Short Term BP Control- Exam 1 Flashcards

1
Q

What does control of blood flow to local tissue depend on?

A

Maintaining a constant pressure drop across the tissue

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2
Q

What two components are involved in maintaing a constant pressure drop across the tissue?

A

Constant mean arterial pressure

Constant central venous pressure

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3
Q

What are some mechanisms for controlling blood pressure?

A
Aldosterone
Baroreceptors
Capillary fluid shift
Chemoreceptors
CNS ischemic response
Renal-blood volume pressure control
Renin-angiotensin-vasoconstriction
Stress relaxation of vasculature
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4
Q

What type of mechanism is aldosterone?

A

Hormonal

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5
Q

What type of mechanism is baroreceptors?

A

Nervous

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6
Q

What type of mechanism is capillary fluid shift?

A

Physiologic

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7
Q

What type of mechanism are chemoreceptors?

A

Nervous

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8
Q

What type of mechanism is CNS ischemic response?

A

Nervous

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9
Q

What type of mechanism is Renal-blood volume pressure control?

A

Kidneys

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10
Q

What type of mechanism is renin-angiotensin-vasoconstriction?

A

Hormonal

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11
Q

What type of mechanism is stress relaxation of the vasculature?

A

Physiologic

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12
Q

Which blood pressure control mechanisms are activated within seconds?

A
  1. Baroreceptors
  2. Chemoreceptors
  3. CNS ischemic response
  4. Stress relaxation
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13
Q

Which blood pressure control mechanisms are activated within minutes?

A
  1. Capillary

6. Fluid Shift

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14
Q

Which blood pressure control mechanisms are activated within hours?

A
  1. Aldosterone

8. Renal-blood volume pressure control

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15
Q

What blood pressure control mechanisms has the greatest ability to create change?

A

Renal-blood volume pressure control

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16
Q

CNS ischemic response mechanism

Range and Peak

A

0 to 75 mmHg

Peak: 0 mmHg

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17
Q

Chemoreceptor response mechanism

Range and Peak

A

20- 110 mmHg

Peak: 60 mmHg

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18
Q

Renin-Angiotensin vasoconstriction

Range and Peak

A

35- 115 mmHg

Peak: 75 mmHg

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19
Q

Baroreceptor response mechanism

Range and Peak

A

50- 225 mmHg

Peak: 115 mmHg

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20
Q

Parasympathetic Nervous Control

A

Regulation of HR
Small affect on contractility
Minimal regulation of circulation

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21
Q

Sympathetic Nervous Control

A

Regulation of circulation

Regulation of contractility

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22
Q

Vasomotor Center

A

Parasympathetic impulses via spinal cord & peripheral sympathetic nerves to all arteries, arterioles, veins

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23
Q

Where do sympathetic nerve fibers exit spinal cord?

A

Via all thoracic spinal nerves & first two lumbar spinal nerves

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24
Q

Where do sympathetic nerve fibers enter the sympathetic chains?

A

Either side of spinal cord

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25
Q

What are the two routes sympathetic nerve fibers go to circulation?

A
  1. Specific sympathetic nerves to vasculature of internal viscera & heart
  2. Peripheral portions of spinal nerves to peripheral vasculature
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26
Q

What tissue receive sympathetic innervation?

A

Arteries, arterioles, venules, veins of most tissues receive sympathetic innervation; some metarterioles & precapillary sphincters of mesenteric blood vessels innervated

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27
Q

Are most sympathetic nerve fibers vasconstrictor or vasodilator?

A

Vasoconstrictor (few vasodilator)

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28
Q

Where is vasoconstriction potent?

A

Kidneys, intestines, spleen, kidney

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29
Q

Where is vasoconstriction weaker?

A

Skeletal muscle and brain

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30
Q

When sympathetic impulses are sent to blood vessels, impulses also go where?

A

Adrenal medulla resulting in secretion of epinephrine and norepinephrine

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31
Q

What is able to change resistance/change flow through each tissue?

A

Small arteries/arterioles

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32
Q

What is able to change volume held in vessels thus changing venous return?

A

Veins

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33
Q

Where is the vasomotor center located?

A

Bilateral

Reticular substance: medulla, lower third of pons

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34
Q

Parasympathetic impulses are via what nerve?

A

Vagus nerve

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35
Q

Sympathetic impulses are via what structures?

