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Block C - Circulation > Physiology Lecture 5 -- Blood Pressure Control Systems > Flashcards

Physiology Lecture 5 -- Blood Pressure Control Systems Flashcards

1
Q

Equation for pulse pressure

A

Pulse P = Systolic P - Diastolic P

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2
Q

Effect of stroke volume on pulse pressure

A

Increase SV = Increase Pulse P

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3
Q

Effect of arterial compliance on pulse pressure

A

Decrease arterial compliance = increase pulse pressure

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4
Q

3 equations for MAP

A 
MAP = Diastolic P + 1/3 pulse pressure
MAP = CO x TPR
MAP = HR x SV x TPR
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5
Q

Normal MAP

A

100 mm Hg

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6
Q

LVP pressure curve: where is diastolic pressure located?

A

When the intraventricular pressure just exceeds the pressure in the aorta

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7
Q

Equation for perfusion pressure

A

Perfusion P = Arterial BP - Venous P

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8
Q

Equation for flow

A

Flow = Perfusion Pressure / TPR

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9
Q

The most important variable in the CV system and why

A

Systemic arterial blood pressure since this is the driving force that pushes blood through each of the organs

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10
Q

3 ways to regulate blood pressure

A

1) Adjust flow according to need (by R)
2) Keep flow constant despite Pa fluctuations (organs autoregulate)
3) Minimize fluctuations in Pa (neuro-hormonal control)

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11
Q

Normal perfusion pressure

A

90 mm Hg

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12
Q

Normal venous pressure

A

10 mm Hg

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13
Q

Define total peripheral resistance in words

A

The resistance experienced by the left ventricle

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14
Q

2 other ways to refer to TPR

A

Peripheral vascular resistance (PVR)

Systemic vascular resistance (SVR)

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15
Q

Equation of TPR

A

TPR = MAP/CO

NOTE: is actually [MAP - RAP]/CO, but RAP usually 0

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16
Q

How to change MAP

A

Changing any of the 3 variables:
Heart rate
Stroke volume
Total peripheral resistance

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17
Q

What variables of the MAP equations can be measured?

A

MAP and CO

TPR can only be calculate from the other two

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18
Q

Relationship between CO and VR

A

CO = VR (unless there is a leak at some point in the system)

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19
Q

Relationship between RAP and CVP

A

RAP is approximately equal to CVP

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20
Q

Normal CVP

A

5 - 10 mm Hg

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21
Q

What systems regulate blood pressure?

A

Negative feedback systems

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22
Q

Range of BP for the CNS ischemic response

A

Very strong reflex that is a last ditch effort to preserve cerebral circulation = only when Pa falls to a very low level (i.e. <60 mm Hg)

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23
Q

Range of BP for baroreceptors

A

Average daily pressures (bell curve 50 - 225 mm Hg)

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24
Q

Location of baroceptors

A

Carotid sinus

Arch of the aorta

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25
Q

What nerves carry the baroreceptor afferent information?

A

Glosspharyngeal nerve –> Vagus nerve

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26
Q

What part of the CNS does afferent information from baroceptors go to?

A

Brain stem

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27
Q

Relationship between action potentials from the baroreceptors and blood pressure

A

Increased BP = increased number of action potentials

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28
Q

Baroreceptor: receptor type

A

Mechanoreceptor (perceives stretching of carotid artery and aorta)

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29
Q

4 system responses to BP falling

A

Increased heart rate
Increased contraction
Increased arteriolar constriction
Increased venoconstriction

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30
Q

Effect of increasing contractility (that will lead to an increase in BP)

A

Increase SV

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31
Q

Effect of increasing arteriolar constriction (that will lead to an increase in BP)

A

Increase TPR

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32
Q

Effect of increasing venoconstriction (that will lead to an increase in BP)

A

Increased VP and MSFP

Starling’s Law –> Increased EDV = increased SV = increased BP

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33
Q

Controlled variable of the cardiovascular negative feedback control systems

A

MAP

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34
Q

Effect of removing baroreceptors

A

Increase of the lability of MAP (beat-to-beat variability)

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35
Q

Another name for the baroreceptor reflex and why

A

Buffer reflex because it keeps MAP in a narrow range

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36
Q

How can the carotid sinus or its nerves be injured?

