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Cardio > Regulation of Blood Pressure > Flashcards

Regulation of Blood Pressure Flashcards

1
Q

What has higher pulse pressure, the femoral artery or the aorta?

A

femoral artery (less compliant than the elastic aorta) but with age, the aorta will become less compliant

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2
Q

What has higher mean arterial pressure, femoral artery or the aorta?

A

aorta (allows blood flow according to Ohm’s law)

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3
Q

How quickly do “rapidly responding systems” work?

A

5 seconds to 1 minute

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4
Q

What is the major function of “rapidly responding systems”?

A

buffer changes of arterial pressure

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5
Q

What is the equation for pulse pressure?

A

pulse pressure = systolic-diastolic pressure

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6
Q

What is the equation for MAP?

A

MAP= pulse presure/3 + diastolic pressure

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7
Q

Can you have an increase in pulse pressure without an increase in MAP?

A

YES (this is usually what happens)

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8
Q

List the 4 “rapidly responding systems”.

A

Baroreceptors
Chemoreceptors
Cerebral ischemia-induced response
Regulation of SV by afterload (arterial pressure)

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9
Q

Baroreceptors provide information to the CNS about what?

A

MAP, pulse pressure, and HR

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10
Q

What is a baroreceptor?

A

stretch-sensitive neuronal-type cells located in aortic arch or carotid sinus that relays information about pressure to the CNS

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11
Q

Aortic baroreceptors signal the CNS through what nerve?

A

vagus nerve

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12
Q

Carotid sinus signals the CNS through what nerve?

A

Herring’s nerve and glossopharyngeal nerve

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13
Q

What has a greater range, aortic baroreceptors or the carotid sinus?

A 
carotid sinus (50-200 mmHg)
ONLY VERY SLIGHT!
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14
Q

What are the effectors of the baroreceptor system?

A

Nucleus tractus solitarius int he medulla of the brain AND the CV system

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15
Q

How do you calculate the “strength” of the feedback of the homeostatic feedback system?

A

GAIN

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16
Q

What is the equation for gain?

A

G= correction of error/error still remaining

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17
Q

What is typical gain for the kidney?

A

infinite! can restore arterial pressure without any errors!

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18
Q

How does carotid sinus nerve activity relate to phasic aortic pressure?

A

as the mean arterial pressure increases, the number of impulses from the carotid sinus increases

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19
Q

In the cruel dog experiment, the pressure sensed by a baroreceptor depends on what?

A

flow from electric pump and degree of occlusion

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20
Q

When you decrease carotid sinus pressure, what is the response of the baroreceptor system?

A

increase systemic arterial pressure by by increasing sympathetic activity and decreasing parasympathetic activity

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21
Q

What are the overall results of a baroreceptor increasing sympathetic activity and decreasing parasympathetic activity (due to low pressure)?

A
  • Increase in CO (increase inotropy and chronotropy)
  • Veins constrict and become less compliant (increases CO)
  • Resistance arterioles constrict to increase TPR
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22
Q

The baroreceptor is most sensitive to what type of changes?

A

best responses are given to changes that are right around the set point (steepest part of slope)

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23
Q

What happens to the MAP if you do not have baroreceptors?

A

MAP stays the same but there is a much greater variability int he blood pressures

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24
Q

What happens as you increase pulse pressure and maintain the MAP?

A

the systemic arterial pressure drops (even though MAP is the same)

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25
Q

How does HR influence baroreceptors?

A

the greater the HR, the greater the baroreceptor activation

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26
Q

What effect do baroreceptors have on prolonged increase in BP?

A

at first, you see a decrease in BP but eventually the baroreceptor activity will not be sufficient to oppose the prolonged increase (resetting)

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27
Q

How do baroreceptor responses differ between normotensive and hypertensive patients?

A

It takes higher diastolic BP to get the baroreceptor response to decrease sympathetic activity in hypertensive patients

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28
Q

Where are chemoreceptors present in the body?

A

carotid body

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29
Q

A what MAP can the chemoreceptor respond?

A

below 80 mmHg

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30
Q

When the MAP is below 80 mmHg, what happens?

A

decreased blood flow to lungs so low oxygen and increased CO2

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31
Q

What happens when chemoreceptors get strongly activated?

A

increase sympathetic activity and parasympathetic activity (but sympathetic increase overrides parasympathetic)

32
Q

What is the overall effect of activated chemoreceptors?

A

increase in arterial BP

33
Q

What does an increase in after load do to arterial pressure?

A

increases

34
Q

What does an increase in afterload (arterial pressure) do to CO?

A

decreases it! (cardiac function curve is shifted down to decrease arterial pressure)

35
Q

When is the cerebral ischemia-induced response activated?

A

at reductions in arterial pressure below 60 mmHg

36
Q

What is the cerebral ischemia-induced response used for?

A

“last-ditch” response to maintain blood flow to brain (defeat hypotension) by activating intense sympathetic activity and a little parasympathetic activity to the aorta (not to the brain vessels)

37
Q

What is the Cushing reaction?

A

increased intracranial pressure leads to constricted resistance arteries (flow goes down and leads to ischemia). Arterial pressure (in aorta) increases to counteract decreased blood flow induced by increased intracranial pressure

38
Q

How long does it take “less rapidly responding systems” to work?

A

1-30 minutes

39
Q

What is the effect of “less rapidly responding systems”?

A

buffer changes in arterial pressure and set levels of pressure

40
Q

List the 5 “less rapidly responding systems”.

