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Biology IB HL - 11.3 The Kidney Part 4
This deck covers key concepts related to kidney function and osmoregulation, focusing on the processes occurring in the nephron, the role of hormones, and the importance of maintaining water balance.
What do the tubules reabsorb?
The tubules reabsorb all glucose, amino acids, vitamins and hormones, along with most of the mineral ions (~80%) and water
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Key Terms
Term
Definition
What do the tubules reabsorb?
The tubules reabsorb all glucose, amino acids, vitamins and hormones, along with most of the mineral ions (~80%) and water
How are mineral ions and vitamins transported in the PCT - (proximal convoluted tubule)?
Mineral ions and vitamins are actively transported by protein pumps and carrier proteins respectively
How is glucose transported in the PCT?
Glucose and amino acids are co-transported across the apical membrane with sodium (symport)
How is water transported in the PCT?
Water follows the movement of the mineral ions passively via osmosis
What is the third process in the nephron?
Osmoregulation is the third of three processes by which blood is filtered and urine is formed
What is osmoregulation? (definition)
Osmoregulation is the control of the water balance of the blood, tissue or cytoplasm of a living organism
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| Term | Definition |
|---|---|
What do the tubules reabsorb? | The tubules reabsorb all glucose, amino acids, vitamins and hormones, along with most of the mineral ions (~80%) and water |
How are mineral ions and vitamins transported in the PCT - (proximal convoluted tubule)? | Mineral ions and vitamins are actively transported by protein pumps and carrier proteins respectively |
How is glucose transported in the PCT? | Glucose and amino acids are co-transported across the apical membrane with sodium (symport) |
How is water transported in the PCT? | Water follows the movement of the mineral ions passively via osmosis |
What is the third process in the nephron? | Osmoregulation is the third of three processes by which blood is filtered and urine is formed |
What is osmoregulation? (definition) | Osmoregulation is the control of the water balance of the blood, tissue or cytoplasm of a living organism |
Where does osmoregulation occur? | Osmoregulation occurs in the medulla of the kidney |
What is the role of the loop of Henle in osmoregulation? | The loop of Henle establishes a salt gradient (hypertonicity) in the medulla |
What is the role of ADH in osmoregulation? | Anti-diuretic hormone (ADH) regulates the level of water reabsorption in the collecting duct |
What is the function of the loop of Henle? | The function of the loop of Henle is to create a high solute (hypertonic) concentration in the tissue fluid of the medulla |
What is the descending limb permeable to? | The descending limb of the loop of Henle is permeable to water but not salts |
What is the ascending limb permeable to? | The ascending limb of the loop of Henle is permeable to salts but not water |
What is the solute like in the loop of Henle descending limb? | This means that as the loop descends into the medulla, the interstitial fluid becomes more salty and hypertonic |
What surrounds the loop of Henle? | Additionally, the vasa recta blood network that surrounds the loop of Henle flows in the opposite direction (counter-current) |
What is the role of the vasa recta? | This means that salts released from the ascending limb are drawn down into the medulla, further establishing a salt gradient |
WATER REABSORPTION What draws out water in the collecting duct? | As the collecting duct passes through the medulla, the hypertonic conditions of the medulla will draw water out by osmosis |
WATER REABSORPTION What controls water reabsorption? | The amount of water released from the collecting ducts to be retained by the body is controlled by anti-diuretic hormone (ADH) |
WATER REABSORPTION When is ADH released and from where? | ADH is released from the posterior pituitary in response to dehydration (detected by osmoreceptors in the hypothalamus) |
WATER REABSORPTION What is the role of ADH? | ADH increases the permeability of the collecting duct to water, by upregulating production of aquaporins (water channels) |
WATER REABSORPTION What do high levels of ADH do to urine? | This means less water remains in the filtrate, urine becomes concentrated and the individual urinates less (i.e. anti-diuresis) |
WATER REABSORPTION What happens when an individual is suitably hydrated? | When an individual is suitably hydrated, ADH levels decrease and less water is reabsorbed (resulting in more dilute urine) Remember: ADH is produced when you Are DeHydrated |
What is critical for the survival of an organism? | Maintaining an appropriate water balance within the body’s tissues and cells is critical to the survival of an organism |
What cannot be maintained if water levels are not regulated? | Homeostasis cannot be maintained if water levels drop (dehydration) or are raised (overhydration) without regulation |
What is dehydration? | Dehydration is a loss of water from the body such that body fluids become hypertonic |
What will individuals experience when dehydrated? | Individuals will experience thirst and excrete small quantities of heavily concentrated urine (to minimise water loss) |