A

During neck surgery or by radiation delivered to the neck (i.e. due to a tumor resection)

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37
Q

Name of condition involving labile MAP

A

Baroreflex failure

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38
Q

Medical device for treatment of drug-resistant hypertension

A

Carotid sinus stimulator

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39
Q

Explain how a carotid sinus stimulator works

A

Stimulates the baroreceptors in the carotid sinus by exciting action potentials to fool the cardiovascular centers in the brain into thinking that BP is higher than it actually is, thus inducing a baroreceptor response

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40
Q

What is essential hypertension?

A

Hypertension without a known cause (idiopathic)

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41
Q

Renin function

A

Convert angiotensinogen to angiotensin I

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42
Q

Angiotensin I function

A

Convert into angiotensin II in the lung

43
Q

Angiotensin II functions

A

1) Constrict arterioles
2) Stimulate pituitary gland to release ADH
3) Stimulate adrenal glands to release aldosterone

44
Q

Effect of ADH

A

Decrease water extraction from blood in the kidney = increase blood volume = increased VR = increased SV = increased MAP

45
Q

Effect of Aldosterone

A

Water retention and decrease Na excretion

46
Q

?Where is renin secreted from?

A

Juxtaglomerular cells of the kidneys

47
Q

When is renin released?

A

When the pressure in the renal artery falls

48
Q

Location of angiotensinogen production

A

Liver

49
Q

How is angiotensin I converted to angiotensin II?

A

ACE (located in lungs)

50
Q

4 types of hypertension drugs affecting the renin-angiotensin-aldosterone (RAA) system

A

Aldosterone receptor antagonists
ACE inhibitors
AT-II receptor blockers
Renin inhibitor

51
Q

Effect of aldosterone receptor antagonists

A

Block aldosterone binding = decrease water and salt retention

52
Q

Effect of ACE inhibitor

A

Decrease angiotensin II levels

53
Q

Effect of AT-II receptor blockers

A

Block angiotensin II binding = no vasoconstriction and ADH/aldosterone secretion

54
Q

Effect of renin inhibitor

A

Decrease angiotensin I

55
Q

Relationship between urine volume and arterial pressure (give name to phenomenon)

A

Increase Pa = increase urine V

“Pressure Diuresis”

56
Q

How determine equilibrium value of Pa using a pressure diuresis curve

A

Intersect the water and salt intake curve with the renal output of water and salt (urine volume curve)

57
Q

Difference between the pressure diuresis curve of an isolated kidney versus an intact animal

A

Intact animal slope is MUCH steeper

58
Q

Why is the slope of the pressure diuresis curve in an intact animal steeper than that of an isolated kidney?

A

Contribution of the RAA system and the influence of the sympathetic nervous system on the kidney

59
Q

What is the significance of the steep pressure diuresis slope?

A

The body will accommodate itself to a very wide range of water intakes without much effect on MAP since any change in MAP will be negated by a change in level of diuresis (and thus blood V)

60
Q

Difference between parasympathetic and sympathetic response of the sinoatrial node

A

Parasympathetic (vagal) response = slow down HR; rapid response

Sympathetic = increase HR; slower onset and much slower decay

61
Q

Post-ganglionic neurotransmitter of parasympathetic system to sinoatrial node

A

Muscarinic acetylcholine

62
Q

Post-ganglionic neurotransmitter of sympathetic system to sinoatrial node

A

Norepinephrine

63
Q

Reason for difference in response rates of sinoatrial node due to parasympathetic vs. sympathetic stimulation

A

Parasympathetic is fast because ACh binds to a receptor that is directly coupled to an ionic channel

Sympathetic is slower because NE binds to a receptor which then instigates a second-messenger intracellular cascade

64
Q

Reason for difference in decay rates of sinoatrial node due to parasympathetic vs. sympathetic stimulation

A

Parasympathetic is fast because ACh in cleft is rapidly hydrolyzed by cholinesterase

Sympathetic NE reuptake from synaptic cleft is slower

65
Q

Define sinus bradychardia

A

<60 beats per minute HR

66
Q

Effect of atropine

A

Muscarinic antagonist = block effect of vagal stimulation to increase HR

67
Q

Effect of cholinesterase inhibitors

A

Decrease heart rate

68
Q

Name of effect of an agent that increases heart rate

A

Positive chronotropic effect

69
Q

Name of effect of an agent that decreases heart rate

A

Negative chronotropic effect

70
Q

What ionic channel are muscarinic ACh receptors coupled to at the sinoatrial node?

