Physiology 4 and 5- Control of BP Flashcards

1
Q

What is blood pressure?

A

The pressure exerted on the blood vessel walls by the blood

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2
Q

What is the systemic systolic blood pressure?

A

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

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3
Q

What is the systemic diastolic blood pressure?

A

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

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4
Q

When will sound be heard when listening to the brachial artery?

A

When there is turbulent blood flow

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5
Q

When is the first Korotkoff sound heard?

A

Peak systolic pressure

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6
Q

When is the second Korotkoff sound heard?

A

Minimum diastolic pressure

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7
Q

What is mean arterial blood pressure?

A

The average arterial blood pressure during a full cardiac cycle including contraction and relaxation of the heart

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8
Q

How can MAP be worked out?

A

[(2 x diastolic pressure) + systolic pressure] / 3
OR
DBP + 1/3rd pulse pressure

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9
Q

What is pulse pressure?

A

Difference between systolic and diastolic pressure

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10
Q

What is the normal range and normal value of MABP?

A

Range- 70-105mmHg

Value- 90mmHg

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11
Q

A MAP of at least 60mmHg is needed for what?

A

To adequately perfuse essential organs e.g. coronary arteries, kidneys and brain

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12
Q

What can happen if MAP is too high?

A

Place extra strain on the heart and damage the blood vessels

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13
Q

What is the TPR?

A

The sum resistance of all peripheral vasculature in the systemic circulation

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14
Q

What are the major resistance vessels?

A

Arterioles

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15
Q

What does parasympathetic stimulation to control the BP act on and what does it do?

A

Acts on the heart to reduce HR, CO and hence MABP

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16
Q

What does sympathetic stimulation to control the BP act on?

A

Heart, veins and arterioles

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17
Q

How does sympathetic stimulation to the heart increase the BP?

A

Increases HR, CO and MAP

Increases FoC, SV, CO and MAP

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18
Q

How does sympathetic stimulation acting on the arterioles increase the BP?

A

Vasoconstriction, increased TPR and BP

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19
Q

How does sympathetic stimulation acting on the veins increase the BP?

A

Vasoconstriction, increased VR, SV, CO and MAP

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20
Q

Any change in BP will be sensed by the ? (pressure sensors) which will then inform the ? (control centre)

A

Baroreceptors

Medulla

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21
Q

What are the effectors involved in the baroreceptor reflex and what do they mediate?

A

Heart- HR and SV

Blood vessels- TPR

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22
Q

What type of feedback mechanism is the baroreceptor reflex?

A

Negative

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23
Q

Where are the baroreceptors?

A

Aortic arch and carotid sinus

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24
Q

The baroreceptors in the aortic arch send signal to the medulla via what cranial nerve?

A

X- vagus

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25
Q

The baroreceptors in the carotid sinus send signal to the medulla via what cranial nerve?

A

IX- glossopharyngeal

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26
Q

What happens to the rate of carotid sinus afferent nerve firing if BP increases or decreases?

A

BP increases- increases

BP decreases- decreases

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27
Q

What happens to the rate of vagal efferent afferent nerve firing if BP increases or decreases?

A

BP increases- increases

BP decreases- decreases

28
Q

What happens to the rate of cardiac sympathetic efferent nerve firing if BP increases or decreases?

A

BP increases- decrease

BP decreases- increase

29
Q

What happens to the rate of sympathetic vasoconstrictor nerve firing if BP increases or decreases?

A

BP increases- decreases

BP decreases- increases

30
Q

What change in BP causes vasoconstriction/vasodilation?

A

Vasoconstriction- decreased MAP

Vasodilation- increased MAP

31
Q

What type of MAP control are the baroreceptors involved in?

A

Short term moment to moment

32
Q

What causes the MAP to decrease when a person stands up from a lying position?

A

Decreased venous return

33
Q

When the MAP decreases, what happens to the firing of the baroreceptors?

A

Firing decreases

34
Q

What happens when the baroreceptor firing decreases?

A

Increased sympathetic tone and decreased vagal tone
Increased HR and SV
Sympathetic constrictor tone increases TPR, VR and SV

35
Q

What causes postural hypotension?

A

Failure of baroreceptor reflex when going from horizontal to vertical

36
Q

What happens to the baroreceptor reflex if high blood pressure is sustained?

A

Firing will decrease and the receptors will effectively ‘reset’

37
Q

What controls MABP in the long term?

A

Blood volume

38
Q

How is blood volume controlled?

A

By controlling the extracellular fluid volume

39
Q

What is the extracellular fluid made up of?

A

Interstitial fluid volume and plasma volume

40
Q

What happens if plasma volume fails?

A

Compensatory mechanisms move fluid from the interstitial fluid compartment

41
Q

The ECFV is affected by ?, some ? act to regulate this

A

Affected by Na+ or H2O deficit or excess

Regulated by some hormones

42
Q

What does the RAAS system regulate?

A

Plasma volume, TPR, MABP

43
Q

Where is renin released from?

A

The kidneys

44
Q

What does renin stimulate?

A

The formation of angiotensin I in the blood from angiotensinogen

45
Q

Where is angiotensinogen produced?

A

Liver

46
Q

What happens to angiotensin I in the RAAS system?

A

It is converted to angiotensin II by angiotensin converting enzyme (ACE)

47
Q

What is ACE produced by?

A

Pulmonary vascular endothelium

48
Q

What does angiotensin II stimulate release of?

A

Aldosterone

49
Q

Where does aldosterone come from?

A

Adrenal cortex

50
Q

As well as stimulating production of aldosterone, what other effects does angiotensin II have?

A

Increases TPR by systemic vasoconstriction

Stimulates thirst and ADH release

51
Q

What is aldosterone?

A

A steroid hormone

52
Q

What does aldosterone do?

A

Acts on the kidneys to increase water and salt retention to increase the plasma volume

53
Q

The RAAS system is regulated by mechanisms which stimulate ? (specifically ?)

A

Renin release from the kidneys

Juxtaglomerular apparatus

54
Q

What are some examples of changes that would stimulate the RAAS system?

A

Renal artery hypotension as a result of systemic hypotension
Stimulation of renal sympathetic nerves
Decreased Na+ in tubular fluid

55
Q

What is the specialised kidney tubule cell which senses changes that regulate the RAAS system?

A

Macula densa

56
Q

What is atrial natriuretic peptide?

A

A peptide stored in atrial muscle cells

57
Q

What is ANP released in response to?

A

Atrial distension (hypovolaemia)

58
Q

What are the 3 actions of ANP?

A

Excretion of salt and water to reduce blood volume and hence blood pressure
Act as a vasodilator to decrease BP
Decrease renin release and counteract RAAS

59
Q

What is ADH?

A

A peptide hormone

60
Q

Where is ADH synthesised and where is it stored?

A

Synthesised in the hypothalamus and stored in the posterior pituitary gland

61
Q

What triggers synthesis of ADH?

A

Decrease in ECFV or increase in ECF osmolarity

62
Q

What is extracellular fluid osmolarity monitored by?

A

Osmoreceptors close to the hypothalamus

63
Q

What does ADH act on and what is the main action?

A

On the kidneys to increase reabsorption of water

64
Q

How does ADH increasing water reabsorption affect BP?

A

Increase ECFV and hence CO and BP

Acts as a vasoconstrictor to increase TPR and BP

65
Q

When is the effect of ADH on BP very important?

A

Hypovolemic shock