deck_1412560 Flashcards
What happens in the glomerulus?
Plasma is filtered through itLarge proteins cannot be filtered but small ions can 20% is filtered whilst 80% remains in the blood
What happens in the proximal convoluted tubule?
Reabsorbs about 67% of ions as well as water– has isosmotic reabsorption
What is isosmotic reabsorption?
The concentrations of ions is the same at the start and the end of the PCT
What ion transporters are found in the PCT?
Na-H antiporter Na-glucose symporter
What is glomerulotubular balance?
The glomerular filtration rate and the reabsorption in the proximal convoluted tubule are matched– always have 67% of Na conc absorbed
Describe the myogenic response
Afferent arteriole dilatation or constriction to control the flow of blood entering the kidneys so that it will always stay similar.
What myogenic response occurs with an increased BP?
Afferent arteriole constriction
What myogenic response occurs with a decreased blood pressure?
Afferent arteriole dilatation
What is the main ion that controls the reabsorption of water?
Sodiumwhich is coupled to chloride movement – it is always assumed that chloride ions will be moving with Na in order to maintain electroneutrality.
What is the effective circulating volume?
The volume of arterial blood effectively perfusing the tissue.
How do chlorine molecules move?Where are most of the chlorine molecules reabsorbed?
Can be: transcellular and active paracellular and passive60% reabsorbed in the proximal convoluted tubule.
What ion channels are found in the loop of henle?
NaKCC2 symporter
What ion channels are found in the early distal tubule?
NaCl symporter
What ion channels are found in the later part of the distal tubule?
ENaC (epithelial Na channels)
What ion channels are found in the collecting duct?
ENaC (epithelial Na channels)
Describe the ion movements that take place in the early PCT
Na uptake is high – is governed by oncotic and hydrostatic forcesCl is not being transported across, so there is a proportional increase in the amount of chloride ions present as H2O is leaving too.
How is Na taken up in the PCT?
Is co-transported with glucoseNa-H exchangeCo-transport with AA/Carboxylic acidsCo-transport with phosphateAquaporin
What ion movements occur in the latter part of the PCT?
Mostly Cl is reabsorbed passively due to electrochemical gradient from Na reabsorption as well as some being transported transcellularly using ATP.
What are some driving forces behind water reabsorption?
- Osmotic gradient established by the solute reabsorption2. Increased hydrostatic forces in the interstitium3. Increased oncotic force in the peritubular capillary due to the loss of 20% of filtrate
Give some characteristics of reabsorption in the loop of henle?
Ascending and descending limb have different tubular cells so have different adaptations for the absorption of different ions.
What reabsorption takes place at the descending limb?
Absorbs water but not NaClHas lots of aquaporin channelsH2O follows osmotic gradient.
What reabsorption takes place at the ascending limb?
Absorbs NaCl but not water. Has tight junctions beween cellsNaCl is reabsorbed by NaKCC2 and Na is moved into the interstitium by Na/K/ATPase. ROMK allows K to leak back into lumen (v. important)
What ion channel do loop diuretics target?
NaKCC2
When is the myogenic response activated?
When there are momentary fluctuations – only used in the short term
What happens at the distal convoluted tubule?How is it controlled?
Reabsorption here depends on the needs of the body. ADH secretion determines water reabsorption.
