Physiology Lecture 5 -- Blood Pressure Control Systems Flashcards Preview

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Flashcards in Physiology Lecture 5 -- Blood Pressure Control Systems Deck (103):
1

Equation for pulse pressure

Pulse P = Systolic P - Diastolic P

2

Effect of stroke volume on pulse pressure

Increase SV = Increase Pulse P

3

Effect of arterial compliance on pulse pressure

Decrease arterial compliance = increase pulse pressure

4

3 equations for MAP

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

5

Normal MAP

100 mm Hg

6

LVP pressure curve: where is diastolic pressure located?

When the intraventricular pressure just exceeds the pressure in the aorta

7

Equation for perfusion pressure

Perfusion P = Arterial BP - Venous P

8

Equation for flow

Flow = Perfusion Pressure / TPR

9

The most important variable in the CV system and why

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

10

3 ways to regulate blood pressure

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)

11

Normal perfusion pressure

90 mm Hg

12

Normal venous pressure

10 mm Hg

13

Define total peripheral resistance in words

The resistance experienced by the left ventricle

14

2 other ways to refer to TPR

Peripheral vascular resistance (PVR)
Systemic vascular resistance (SVR)

15

Equation of TPR

TPR = MAP/CO

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

16

How to change MAP

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

17

What variables of the MAP equations can be measured?

MAP and CO
(TPR can only be calculate from the other two)

18

Relationship between CO and VR

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

19

Relationship between RAP and CVP

RAP is approximately equal to CVP

20

Normal CVP

5 - 10 mm Hg

21

What systems regulate blood pressure?

Negative feedback systems

22

Range of BP for the CNS ischemic response

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)

23

Range of BP for baroreceptors

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

24

Location of baroceptors

Carotid sinus
Arch of the aorta

25

What nerves carry the baroreceptor afferent information?

Glosspharyngeal nerve --> Vagus nerve

26

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

Brain stem

27

Relationship between action potentials from the baroreceptors and blood pressure

Increased BP = increased number of action potentials

28

Baroreceptor: receptor type

Mechanoreceptor (perceives stretching of carotid artery and aorta)

29

4 system responses to BP falling

Increased heart rate
Increased contraction
Increased arteriolar constriction
Increased venoconstriction

30

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

Increase SV

31

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

Increase TPR

32

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

Increased VP and MSFP
Starling's Law --> Increased EDV = increased SV = increased BP

33

Controlled variable of the cardiovascular negative feedback control systems

MAP

34

Effect of removing baroreceptors

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

35

Another name for the baroreceptor reflex and why

Buffer reflex because it keeps MAP in a narrow range

36

How can the carotid sinus or its nerves be injured?

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

37

Name of condition involving labile MAP

Baroreflex failure

38

Medical device for treatment of drug-resistant hypertension

Carotid sinus stimulator

39

Explain how a carotid sinus stimulator works

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

40

What is essential hypertension?

Hypertension without a known cause (idiopathic)

41

Renin function

Convert angiotensinogen to angiotensin I

42

Angiotensin I function

Convert into angiotensin II in the lung

43

Angiotensin II functions

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

44

Effect of ADH

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

45

Effect of Aldosterone

Water retention and decrease Na excretion

46

?Where is renin secreted from?

Juxtaglomerular cells of the kidneys

47

When is renin released?

When the pressure in the renal artery falls

48

Location of angiotensinogen production

Liver

49

How is angiotensin I converted to angiotensin II?

ACE (located in lungs)

50

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

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

51

Effect of aldosterone receptor antagonists

Block aldosterone binding = decrease water and salt retention

52

Effect of ACE inhibitor

Decrease angiotensin II levels

53

Effect of AT-II receptor blockers

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

54

Effect of renin inhibitor

Decrease angiotensin I

55

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

Increase Pa = increase urine V
"Pressure Diuresis"

56

How determine equilibrium value of Pa using a pressure diuresis curve

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

57

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

Intact animal slope is MUCH steeper

58

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

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

59

What is the significance of the steep pressure diuresis slope?

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

Difference between parasympathetic and sympathetic response of the sinoatrial node

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

Sympathetic = increase HR; slower onset and much slower decay

61

Post-ganglionic neurotransmitter of parasympathetic system to sinoatrial node

Muscarinic acetylcholine

62

Post-ganglionic neurotransmitter of sympathetic system to sinoatrial node

Norepinephrine

63

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

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

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

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

Sympathetic NE reuptake from synaptic cleft is slower

65

Define sinus bradychardia

<60 beats per minute HR

66

Effect of atropine

Muscarinic antagonist = block effect of vagal stimulation to increase HR

67

Effect of cholinesterase inhibitors

Decrease heart rate

68

Name of effect of an agent that increases heart rate

Positive chronotropic effect

69

Name of effect of an agent that decreases heart rate

Negative chronotropic effect

70

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

Potassium channels (hyperpolarizes membrane when open)

71

Type of receptor at sinoatrial node for sympathetic stimulation

B1-adrenergic receptor

72

Effect of propranolol

B-adrenergic blocker = slow down HR

73

Effect of isproterenol

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

74

Chemical effect of sympathetic system

Release of NE from nerve terminals in the heart
Increase in circulating levels of catecholamines (epinephrine and NE)

75

Use of adrenaline administration in a cardiac arrest

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

Define vagal tone

Resting parasympathetic tone

77

Compare vagal tone to resting sympathetic tone in sinoatrial node

Vagal tone > resting sympathetic tone

78

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

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

79

Effect of massaging carotid sinus regularly and in hypersensitive individuals

Stimulate baroreceptor reflex
In some hypersensitive individuals, may cause sinus arrest and syncope

80

Major physiologic controller of cardiac contractility

Sympathetic nervous system

81

Location of B1-receptors for sympathetic control of contractility

Ventricular myocytes

82

Effect of sympathomimetic agents

Increase SV, CO, BP

83

Poisseuille's Law

R ~ 1/r^4

84

Define resting tone of arterioles

Usually partially constricted

85

Purpose of arteriolar resting tone

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

Two components of resting tone of arterioles

Basal tone
Neurogenic tone

87

Define basal tone

A component intrinsic to the smooth muscle surrounding arterioles

88

Define neurogenic tone

An additional component due to the resting activity of the ANS

89

What determines the overall sympathetic tone

Pressor and depressor centres in the brainstem

90

Neurotransmitter released post-ganglionically to sympathetically control blood vessels

Norepinephrine

91

Sympathetic receptors on blood vessels

alpha and beta adrenergic receptors

92

Effect of sympathetic nerve stimulation on blood vessels

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

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

93

Define shock

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

94

Important factor in shock

Constriction of both arterioles and veins

95

Effect of increase arteriolar resistance in shock

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

96

Effect of venoconstriction in shock

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

Receptor type on vessels in organs

B2-receptors

98

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

Works towards producing dilation

99

Effect of parasympathetic innervation on blood vessels in organs

Vasodilation

100

Effect of sympathetic stimulation on adrenal medulla

Release of epinephrine and norepinephrine

101

When do circulating catecholamines have a significant effect?

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

What is pheochromocytoma

Tumor of adrenal medulla

103

Effect of pheochromocytoma

Secretion of abnormally large amounts of catecholamines; often have hypertension