Homeostasis and the kidney Flashcards
What are the kidney’s 2 main functions
Osmoregulation
Removal of metabolic waste
What are the excretory products in humans
Bile products
CO2
Urea
What is the excretory product in birds
uric acid
What is the excretory product in fish
ammonia
How are excess amino acids broken down
In the liver in a deamination reaction to produce urea which is a safe waste product
What is homeostasis
The maintenance of constant internal conditions
What is negative feedback
Negative feedback is a reaction that causes a decrease in function. It occurs in response to some kind of stimulus. Often it causes the output of a system to be lessened; so, the feedback tends to stabilize the system.
Name the parts of the nephron in the order blood passes through them
Glomerulus Bowman's Capsule Proximal Convoluted Tubule Loop of Henle Distal Convoluted Collecting Duct
Name the parts of the kidney from the centre outwards
Pelvis
Medulla
Cortex
What is the function of the glomerulus and Bowman’s Capsule
Ultrafiltration. High hydrostatic pressure in the capillary knot of the glomerulus forcing small molecules into the Bowman’s capsule.
How is high hydrostatic pressure generated in the glomerulus
Blood enters in the afferent arteriole which is wider than the efferent arteriole through which it leaves, causing a build up of pressure
What are the layers in the Bowman’s space
Capillary Walls
Basement Membrane
Squamous epithelial layer
How do you calculate the blood filtration rate
volume of filtrate produced/volume of blood entered x100
Where does selective reabsorption occur
In the proximal convoluted tubule
How does selective reabsorption occur
Useful substances are reabsorbed through active transport and diffusion by vasa recta capillaries
How do glucose and amino acids enter cells in the PCT to be reabsorbed
Co transport with sodium ions
How do chloride ions and water enter the cells in the PCT to be reabsorbed
Facilitated diffusion and osmosis
How do the following leave the cells in the PCT to enter the bloodstream
- glucose
- amino acids
- water
- chloride ions
- sodium ions
- facilitated diffusion and secondary active transport
- facilitated diffusion
- osmosis
- facilitated diffusion
- sodium-potassium pump by active transport
What is the glucose threshold
If the concentration of glucose in the blood is too high the intrinsic proteins are limited and not all the glucose is reabsorbed and so passes out in the urine
Where does the reabsorption of water occur
In the loop of henle
Describe the permeability of the descending limb of the loop of henle
Permeable to water, impermeable to salts
Describe the permeability of the ascending limb of the loop of henle
Impermeable to water, permeable to salts
What is the fluid inside the loop of henle referred to
filtrate
What is the fluid around the loop of henle referred to
tissue fluid
Describe how the reabsorption of water works
NaCl is actively pumped out in the ascending limb, leaving water behind. This lowers the water potential in the tissue fluid, which draws in water from the descending limb. Therefore, the filtrate is its most concentrated at the apex.
How are animals’ loop of henle adapted to their environment
Longer loops allow for more water reabsorption, so desert animals have longer loops
How is homeostasis restored when you’re dehydrated
Blood will have a low water potential which will be detected by the hypothalamus, which signals to the posterior pituitary gland to release ADH. This makes the DCT and convoluted tubule more permeable to water which means more is reabsorbed
What is the action of ADH
Increases reabsorption of water
What is the purpose of aquaporins
ADH binds to ADH receptors on the cell membrane when it is released. This causes vesicles of aquaporins to bind with the cell membrane, increasing permeability which increases the amount of water reabsorbed.
How is a dialysis machine adapted to work
Counter current flow
Increased surface area
Temperature controlled
Dialysis fluid constantly replaced to maintain conc. gradient
What is a consequence of having a kidney transplant
You must take immunosuppressants for the rest of your life
What conditions can cause kidney failure
Diabetes and high blood pressure
Name two types of dialysis
Haemodialysis and peritoneal
