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BMS10 > Control of Vasculature & Blood Pressure > Flashcards

Control of Vasculature & Blood Pressure Flashcards

1
Q

What is the difference between extrinsic and intrinsic influences?

A

Extrinsic = not locally generated

Intrinsic = locally generated

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2
Q

What are the two types of extrinsic influences?

A

Neural - autonomic NS

Hormonal/endocrine

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3
Q

What is the cardiovascular control centre called?

A

Medulla oblongata

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4
Q

Explain how the parasympathetic NS decreases heart rate

A

Release ACh (vagus nerve)

Binds to muscarinic (M2) receptors on pacemaker cells

Hyperpolarisation = decreased rate of decay of pacemaker potential

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5
Q

Explain how the sympathetic NS increases heart rate and contractility

A

Release noradrenaline

Binds to b1-adrenoceptors on pacemaker cells and myocardium (esp. ventricular)

Increased rate of decay of pacemaker potential

Increase sarcomere length and Ca2+ sensitivity

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6
Q

What part of the nervous system innervates most systemic arterioles?

A

Sympathetic NS

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7
Q

Explain how sympathetic stimulation affects systemic arterioles

A

Release of noradrenaline (post-ganglionic)

Binds to a1-adrenoceptors on smooth muscle cells

Vasoconstriction

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8
Q

What does depressed firing of sympathetic neurons promote in systemic arterioles?

A

Vasodilation

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9
Q

What hormone reinforces noradrenaline-vasoconstriction?

A

Adrenaline

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10
Q

Which out of adrenaline or noradrenaline has a higher affinity for a1-adrenoceptors?

A

Noradrenaline

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11
Q

Why is adrenaline important in vasculature during ‘fight or flight’ responses?

A

Supports noradrenaline vasoconstriction

Binds to b2-adrenoceptors in specific tissues to promote vasodilatation (heart, liver, skeletal muscle arterioles)

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12
Q

What does the parasympathetic nervous system do in regards to vasculature?

A

Innervates few arterioles

Promotes vasodilatation in select vascular beds, salivary glands, pancreas, intestinal mucosa and sex organs

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13
Q

Which division of the autonomic NS can affect TPR?

A

Sympathetic NS

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14
Q

What effect does angiotensin II have on vasculature?

A

Vasoconstriction

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15
Q

What effect does vasopressin/ADH have on vasculature?

A

Vasoconstriction (also increases blood volume)

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16
Q

What effect does atrial natriuretic peptide have on vasculature?

A

Vasodilation

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17
Q

What is autoregulation (vasculature)?

A

Arterioles respond to changes in internal blood pressure by contracting/relaxing to alter blood flow and capillary perfusion pressure

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18
Q

How is the glomerulus protected from high blood pressure?

A

Pressure increase causes vasoconstriction to slow blood flow

Prevent damage of glomerulus

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19
Q

When is histamine released and from what cells?

A

By mast cells in response to allergic reactions/inflammation

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20
Q

What does histamine do?

A

Increase vascular permeability

Increase nitric oxide production and release (=vasodilatation)

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21
Q

Describe nitric oxide production in endothelial cells

A

Laminar flow activates eNOS/inflammatory mediators activate iNOS

Increase in Ca2+ in endothelial cells required for calmodulin binding to eNOS

Activated eNOS converts L-Arg to NO and L-citrulline

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22
Q

What does nitric oxide do after synthesis in endothelial cells?

A

Diffuses into smooth muscle cells

cGMP used in pathway with nitric oxide to induce vasodilatation (prevents rise in Ca2+ for contraction)

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23
Q

What is metabolic hyperaemia?

A

Increased metabolism enhances production of substances which cause local dilatation of arterioles

Blood flow matches work effort of tissue

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24
Q

What substances are produced in metabolic hyperaemia?

A

K+

H+

CO2

Lactic acid

Adenosine

25
Q

What is reactive hyperaemia?

A

Local blood flow cut off

Metabolites accumulate and cause vasodilatation

Blood flow returns = vasodilatation allows quick washing out then returns to normal

26
Q

What is the change in cardiac output from rest to exercise?

A

5900ml/min to 24000ml/min

27
Q

What is the change in the percentage of cardiac output received by active muscle from rest to exercise?

A

11% to 87%

28
Q

What is the change in the percentage of cardiac output received by kidney/liver/GI tract from rest to exercise?

A

53% to 3%

29
Q

What structural adaptation of the cutaneous circulation aids thermoregulation?

