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HSF - Viscera > Blood Pressure Regulation > Flashcards

Blood Pressure Regulation Flashcards

1
Q

Factors affecting blood pressure

A

Total peripheral resistance
Cardiac output
Blood volume
Elasticity

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2
Q

What are resistance vessels?

A

Arterioles

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3
Q

What are muscular arterioles?

A

Resistance vessels

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4
Q

What is systolic blood pressure?

A

Maximum pressure in arteries

When blood is ejected into them during systole

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5
Q

What is diastolic pressure?

A

Minimum pressure in arteries

Blood draining into remaining vessels in diastole

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6
Q

Pulse pressure

A

Difference between systolic and diastolic pressure

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7
Q

Mean arterial pressure

A

Average pressure responsible for driving blood forward through vessels into tissues throughout cardiac cycle

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8
Q

How many cm of water does 1mmHg equal?

A

1.36 cmH2O

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9
Q

Different pressures in circulatory system
1)
2)
3)

A

1) Driving pressure
2) Transmural pressure
3) Hydrostatic pressure

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10
Q

Driving pressure

A

Difference in blood pressure between different parts of the vasculature

EG: Diff between arteries and veins

Vector parallel and in the same direction as blood flow

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11
Q

Transmural pressure

A

Pressure inside vessel vs pressure outside vessel

Runs perpendicular to driving pressure

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12
Q

Effect if transmural pressure is negative

A

No blood flow

Pressure outside vessel is greater than inside

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13
Q

Hydrostatic pressure

A

Difference in pressure form height of blood

Function of potential energy

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14
Q

Difference in blood pressure between heart and head

A

~85mmHg (if head is 50cm higher than heart)

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15
Q 
Factors contributing to pressure in circulation
1)
2)
3)
4)
A

1) Gravity
2) Compliance of vessel
3) Viscous resistance
4) Intertia

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16
Q

Effect of gravity on blood pressure

A

Causes hydrostatic pressure when there is a change in height

Doesn’t affect driving pressure

Rho G H

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17
Q

Vascular compliance

A

Increase in volume/Increase in pressure

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18
Q 
Factors determining viscous resistance of blood
1)
2)
3)
4)
5)
A

1) Fibrinogen concentration
2) Haematocrit
3) Vessel radius
4) Linear velocity
5) Temperature

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19
Q

Velocity of blood at vessel wall

A

Zero

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20
Q

Area where blood velocity is maximum

A

Centre of vessel

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21
Q

Effect of increased blood velocity

A

Decreased pressure

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22
Q

Why does blood pressure decrease when velocity increases?

A

Law of conservation of energy

As kinetic energy (velocity) rises, potential energy (pressure) must decrease

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23
Q

Delta P (pressure)

A

Flow x resistance

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24
Q

Issues for Poiseuille’s law in the human body

A

1) Rule is only true for an incompressible liquid
2) Constant velocity
3) Straight, rigid, unbranched tube
4) Steady, not pulsatile flow
5) Uniform flow in a tube

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25
Q

What is conductance in a blood vessel?

A

Measure of blood flow through a vessel for a given pressure difference

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26
Q

Ways to calculate conductance

A

1/Resistance

Flow/Change in pressure

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27
Q

What happens to resistance if tubes are in series?

A

Increases

28
Q

What happens to resistance if tubes are in parallel?

A

Decreases

29
Q

Is total resistance higher in arterioles or capillaries?

A

Arterioles

30
Q

Why do arterioles have higher total resistance than capillaries?

A

Capillaries have a narrower aperture
BUT
Capillaries have more vessels in parallel

31
Q

Role of elasticity in blood pressure

A

Maintains a steady pressure and flow despite pulsatile heartbeat

32
Q

Does the heart spend more time in systole or diastole?

A

Diastole

33
Q

Why is vasoconstriction so effective in increasing blood pressure?

A

Poisuille’s equation (radius^4)

60% of blood is in systemic veins –> pushes extra blood into arteries

34
Q

What determines mean arterial pressure?

