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Physiology Exam 2 > 23 and 24 - Blood Pressure Regulation I and II > Flashcards

23 and 24 - Blood Pressure Regulation I and II Flashcards

1
Q
  1. Diagram and label the aortic pressure pulse. (Include on your diagram (1) the dichrotic notch (Incisura) (2) the diastolic runoff (3) the systolic pressure (4) the diastolic pressure and (5) the pulse pressure
A

Aa

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2
Q

Why is the true mean pressure of an artery different from the estimated mean pressure of the same artery?

A

Because in order to obtain a true mean pressure, we would need to integrate information obtained over a period of time

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3
Q

How do we estimate the mean pressure?

A

Estimated mean pressure = diastolic pressure + ((1/3)(pulse pressure))

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4
Q

What is the pulse pressure?

A

Systolic - diastolic

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5
Q

What is the result of the mean pressure being estimated this way?

A

This will result in a pressure that is closer to the diastolic pressure because according to the curve, more time is spent in diastole

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6
Q

What is the equation to estimate mean pressure if you are given the systolic and diastolic pressure?

A

Mean pressure = diastolic pressure + (1/3 ((systolic - diastolic))

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7
Q

Why would the pressure pulse travel much faster than the blood within the artery?

A
  • Pressure pulse and blood flow are two independent occurrences
  • Pressure pulse is just a shockwave traveling through the medium
  • The velocity of the medium (blood) does NOT matter
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8
Q

What is the pressure pulse again?

A

The difference between systolic pressure and diastolic pressure

Systolic - Diastolic

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9
Q

Why does the shape of the pressure pulse curve change as the pressure pulse travels down the arterial tree?

A

The pressure curve changes as the pulse changes velocity

  • Generally, as the arteries become less compliant (more stiff), the pulse moves faster
  • As the velocity changes, different components of the pressure pulse will be shifted
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10
Q

What is the effect of compliance (elasticity, stiffness) on the velocity of conduction?

A

Conduction

- Low arterial compliance (pretty stiff) means that the wave will move faster

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11
Q

What is the effect of compliance (elasticity) on the velocity of conduction of the pressure pulse?

A

Pressure pulse conduction

- The greater the compliance (less stiff), the slower the propagation of the pressure pulse

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12
Q

What is the effect of vasoconstriction on the arterial diastolic blood pressure?

A

Increases

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13
Q

What is the effect of vasoconstriction on the capillary hydrostatic blood pressure?

A

Decreases

More blood remains in the arterial system per unit time

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14
Q

What is the effect of vasodilation on the arterial diastolic pressure?

A

Decreases

Vasodilation means increased sympathetic tone

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15
Q

What is the effect of vasodilation on the capillary hydrostatic pressure?

A

Increases

This is due to teh increased blood volume flow

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16
Q

What is the effect of increased sympathetic tone on the arteriolar diameter?

A

When sympathetic tone increases, vasodilation occurs

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17
Q

What is the effect of decreased sympathetic tone on the arteriolar diameter?

A

When sympathetic tone decreases, vasoconstriction occurs

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18
Q

What is the mechanism of vasoconstriction with increased sympathetic tone?

A
  • Alpha-1 receptors are stimulated
  • Resistance is increased
  • Blood profusion is decreased in the periphery
  • This increases the diastolic pressure
  • The slope of the curve decreases
  • Capillary pressure decreases
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19
Q

What is the mechanism of vasodilation with decreased sympathetic tone?

A
  • Reduced alpha-1 receptor activation
  • Increased blood flow due to vasodilation
  • Diastolic pressure decreases
  • The slope of the pressure curve increases
  • Calcium channel blockers will cause edema
  • Capillary pressure increases
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20
Q

How does the parasympathetic nervous system contribute to the control of vessel diameter?

A

Innervation has no effects on vessel diameter, this is mainly controlled by sympathetic tone

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21
Q

What are the four medullary cardiovascular centers that are important in controlling blood pressure?

A

1 - Vasoconstrictor centers
2 - Vasodilator centers
3 - Cardioexcitatory centers
4 - Cardioinhibitory centers

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22
Q

What are vasoconstrictor centers?

A

Pressure centers

They are groups of cells that, when stimulated, result in vasoconstriction of the arterioles

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23
Q

What are vasodilator centers?

A

Depressor centers

They are groups of cells that, when stimulated, result in vasodilation of the arterioles

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24
Q

What are cardioexcitatory centers?

A

A group of cells that, when stimulated, cause an increase in the sympathetic activity and therefore increase the heart rate, contractability and conduction velocity of action potentials

Beta-1 receptors are activated in this case

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25
Q

What are cardioinhibitory centers?

A

A group of cells that, when stimulated, increase vagus tone, which therefore decreases the heart rate

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26
Q

What is the effect of an acute decrease in arterial blood pressure on the vasoconstrictor centers?

