Control of Vasculature & Blood Pressure

Question 1

What is the difference between extrinsic and intrinsic influences?

Answer 1

Extrinsic = not locally generated

Intrinsic = locally generated

Question 2

What are the two types of extrinsic influences?

Answer 2

Neural - autonomic NS

Hormonal/endocrine

Question 3

What is the cardiovascular control centre called?

Answer 3

Medulla oblongata

Question 4

Explain how the parasympathetic NS decreases heart rate

Answer 4

Release ACh (vagus nerve)

Binds to muscarinic (M2) receptors on pacemaker cells

Hyperpolarisation = decreased rate of decay of pacemaker potential

Question 5

Explain how the sympathetic NS increases heart rate and contractility

Answer 5

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

Question 6

What part of the nervous system innervates most systemic arterioles?

Answer 6

Sympathetic NS

Question 7

Explain how sympathetic stimulation affects systemic arterioles

Answer 7

Release of noradrenaline (post-ganglionic)

Binds to a1-adrenoceptors on smooth muscle cells

Vasoconstriction

Question 8

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

Answer 8

Vasodilation

Question 9

What hormone reinforces noradrenaline-vasoconstriction?

Answer 9

Adrenaline

Question 10

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

Answer 10

Noradrenaline

Question 11

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

Answer 11

Supports noradrenaline vasoconstriction

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

Question 12

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

Answer 12

Innervates few arterioles

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

Question 13

Which division of the autonomic NS can affect TPR?

Answer 13

Sympathetic NS

Question 14

What effect does angiotensin II have on vasculature?

Answer 14

Vasoconstriction

Question 15

What effect does vasopressin/ADH have on vasculature?

Answer 15

Vasoconstriction (also increases blood volume)

Question 16

What effect does atrial natriuretic peptide have on vasculature?

Answer 16

Vasodilation

Question 17

What is autoregulation (vasculature)?

Answer 17

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

Question 18

How is the glomerulus protected from high blood pressure?

Answer 18

Pressure increase causes vasoconstriction to slow blood flow

Prevent damage of glomerulus

Question 19

When is histamine released and from what cells?

Answer 19

By mast cells in response to allergic reactions/inflammation

Question 20

What does histamine do?

Answer 20

Increase vascular permeability

Increase nitric oxide production and release (=vasodilatation)

Question 21

Describe nitric oxide production in endothelial cells

Answer 21

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

Question 22

What does nitric oxide do after synthesis in endothelial cells?

Answer 22

Diffuses into smooth muscle cells

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

Question 23

What is metabolic hyperaemia?

Answer 23

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

Blood flow matches work effort of tissue

Question 24

What substances are produced in metabolic hyperaemia?

Answer 24

K+

H+

CO2

Lactic acid

Adenosine

Question 25

What is reactive hyperaemia?

Answer 25

Local blood flow cut off Metabolites accumulate and cause vasodilatation Blood flow returns = vasodilatation allows quick washing out then returns to normal

Question 26

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

Answer 26

5900ml/min to 24000ml/min

Question 27

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

Answer 27

11% to 87%

Question 28

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

Answer 28

53% to 3%

Question 29

What structural adaptation of the cutaneous circulation aids thermoregulation?

Answer 29

Arteriovenous anastamoses/shunts

Question 30

Where are arteriovenous anastamoses mainly found?

Answer 30

Extremeties (hands, feet, ears) Nasal mucosa

Question 31

What regulates the blood flow in the cutaneous circulation?

Answer 31

Hypothalamic thermoregulators Sympathetic NS

Question 32

What happens in the cutaneous circulation when it is cold?

Answer 32

Increased sympathetic drive Vasoconstriction shunts blood away from venules

Question 33

What happens in the cutaneous circulation when it is warm?

Answer 33

Decreased sympathetic drive Vasodilatation so blood can flow into dermal venous plexus Increase radiation of heat through blood vessels closer to skin surface

Question 34

What two functional adaptations are present in skeletal muscle circulation?

Answer 34

Metabolic hyperaemia Skeletal muscle pump

Question 35

Why is metabolic hyperaemia important in skeletal muscle?

Answer 35

Overrides sympathetic tone so no vasoconstriction (during exercise)

Question 36

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

Answer 36

80%

Question 37

Which vascular beds are the largest contributors to TPR?

Answer 37

Muscle

Question 38

What is the function of the skeletal muscle pump?

Answer 38

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

Question 39

How does the skeletal muscle pump aid venous return?

Answer 39

Muscle contraction during static exercise compresses veins to increase venous pressure

Question 40

What factors affect blood pressure?

Answer 40

Cardiac output (=> stroke volume and heart rate) TPR CVP Blood volume

Question 41

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

Answer 41

Carotid sinus (vagus) Aortic arch (glossopharyngeal)

Question 42

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

Answer 42

Carotid sinus Thinner wall

Question 43

What occurs when there is a decrease in blood pressure?

Answer 43

Decreased firing of baroreceptors Centrally mediated response Decreased parasympathetic and increased sympathetic drive Increased cardiac output, CVP and TPR (vasoconstriction)

Question 44

When can the blood pressure set point be altered?

Answer 44

During exercise As you age

Question 45

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

Answer 45

Blood volume

Question 46

What happens when blood volume increases?

Answer 46

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

Question 47

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

Answer 47

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

Question 48

How does vasopressin work?

Answer 48

Activates V2 receptor Aquaporin insertion Increased water reabsorption in distal nephron

Question 49

What is the possible range of urine produced per day?

Answer 49

0.4 - 25 L/day

Question 50

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

Answer 50

Plasma osmolarity

Question 51

What do stretch receptors detect and where are they?

Answer 51

Increased CVP caused by increased blood volume In atria and venoatrial junction

Question 52

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

Answer 52

Promotes atrial natriuretic peptide release from atrial myocytes Promotes diuresis and natriuresis Decreased blood volume

Question 53

What is pressure natriuresis?

Answer 53

Increased arterial pressure Increased local metabolite release in renal artery = vasodilatation Increased blood flow = increased filtration More Na+ excreted

Question 54

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

Answer 54

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)

Question 55

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

Answer 55

Potent vasoconstrictor Stimulates ADH release Stimulates aldosterone release from adrenals

Question 56

What does aldosterone promote?

Answer 56

Na+ reabsorption

Question 57

What can vasovagal syncope be triggered by?

Answer 57

Sight of blood or needles

Question 58

What is another term for vasovagal syncope?

Answer 58

Neurocardiogenic syncope

Question 59

Describe the process of vasovagal syncope

Answer 59

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