A

Arteriovenous anastamoses/shunts

30
Q

Where are arteriovenous anastamoses mainly found?

A

Extremeties (hands, feet, ears)

Nasal mucosa

31
Q

What regulates the blood flow in the cutaneous circulation?

A

Hypothalamic thermoregulators

Sympathetic NS

32
Q

What happens in the cutaneous circulation when it is cold?

A

Increased sympathetic drive

Vasoconstriction shunts blood away from venules

33
Q

What happens in the cutaneous circulation when it is warm?

A

Decreased sympathetic drive

Vasodilatation so blood can flow into dermal venous plexus

Increase radiation of heat through blood vessels closer to skin surface

34
Q

What two functional adaptations are present in skeletal muscle circulation?

A

Metabolic hyperaemia

Skeletal muscle pump

35
Q

Why is metabolic hyperaemia important in skeletal muscle?

A

Overrides sympathetic tone so no vasoconstriction (during exercise)

36
Q

Up to what percentage can blood flow drop by upon strong sympathetic stimulation?

A

80%

37
Q

Which vascular beds are the largest contributors to TPR?

A

Muscle

38
Q

What is the function of the skeletal muscle pump?

A

Aids venous return from legs and reduces blood pressure in lower extremities

39
Q

How does the skeletal muscle pump aid venous return?

A

Muscle contraction during static exercise compresses veins to increase venous pressure

40
Q

What factors affect blood pressure?

A

Cardiac output (=> stroke volume and heart rate)

TPR

CVP

Blood volume

41
Q

Where are the blood pressure baroreceptor nerve endings in the body?

A

Carotid sinus (vagus)

Aortic arch (glossopharyngeal)

42
Q

Which blood pressure baroreceptor nerve endings are more sensitive and why?

A

Carotid sinus

Thinner wall

43
Q

What occurs when there is a decrease in blood pressure?

A

Decreased firing of baroreceptors

Centrally mediated response

Decreased parasympathetic and increased sympathetic drive

Increased cardiac output, CVP and TPR (vasoconstriction)

44
Q

When can the blood pressure set point be altered?

A

During exercise

As you age

45
Q

What is altered in the long-term control of blood pressure?

A

Blood volume

46
Q

What happens when blood volume increases?

A

Increase in MABP

Promotes excess fluid and salt excretion to decrease blood volume and decrease MABP again

47
Q

What happens when there is an increase in Na+ intake or dehydration?

A

Increased plasma osmolarity detected by hypothalamic osmoreceptors

Increased thirst = increased water ingestion = decreased plasma osmolarity

Posterior pituitary gland secretes (more) ADH/vasopressin = increased water reabsorption in distal nephron = decreased plasma osmolarity

48
Q

How does vasopressin work?

A

Activates V2 receptor

Aquaporin insertion

Increased water reabsorption in distal nephron

49
Q

What is the possible range of urine produced per day?

A

0.4 - 25 L/day

50
Q

Is plasma osmolarity or blood volume more important to be regulated?

A

Plasma osmolarity

51
Q

What do stretch receptors detect and where are they?

A

Increased CVP caused by increased blood volume

In atria and venoatrial junction

52
Q

How does increased CVP detected by stretch receptors affect blood volume?

A

Promotes atrial natriuretic peptide release from atrial myocytes

Promotes diuresis and natriuresis

Decreased blood volume

53
Q

What is pressure natriuresis?

A

Increased arterial pressure

Increased local metabolite release in renal artery = vasodilatation

Increased blood flow = increased filtration

More Na+ excreted

54
Q

How is the juxtaglomerular apparatus important in blood volume regulation (decreased blood volume)?

A

Increased renal sympathetic drive

Afferent arteriole constriction and renin release from juxtaglomerular cells

Angiotensin II produced

Angiotensin II = potent vasoconstrictor, stimulates ADH release, stimulates aldosterone release (adrenals)

55
Q

What is the function of angiotensin II in blood volume/pressure regulation?

A

Potent vasoconstrictor

Stimulates ADH release

Stimulates aldosterone release from adrenals

56
Q

What does aldosterone promote?

A

Na+ reabsorption

57
Q

What can vasovagal syncope be triggered by?

A

Sight of blood or needles

58
Q

What is another term for vasovagal syncope?

A

Neurocardiogenic syncope

59
Q

Describe the process of vasovagal syncope

A

Increased parasympathetic and decreased sympathetic drive

Decreased heart rate and widespread vasodilatation

Decreased cardiac output and TPR

Fall in blood pressure

Decreased blood flow to brain

BMS10 (13 decks)

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