A

When the blood pressure drops, the vasoconstrictor centers are activated

This occurs by reduced baroreceptor inhibitory signals, which also function to inhibit the vasodilator center

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27
Q

What will inhibiting the vasodilator center do??

A

It will also inhibit the cardioinhibitory center

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28
Q

Is the vasoconstrictor center typically inhibited or activated?

A

Inhibited

By removing inhibition, there is activation

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29
Q

Why would the vessels constrict in this case?

A

To raise arteriolar blood pressure

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30
Q

Once the vasoconstrictor center is activated, what else becomes activated?

A

The cardioexcitatory center

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31
Q

This is sympathetic activity within the heart, so what will the effect on the heart be?

A

Increased heart rate and increased force of contraction

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32
Q

There is another effect of inhibiting the cardioinhibitory center. What is it?

A

Decreased parasympathetic tone (vagus)

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33
Q

What is the effect of an acute increase in arterial blood pressure on the vasoconstrictor centers?

A

When the blood pressure increases, the vasoconstrictor center is inhibited

This occurs by increased stimulation of baroreceptors

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34
Q

Does this mean there is more or less sympathetic stimulation?

A

Less sympathetic stimulation, which therefore results in activation of the vasodilator center

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35
Q

What happens when there is less activation of the vasodilator center?

A

There is a decrease in vasoconstriction and therefore the blood pressure is lowered

36
Q

Activation of the vasodilator center effects the cardioinhibitory center as well. What happens?

A

There is activation of the cardioinhibitory center

This increases vagal tone which therefore decreases the heart rate

37
Q

How does a decrease in PO2, decrease in pH and an increase in PCO2 effect the vasoconstrictor center?

A

They all result from inadequate blood supply to the brain (ischemic stroke)

They activate the vasoconstrictor center which in turn leads to increased contractility, increased heart rate and vasoconstriction

38
Q

During an ischemic stroke (inadequate blood supply to the brain), what will be the effect on the PO2 in the brain?

A

Decreased oxygen = decreased PO2

39
Q

During an ischemic stroke (inadequate blood supply to the brain), what will be the effect on the PCO2 in the brain?

A

Decreased oxygen = increased CO2 = increased PCO2

40
Q

During an ischemic stroke (inadequate blood supply to the brain), what will be the effect on the pH in the brain?

A

The pH will decrease due to the buildup of acidic CO2

41
Q

What are the effects of increasing PCO2 in the brain, specifically in the tissues of the medullary vasoconstictor center?

A

Simultaneous…

  • Vasodilation of the brain medullary arterioles
  • Vasoconstriction of peripheral blood vessels
42
Q

What is the mechanism of vasodilation in the case of increased PCO2?

A

The increased level of CO2 exerts a local effect on the brain that causes a relaxation in the vascular smooth muscle, resulting in vasodilation

This means that LCOALLY, in the brain, there will be vasodilation of the arterioles

43
Q

What is the mechanism of vasoconstriction in the case of increased PCO2?

A

The vasoconstrictor center will systemically vasoconstrict in an attempt to raise the blood pressure

This means that in the PERIPHERY of the body, there will be vasoconstriction

44
Q

So, what two things happen at once in the case of increased PCO2?

A
  • Vasodilation in the brain

- Vasoconstriction in the periphery

45
Q

What is the goal of these two simultaneous (and seemingly contradictory) occurrences?

A

The goal of these two mechanisms is to keep the blood supply to the brain constant for as long as possible in the case of a trauma

This means that the body will place a priority on the brain and NOT on the other organs in the body

46
Q

What are two functions of the cholinergic sympathetic fibers?

A
  • Vasodilation in anticipation of activity (exercise)

- Sweat gland activation in anticipation of activity (exercise)

47
Q

What is the carotid sinus?

A

The carotid sinus is at the origin of the internal carotid artery

48
Q

What are baroreceptors?

A

sensors located in the blood vessels of all vertebrate animals. They sense the blood pressure and relay the information to the brain, so that a proper blood pressure can be maintained.

49
Q

What is the effect of an acute increase in blood pressure on the firing response from a carotid sinus baroreceptor?

A
  • Increasing the blood pressure increases the stretch on the baroreceptors
  • This causes an INCREASED firing rate of the baroreceptors
50
Q

What is the effect of this increased firing rate?

A

An increase in the inhibition of the vasoconstrictor center

51
Q

What happens to the baroreceptors in cases of prolonged hypertension?

A

They adapt to the condition of hypertension - They “reset” their base line and assume that the new high pressure is the normal pressure

52
Q

When you give medication to lower the blood pressure, what happens to baroreceptors that have already gotten used to this new, high pressure?

A

They will perceive the body as being in a state of hypotension, not because the blood pressure is low, but because it is lower than it is used to

53
Q

How do the baroreceptors respond in this situation?

A

They decrease their firing rate so that the vasoconstrictor center is activated and increases sympathetic tone

This is an attempt to bring the blood pressure back up to what it thinks is normal

54
Q

What side effects are there of this increased sympathetic tone?

