Physiological BP control

Question 1

D: Blood Pressure

Answer 1

the outwards (hydrostatic) pressure exerted by the blood on blood vessel walls

Question 2

D: Systolic Arterial Blood Pressure

Answer 2

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

Question 3

D: Diastolic Arterial Blood Pressure

Answer 3

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

Question 4

D: Hypertension

Answer 4

Clinic blood pressure of 140/90 mmHg or higher and day time average of 135/85 mmHg or higher

Question 5

D: Pulse pressure

Answer 5

Is the difference between systolic and diastolic blood pressures

Question 6

What drives systemic circulation?

Answer 6

the pressure gradient between the aorta and the right atrium

Question 7

Pressure gradient =

Answer 7

Mean Arterial Pressure (MAP) – Central Venous (right atrial) Pressure (CVP)

Question 8

D: Mean Arterial Blood Pressure (MAP)

Answer 8

the average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart

Question 9

MAP =

Answer 9

[(2x diastolic pressure) + systolic pressure]/3 OR DBP + 1/3 Pulse Pressure

Question 10

What is the MAP required to perfuse the coronary arteries, brain and kidneys?

Answer 10

at least 60 mmHg

Question 11

normal systolic arterial blood pressure

Answer 11

shouldn’t exceed 140 mm Hg

Question 12

normal diastolic arterial blood pressure

Answer 12

shouldn’t exceed 90 mm Hg

Question 13

How is it possible to manually measure blood pressure with a cuff and stethoscope?

Answer 13

If there is laminar flow, blood flow can’t be heard
If blood flow is restricted by external pressure this causes turbulent flow which can be heard through a stethoscope
The 1st sound is at peak systolic pressure
The 5th (last) sound is at diastolic blood pressure measuremenr

Question 14

What vessels cause the greatest systemic vascular resistance?

Answer 14

The arterioles

Question 15

MAP is a product of

Answer 15

CO x SVR = HR x SV x SVR

Question 16

What are the receptors responsible in the acute regulation of blood pressure?

Answer 16

Baroreceptors

Question 17

How do the baroreceptors aid in acute blood pressure regulation?

Answer 17

They send a signal to the medulla when blood pressure is beyond limits, the medula is the control centre and then causes the autonomic nervous system to appropriately signal the effectors and correct the MAP

Question 18

What happens when a person stands up from a lying position in relation to their blood pressure?

Answer 18

• venous return to the heart decreases due to the effect of gravity MAP very transiently decreases
• baroreceptors decrease vagal tone to the medulla causing a greater sympathetic output to the heart
• increase sympathetic tone causes increased HR, SV and constrictor tone - increased SVR -The sympathetic constrictor tone to the veins increases the venous return (VR) to the heart and stroke volume
• The result is: rapid correction of the transient fall in MAP: HR INCREASES; SV INCREASES; SVR INCREASES

Question 19

D: Postural Hypotension

Answer 19

a drop, within 3 minutes of standing from lying position:

• in systolic blood pressure of at least 20 mmHg (with or without symptoms) or
• a drop in diastolic blood pressure of at least 10 mm Hg (with symptoms)

Question 20

Risk factors of Postural Hypotension

Answer 20

Age related
Medications
Certain diseases
Reduced intravascular volume
Prolonged bed rest

Question 21

Symptoms of postural (orthostatic) hypotension

Answer 21

• lightheadedness
• dizziness
• blurred vision
• faintness
• falls

Question 22

Total body fluid =

Answer 22

Intracellular fluid (2/3rds) + Extracellular fluid (1/3rd)

Question 23

ECF volume =

Answer 23

Plasma volume + interstitual fluid volume

Question 24

What happens physiologically when the plasma volume falls?

Answer 24

compensatory mechanisms move fluid from the interstitual compartment

Question 25

What are the 2 main factors influencing ECF volume?

Answer 25

1. Water excess or deficit | 2. Na+ excess or deficit

Question 26

What are the effectors for the regulation of the ECF volume (which influence water and salt balance)?

Answer 26

3 hormones 1. The Renin-Angiotensin-Aldosterone (RAAS) 2. Natriuretic Peptides (NPs) 3. Antidiuretic Hormone (Arginine Vasopressin) ADH

Question 27

What is the role of the Renin-Angiotensin-Aldosterone System?

Answer 27

- important to regulate PV & SVR and hence MAP - Renin is made in the kidneys and causes the formation of angiotension I in the blood from angiotensinogen - Angiotensin I is converted to angiotensin II by ACE (angiotensin converting enzyme) - Angiotension II stimulates Aldosterone release from the adrenal cortex - Angiotension II causes systemic vasoconstriction increasing SVR & stimulates thirst - Aldosterone acts on the kidneys increasing sodium and water retention, increasing plasma volume

Question 28

How is the renin-angiotensin-aldosterone system regulated?

Answer 28

by the mechanisms which stimulate Renin release from the juxtaglomerular apparatus in the kidney 1. renal artery hypotension due to systemic hypotension 2. stimulation of renal sympathetic nerves 3. decreased (Na+) in renal tubular fluid sensed by macula densa (specialised kidney tubules)

Question 29

What is the role of the Natriuretic Peptides?

Answer 29

to counteract the RAAS

Question 30

What are NPs?

Answer 30

peptide hormones synthesised by the heart (as well as the brain and other organs)

Question 31

What triggers natriuretic peptides?

Answer 31

cardiac distension or neurohormonal stimuli

Question 32

What is the effect of Natriuretic peptides?

Answer 32

1. increased excretion of salt and water in the kidneys, reducing blood volume and blood pressure 2. decrease renin release - decrease blood pressure 3. act as vasodilators decreasing SVR and blood pressure

Question 33

What are the main 2 types of natriuretic peptides released by the heart?

Answer 33

1. Atrial natriuretic peptide - 28 amino acid peptide synthesised and stored in atrial myocytes - ANP is released in response to atrial distension 2. Brian-type Natriuretic Peptide (BNP) - 32 amino acid peptide, synthesised by ventricles - BNP is 1st synthesised as prepro-BNP, then cleaved to pro-BNP (108 amino acids) and finally BNP (32 amino acids) - serum BNP & N terminal od pro-BNP is a measure in patients with suspected heart failure

Question 34

What is vasopressin?

Answer 34

aka ADH, it is derives from a prehormone precursor synthesised by the hypothalamus and is stored in the posterior pituitary

Question 35

What stimulates the secretion of ADH/vasopressin?

Answer 35

reduces extracellular fluid volume or increased extracellular fluid osmolality

Question 36

What is plasma osmolality?

Answer 36

- it indicates relative solute-water balance | - monitored by osmoreceptors mainly in the brain in close proximity to the hypothalamus

Question 37

What is the effect of ADH?

Answer 37

- increases reabsorption of water in the kidney tubules , increasing extracellular and PV & hence increasing CO and blood pressure - also causes vasoconstriction, increasing SVR