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Cardiovascular > Physiology 4+5 > Flashcards

Physiology 4+5 Flashcards

1
Q

What is blood pressure?

A

Outward hydrostatic pressure exerted by blood on blood vessel walls

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2
Q

What is systolic arterial blood pressure?

A

Pressure exerted by blood on walls of the aorta and systemic arteries when the heart contracts

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3
Q

What is normal value for systolic arterial blood pressure?

A

Should not reach or exceed 140 mm Hg under resting conditions

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4
Q

What is diastolic arterial blood pressure?

A

Pressure exerted by blood on walls of the aorta and systemic arteries when the heart relaxes

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5
Q

What is normal value for diastolic arterial blood pressure?

A

Should not reach or exceed 90 mm Hg under resting conditions

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6
Q

What is hypertension? (2)

A
  • Clinic blood pressure of 140/90 mmHg or higher

* Day time average of 135/85 mmHg or higher

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7
Q

What is pulse pressure?

A

Difference between systolic and diastolic blood pressures

e.g. 120 - 80 = 40 mm Hg

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8
Q

What are normal values for pulse pressure?

A

Between 30 and 50 mmHg

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9
Q

What is a sphygmomanometer used for?

A

Indirect measurement of arterial blood pressure

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10
Q

What is the normal flow of blood in an artery?

A

Laminar

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11
Q

Is laminar flow audible through stethoscope?

A

No, no sound heard in normal patent artery

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12
Q

What will happen if external pressure (e.g. cuff) exceeds systolic blood pressure?

A

Will occlude artery and no sound is heart through stethoscope

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13
Q

When is arterial blood flow heard through a stethoscope?

A
  • When external pressure kept between systolic and diastolic pressure, flow will become turbulent when blood pressure exceeds cuff pressure
  • Turbulent flow is audible through stethoscope
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14
Q

What is first korotkoff sound?

A

Heard at peak systolic pressure (when blood pressure first exceeds cuff pressure)

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15
Q

What are korotkoff sounds 2 + 3?

A

Intermittent sounds due to turbulent spurts of flow

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16
Q

What is 4th korotkoff sound?

A

Heard at minimum/diastolic pressure (muffled, muted sound)

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17
Q

What is 5th Korotkoff “sound”?

A

No sound is heard because of smooth laminar flow

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18
Q

What point is diastolic pressure recorded? Why?

A
  • 5th Korotkoff sound (point at which sound disappears)

* More reproducible

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19
Q

What drives blood around systemic circulation?

A

Pressure gradient between aorta and right atrium

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20
Q

What is the main driving force for blood flow?

A

Mean arterial pressure (MAP) because RA pressure is close to zero

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21
Q

What is the equation for pressure gradient between RA and aorta?

A

Pressure gradient = Mean Arterial Pressure (MAP) - Central Venous (right atrial) Pressure (CVP)

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22
Q

What is Mean Arterial blood Pressure?

A

Average arterial blood pressure during a single cardiac cycle

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23
Q

What is the equation for Mean Arterial blood Pressure using systolic diastolic pressures?

A

MAP = [(2 x diastolic pressure) + systolic pressure] / 3

OR

MAP = DBP + 1/3 pulse pressure

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24
Q

What is normal arterial blood pressure?

A

<140 systolic

<90 diastolic

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25
Q

What is the normal range of Mean Arterial blood Pressure?

A

70 - 105 mm Hg

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26
Q

How high does MAP have to be to perfuse coronary arteries, brain and kidneys?

A

At least 60 mm HG

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27
Q

Why must MAP be regulated within narrow ranges? (2)

A

To ensure

  • Pressure is high enough to perfuse brain, heart and kidneys
  • Pressure is not too high to damage blood vessels or put extra strain on heart
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28
Q

What is the equation for MAP without using systolic and diastolic blood pressures?

A

MAP = Cardiac output (CO) x Systemic Vascular Resistance (SVR)

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29
Q

Equation for cardiac output?

A

CO = HR x SV

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30
Q

What is systemic vascular resistance (total peripheral resistance)?

A

Sum of resistance of all vasculature in systemic circulation

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31
Q

In systemic vascular resistance, what are the major resistance vessels?

A

Arterioles

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32
Q

What is the effect of parasympathetic stimulation of the heart?

A

Decrease in heart rate, which results in decreased cardiac output, resulting in decreased MAP

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33
Q

What is the effect of sympathetic stimulation of the heart? (2)

A
  • Increase in heart rate, resulting in increased cardiac output and MAP
  • Increase in force of contraction which increases SV, leading to increased CO and MAP
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34
Q

What is the effect of sympathetic stimulation of arterioles?