A

Cardiac output x total peripheral resistance

35
Q

Equation for MAP

A

Diastolic pressure + 1/3(Systolic - Diastolic)

36
Q

Preload

A

What’s in the heart before contraction

37
Q

Frank-Starling law

A

Relationship between stretch and force

Force increases as stretch increases, until a point where it plateaus (sarcomeres stretched too much, heart begins to fail)

38
Q

Cardiac output

A

Heart rate x stroke volume

39
Q

Average cardiac output

A

5L/min

40
Q

Stroke volume

A

End diastolic volume - end systolic volume

41
Q

Average stroke volume at rest

A

70mL

42
Q

Inotropy

A

Force of ventricular contaction

43
Q

Factors affecting stroke volume

A

Inotropy

44
Q

Factors affecting inotropy

A

Preload
Contractility
Afterload

45
Q

What determines end diastolic volume (afterload)

A

Venous return

  • Skeletal muscle pump, thoracic pump
  • Varying degrees of vasoconstriction
46
Q

Increasing afterload increases what?

A

Resistance
Harder to get blood into the heart
Decrease stroke volume, increase end systolic pressure

47
Q

Effect of increasing preload

A

Increase stroke volume

Increase end diastolic volume

48
Q

Effect of increasing inotropy

A

Increase stroke volume

Decrease end systolic volume

49
Q

How is the heartrate modulated?

A

By autonomic nervous system

50
Q 
Effect of sympathetic stimulation on heart
1)
2)
3)
4)
5)
A

1) Changes ion permeability
2) Depolarises
3) Reaches threshold sooner
4) Beta1 noradrenaline receptors
5) Enhances rate of transmission of AP through AV node

51
Q 
Effect of parasympathetic stimulation of the heart
1)
2)
3)
4)
5)
A

1) Changes ion permeability
2) Hyperpolarises
3) Harder to reach threshold
4) ACh muscarinic receptors
5) Slows conduction of AP through AV node

52
Q

Short term blood pressure regulation

A

Barroreflex

Neural

53
Q

Where are baroreceptors located?

A

Carotid sinus

Aortic arch

54
Q

What do baroreceptors in the carotid sinus and aortic arch do?

A

1) Fire constantly
2) Respond rapidly to changing blood pressure, within 1 - 2 cycles
3) Synapse in medullary cardiovascular control centre

55
Q

Short-term blood pressure homeostais
1)
2)
3)

A

1) Change in BP detected by baroreceptors in aortic arch, carotid sinus
2) Medullary cardiovascular control centre
3) Either sympathetic or parasympatheitc activation of vasculature

56
Q 
Result of activating sympathetic nervous system
1)
2)
3)
4)
5)
A

1) Increase heart rate
2) Increase contractility
3) Increase total peripheral resistance
4) Increase venous tone
5) Decrease AV conduction time

57
Q

Result of activating parasympathetic nervous system
1)
2)

A

1) Decrease heart rate

2) Increase AV conduction time

58
Q 
Homeostatic mechanisms for blood pressure when you stand up
1)
2)
3)
4)
5)
A

1) Decrease in MAP
2) Decrease in baroreceptor stretch
3) Decrease in nerve firing to cardiovascular medullary center
4) Increase sympathetic response –> Increase HR, contractility, TPR of arteries
5) Decrease parasympathetic response

59
Q

Homeostatic mechanisms for blood pressure when you lie down

A

1) Increase in MAP
2) Increase baroreceptor stretch
3) Increase in nerve firing to cardiovascular medullary center
4) Reduce sympathetic response –> decrease TPR of arteries, vascular resistance
5) Increase parasympathetic response –> Decrease heart rate

60
Q

Long-term blood pressure regulation

A

Chemoreceptors
Detect pH, [O2], [CO2]
Increase respiration

61
Q

Hormonal ways to increase cardiac output

A

Increase extracellular fluid

Decrease renal salt excretion

62
Q

Hormonal ways to increase TPR

A

Thicken arterial wall (hypertrophy)

Vasoconstrictive hormones

63
Q

Where are low pressure receptors located?

A

Atrial baroreceptors

64
Q

Factors determining MAP

A

1) Blood volume
2) Cardiac output
3) Resistance
4) Distribution of blood between arterial and venous blood vessels

65
Q

What determines resistance to blood flow?

A

Diameter of arterioles

66
Q

What determines the distribution of blood between arterial and venous systems?

A

Diameter of veins

HSF - Viscera (12 decks)

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