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Physiology > Cardiovascular - Control of Arterial Blood Pressure > Flashcards

Cardiovascular - Control of Arterial 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 the systolic 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 the diastolic 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

When does the first Korotkoff sound occur?

A

At peak systolic pressure.

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5
Q

What are Korotkoff sounds 2 & 3 caused by?

A

Intermittent sounds heard as blood pressure cyclically exceeds cuff pressure.

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6
Q

What is the fourth Korotkoff sound?

A

The last sound which is heard at diastolic pressure (muffled/muted).

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7
Q

What is the fifth Korotkoff sound?

A

The point at which sound disappears.

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8
Q

What is the driving force for blood flow?

A

The difference between the central venous pressure and the mean arterial pressure.

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9
Q

What is the Mean Arterial Pressure (MAP)?

A

The average arterial blood presure during a single cardiac cycle.

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10
Q

How do you calculate the Mean Arterial Pressure?

A

MAP = 2/3 diastolic pressure + 1/3 systolic pressure

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11
Q

How do you calculate the Mean Arterial Pressure from the pulse pressure?

A

MAP = diastolic + 1/3 pulse pressure.

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12
Q

What is the pulse pressure?

A

The difference between the systolic and the diastolic pressure.

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13
Q

What is the normal range of Mean Arterial Pressure?

A

70-105 mmHg

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14
Q

What is the minimum Mean Arterial Pressure required to perfuse the coronary arteries, brain and kidneys?

A

60mmHg

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15
Q

Why must the Mean Arterial Pressure be maintained within a narrow range?

A

To ensure adequate perfusion of internal organs without damaging blood vessels or putting extra strain on the heart.

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16
Q

What is the Total Peripheral Resistance?

A

The sum resistance of all peripheral vasculature in the systemic circulation.

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17
Q

What is the relationship between the Mean Arterial Pressure and the Total Peripheral Resistance?

A

MAP = Cardiac output x Total Peripheral Resistance

or

MAP = Stroke Volume x Heart Rate x Total Peripheral Resistance.

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18
Q

What are the main resistance vessels?

A

The arterioles.

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19
Q

What is the function of the baroreceptor reflex?

A

Short-term regulation of mean arterial blood pressure.

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20
Q

Where are the baroreceptors?

A

In the aortic arch and the carotid sinus.

21
Q

How do the aortic baroreceptors signal to the brain?

A

To the medulla, via the Vagus nerve (CN X)

22
Q

How do the carotid baroreceptors signal to the brain?

A

To the medulla, via Hering’s nerve which is a branch of the the Glossopharyngeal nerve (CN IX)

23
Q

What is the main preventor of postural hypotension?

A

The baroreceptor reflex.

24
Q

What happens when the mean arterial pressure transiently decreases?

A

The rate of firing of the baroceptors decreases.

25
Q

What does the reduction in baroreceptor firing trigger?

A

Decrease in vagal tone and increase in sympathetic tone to the heart.

Increase in sympathetic constrictor tone to arterioles, increasing total peripheral resistance.

Increase in sympathetic constrictor tone to veins, increasing venous return to the heart, and thus stroke volume.

26
Q

What part of the brain processes the signals from the baroreceptors?

A

The Cardiovascular Integrating Centre, in the medulla.

27
Q

What provides the long term control of Mean Arterial Pressure?

A

Blood volume.

28
Q

How is the total body fluid normally distributed?

A

2/3 intracellular and 1/3 extracellular.

29
Q

How is the extracellular fluid distributed?

A

Between the plasma volume and the interstitial fluid volume.

30
Q

What happens when plasma volume falls?

A

Compensatory mechanisms shift fluid from the interstitial compartment to the plasma compartment.

31
Q

What are the main factors affecting extracellular fluid volume?

A

Water excess or deficit

and

Na+ excess or deficit.

32
Q

Which hormones regulate extracellular fluid volume?

A

Rennin-Angiotensin-Aldosterone System (RAAS)

Atrial Natriuretic Peptide (ANP)

Antidiuretic Hormone (ADH)

33
Q

What is the rate limited step for RAAS?

A

Rennin Secretion.

34
Q

Which cells release renin?

A

Juxtaglomerular cells

35
Q

Where are the juxtaglomerular cells found?

A

They are special smooth muscle cells in the blood vessels of the kidney.

36
Q

What triggers the release of renin?

A

Low blood pressure

Sympathetic innervation

Prostaglandins

37
Q

Which cells in the kidney release prostaglandin in response to low Na+?

A

Macula densa cells, in the distule tubules of the nephron.

38
Q

Where is angiotensinogen released?

A

The liver.

39
Q

What does renin catalyse?

A

The conversion of angiotensinogen to angiotensin I

40
Q

Which enzyme catalyses the conversion of angiotensin I to angiotensin II?

A

Angiontensin Converting Enzyme (ACE)

41
Q

Where is Angiotensin Converting Enzyme (ACE) found?

A

On the surface on endothelial cells

42
Q

Which vasodilator is inactivated by ACE?

A

Bradykinin

43
Q

What function does Angiotensin II perform?

A

It is a vasodilator.

44
Q

Where does Angiotensin II produce its affects?

A

Smooth muscle of blood vessels - increase resistance

Pituitary gland - stimulates secretion of ADH

Adrenal Gland - stimulates secretion of aldosterone

Kidney - increases water retention

45
Q

On which receptor does Angiotensin II act?

A

The AT1 receptor (G-protein coupled receptor)

46
Q

What effect does angiotensin II have on cells in the heart and arteries?

A

Cell growth.

47
Q

What is the site of the first synapse for all CVS afferents in the medulla?

A

Nucleus tractus solitarius

48
Q

Which area of the medulla handles vagal outflow in the heart?

A

Nucleus ambiguus

Physiology (8 decks)

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