
Q

As arteries branch into medium-size vessels approaching the organs, the walls become less elastic and more muscular, known as ________________________

A

Muscular arteries

49
Q

What happens during ventricular systole?

A

More blood enters the arteries from the heart than leaves them due to greater resistance in the smaller arterioles

50
Q

Why do Elastic arteries expand?

A

To temporarily hold the excess volume of blood, storing PRESSURE ENERGY in their stretched walls

51
Q

What happens when the heart relaxes?

A

The stretched arterial walls PASSIVELY RECOIL exerting pressure on the blood in the LARGE ARTERIES during DIASTOLE -> Elastic recoil pushes the EXCESS BLOOD contained in the arteries into the vessels DOWNSTREAM -> Ensures continued blood flow to the organs when the heart is not actively pumping blood

52
Q

What are the three tunics that make up the walls of arteries and veins?

A
  • TUNICA INTIMA (Endothelium, Basement membrane, Internal elastic lamina)
  • TUNICA MEDIA (Smooth muscle)
  • TUNICA ADVENTITIA (Connective tissue)
53
Q

What does blood pressure depend on?

A
  • Volume of blood
  • Compliance of vessel walls
54
Q

During ____________, no blood enters the arteries but blood continues to leave due to elastic recoil

A

Diastole

55
Q

Why doesn’t Arterial pressure fall to 0mm Hg during diastole?

A

Since the next cardiac contraction refills the arteries before all the blood drains off

56
Q

What is the difference between Pulse pressure and Pulse rate?

A

THE PULSE PRESSURE = the difference between systolic and diastolic pressures and can be felt as a surge in pressure during systole

THE PULSE RATE = measured by feeling the pulse each time blood is pumped into the arteries and is a measure of the heart rate

57
Q

What happens when cuff pressure is greater than 120mmHg and exceeds blood pressure throughout the cardiac cycle?

A
  • No blood flows through the vessel
  • No sound is heard because no blood is flowing
58
Q

What happens when cuff pressure is between 120 and 80mmHg?

A
  • Blood flow through the vessel is TURBULENT whenever blood pressure exceeds cuff pressure
  • First sound is heard at peak systolic pressure
  • Intermittent sounds are produced by TURBULENT SPURTS of flow as blood pressure cyclically exceeds cuff pressure
59
Q

What happens when cuff pressure is less than 80mmHg and is below blood pressure throughout the cardiac cycle?

A
  • Blood flows through the vessel in smooth, laminar fashion
  • Last sound is heard at MINIMUM DIASTOLIC PRESSURE
  • No sound is heard after because of uninterrupted, smooth, laminar flow
60
Q

How can Arterial pressure changes be measured?

A

Directly by connecting a PRESSURE-MEASURING DEVICE to an artery or indirectly with a SPHYGMOMANOMETER

61
Q

Which artery is cuff pressure balanced against?

A

Brachial artery

62
Q

Blood pressure is determined using a stethoscope placed over the brachial artery below the cuff to detect which sounds?

A

Korotkoff sounds

63
Q

Describe how blood pressure is determined using a stethoscope

A

1) Cuff is inflated above SYSTOLIC BLOOD PRESSURE, completely closing the brachial artery and no sound is heard
2) As cuff pressure is slowly released, the artery transiently opens during SYSTOLE, allowing blood to escape creating a TURBULENT SOUND (FIRST SOUND = SYSTOLIC PRESSURE)
3) Lowest cuff pressure at which the last sound is heard = DIASTOLIC PRESSURE

64
Q

What is the Mean Arterial Pressure?

A

Average pressure driving blood forward into tissues throughout the cardiac cycle

65
Q

What is the formula for approximating mean arterial pressure?

A

Mean arterial pressure = diastolic pressure + 1/3 pulse pressure

66
Q

Arterial pressure including systolic, diastolic, pulse and mean pressure is the same in all arteries (TRUE/FALSE)

A

TRUE

PHYSIOLOGY II (15 decks)

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