Urine Production and Osmoregulation

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  • Created by: Lotto65
  • Created on: 13-10-17 19:12
What process occurs in the proximal convoluted tubule?
Selective resabsorption
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What is the function of the microvilli in the lumen of the PCT?
Large surface area for absorption
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What do the pump proteins do in the PCT cells?
Reabsorb useful substances by active transport
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What in the cells of the PCT allow active transport to take place?
Lots of mitochondria to produce ATP for active transport
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All of the ... is reabsorbed in the PCT
Glucose
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80% of the ... are reabsorbed in the PCT
Mineral ions (including sodium)
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If substances are transported by active transport, then there is a higher concentration of solutes where?
In the cells of the PCT (rather than the filtrate)
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What causes the movement of water in the PCT and how?
There are more solutes in the wall of the PCT which causes water to enter the cells by osmosis and then pass on into the blood
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Descending limbs of the loop of henle are permeable and impermeable to what?
Impermeable to ions and permeable to water
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The ascending limbs of the loop of henle are permeable and impermeable to what?
Impermeable to water but permeable to ions
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What happens to the ions in the ascending limb of the loop of henle?
They are pumped by active transport from the filtrate to the medulla to create a high concentration of solutes
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The high concentration of solutes in the medulla causes what to happen to water?
Water is drawn out of the descending loop of henle by osmosis to dilute the fluid in the medulla slightly
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How do we know the overall effect of the loop of henle is to increase solute concentration in the medulla?
The fluid leaving the loop of henle is more dilute than the fluid entering it
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What is the overall role of the loop of henle?
To create a higher concentration of solutes in the medulla than in normal body fluids (hypertonic)
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What happens in the distal convoluted tubule?
The filtrate passes through the distal convoluted tubule where ions can be exchanged between the filtrate and blood to adjust blood levels
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Give an example of a salt ion that is regulated by the DCT?
Calcium
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Name the substances reabsorbed in the PCT
Water, glucose, salts
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How are glucose and salts reabsorbed in the PCT?
Active transport
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What is the purpose of the intercellular and subcellular spaces in the PCT?
Increase surface area for export
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What does the active transport of glucose and salts do?
Creates an osmotic gradient for water to follow
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What is the interstitial fluid?
The fluid region between the ascending and descending limb of each loop of henle
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Water leaves the ascending limb of the loop of henle and enters...
The blood
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What is the name of the overall effect in the loop of henle and why is it called that?
Counter-current multiplier (ascending and descending limbs flow in opposite directions)
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What type of epithelium cells line the PCT?
Cuboid epithelium cells
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Glucose and amino acids are transported out of the PCT by...
A co-transport method
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The presence of glucose in the filtrate after the PCT indicates...
Diabetes
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Why do some animals have long loops of henle?
So lots of water is retained and not excreted
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What is osmoregulation?
The control of solute concentrations in the body fluids, especially blood plasma
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What is the function of the collecting duct?
Osmoregulation
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What does ADH stand for?
Anti-diuretic hormone
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Which gland secretes ADH?
Pituitary
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What is the reason for ADH secretion?
If water content in the blood is too low
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What is another word for ADH?
Vasopressin
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What does ADH do physically?
Increases the permeability of cells in the collecting duct to water by putting water channels into their membranes
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What is the name for the water channels in plasma membranes?
Aquaporins
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What causes water to be reabsorbed from the collecting duct?
High concentration of solutes in the medulla leads to water leaving the collecting duct by osmosis and reabsorbed
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In terms of solutes, when is ADH secreted?
When the internal solute concentration of body fluids is too high
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What sort of urine is produced with secretion of ADH?
Concentrated
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What happens to the water concentration of blood plasma when ADH is secreted?
Increases
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Is ADH secreted when the solute concentration of blood plasma is low?
No
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What happens physically if ADH is not secreted?
Collecting duct is less permeable to water due to removal of aquaporins from the membrane
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If ADH is secreted, will any water get through the collecting duct membrane?
Only a small amount
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What sort of urine is produced when ADH is not secreted?
Dilute
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What happens to the solute concentration of the blood if ADH is not secreted?
Increases
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As filtrate flows down the collecting duct, what is the interstitial fluid like?
Increasingly hypertonic
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What is created between the filtrate and interstitial fluid at the collecting duct?
An osmotic gradient
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What is another word for dilute urine?
Hypotonic
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What detects that the blood water concentration is too low?
Osmoreceptors in the hypothalamus
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What is another word for concentrated urine?
Hypertonic
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What type of feedback system is ADH? Why?
Negative feedback because as more water is transferred in to the blood and concentration regulates, ADH secretion stops
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What allows water balance to be tightly controlled?
ADH has a half-life of 15-20 minutes
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Why is blood flow in the opposite direction to filtrate flow in the collecting duct?
Allows a constant osmotic gradient between filtrate and blood
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Name a protein that is able to get into the filtrate?
hCG (gets through basement membrane)
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Is all urea filtered out?
Not all as ultafiltration is a passive process so not all passes into the filtrate and some is reabsorbed back into the blood
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Other cards in this set

Card 2

Front

What is the function of the microvilli in the lumen of the PCT?

Back

Large surface area for absorption

Card 3

Front

What do the pump proteins do in the PCT cells?

Back

Preview of the front of card 3

Card 4

Front

What in the cells of the PCT allow active transport to take place?

Back

Preview of the front of card 4

Card 5

Front

All of the ... is reabsorbed in the PCT

Back

Preview of the front of card 5
View more cards

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