Fluid Electrolyte Homeostasis Flashcards
what does sodium transport facilitate
reabsorption of nutrients, water and ions
how much filtrate is absorbed in the proximal convoluted tubule
65%
how much filtrate absorbed in the ascending loop of henle
25%
where in the kidneys is sodium transported regulated depending on the body’s requirements
in the distal convoluted tubule
which hormone inserts aquaporins into the distal convoluted tubule
adh / vasopressin
which hormone inserts sodium channels into the distal convoluted tubule
aldosterone
what kind of urine is produced from the actions of aldosterone and adh
small volume of concentrated urine
what does ANP do to the distal convoluted tubule
blocks the actions of adh and aldosterone to encourage fluid excretion and the production of a large volume of dilute urine
what is the importance of the hormonal regulation of filtrate composition in the DCT
overall homeostatic regulation of blood volume and pressure
what effects the levels of adh aldosterone and anp in the DCT
the changes in systemic blood pressure
what is the glomerular filtrate rate defined as
the rate at which blood plasma is filtered through the glomerulus into the bowman’s capsule
what influences the GFR
- glomerular hydrostatic pressure
- capsular hydrostatic pressure
- glomerular osmotic pressure
- systemic blood pressure
- renin angiotensin aldosterone system
- disease
what do the kidneys measure GFR as a proxy for
the systemic blood pressure
what generates the glomerular hydrostatic pressure
the fact that blood is arriving faster than it can leave
what is the osmotic potential determined by
the proteins staying in the blood that hold onto some of the fluid
list what is absorbed in the PCT
- 65% sodium and water
- 100% glucose and amino acids
- 50% waste, urea
what is absorbed in the descending loop of henle
water
what is absorbed in the thick ascending limb
25% sodium and potassium and chlorine
where in the kidneys can water be absorbed
- PCT
- descending loop of henle
- DCT
- collecting duct
why is the concentration of sodium in the filtrate higher if the blood pressure is higher
because the hydrostatic pressure is greater meaning the filtrate flows much faster and there is less time for the sodium to move out
what does the juxtaglomerular apparatus do
it connects the distal convoluted tubule with the glomerulus, and measures and responds to changes in the sodium concentration of the filtrate
describe the location of the juxtaglomerular apparatus
it is next to the glomerulus, and is surrounding the afferent arteriole. connects glomerulus to DCT
what does the macula densa do
detects the sodium concentration
what do the juxtaglomerular cells do
they adjust the diameter of the afferent arteriole depending on sodium concentration being detected by the macula densa
what are juxtaglomerular cells
modified smooth muscle cells
describe how blood pressure affects sodium filtrate concentration
blood pressure affects glomerular hydrostatic pressure which affects glomerular filtrate rate which affects the sodium filtrate concentration
describe the state of the juxaglomerular apparatus when blood pressure is homeostatic
- no issues sensed in the macula densa
- no signals sent to JG cells
- diameter of afferent greater than efferent
describe the state of the JG apparatus when the blood pressure is elevated
- increased blood pressure
- increased hydrostatic pressure
- increased sodium concentration in the filtrate
- macula densa take up the sodium and water will follow due to osmosis
- the cells swell and release adenosine from basolateral membrane
- adenosine acts on JG cells to make them constrict and reduce the diameter of the afferent arteriole to reduce the hydrostatic pressure
what is the name of the feedback system in the JG apparatus to regulate the blood pressure
tubuloglomerular feedback
describe the state of the JG apparatus when blood pressure decreases
- decreased BP
- decreased glomerular hydrostatic pressure
- decreased glomerular filtrate rate
- decreased sodium filtrate concentration
- macula densa senses this, water and sodium drawn out of macula densa making it shrivel
- release of prostaglandins from macula densa
- act on JG cells to dilate the diameter of the afferent arteriole and will also release renin to activate RAAS
- blood pressure restored
describe the series of events in the RAAS system
- angiotensinogen released into circulation
- renin converts angiotensinogen into angiotensin I
- angiotensinogen convert ing enzyme converts angiotensin I into angiotensin II
- angiotensin II potent vasoconstrictor and will rapidly increase blood pressure
list all the actions of angiotensin II
binds to target receptors on the following:
- arterioles for constriction
- hypothalamus to stimulate thirst
- pituitary gland to release ADH
- adrenal cortex to release aldosterone
how does RAAS ultimately restore blood volume
via increased fluid and salt retention
what happens in the kidneys when there is raised blood pressure
baroreceptors detect this and stimulate the release of ANP to counteract the actions of adh and aldosterone and increase water and salt excretion
chronic kidney disease reduced GFR. what does this cause
- inadequate removal of fluid and waste products of metabolism
- inappropriate activation of RAAS
what can cause chronic kidney disease
- hypertension
- diabetes
- high cholesterol
- kidney infections
- glomerulonephritis
- polycystic kidney disease
- kidney stones
- long term use of NSAIDS
what are kidney stones
waste products of metabolism that start to crystallise, some can be passed without notice but some can be very painful
what are the symptoms of chronic kidney disease
- hypertension
- nausea
- oedema
- blood or proteins in the urine
- aneamia
- weak or painful bones
where is oedema likely to occur in cases of chronic kidney disease
ankles, hands, feet and lungs
how can hypertension be regulated
- diet and weight loss
- combination of anti hypertensive treatments
- diuretics
- ace inhibitor/angiotensin receptor blocker
- aldosterone agonists
what is furosemide an example of
a diuretic drug
what does furosemide target
NKCC2
what does NKCC3 regulate
the sodium reabsorption on the apical membrane in the kidneys
how much kidney function is there in stage five kidney failure
15%
what is dialysis
the artificial removal of waste, solutes, water and toxins from blood
what are the two types of dialysis
haemodialysis
peritoneal dialysis
what is the renal blood flow rate
1.2 litres a minute