A

Potassium channels (hyperpolarizes membrane when open)

71
Q

Type of receptor at sinoatrial node for sympathetic stimulation

A

B1-adrenergic receptor

72
Q

Effect of propranolol

A

B-adrenergic blocker = slow down HR

73
Q

Effect of isproterenol

A

B-adrenergic agonist/sympathomimetic agent = tend to increase HR

74
Q

Chemical effect of sympathetic system

A

Release of NE from nerve terminals in the heart

Increase in circulating levels of catecholamines (epinephrine and NE)

75
Q

Use of adrenaline administration in a cardiac arrest

A

Increase the rate of a subsidiary pacemaker that has taken over the pacing of the heart, or provoke the emergence of such a pacemaker

76
Q

Define vagal tone

A

Resting parasympathetic tone

77
Q

Compare vagal tone to resting sympathetic tone in sinoatrial node

A

Vagal tone > resting sympathetic tone

78
Q

How can you tell that the vagal tone greater than the resting sympathetic tone in the sinoatrial node?

A

Simultaneous blockade of both ANS branches results in a heart rate (“intrinsic heart rate”) that is typically about 100 bpm (higher than resting)

79
Q

Effect of massaging carotid sinus regularly and in hypersensitive individuals

A

Stimulate baroreceptor reflex

In some hypersensitive individuals, may cause sinus arrest and syncope

80
Q

Major physiologic controller of cardiac contractility

A

Sympathetic nervous system

81
Q

Location of B1-receptors for sympathetic control of contractility

A

Ventricular myocytes

82
Q

Effect of sympathomimetic agents

A

Increase SV, CO, BP

83
Q

Poisseuille’s Law

A

R ~ 1/r^4

84
Q

Define resting tone of arterioles

A

Usually partially constricted

85
Q

Purpose of arteriolar resting tone

A

Allows them to either increase or decrease their diameter to either increase or decrease the resistance to flow, thus increasing or decreasing blood flow (according to Poisseuille’s Law)

86
Q

Two components of resting tone of arterioles

A

Basal tone

Neurogenic tone

87
Q

Define basal tone

A

A component intrinsic to the smooth muscle surrounding arterioles

88
Q

Define neurogenic tone

A

An additional component due to the resting activity of the ANS

89
Q

What determines the overall sympathetic tone

A

Pressor and depressor centres in the brainstem

90
Q

Neurotransmitter released post-ganglionically to sympathetically control blood vessels

A

Norepinephrine

91
Q

Sympathetic receptors on blood vessels

A

alpha and beta adrenergic receptors

92
Q

Effect of sympathetic nerve stimulation on blood vessels

A

a1-adrenergic effect –> arteriolar constriction –> increased resistance + decreased blood flow

a1-adrenergic effect –> venule constriction –> decreased blood volume present in tissue

93
Q

Define shock

A

A situation in which tissue perfusion is inadequate to supply the metabolic demands of the tissue

94
Q

Important factor in shock

A

Constriction of both arterioles and veins

95
Q

Effect of increase arteriolar resistance in shock

A

Maintain the mean systemic arterial blood pressure (since MAP = CO x TPR)

96
Q

Effect of venoconstriction in shock

A

Shunts blodo out of organs where it is not needed (i.e. skin, skeletal muscle, gut) = help increase mean circulatory pressure, VR, CO = preserve Pa

97
Q

Receptor type on vessels in organs

A

B2-receptors

98
Q

Effect of adrenal-originated epinephrine binding to B2-receptors of vessels in organs

A

Works towards producing dilation

99
Q

Effect of parasympathetic innervation on blood vessels in organs

A

Vasodilation

100
Q

Effect of sympathetic stimulation on adrenal medulla

A

Release of epinephrine and norepinephrine

101
Q

When do circulating catecholamines have a significant effect?

A

Usually less important under normal circumstances. Become significant in patients with transplanted hearts, who have a surgically induced autonomic denervation = increased sensitivity to circulating catecholamines (denervation hypersensitivity) –> good cardiac response to exercise

102
Q

What is pheochromocytoma

A

Tumor of adrenal medulla

103
Q

Effect of pheochromocytoma

A

Secretion of abnormally large amounts of catecholamines; often have hypertension

Block C - Circulation (26 decks)

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