A

1) Low pressure receptor-mediated reflex mechanisms (via stretch receptors)
2) Atrial natriuretic factor
3) Capillary fluid transfer
4) Vascular stress relaxation
5) Renin-Angiotensin-Aldosterone system

41
Q

How do Low pressure receptor-mediated reflex mechanisms work?

A

Increased plasma volume increases fill pressure with an increase in atrial and arterial pressure. Increased atrial pressure decreases renal sympathetic activity and decreases vasopressin (which increases renal fluid output). This results in reduced plasma volume and arterial pressure.

42
Q

Where are the Low pressure receptors located?

A

aorta and great veins

43
Q

What is ANP? What releases it?

A

atrial natriuretic factor released from the heart

44
Q

What stimulates the release of ANP?

A

atrial stretch due to increased plasma volume and arterial pressure

45
Q

What is the effect of ANP?

A

increases renal fluid output and decreases plasma volume and arterial pressure

46
Q

What leads to increase in capillary pressure?

A

increase in atrial pressure
decrease in vascular resistance (due to sympathetic response to high arterial pressure)
increase in arterial pressure (very minor influence)

47
Q

What happens when you increase capillary pressure?

A

increase in capillary filtration, decrease in blood volume, and decrease in atrial pressure

48
Q

What is stress relaxation?

A

when stretched (increased venous pressure), venous smooth muscle cells have the capacity to relax

49
Q

What does stress relaxation in response to increased plasma volume lead to?

A

increased unstressed volume (larger veins) with DECREASED fill pressure (so decrease CO and arterial pressure)

50
Q

Decreases in arterial pressure have what effect on renin?

A

release it from the kidney

51
Q

Where is angiotensin I converted to angiotensin II?

A

the lung (by converting enzyme)

52
Q

What does antiotensin II do?

A

1) circulates and increases arteriolar/venous constriction (and increases TPR and fill pressure)
2) increase aldosterone release from adrenals and decrease renal fluid output (increase blood volume)
* *INCREASE BLOOD PRESSURE!

53
Q

Name the “rapid effect” of physiological regulation of blood volume.

A

Capillary-fluid transfer

54
Q

Name the “slow effects” of physiological regulation of blood volume.

A

Renal output

GI output

55
Q

How long does it take “slow responding systems” to work?

A

days to months

56
Q

What is the major effect of “slow responding systems”?

A

set the long-term level or pressure

57
Q

What organ plays a predominant role in regulating the set point of arterial pressure?

A

kidneys

58
Q

What does the renal function curve define?

A

renal fluid output (y axis) as a function of ARTERIAL pressure (x axis)

59
Q

How does increased arterial pressure increase renal output?

A

pressure diuresis (very sensitive)

60
Q

How do you define steady state arterial pressure?

A

point of intersection of the renal function curve with the fluid intake line

61
Q

If you increase fluid intake to a point that exceeds fluid output, what will happen to blood volume?

A

it will increase (and thus increase filling pressure and CO)

62
Q

If you increase fluid intake to a point that exceeds fluid output, what will happen to steady state arterial pressure?

A

the blood pressure will increase to a new set point until renal output matches fluid intake

63
Q

What happens if you increase blood pressure with no change in the renal function curve?

A

you get more output than input (blood volume drops, CO drops, and arterial pressure drops) until you reach steady state

64
Q

What causes a right shift in the renal function curve?

A 
Sympathetic activity
Angiotensin II
Aldosterone
Vasopressin
Obesity
Renal disease
65
Q

What happens if the renal curve is shifted to the right?

A

*get a new, increased steady state blood pressure
decrease in fluid output, increase in blood volume, increase in filling pressure, increase in CO, increase in arterial pressure until fluid output matches fluid intake (adjustment)

66
Q

What causes a left shift in the renal function curve?

A

ANP, NO, some prostaglandins, diuretics, beta blockers

67
Q

What happens if the renal curve is shifted to the left?

A

decrease in steady state blood pressure, so increased fluid output

68
Q

How does increased salt intake affect fluid intake?

A

it automatically results in increased fluid intake (via centrally mediated systems)

69
Q

How does the appearance of a normal renal curve differ from a salt sensitive curve?

A

salt sensitive curve is less steep than the normal

70
Q

What will increasing salt intake do to a salt-sensitive renal curve?

A

it will result in greater increases in arterial pressure than in normal individuals (where increase in salt intake has VERY small effect on the arterial pressure)

71
Q

What will renal disease/aging do to the renal function curve?

A

hypertension (shift to right)

increased salt sensitive (less steep)

72
Q

When the rats had their kidneys almost fully removed and had increased blood volume, what happened to TPR?

A

TPR decreased (because baroreceptors were activated by the increased CO and arterial pressure from increase blood volume- that decreased the sympathetic activity)

73
Q

Over time, what happened to these poor rats with little kidneys?

A

decreased CO back to normal and increased TPR

74
Q

Why did these rats have a reversal in their CO and TPR?

A

1) Baroreceptors adapted to sustained arterial pressure

2) Whole body autoregulation

75
Q

What is whole body autoregulation?

A

increased organ perfusion rate causes increase of organ vascular resistance (to decrease total flow (to get a normal CO) but increase TPR)

76
Q

What happened to arterial pressure in the rat experiment? Why?

A

arterial pressure remained elevated (because it is ONLY dependent on fluid intake line and renal function)

Cardio (24 decks)

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