A

Spinal cord & peripheral sympathetic nerves to all arteries, arterioles, veins

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36
Q

What does the vasomotor center do?

A

Regulates amount of vascular constriction and cardiac activity (i.e. heart rate and contractility)

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37
Q

3 components of the vasomotor center

A

Vasoconstrictor area
Vasodilator area
Sensory area

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38
Q

Where is the vasoconstrictor area?

A

Bilateral; anterolateral part of upper medulla

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39
Q

What does the vasoconstrictor area of the vasomotor center do?

A

Sends fibers to all areas of spinal cord; fibers excite vasoconstrictor neurons of sympathetic system

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40
Q

Where is the vasodilator area?

A

Bilateral; anterolateral part of the lower medulla

41
Q

What does the vasodilator area of the vasomotor center do?

A

Sends fibers to vasoconstrictor area; fibers inhibit activity of vasoconstrictor area

42
Q

Where is the sensory area of the vasomotor center?

A

Bilateral in tractus solitarus in posterolateral part of medulla & lower pons

43
Q

What does the sensory area of the vasomotor center do?

A

Sends output to vasoconstrictor and vasodilator areas; allows control of vasoconstrictor/vasodilator areas based on input from circulatory system

44
Q

Where does the sensory area receive sensory signals from?

A

Circulatory system vai vagus and & glossopharyngeal nerves

45
Q

What do lateral portions of the vasomotor center do?

A

Send excitatory impulses via sympathetic nerves to the heart [ increased HR and contractility ]

46
Q

What do medial portions of the vasomotor center do?

A

Sends impulses to dorsal motor nuclei of vagus nerves which sends parasympathetic impulses to heart [decrease heart rate and some decrease in contractility ]

47
Q

Normally, what happens when the vasoconstriction center is stimulated?

A

Increased cardiac activity

48
Q

Normally, what happens when the vasoconstriction center is inhibited?

A

Decreased cardiac activity

49
Q

Amount of vascular constriction is proportional to what?

A

Number of impulses set out by vasoconstrictor area

more impulses, increased constriction

50
Q

Normally, vasoconstrictor center sends how many impulses per second?

A

1.5 to 2.0 impulses per second

Results in partial constriction (normal vasomotor tone)

51
Q

Total spinal anesthesia blocks what?

A

Transmission of sympathetic impulses from spine to periphery; stops transmission of impulses from vasoconstrictor center

52
Q

CNS Control of vasomotor center consists of what 3 areas of the brain?

A

pons, mesencephalon, diencephalon

53
Q

Lateral/superior portions of CNS_________vasomotor center.

A

Excite

54
Q

Medial/Inferior portions of CNS ________ vasomotor.

A

Inhibit

55
Q

What part of the hypothalamus excite the vasomotor center?

A

Posterolateral portions

56
Q

Stimulation of the anterior portion of the hypothalamus results in what?

A

Mild excitation or inhibition; depends on which part of the anterior portion is stimulated

57
Q

What part of the cerebral cortex stimulates the vasomotor center?

A

Motor cortex; multiple areas can excite or inhibit depending on specific area stimulated

58
Q

Nervous control can double blood pressure within how many seconds?

A

5 to 10 seconds

59
Q

Stimulation of nervous control results in what?

A

Stimulation vasoconstrictor area (sympathetic)
Stimulation increases cardiac activity (sympathetic)
Inhibit parasympathetic vagal signals to heart

60
Q

What is the physiologic response of stimulating nervous control?

A

Constriction of most arterioles of systemic circulation
Strong constriction of veins/larger arteries
Increased cardiac performance

61
Q

Where are baroreceptors?

A

Walls of most large arteries of the thorax and neck
Many in wall of internal carotid arteries above the bifurcation (carotid bodies in carotid sinus) and in wall of aortic arch

62
Q

How do carotid baroreceptors send impulses?

A

Hering’s nerves to glosspharyngeal nerves which carry inpulses to sensory area of vasomotor center

63
Q

Where do aortic baroreceptors send impulses to?

A

Vasomotor center via vagus nerves

64
Q

At what pressures are carotid baroreceptors stimulated?

A

50 to 60 mmHg

65
Q

At what pressures are aortic baroreceptors stimulated?

A

80 to 90 mmHg

66
Q

When do receptors produce a greater response?

A

When pressure changing (could be twice the response)

67
Q

Baroreceptors stimulate changes in __________ and __________.