A

Vasoconstriction, increasing SVR, resulting in increased MAP

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35
Q

What is the effect of sympathetic stimulation of veins?

A

Vasoconstriction, causing increased venous return (EDV), resulting in increased SV, CO and MAP

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36
Q

What is the baroreceptor reflex?

A

Short-term regulation of Mean Arterial blood Pressure

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37
Q

What are the components of baroreceptor reflex? (3)

A
  • Pressure sensors - baroreceptors
  • Control centre - medulla
  • Effectors - Heart (HR, SV) and blood vessels (SVR)
38
Q

How does baroreceptor reflex regulate MAP?

A

Negative feedback

39
Q

What are the 2 types of baroreceptors? How do signals from them reach the medulla?

A
  • Carotid baroreceptors - glossopharyngeal nerve (CN IX)

* Aortic baroreceptor - vagus nerve (CN X)

40
Q

Where are aortic baroreceptors found? Carotid?

A
  • Aortic arch

* Carotid sinus

41
Q

What are baroreceptors?

A

Stretch receptors

42
Q

What are baroreceptor responses to increased BP? (4)

A
  • Increase in carotid and aortic baroreceptor firing
  • Increased vagal efferent activity
  • Decrease in sympathetic efferent activity
  • Decrease in sympathetic vasoconstrictor activity
43
Q

What are baroreceptor responses to decreased BP? (4)

A
  • Decrease in carotid and aortic baroreceptor firing
  • Decreased vagal efferent activity
  • Increase in sympathetic efferent activity
  • Increase in sympathetic vasoconstrictor activity
44
Q

What happens when a normal person suddenly stands up from lying position? (3)

A
  • Venous return to heart decreases (effect of gravity)
  • MAP decreases
  • Baroreceptor firing rate decreases
45
Q

How do baroreceptors prevent postural hypotension?(3)

A
  • Vagal tone to heart decreases and sympathetic tone increases - increased HR and SV
  • Sympathetic constrictor tone to arterioles increases - increases SVR
  • Sympathetic constrictor tone to veins increases - increases venous return and SV
46
Q

What is the result of the baroreceptor response to postural hypotension? (4)

A
  • Rapid correction of fall in MAP
  • HR increases
  • SV increases
  • SVR increases
47
Q

What does the increase in SVR result in when healthy people stand from lying position?

A

Slight increase in DBP

48
Q

What does postural hypotension result from?

A

Failure of baroreceptor responses to gravitational shifts in blood when moving from horizontal to vertical position

49
Q

What is baroreceptor response to increased blood pressure?

A
  • Baroreceptor firing rate increases
  • Vagal tone to heart increases and sympathetic tone decreases - decreased HR and SV
  • Sympathetic constrictor tone to arterioles decreases - decreases SVR
  • Sympathetic constrictor tone to veins decreases - decreases venous return and SV
50
Q

What happens to baroreceptor firing if blood pressure is sustained? Therefore, what information cannot be provided by baroreceptors?

A
  • Baroreceptor firing decreases

* Cannot supply info about prevailing steady state blood pressure

51
Q

What is the only thing baroreceptors respond to?

A

Acute changes in blood pressure

52
Q

If baroreceptor firing decreases if high blood pressure is sustained, what is MAP controlled by in the longer term?

A

Blood volume

53
Q

How can blood volume (and thus MAP) be controlled?

A

By controlling extracellular fluid volume

54
Q

What percentage of body weight in a 70kg man is water?

A

60% (~42 L)

55
Q

What is the equation for total body fluid?

A

Total body fluid = intracellular fluid (2/3) + extracellular fluid (1/3)

56
Q

What proportion of total body fluid is intracellular fluid? Extracellular fluid?

A
  • 2/3rds

* 1/3rd

57
Q

What is the equation for ECF volume?

A

ECFV = plasma volume (PV) + interstitial fluid volume (IFV)

58
Q

What is interstitial fluid?

A

Fluid that bathes the cells and acts as go-between for blood and body cells

59
Q

What happens if plasma volume falls?

A

Compensatory mechanisms shift fluid from interstitial compartment to plasma compartment

60
Q

How is PV and hence ready state blood volume and MAP controlled?

A

Controlling ECFV

61
Q

What 2 main factors affect extracellular fluid volume?

A
  • Water excess or deficit

* Na+ excess or deficit

62
Q

How do hormones act as effectors to regulate water ECFV?

