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Physiology and Pharmacology > Control of arterial blood pressure > Flashcards

Control of arterial blood pressure Flashcards

1
Q

What is blood pressure?

A

The pressure blood exerts on the walls of blood vessels

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2
Q

What are the two distinct mechanisms which both provide influence over blood pressure?

A

Short term- Baroreceptor (neural control)

Long-term- renin-angiotensin aldosterone system (hormonal control)

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3
Q

Short term control of blood pressure is mediated by the baroreceptor reflex. How does it function?

A

Feedback loop of

  • Stretch sensitive baroreceptors acting as the sensors (afferents)
  • Cardiovascular control centre in the Medulla Oblongata acting as the integrator
  • Autonomic neurons acting as the effectors (efferents)
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4
Q

How long does the baroreceptor take?

A

seconds

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5
Q

Arterial blood pressure is monitored by peripheral sensors. Describe the anatomy of arterial baroreceptors. Name two examples

A

Afferent nerve fibres which relay information to brain about blood pressure- achieved because they are ideally located stretch receptors
Carotid sinus
Aortic arch

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6
Q

Describe cardiopulmonary baroreceptors. Give two examples

A

Afferent fibres of 4 types (myelinated vena-arterial mechanoreceptors, non-myelinated mechanoreceptors, coronary artery baroreceptors and chemosensory)
Heart
Pulmonary artery

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7
Q

What is short-term control of blood pressure achieved by principally?

A

Arterial baroreceptors

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8
Q

Carotid sinus firing frequency is in response to what?

A

Mean arterial blood pressure

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9
Q

Describe each step of the process of baroreceptor activation

A
  • Increase in blood pressure actiavtes the stretch receptors in the carotid sinus
  • Impulses are transmitted to glossopharyngeal nerve
  • Impulses are transmitted to nuclei tracts solitary (NTS)
  • Stimulation of NTS
  • Inhibition of SNS
  • Reduction in smooth muscle contraction
  • Vasodilation
  • Fall in BP
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10
Q

In what part of the heart are cardiopulmonary baroreceptors located?

A

-low-pressure regions’ in the heart and vasculature

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11
Q

What does it mean by not all baroreceptors being created equal?

A
  • Carotid sinus baroreceptors are more sensitive

- They cause greater chainges in blood pressure that aortic arch baroreceptors

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12
Q

Both the carotid sinus and aortic arch contain fibres which help deal with normal and high level blood pressure. What are these fibres?

A

A-fibres- Deal with normal range blood pressure changes

C-fibres- Deal with high level blood pressure changes

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13
Q

What does long term control of blood pressure rely on and involve?

A

Control of blood pressure

Involves kidneys

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14
Q

In long-term control, blood comprises red blood cells and plasma. These are both influenced on what?

A

Kidneys

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15
Q

What are red blood cells mass altered by?

A

Erythropoietin

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16
Q

How is plasma volume altered?

A
  • Altered by salt excretion by renin-angiotensin aldosterone system (RAAS)
  • Altered by antidiuretic hormone (ADH)
  • Altered by atrial natriuretic peptide (ANP)
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17
Q

In long-term control, how is the state of the circulation (i.e blood volume) communicated to the kidneys?

A
  • Hormones

- Pressure natriuresis

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18
Q

Hormones which control water excretion and renal salts are influenced by what?

A

Cardiovascular receptors and initiates hormonal control

19
Q

How does renin-angiotensin-aldosterone (RAAS) function?

A
  • Decreased renal perfusion pressure aka a decrease in effective circulating volume
  • Rise in sympathetic nervous system activity to kidneys
  • Decreased NaCl concentration in the macula densa
  • production increases after fall in BP
20
Q

In RAAS, recovery of BP is achieved by what?

A

Angiotensin II stimulating aldosterone, angiotensin II stimulates generalised vasoconstriction, angiotensin II stimnulates thirst

21
Q

Angiotensin II production is stimulated by the secretion of what?

