Regulation of ECF volume Flashcards
What are the major ECF osmoses which dictate fluid movement?
Na & Cl
What % of the body is composed of water?
60% (42L)
In TBW, what does ICF make up?
2/3
28L
In TBW, what is the volume of plasma?
3L
What composes the ECF?
Interstitial fluid
Plasma
What is the volume of ECF?
14L (1/3)
What volume does the interstitial fluid compose?
11L
In what circumstances can high volumes of water be lost?
Vomiting
Diarrhoea
Excess sweating
A decrease in plasma volume resulting in a reduction in ____ to the heart.
Venous return
A reduction in venous return will result in a reduction in ___, ____ &____
SV
CO
BP
A drop is BP will be detected by which baroreceptors?
Carotid sinus baroreceptors
When the baroreceptors detect a drop in BP, what happens?
Sympathetic discharge
What does sympathetic activity do to the vasculature?
Increases TPR
Increases BP
What is released from the pituitary in response to hypovolaemia?
ADH
What does sympathetic activity do at the kidneys?
Increased renal arteriole constriction
Renin secretion
What does renin convert angiotensinogen to?
Angiotensin I
What converts Angiotensin I to Angiotensin II?
ACE
What effect does angiotensin II have at the peritubular capillaries?
Increases Na reabsorption at proximal tubule
What does angiotensin II stimulate the secretion of from the adrenal cortex?
Aldosterone
Where does aldosterone mediate its action?
Distal tubule
What maintains GFR?
Autoregulation
Where is the majority of water/ Na reabsorbed?
Proximal tubule
What is responsible for the constriction of afferent renal arterioles?
Sympathetic innervation
What is responsible for the constriction of efferent renal arterioles?
Angiotensin II
What is responsible for the control of Na reabsorption at the distal tubule?
Aldosterone
What type of hormone is Aldosterone?
Adrenal cortical steroid hormone
What mediates the release of aldosterone?
Kidneys
Where are the juxtaglomerular cells (JG) found?
In the afferent arteriole, just before the glomerulus
What is the specialised loop of the distal tubule called?
Macula densa
What forms the juxtaglomerular apparatus?
Juxtaglomerular cells
Macula densa
What cells produce the hormone renin?
JG cells
What is renin?
A proteolytic enzyme
What does renin act on?
Angiotensinogen
Where is angiotensinogen constantly produced from?
Liver
Where is ACE found?
Vascular endothelium
Pulmonary circuit
What does angiotensin II stimulate the release of from the adrenal cortex?
Aldosterone
Where in the adrenal cortex is aldosterone produced?
Zona Glomerulosa
What is the rate - limiting step in the RAAS pathway?
Production of renin
When is renin released?
When pressure in the afferent arteriole decreases, detected by JG cells
Sympathetic innervation
What are the JG cells described as?
Renal baroreceptors
When NaCl levels reduce, what happens to renin production?
Increases
What inhibits renin production?
Angiotensin II
ADH
In the kidneys, what detects changes in osmolarity?
Macula densa
In hypovoleamia, where does Na reabsorption occur?
Proximal & distal tubules
What 3 things does Angiotensin II mediate?
Aldosterone secretion
Potent vasoconstriction
Stimulates ADH secretion
What does auto regulation ensure?
GFR maintained
What has the biggest effect on ECF composition, volume or osmolarity in hypovolaemic conditions?
Volume
With a small reduction in ECF volume, what is there a large increase in?
ADH secretion
What has the biggest effect on ADH secretion, volume or osmolarity in normovolaemic conditions?
Osmolarity
What does ANP promote?
Na excretion
What happens to K levels in the presence of Aldosterone?
Loss of K, reabsorption of Na
What effect does aldosterone have on fluid volume?
Increased volume
What is the urination of Na called?
Natruiresis
What overrides Aldosterone?
ANP
What is Conn’s syndrome?
Hyperaldosteronism
Tumour of the adrenal cortex
Where is ANP secreted from in response to what?
Atrial cells
Increased blood volume
What does hyperglycaemia lead to? Why?
osmotic diuresis
Exceeds maximum reabsorptive capacity
In DM, does water move out at the descending Loop of Henle? Why?
No
High levels of Na & glucose present therefore osmotically active
Because water does not move out at the descending limb, the fluid will be less ____ in the ascending limb in DM.
Concentrated
In DM, a large volume of ____ & ____ is delivered to the distal tubule.
NaCl
Water
In DM, what happens to the medullary interstitial gradient?
Lost
Under normal conditions, a large volume of NaCl & water delivered to the distal tubule will result in…
Diuresis, loss of NaCl & water
If a large amount of NaCl is delivered to the distal tubule, what happens to renin secretion?
Inhibits renin secretion
In DM, why does ADH have little effect at the CD?
Loss of the medullary interstitial gradient
In DM, urinary diuresis occurs resulting in how much urine being produced/ day?
6-8L/day
What is one of the first symptoms experienced in DM?
Thirst
In DM, if diuresis occurs what will happen to the BP? What will be the worst outcome?
Hypotension
Hyperglycaemic coma
Why does hyperglycaemic coma occur?
Inadequate blood flow to the brain
Why does hypoglycaemic coma occur?
Inadequate glucose to the brain
What can loop diuretics cause?
K loss
Why is K lost with the use of loop diuretics?
Inhibits Na-K-Cl cotransporter.