A

Vascular resistance; cardiac performance

68
Q

What would happen if the baroreceptors were denervated?

A

Huge variations in blood pressure moment to moment due to buffer function of the baroreceptors

69
Q

What would happen to baroreceptors if pressure changes and remains at a new level?

A

Baroreceptors will reset to new level

70
Q

How long does it take for baroreceptors to reset to a new level?

A

1 to 2 days; happens no matter which way the pressure changes

71
Q

What are the function of baroreceptors, long-term?

A

May mediate changes in sympathetic tone to the kidneys

72
Q

How do baroreceptors mediate changes in sympathetic tone to the kidneys?

A

Increased pressure
Mediate decreased sympathetic tone to kidneys
Promotes increased sodium and water excretion

73
Q

What are chemoreceptors sensitive to?

A

Lack of oxygen and excess carbon dioxide and hydrogen ions

74
Q

Where are chemoreceptor located?

A
Carotid bodies (2) in bifurcation of each common carotid artery
Artery bodies (1 to 3) adjacent to aorta
75
Q

Chemoreceptors excite which nerve fibers?

A

Nerve fibers that pass through Hering’s nerves and vagus nerves to vasomotor center

76
Q

What ensures good supply of blood to each body?

A

Nutrient artery

77
Q

Decreased flow through nutrient artery results in what?

A

Increased impulse generation; results in excitation of vasomotor center

78
Q

When do chemoreceptors kick in with increased impulses? (What pressure)

A

excite vasomotor center, when pressure falls below 80 mmHg

79
Q

What is the direct response of vasomotor center to ischemia?

A

CNS Ischemic Response

80
Q

What is the CNS ischemic response mediated by?

A

Vasoconstrictor and cardioaccelerator portions in response to increasing levels of carbon dioxide (may include other substance such as lactic acid)

81
Q

What can the CNS ischemic response increased BP to?

A

250 mmHg (very powerful)

82
Q

What does the CNS ischemic response do to flow to less important tissues?

A

Completely cuts off flow to less important tissues (kidneys)

83
Q

At what pressure is the CNS ischemic response initiated?

A

When BP falls below 60 mmHg

84
Q

When does the CNS ischemic response reach greatest level of stimulation?

A

15 to 20 mmHg

85
Q

What are atrial/pulmonary stretch receptors?

A

Low-pressure receptors- similar to baroreceptors of large systemic arteries; minimize changes in arterial pressure due to sudden changes in blood volume

86
Q

Where are atrial/pulmonary stretch receptors located?

A

Walls of atria and pulmonary arteries

87
Q

What happens if you infuse 300 mls of blood into dog?

A

Only 15 mmHg increase in BP if all receptors intact
40 mmHg increase in BP if baroreceptors deactivated
100 mmHg increase in both baroreceptors and low-pressure receptors deactivated

88
Q

Bainbridge Reflex

A

Increase in atrial pressure causes an increase in heart rate; part of hte response due to direct stretch of the sinus node (can increase HR up to 15 %) an additional 40 to 60% increase caused by Bainbridge reflex

89
Q

What does increased atrial stretch result in? (Bainbridge Reflex)

A

Increased impulses via vagus nerve to medulla

90
Q

What do increased impulses to medulla result in? (Bainbridge Reflex)

A

Increased sympathetic impulses to heart increasing HR and contractility

91
Q

What are respiratory waves?

A

Change in arterial pressure of 4 to 6 mmHg during each inspiration/expiration cycle

92
Q

Inspiration

A

Expansion of blood vessels decreases venous return which decreases cardiac output and arterial pressure

93
Q

Expiration

A

Constriction of blood vessels increases venous return which increases cardiac output and arterial pressure

94
Q

Pressure changes in thoracic vessels can stimulate what?

A

Vascular and atrial stretch receptors

95
Q

Vasomotor Waves

A

Possible to see slow oscillation in arterial pressure waveform of 10 to 40 mmHg

96
Q

What is the cycle duration for vasomotor waves?

A

7 to 10 seconds

97
Q

What causes vasomotor waves (cycle of pressure oscillations)?

A

Increased pressure increase baroreceptor response (dilate)

Decrease pressure decreases baroreceptor response (constricts)

98
Q

Increased atrial stretch has what kidney reflex?

A
  1. Signals to hypothalamus to produce less ADH

2. Reflex dilation afferent arterioles of kidney