Control of Arterial Blood Pressure Lecture 2

Question 1

how is blood volume and MAP controlled?

Answer 1

by controlling the extracellular fluid volume

Question 2

60 percent of body weight is water. what are the two fatcors contributing to total body fluid?

Answer 2

intracellular fluid (2/3rd) and extracellular fluid (ECF) - normally 1/3rd of the total

Question 3

what two things make yo the ECF?

Answer 3

plasma volume (PV) and interstitial volume (IFV)

Question 4

what is the IFV?

Answer 4

the fluid which bathes the cells and acts as the go between the blood and body cells

Question 5

what happens to the volume in the IFV when PV falls?

Answer 5

compensatory mechanisms move fluid from the IFVto the PV

Question 6

what two main factors affect EFV?

Answer 6

1. water excess or deficit

2. Na excess or deficit

Question 7

how is the EFV regulated?

Answer 7

by hormones that regulate the water and salt balances in our bodies

Question 8

healthy people stay in a stable water and salt balance where…

Answer 8

water input = water output

Question 9

what three hormones regulate the EFV ?

Answer 9

1. the renin-angiotensin-aldosterone - RAAS
2. atrial netriuretic peptide - ANP
3. Antidiuretic hormone (arginine vasopressin)

Question 10

what are the three components of RAAS?

Answer 10

renin

angiotensin and aldosterone

Question 11

where is renin released?

Answer 11

from the kidneys

Question 12

what does renin stimulate?

Answer 12

the formation of angiotensin 1 in the blood from angiotensinogen

Question 13

where is angiotensinogen produced?

Answer 13

in the liver

Question 14

what is the angiotensin 1 converted to?

Answer 14

angiotensin 2 by the angiotensin converting enzymes

Question 15

where is ACE produced?

Answer 15

by the pulmonary vascular endothelium - the inner lining of blood vessels

Question 16

what does angiotensin 2 stimulate?

Answer 16

the release of aldosterone

Question 17

where is aldosterone released from?

Answer 17

the adrenal cortex

Question 18

what does angiotensin do?

Answer 18

causes systemic vasoconstriction which increases the TPR

it also stimulates thirst and ADH release i.e. contributes to increasing PV mainly brought about by aldosterone

Question 19

what effect does aldosterone have on the kidneys?

Answer 19

increases sodium and water retention - increases the PV

Question 20

what is the renin angiotensin aldosterone system regulated by?

Answer 20

mechanisms which stimulate the release of renin from the juxtaglomerular apparatus in the kidney

Question 21

what are the three reasons for increased renin release?

Answer 21

1. renal artery hypotension - casued by systemic hypotension (low BP)
2. stimulation of renal sympathetic nerves
3. decreased Na in renal tubular fluid

Question 22

what senses the decreased Na in renal tubular fluid?

Answer 22

macula densa (specialised cells of the kidney tubules)

Question 23

what is the juxtaglomerula apparatus ?

Answer 23

a region comprising the macula densa, extraglomerular mesangial cells and granular cells (release renin)

Question 24

what do granular cells do?

Answer 24

release renin

Question 25

where is the atrial Natriuretic peptide synthesised?

Answer 25

28 amino acid peptide hormone synthesised and stored by atrial muscle cells (atrial myocytes)

Question 26

what stimulates the release of ANP?

Answer 26

atrial distension - hypervolaemic states

Question 27

what does ANP cause?

Answer 27

the excretion of salt and water in the kidneys

acts as a vasodilator

decreases renin release so acts as a counter regulatory mechanism for RAAS

Question 28

what does the excretion of salt and water in the kidneys due to ANP lead to?

Answer 28

a reduced blood volume and blood pressure

Question 29

what is ADH?

Answer 29

peptide hormone derived from a prehormone precursor

Question 30

where is ADH synthesised and stored?

Answer 30

synthesised in the hypothalamus and stored in the posterior pituitary

Question 31

what stimulates the release of ADH? 2 things

Answer 31

1. reduced EFV

2. increased EF osmolarity (main stimulus)

Question 32

what is the normal osmolarity of EF?

Answer 32

about 280 milli-osmoles

Question 33

what is plasma osmolarity monitored by?

Answer 33

osmoreceptors mainly in the brain in close proximity to the hypothalamus

Question 34

what does ADH do?

Answer 34

acts on the kidney tubules to increase reabsorption of water (conserve water) i.e. concentrate urine (antidiuresis)

Question 35

WHAT DOES THIS INCREASE in water reabsorption by ADH do?

Answer 35

increases the extracellular and plasma volume and hence CO and BP

Question 36

what does ADH do to the blood vessels ?

Answer 36

causes vasoconstriction which increases TPR and blood pressure; the effect is small in normal people but becomes important in hypovolaemic shock ( haemorrhage)