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Cardiovascular > Control of Blood Pressure > Flashcards

Control of Blood Pressure Flashcards

1
Q

What is Blood Pressure?

A

The outwards (hydrostatic) pressure exerted by the blood on blood vessel walls

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2
Q

What is systemic systolic arterial blood pressure?

A

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

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3
Q

What is systemic diastolic arterial blood pressure?

A

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

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4
Q

What is normal blood pressure?

A

120/80 mmHg

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5
Q

What is hypertension?

A

A clinical blood pressure of 140/90 mmHg or higher and a day time average of 135/85 mmHg or higher

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6
Q

What is pulse pressure?

A

The difference between systolic and diastolic blood pressures

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7
Q

What is the normal pulse pressure value?

A

between 30-50 mmHg

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8
Q

What is normal blood flow called?

A

Laminar flow ( not audible)

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9
Q

When can you heard blood flow?

A

When cuff pressure is kept between systolic and diastolic pressure. Flow becomes turbulent and can be heard through a stethoscope

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10
Q

When is diastolic pressure recorded?

A

At the fifth Korotkoff sounds (point at which sound disappears)

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11
Q

What is the first Korotkoff sound?

A

Peak systolic pressure

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12
Q

What drives blood around the systemic circulation?

A

A pressure gradient between the aorta and the right atrium

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13
Q

What is mean arterial blood pressure (MAP)?

A

The average arterial blood pressure during a single cardiac cycle which involves contraction and relaxation of the heart

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14
Q

How can Mean arterial pressure be calculated?

A 
MAP = [(2xdiastolic pressure) + systolic pressure]/3 
MAP = DBP + 1/3 Pulse Pressure
MAP = Cardiac output (CO) x Systemic vascular resistance (SVR)
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15
Q

What is a normal Mean Arterial Blood Pressure value?

A

Between 70-105 mmHg

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16
Q

What is the minimum value of MAP needed to perfuse the coronary arteries, brain and kidneys

A

60mmHg

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17
Q

What is Cardiac output?

A

The volume of blood pumped by each ventricle of the heart per minute

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18
Q

How is cardiac output calculated?

A

CO = Stroke volume (SV) x Heart Rate (HR)

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19
Q

What is Stroke Volume?

A

The volume of blood pumped by each ventricle of the heart per heart beat

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20
Q

What is systemic vascular resistance (SVR)?

A

Also called Total Peripheral Resistance

The sum of resistance of all vasculature in the systemic circulation

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21
Q

What are the major resistance vessels and how is this known?

A

The arterioles are the major resistance vessels. This is where the biggest drop in Blood pressure is seen

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22
Q

What sort of receptors are baroreceptors?

A

Pressure receptors

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23
Q

Where are the baroreceptors located?

A

In the carotid sinus’ and in the aortic arch

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24
Q

What happens when a person suddenly stands up from lying position?

A

Venous return to the heart decreases (gravity)
MAP very transiently decreases
This reduced the rate of firing of baroreceptors
Vagal tone to the heart decreases and sympathetic tone to the heart increases
This increases heart rate (HR) and stroke volume (SV)
Sympathetic constrictor tone increases. This increases the systemic vascular resistance (SVR)
The sympathetic constrictor tone to the veins increases the venous return (VR) to the heart and stroke volume
Results in: HR increasing, SV increasing, SVR increasing

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25
Q

What is postural hypotension?

A

The failure of baroreceptor response to gravitational shifts in blood, when moving from horizontal to vertical position

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26
Q

Risk factors for postural hypotension?

A 
Age related 
Medications
Certain diseases
Reduced intravascular volume
Prolonged bed rest
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27
Q

What is a positive test for postural hypotension?

A

Positive test is a drop within 3 minutes of standing from lying position:
in systolic blood pressure of at least 20 mmHg (with or without symptoms) OR
a drop in diastolic blood pressure of at least 10 mmHg (with symptoms)

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28
Q

Symptoms of postural hypotension?

A 
Lightheadedness
Dizziness
Blurred vision
Faintness
Falls
29
Q

What sort of changes to baroreceptors respond to?

A

Acute changes only. Baroreceptor firing will decrease if high blood pressure is sustained

30
Q

Why is MAP not calculated by averaging the systolic and diastolic blood pressures?

A

The relaxation (diastolic) portion of the cardiac cycle is about twice as long as the contraction (systolic) portion of the cardiac cycle

31
Q

Where is the cardiovascular control centre?

A

In the medulla

32
Q

What are the effectors in the baroreceptor reflex?

A

The heart and blood vessels

33
Q

When does the firing rate in baroreceptor afferent neurons increase?

A

When the mean arterial blood pressure (MAP) decreases

34
Q

Describe the process of baroreceptors firing to produce a response

A

The cardiovascular control centre receives CVS afferent information
Nucleus tarts solitarius (NTS) is site of 1st synapse for all CVS afferents in the medulla
NTS relays information to other regions in the brain e.g. medulla, hypothalamus, cerebellum
Generates vagal (parasympathetic) outflow to heart - really to nucleus ambiguus in the medulla
Regulates spinal sympathetic neurones

35
Q

How is the MAP regulated?

