Blood Volume

Question 1

– Renal-body fluid feedback system

Answer 1

• When arterial pressure increases, urine production increases
• When arterial pressure decreases, urine production decreases

Question 2

Two primary determinants

Answer 2

–The renal output curve for salt and water –The level of salt and water intake

Question 3

Antidiuretic hormone

Answer 3

Released by the pituitary gland

Question 4

ADH is released in response to

Answer 4

– ↑ osmotic pressure
• Hypothalmic osmoreceptors

– Hypovolemia (10% loss or greater)
• Atrial baroreceptors normally inhibit ADH release
• ↓ volume leads to ↓ firing rate  ↑ ADH release

– Hypotension
• ↓ arterial baroreceptor firing
• ↑ sympathetic activity and ↑ ADH release

– Angiotensin II

Question 5

ADH increases blood volume by

Answer 5

– ↑ water permeability in renal collecting ducts •  ↓ urine produc2on

Question 6

ADH action in severe hypovolemic shock

Answer 6

– ADH release is high
– Causes vasoconstriction
• ↑ total peripheral resistance

Question 7

Renin

Answer 7

Proteolytic enzyme released from the kidneys (juxtaglomerular cells)

Question 8

renin is released in response to what

Answer 8

– Sympathetic nerve activation
• Mediated by baroreceptor feedback

– Renal artery hypotension
• Independent of baroreceptor feedback

– Decreased sodium in kidney distal tubules

Question 9

the production of angiotensin II

Answer 9

decreased arterial pressure
renin released
renin substrate released from the liver (angiotensinogen)
these mix in the venous system to break down to form angiotensin I
which then travels through the lung and is converted by an enzyme into angiotensin II

Question 10

Angiotensin II

Answer 10

acts on resistance vessels

– ↑total peripheral resistance

Question 11

Angiotensin II acts directly on the kidneys

Answer 11

– Constrictsrenalarteries↓ blood flow via kidneys

Question 12

what effect does angiotensin II have un the adrenal glands

Answer 12

release of aldosterone

– ↑ Na+ and water reabsorption

Question 13

angiotensin II stimulates the release of what from the pituitary

Answer 13

ADH

Question 14

Atrial-natriuretic hormone

Answer 14

28-amino acid peptide synthesised and stored in muscle cells of the atria

Question 15

when is the atrial-natriuretic hormone

Answer 15

– Released in response to stretch of the atria – Helps oppose the effects of the RAAS system

Question 16

Hypovolaemia

Answer 16

– Loss of blood volume
• ↓ whole blood, e.g. hemorrhage 
• ↓ plasma, e.g. burns
• ↓ sodium, e.g. vomitting
– ↓↓ in blood pressure

Question 17

Classification of shock

Answer 17

– Class 1, 10-15% blood loss
– Class 2, 15-30% blood loss
– Class 3, 30-40% blood loss
– Class 4, >40% blood loss

Question 18

Immediate (reflex) response to hypovolemia - effect on SV

Answer 18

decreases on haemorrhage then compensates slightly when baroreceptors kick in

Question 19

Immediate (reflex) response to hypovolemia - effect on HR

Answer 19

remains the same until baroreceptors kick in and then there is a slight increase

Question 20

Immediate (reflex) response to hypovolemia - effect on cardiac output

Answer 20

drop significantly on haemorrhage then when baroreceptors kick in it makes a compensation

Question 21

Immediate (reflex) response to hypovolemia - effect on total peripheral resistance

Answer 21

this remains the same until baroreceptors kick in and then it increases

Question 22

Immediate (reflex) response to hypovolemia - effect on mean arterial blood pressure

Answer 22

this decreases on haemorrhage and then makes a full compensation when baroreceptors kick in

Question 23

Later response to hypovolemia

Answer 23

Arteriolar constriction
– ↓ hydrostatic pressure in the capillaries
– Favours fluid reabsorption
– Temporary redistribution

Decreased renal blood flow Baroreceptors plus thirst

Question 24

Severe hypovolemia

Answer 24

– Damage to tissues and organs can occur
– Heart fails

Fluid replacement required

Question 25

– Resuscitation fluids

Answer 25

• Colloid (gel/starch/albumin) or Hartmann’s
• Blood

– Fluid challenge algorithm
• Whilst monitoring central venous pressure

Question 26

Cortex

Answer 26

– Conscious effects of emotions

• Nerves from cortex to medullary CVC centre

Question 27

Time of day

Answer 27

– Diurnal variations due to hormones and cortical input

Question 28

Respiration

Answer 28

– Via mechanical movements
– Via chemoreceptors
• Aortic and carotid bodies detect changes in pO2
• If↓pO2 thenrateoffiring↑