Kidney biology! Flashcards
what are the four most important features of our internal environment that need to be kept constant
Chemical composition, Blood pH, osmotic pressure, and temperature.
In terms of temperature, catagorise the classes of fish, mammals, birds and amphibia
Mammals and birds regulate their temps (endotherms) and fish and amphibia dont regulate their temps (ectotherms)
How can ectothermic organisms help control their temperatures?
Behaviours like basking, muscle movement or conforming to their environment.
What can be named as the “control centre” for temperature regulation?
The hypothalmus.
What are some of the response mechanisms that are displayed for thermoregulation?
Blood vessels dialating or constricting, sweating, piloerection (hairs sticking up), shivering
What does it mean if one solution is said to be HYPERosmotic to another?
That that solution contains MORE solutes than the other. Therefore contains LESS water.
What does it mean if one solution is said to be HYPO-osmotic to another?
That that solution contains LESS solutes than the other. Therefore contains MORE water.
Which way will water move in relation to a hyperosmotic solution?
Hyperosmotic solutions contain less water therefore water will move into these solutions to try and balance concentrations.
How can you work out the number of osmoles solute per litre of solution?
Osmolarity/solute concentration.
Name three functions of the kidneys
Removal of nitrogenous waste, regulation of water content in the body, and regulation of salt balance.
What are the three types of substances which remove nitrogenous substances called?
Urea, Uric acid, and Ammonia
Why do the kidneys receive so much of our cardiac output?
They control the chemical composition of blood in our body.
Name the two types of kidney nephrons and their functions
Juxta-medullary which help to produce very concentrated urine. Cortical which produce less concentrated urine
What type of kidney nephron is most abundant?
Cortical (85%)
How does fluid move in Bowman’s capsule? Describe this method.
Via ultrafiltration - the blood pressure forces fluid through the glomerular capillaries into bowman’s capsule.
Why do not all substances pass into bowman’s capsule?
As molecules over a certain size are too large to fit through the podocyte split-pores.
How can you work out the glomerular ultrafiltrate?
Blood plasma minus plasma protiens.
Define hydrostatic force
The force a liquid exerts on the walls of whatever is containing it
Why is blood pressure high in glomerular capillaries?
Constriction of the arteriole, number of capillaries, low resistance input pathway.
what does Glomerular hydrostatic pressure promote?
The movement of fluid and molecules out of the plasma and into bowman’s capsule.
What does glomerular colloid osmotic preessure promote?
The movement of water back into the capillaries.
What is the glomerular filtration rate?
How much of the blood plasma is filtered into the kidney tubules per minute
True or false: Kidneys do not show selective excretion
False - kidneys do show selective excretion.
What are the two mechanisms to form urine?
Tubular REabsorption of water and solutes into the body. Substances are selectively secreted from the body into the tubule.
What percentage of solutes and water are reabsorbed in proximal and distal tubules?`
70-75%
How are molecules actively transported out of the tubules?
Specificity of substrate and enzyme cause a conformational change when they bond which moves the molecule outwards.
What is the renal threshold mechanism?
When kidneys regulate the concentration of a substance in the blood.
What is glucose in the urine a sign of?
Diabetes mellitus
What is the renal threshold for glucose?
180mg/100ml
How does the loop of Henle aid water reabsorption?
Through a countercurrent multiplier system
Why do mammals need to produce urine which is hyperosmotic to blood?
To conserve water - blood should reabsorb lots of the water.
What part of the kidney is maintained at a high osmolarity to provide the force for recovering water?
The medulla
How does the Countercurrent multiplier system work?
Traps heat in the body core, thus reducing heat loss to extremities. Veins absorb some of the heat from the arteries.
In the ASCENDING limb of the loop of Henle, what substance leaves, and is this process active or passive?
NaCl is transported out both passively (in the inner medulla) and actively (outer medulla)
IN the DESCENDING limb of the loop of Henle, water leaves. By what process does this occur, and why?
Water moves outwards by osmosis due to the increasing concentration of NaCl in the interstitial fluid of the medulla.
What leaves the collecting ducts? What does this mean for the end concentrations in the urine when compared to the blood?
Urine is isosmotic to the medulla but hyperosmotic to the blood.
What does the loop of Henle maintain in the medulla?
A global NaCl gradient
True or false: Some urea is lost by diffusion?
True
Where are the places with the highest osmolarity in the medulla?
The hairpin of the loop of Henle and the bottom of the collecting duct.
Offer an explanation as to why DESERT mammals would only have juxta-medullary nephrons.
They live in very hot climates so need to conserve as much water as possible. Juxta-medullary nephrons are responsible for creating very concentrated urine (contains less water)
True pf false: Kidneys are the only organ which control osmoregulation?
False - other organs are involved too (e.g. gills in fish.)
Which kind of nephrons do reptiles have?
Cortical
Offer an explanation as to why freshwater fish dont have loop of Henle’s.
They are hyperosmotic to their surround (surrounded by water) therefore do not need to the loop of Henle’s to ensure concentrated urine.
What are the receptors for the control system of dehydration in mammals?
osmoreceptors in the hypothalamus and the caroid artery
What is the effector in the control of dehydration in mammals? Where is this released from?
ADH released (vasopressin) from the posterior pituitary gland.
What effect does ADH have on the kidneys?
Increases the permeability of the collecting ducts - triggers the insertion of proteins (aquaporins) onto the apical membranes.
Where does ADH bind to?
Receptors on the basal membrane of the collecting ducts
How is over-hydration controlled in mammals?
Decreased stimulation of osmoreceptors inhibits secretion of ADH. Collecting ducts then become less permeable to water.
What characterizes diabetes insipidus?
The lack of ability to produce/react to ADH
