control of blood volume

Question 1

what happens to urine production when arterial pressure increases?

Answer 1

urine production increases (so blood volume decreases)

Question 2

what happens to urine production when arterial pressure decreases?

Answer 2

urine production decreases (so blood volume increases)

Question 3

where is ADH released from?

Answer 3

the pituitary gland

Question 4

what causes ADH to be released?

Answer 4

• an increase in osmotic pressure ( i.e. higher concentration of solute in the blood)
• hypovolemaia (low blood volume)
• hypotension
• angiotensin II

Question 5

do atrial baroreceptors normally inhibit or promote ADH release?

Answer 5

inhibit

Question 6

how does ADH increase blood volume?

Answer 6

by increasing water permeability in renal collecting ducts, therefore decreasing urine production

Question 7

what does ADH cause in severe hypovolemic shock?

Answer 7

a high release of ADH causes vasoconstriction, increasing total peripheral resistance

Question 8

what area of the brain detects a change in blood osmotic pressure, causing a release of ADH?

Answer 8

the hypothalamus

Question 9

what type of protein is Renin?

Answer 9

a proteolytic enzyme

Question 10

what causes renin release?

Answer 10

• sympathetic nerve activation
• renal artery hypotension
• decreased sodium in kidney distal tubules

Question 11

which cells in the kidneys release Renin?

Answer 11

juxtaglomerular cells

Question 12

what is the substrate for renin?

Answer 12

angiotensinogen

Question 13

where is the angiotensin converting enzyme (ACE) found?

Answer 13

in the lungs (converts angiotensin 1 to angiotensin 2)

Question 14

what is the DIRECT effect of renin on the kidneys?

Answer 14

constricts renal arteries, therefore decreasing blood flow to the kidneys and less urine output

Question 15

what substance does renin cause to be released which increases sodium and water resorption?

Answer 15

aldosterone (released from adrenal glands)

Question 16

what other hormone does renin cause to be released?

Answer 16

ADH

Question 17

what is the name of the hormone released in response to stretch of the atria which increases urine output and so decreases blood volume?

Answer 17

atrial natriuretic hormone (28 amino acid peptide)

Question 18

a 10-15% blood loss results in which class of shock?

Answer 18

class 1

Question 19

a >40% blood loss results in which class of shock?

Answer 19

class 4

Question 20

a 15-30% blood loss results in which class of shock?

Answer 20

class 2

Question 21

a 30-40% blood loss results in which class of shock?

Answer 21

class 3

Question 22

what happens to stroke volume (SV) in response to hypovolemia?

Answer 22

sympathetic activity results in an increase in contractility which increases stroke volume

Question 23

what happens to heart rate (HR) in response to hypovolaemia?

Answer 23

reflex actions increase heart rate

Question 24

what happens to CO in response to hypovolaemia?

Answer 24

as SV and HR have both increased, CO also increases

Question 25

what happens to total peripheral resistance in response to hypovolaemia?

Answer 25

increases to try and restore mean arterial blood pressure to as near normal values as before

Question 26

what are the three main LATER responses to hypovolaemia?

Answer 26

• arterial constriction (decreases fluid loss from capillaries and favours fluid reabsorption)
• decreased renal blood flow
• thirst

Question 27

how does the cerebral cortex affect the control of blood pressure?

Answer 27

conscious effects of emotions send nerves to the medullary CVC centre

Question 28

how does the time of day affect the control of Bp?

Answer 28

diurnal variations in circulation of hormones and cortical input

Question 29

how does respiration affect control of Bp?

Answer 29

mechanical movements (decrease/increase in pressure in blood vessels inside/outside the thorax)
- also via chemoreceptors (aortic and carotid bodies detect changes in pO2 and alter rate of firing)