A

By regulating Heart Rate, Stroke Volume end Systemic Vascular Resistance

36
Q

What effect does sympathetic stimulation have on the heart rate?

A

Increases it

37
Q

What effect does parasympathetic stimulation have on heart rate

A

Stimulation of vagus nerve slows the heart rate

38
Q

How is stroke volume increased?

A

By increasing the contractile strength of the heart

39
Q

What sort of nerve fibres supply the vascular smooth muscle?

A

Sympathetic. Noradrenaline acts on alpha receptors

40
Q

What is vasomotor tone?

A

The partially constriction of vascular smooth muscles at rest

41
Q

What is vasomotor tone caused by?

A

Caused by the tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

42
Q

How is vasomotor tone increased? and what does this cause?

A

Increased by increasing sympathetic discharge. Results in vasoconstriction (increases SVR and MAP upstream)

43
Q

Is there any parasympathetic innervation of arterial smooth muscles?

A

No. Apart form the penis and clitoris

44
Q

How is blood volume and MAP controlled?

A

By controlling the extracellular fluid volume

45
Q

What two factors affect extracellular fluid volume?

A
  1. Water excess or deficit

2. Na+ excess or deficit

46
Q

How is the extracellular fluid volume regulated?

A

Hormones act as effectors and regulate the water and salt balance in our bodies

47
Q

What hormones regulate the extracellular fluid volume?

A
  1. The Renin-Angiotensin-Aldosterone System (RAAS)
  2. Natriuretic Peptides (NPs)
  3. Antidiuretic Hormone (Arginine Vasopressin) - ADH
48
Q

What are the 3 main components of the RAAS system?

A

Renin
Angiotensin
Aldosterone

49
Q

Where is renin released from and what does it do?

A

Released from the kidneys and stimulates the formation of angiotensin I in the blood from angiotensinogen (produced by the liver)

50
Q

What does angiotensin converting enzyme (ACE) do and where is it made?

A

Converts angiotensin I to angiotensin II

Mainly produced by pulmonary vascular endothelium

51
Q

What 2 things does Angiotensin II do?

A
  1. Stimulates the release of aldosterone from the adrenal cortex
  2. Causes systemic vasoconstriction (increases SVR)

Also stimulates thirst and ADH release i.e. contributes to increasing plasma volume mainly Brough about by aldosterone

52
Q

What does aldosterone do?

A

Acts on the kidneys to increase sodium and water retention - increases plasma volume

53
Q

What is the rate limiting step for the RAAS system?

A

Renin secretion

54
Q

Where is renin released from?

A

The juxtaglomerular apparatus in the kidney

55
Q

What mechanisms regulate renin release?

A
  1. Renal artery hypotension (caused by systemic hypotension)
  2. Stimulation of renal sympathetic nerves
  3. Decreased [Na+] in renal tubular fluid (sensed by macula densa
56
Q

What are Natriuretic Peptides (NPs)?

A

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

57
Q

When are Natriuretic peptides released?

A

In response to cardiac distension or neurohormonal stimuli

58
Q

What does Natriuretic peptides cause?

A

Cause excretion of salt and water in the kidneys thereby reducing blood volume and blood pressure
Decrease renin release (decreased BP)
Act as vasodilators (decrease SVR and BP)

59
Q

What two types of NPs are released by the heart?

A

Atrial Natriuretic Peptide (ANP) and Brain-type Natriuretic Peptide (BNP)

60
Q

What produces ANP?

A

Synthesise and stored by atrial muscle cells (atrial myocytes)

61
Q

When is ANP released?

A

Released in response to atrial distension (hypervolemic states)

62
Q

What produces BNP?

A

Synthesised by hear ventricles, brain and other organs

63
Q

What use does BNP have?

A

Serum BNP and the N-terminal piece of pro-BNP (NT-pro-BNP) can be measured in patients with suspected heart failure

64
Q

What is another name for Antidiuretic Hormone(ADH)?

A

Vasopressin

65
Q

Where is ADH synthesised and stored?

A

Synthesised by the hypothalamus and stored in the posterior pituitary

66
Q

What stimulates the secretion of ADH?

A
  1. Reduced extracellular fluid volume

2. increased extracellular fluid osmolality (main stimulus)

67
Q

What does plasma osmolality indicate and what monitors it?

A

Plasma osmolality indicates relative solute-water balance

Monitored by osmoreceptors mainly in the brain in close proximity to hypothalamus

68
Q

What does ADH do?

A
  1. Acts on kidney tubules to increase the reabsorption of water (increases extracellular and plasma volume and hence cardiac output and BP)
  2. Acts on blood vessels to cause vasoconstriction which increases SVR and blood pressure

Cardiovascular (6 decks)

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