A
  • Heart palpitations

- Activation of renin-angiotensin-aldosterone system (edema)

55
Q

What does the activation of the renin-angiotensin-aldosterone system do?

A
  • Activates beta-1 receptors in nearby cells

- This causes the retention of Na+. which causes water retention

56
Q

What will you need to treat this water retention?

A

Two options

  • Diuretics
  • Beta-blockers
57
Q

What beta-blockers do to combat the water retention (edema)?

A

They decrease the heart rate and contractility as well as water retention

58
Q

What is the carotid sinus reflex?

A

A reflex that kicks in when an individual changes position from reclining to standing

59
Q

What will going from laying down to standing do to the pressure in the carotid sinus?

A

Decrease

60
Q

What does this mean for the flow of blood to the brain?

A

The decrease in pressure will result in a decreased flow to the brain

61
Q

If there was not a carotid sinus reflex to intervene in this case, what would be the result when we stand up?

A

Fainting

62
Q

How will the baroreceptors respond to this decreased pressure and flow?

A

The decrease their firing rate

63
Q

What does decreasing the firing rate of the baroreceptors do to the vasoconstrictor center?

A

Activates the vasoconstrictor center

We will see an increase in sympathetic tone and therefore vasoconstriction

64
Q

What does decreasing the firing rate of baroreceptors do to the cardioexcitatory center?

A

It activates the cardioexcitatory center

We will see an increase in heart rate and an increase in contractility

65
Q

What is the overall result of the carotid sinus reflex?

A

An increase in the systemic blood pressure, which prevents fainting and balances out the blood pressure

66
Q

What are the five things that will be affected from long-term low blood pressure?

A

1 - Capillary filtration and reabsorption
2 - ADH release
3 - Atriopeptin (ANF) release
4 - GFR (glomerular filtration rate)
5 - Sympathetic tone and the renin-angiotensin-aldosterone system

67
Q

Describe systemic capillary filtration and reabsorption in terms of long term low BP

A

Throughout the body, there will be decreased filtration of the blood and increased reabsorption

68
Q

Describe how the atrial pressure affects ADH (anti-diuretic hormone) release

A

The low BP will result in an increase of ADH release

This means there will be an increase in the renal retention of water

69
Q

Describe how the atrial pressure affects ANF (atriopeptin) release

A

The low BP will result in a decrease of atriopeptin (ANF)

This means there will be a decrease in the loss of Na+ (more is retained) and therefore more water is retained

70
Q

Describe how the glomerular filtration rate is affected by a long term low BP

A

The decrease in BP will result in a decrease of the glomerular filtration rate

This means there will be increased water retention

71
Q

Describe how sympathetic tone will be affected by a long term low BP

A

Sympathetic tone will be increased

72
Q

What is the affect of this increased sympathetic tone?

A
  • Activation of the vasoconstrictor center

- Activation of the renin-angiotensin-aldosterone system

73
Q

What is the renin-angiotensin-aldosterone system?

A

A hormone system that regulates blood pressure and water (fluid) balance

74
Q

Which hormone of the renin-angiotensin-aldosterone system is at play during low blood pressure?

A

Angiotensin II

75
Q

What does angiotensin II do?

A
  • Increases aldosterone production, which increases water reabsorption
  • Causes short term vasoconstriction
  • Activates the thirst center in the brain
76
Q

What do all of these effects contribute to during a long-term period of low blood pressure?

A

Increase water retention

77
Q

What is the function of this increased water retention?

A

It is an attempt to compensate for the low blood pressure by increasing blood volume

78
Q

What is the major receptor involved in vasodilation?

A

Alpha-1 receptors

79
Q

Is this under sympathetic or parasympathetic control?

A

Sympathetic control

Leads to decreased sympathetic tone

80
Q

What is the major receptor involved in vasoconstriction?

A

Alpha-1 receptors

81
Q

Is this under sympathetic or parasympathetic control?

A

Sympathetic

Leads to increased sympathetic tone

82
Q

What are the major receptors involved in heart rate control?

A
  • Muscarinic receptors

- Beta adrenergic

83
Q

What are the effects of these two receptors?

A

Muscarinic = decreased heart rate

Beta adrenergic = increased heart rate

84
Q

What is the major receptor involved in contractility?

A

Beta adrenergic = increased heart rate

85
Q

How does a carotid sinus massage help to eliminate supraventricular tachycardia?

A
  • The baroreceptors of the carotid sinus are actually stretch receptors
  • By massaging and causing a stretch, you can induce an increased firing of the receptors
86
Q

What does the increased firing of the receptors cause?

A

The increased firing would increase the inhibition of the vasoconstrictor and cardioexcitatory centers of the medulla

87
Q

What is the result of this?

A

This would allow the vasodilator and cardioinhibitory centers to predominate, thereby slowing the heart rate

Physiology Exam 2 (11 decks)

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