A

Secretion of renin

22
Q

What is renin, where is it stored and what does it begin with?

A

Proteolytic
Stored in afferent arterioles of kidneys
Renin begins a cleavage cascade whihc results in generation of angiotension II

23
Q

What does angiotensin II stimulate and where is it stimulated from?

A

Aldosterone

Adrenal cortex

24
Q

Aldosterone stimulates Na+ reabsorption. What does this require?
What does this is affect stimulate?

A

Na+/K+ pump insertion on basal membrane
Na+ channel on apical membrane
Osmosis

25
Q

What does the stimulation of osmosis contribute to the maintenance of?

A

Plasma volume and blood pressure

Improve circulatory volume and arterial blood pressure

26
Q

What type of hormone is aldestorone?

A

Steroid

27
Q

How does angiotensin II stimulate vasoconstriction?

A

An.. II binds to AT1 receptor on vadcular cells
This stimulates contraction and therefor vasoconstriction
This contributes to changes in total peripheral resistance (TPR)

28
Q

Direct vasoconstriction via AT1 is not the only means of changing total peripheral resistance. What is the other way and how?

A

Increases sympathetic outflow directly in brain

Stimulates sympathetic nervous system action potential generation

29
Q

What is renin released as a result of?

Describe in terms of juxtaglomerular cells

A

Hypotension

Juxtaglomerular cells in arterioles inhibited by stretch, fall in blood pressure causes release

30
Q

Increased renal sympathetic nervous system activity stimulates renin secretion by what?

A

Activation of adrenergic receptors

31
Q

A fall in NaCl concentration starts a cascade of renin from where?

A

Macula densa

32
Q

What does ACE mean?

A

Angiotensin converting enzyme

33
Q

AVP is what type of hormone?

A

Antidiuretic hormone

34
Q

Briefly explain additional hormal control of blood pressure (AVP & ANP)

A

Arginine vasopressin (AVP aka anti-diuretic hormone)-release is influenced by reduced veno-arterial receptor traffic

Atrial natriuretic peptide (ANP)- released in response to atrial stretch

35
Q

What is hypertension and hypertension?

A

Hyper- high blood pressure

Hypo- Low blood pressure

36
Q

What is hypertension considered in mmHg?

What percentage of adults are affected?

A

Clinic blood pressure 140/90mmHg

29% in Scotland

37
Q

What therapeutic interventions can be used to control hypertension?

A
  • Angiotensin-converting enzyme inhibitor (ACEi)
  • Angiotensin-II receptor blocker (ARB)
  • Calcium channel blocker (CCB)
  • Thiazide-like diuretic
38
Q

What methods would be used to reduce hypertension before therapeutic uses?

A
  • Reduce calories
  • More exercise
  • Stop smoking
  • Reduce body mass
39
Q

How does ACEi work?

A

Vasoconstrictive peptide
Decreases thirst and AVP secretion, aldosterone secretion and renal heamodynamics
-Decreases circulating blood volume and incraeses blood pressure

40
Q

What is the first line treatment for hypertension?

What category of people is this method not as effective for?

A

ACEi

>55 years and people with type II diabetes or of black African or African-caribbean family origin

41
Q

What do ARB do?

A

Antagonists that block the type I AT1 on blood vessels

42
Q

What happens when ARBs bind to the receptors?

A

Dilate arteries and veins
Reduce arterial blood pressure, reduces workload of heart
Downregulate symPathetic activity- blocks AT2 on nerves
Promotes renal excretion of sodium and water-natrietic and diuretuc doing this by blocking AT2 on aldosterine secretion

43
Q

What is the first line treatment for hypertension in patients with type II diabetes?

A

Angiotensin-II receptor blockers (ARB)

44
Q

What are the three fold ooutcomes of RAAS?

A
  • Direct action on the hypothalamus- thirst and AVP
  • Direct action on the adrenal gland-Aldosterone
  • Direct action on the kidney-renal haemodynamics

Physiology and Pharmacology (22 decks)

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