A

Regulate water and sat balance in the body

63
Q

What is the water and salt balance in healthy people?

A

Stable water and salt balance where water input = water output

64
Q

What hormones regulate ECFV? (3)

A
  • The Renin-Angiotensin- Aldosterone System - RAAS
  • Natriuretic Peptides – NPs
  • Antidiuretic Hormone (Arginine Vasopressin) - ADH
65
Q

What is the role of the Renin-Angiotensin-Aldosterone System?

A

Regulation of plasma volume and SVR (hence regulation of MAP)

66
Q

What are the components of the RAA system? (3)

A
  • Renin
  • Angiotensin
  • Aldosterone
67
Q

Explain how RAAS increases blood pressure (MAP)

A
  • Renin released from kidneys and stimulates formation of angiotensin I in the blood from angiotensinogen
  • Angiotensin I converted to angiotensin II by Angiotensin converting enzyme - ACE
  • Angiotensin II stimulates release of Aldosterone from adrenal cortex and causes systemic vasoconstriction (increases SVR) - also stimulates thirst and ADH release (increases plasma volume)
  • Aldosterone acts on kidneys to increase sodium and water retention – increases plasma volume
68
Q

What is angiotensinogen produced by? ACE?

A
  • Angiotensinogen - liver

* ACE - pulmonary vascular endothelium

69
Q

What is aldosterone?

A

Steroid hormone

70
Q

What is the rate limiting step for RAAS?

A

Renin secretion

71
Q

What is RAAS regulated by? What are these mechanisms? (3)

A

Mechanisms that stimulate release of renin from juxtaglomerular apparatus in the kidney

  • Renal artery hypotension
  • Stimulation of renal sympathetic nerves
  • Decreased [Na+] in renal tubular fluid
72
Q

What causes renal artery hypotension? What detects decreased [Na+] in renal tubular fluid?

A
  • Systemic hypotension (decreased blood pressure)

* Decreased [Na+] sensed by macula densa (specialised cells in kidney tubules)

73
Q

Wha are natriuretic peptides (NPs)?

A

Peptide hormones synthesised by heart (also brain and other organs)

74
Q

When are NPs released? (2)

A

In response to cardiac distension or neurohormonal stimuli

75
Q

What is the role of NPs? (3)

A
  • Cause excretion of salt and water in the kidneys so reduce blood volume and blood pressure
  • Decrease renin release, decrease BP
  • Vasodilators, decrease SVR and BP
76
Q

What do NPs counter-regulate?

A

Renin-Angiotensin-Aldosterone System

77
Q

What natriuretic peptides are released by the heart? (2)

A
  • Atrial Natriuretic peptide (ANP)

* Brain-type Natriuretic Peptide (BNP)

78
Q

What is ANP?

A

28 amino acid peptide produced and stored by atrial myocytes

79
Q

When is ANP released?

A

In response to atrial distension (e.g. in hypervolemia)

80
Q

What is BNP?

A

32 amino acid peptide synthesised by heart, brain and other organs

81
Q

How is BNP produced? (3)

A
  • First synthesised as prepro-BNP
  • Cleaved to pro-BNP (108 amino acids)
  • Cleaved to BNP (32 amino acids)
82
Q

What can be measured in patients with suspected heart failure? (2)

A
  • Serum BNP

* NT-pro-BNP (76 amino acids)

83
Q

What is antidiuretic hormone (ADH)?

A

Peptide hormone derived from pre-hormone precursor synthesised by hypothalamus and stored in posterior pituitary

84
Q

What is the other name for ADH?

A

Vasopressin

85
Q

What is ADH secretion stimulated by? (2)

A
  • Reduced ECF volume

* Increased ECF (plasma) osmolality

86
Q

What is does plasma osmolality reflect?

A

Solute-water balance

87
Q

What is plasma osmolality monitored by?

A

Osmoreceptors in brain close to hypothalamus

88
Q

What does ADH do?

A
  • Acts in kidney tubules to increase reabsortion of water (concentrates urine) - increases extracellular and plasma volume and so cardiac output and BP
  • Vasoconstriction - increases SVR and BP
89
Q

When is vasoconstrictive effect on ADH important?

A

Hypovalaemic shock (e.g. haemorrhage)

90
Q

What is short-term regulation of MAP controlled by? Long term?

A
  • Short term = baroreceptor reflex

* Long term = controlling blood volume by hormones

91
Q

What is the purpose of ADH?

A

Helps body deal with fluid loads/deficits

Cardiovascular (28 decks)

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