control of blood volume

Question 1

Where is blood volume controlled on the long term?

Answer 1

controlled in the kidneys. the renal body fluid feedback system

Question 2

What effect does increased arterial pressure have on urine production?

Answer 2

increases urine production

Question 3

What does an increase in hydrostatic pressure in the kidneys mean?

Answer 3

increase across the kidneys and the glomeruli will push out more fluid into the bladder

Question 4

what effect does increase in blood pressure have on sodium ions? What effect do sodium ions have on water?

Answer 4

• more sodium ions are pushed out

- water follows sodium hence more water will be pushed out

Question 5

what happens to renal output when salt and water intake is increased?

Answer 5

kidney function takes on a more chronic regulation to keep blood pressure low

Question 6

what happens to renal output if blood pressure increases?

Answer 6

increases renal output of water and salt causing blood pressure to go back down again by reducing blood volume

Question 7

what are the meanings of volume and osmolarity?

Answer 7

volume- total amount of blood in the system

osmolarity- right concentration of blood

Question 8

how is blood osmolarity sensed?

Answer 8

osmotic receptors in the hypothalamus

Question 9

what hormone is released by the hypothalamus?

Answer 9

antidiuretic hormone ADH

Question 10

what stimulates ADH to be released?

Answer 10

released in response to increased osmotic pressure detected in the hypothalamus

Question 11

what effect does hypovolemia have on ADH release? Explain the mechanism

Answer 11

• arterial baroreceptors normally inhibit ADH release however the decrease in volume therefore decreases the firing rate and hence
• increases ADH release

Question 12

How does ADH reduce urine output?

Answer 12

increases water permeability in renal collecting ducts by increasing the tuber of aquoporins there hence decreasing urine production

Question 13

Which system is involved in the long term control of blood volume and plasma salt composition?

Answer 13

renin angiotensin aldosterone system

RAAS

Question 14

how is decreased blood volume controlled by the long term control RAAS?

Answer 14

• decrease in blood volume decreases mean arterial blood pressure sensed by baroreceptors
• baroreceptors feed the info to the MCVCC
• increase in renal sympathetic nerves increases kidney renin output decreasing urine formation

Question 15

What are the component parts of the RAAS?

Answer 15

-renin (an enzyme)

angiotensin 2

Question 16

what does Angiotensin 2 act on? what 2 things does it do?

Answer 16

• directly on the kidney
• constricts arteries in the kidneys decreasing blood flow to kidneys and stimulates the release of aldosterone from adrenal glands which increases sodium and therefore water reabsorption

Question 17

how and where is angiotensin 2 formed?

Answer 17

• angiotensin 1 is pumped through the system to heart and then when it arrives in the pulmonary circulation it meets an enzyme
• enzyme converts 1 into 2

Question 18

what are the 4 functions of angiotensin 2?

Answer 18

• vasoconstriction
• renal retention of sodium and therefore water
• increased arterial pressure
• increase release of ADH

Question 19

what is produced by atrial cells when the atrial wall is stretched?

Answer 19

atrial natriuretic peptide ANP

Question 20

what is the structure of ANP? Where is it stored? what is its function?

Answer 20

• 28 amino acid peptide
• stored in muscle cells of the atria
• released in response to the stretch of the atria and helps oppose effects of RAAS

Question 21

what effect does haemorrhage have on the blood volume?

Answer 21

decrease blood volume, decreased venous return, decreased arterial pressure, decreased end diastolic volume

Question 22

what features are involved in the baroreceptor reflex response to haemorrhage?

Answer 22

Stroke volume, hear rate, cardiac output, total peripheral resistance, mean arterial blood pressure

Question 23

What happens to SV during haemorrhage?

Answer 23

• decreases at the point of haemorrhage

- then is increased since veins are squeezed in response however it does not increase to the same level it was at

Question 24

what happens to heart rate during haemorrhage?

Answer 24

remains constant at time of haemorrhage then increases with sympathetic nerve stimulation to increase CO

Question 25

what happens to total peripheral resistance as a result of haemorrhage?

Answer 25

increases because veins constrict to decrease capacity in order to push blood back to the heart in response to sympathetic innervation

Question 26

What other conditions cause hypovolemia?

Answer 26

• decreased plasma as a result of burns
• decreased sodium form vomiting
• decreased blood pressure

Question 27

what is the later response to hypovolemia since nerve innervation reflex mechanisms are short term?

Answer 27

• arteriole constriction to decrease hydrostatic pressure in capillaries favouring fluid reabsorption
• temporary redistribution of blood flow
• decreased renal blood flow, decreased urine output

Question 28

what happens in severe hypovolemia?

Answer 28

if fluid lost can’t be compensated fro damage to tissue and organs may occur
-can lead to heart failure

Question 29

how is severe hypovolemia treated?

Answer 29

-fluid replacement is required: resuscitation fluids, colloid, blood

Question 30

what factors input into the medullary cardiovascular control centre?

Answer 30

cortex, blood hormone levels, posture and movements, hypothalamus and thalamus