homeostasis and the kidney Flashcards
Explain the function of the loop of henle is osmoregulation (4)
- water leaves the descending limb
- at apex Na+ is very concentrated
- Na+ is pumped out of the ascending limg
- lowering the water potential in the medulla
- ascending limb is impermeable to water
- counter current system = neutral
Describe how hormonal control affects the final concenrtration and volume of urine produced when someone is dehydrated (4)
- low water potential of blood detected by osmoreceptors/hypothalmus
- secretion of ADH by posterior pituitary gland
- causes collecting duct to become more pereable to water
- water moves into the medulla vi osmosis
- quickly removed by the vasa reca
- low volumes of concentrated urine produced
Explain what is meant by the term homeostasis (2)
- maintenance of an intrnaal environmenrt
- despite internal and external changes
Apart from water and glucose name two substances which will be present in the filtrate (1)
- urea
- amino acids
- fatty acids /glycerol
- small proteins
- inorganic ions
- salt
Name the process which seperates these molecules from the blood plasma (1)
ultrafiltration
The filtration rate is the total volume of filtrate formed per minute. explain the effect of a large loss of blood from the body on the filtration rate (2)
- blood pressure decreases
- less filtrate formed
Name the part of the nephron which provies the osmotic gradient for reabsorption (1)
loop of henle
Suggest one way in which the loop of henle might be modified in desert animals (1)
increased length/longer
What i the main excretorry product for freshwater fish , bird and mammals (3)
- fish - ammonia
- bird - uric acid
- mammal - urea
Wich excretory product requires the least volume of water for it’s excretion (1)
explain one further advantage of the excretory product (1)
- uric acid
- little mass for storage in eggs/light for flight
Describe the mechanisms that are triggered in the mammalian body when water intake is reduced (6)
- low water levels/ low water potential in blood
- detected by osmoreceptor
- in hypothalmus
- more ADH secreted from posteriori pituitary gland
- travels into blood
- collecting duct/ distal convoluted tubule becomes more permeable/more aquaporins
- water absorbed
- because of low water potential in the medulla
Suggest a condition which might stimulate ADH secretion (1)
- blood loss
- vomiting
Explain how the nephron and its blood supply is adapted for ultrafiltration (5)
- mention of glomerelus and bowmans capsule
- glomerlus has a high blood pressure
- fferent arterioles is wider than efferent
- glomerelus capillaries have manhy fenstrations
- basement membrane allows filtrate throguh
- allowings small molecules -large proteins throguh
- coorect function of podocytes and filtration slits
Use you knowledge of the role of the kidney suggest why a protein controlled diet and low sodium chloride intake is recommended (3)
- protein controlled diet - high protein more urea cannot be removed
- low sodium chloride - excess salt does not need to be removed
- high salt cuases high blood pressure
Give two eamples of what might cuse a rie in blood solute concentration (1)
- high solute intake
- sweating / low water intake / vomiting / diahrrea
What would be the result of high levels of ADH at the collecting duct (1)
- increased peremeability of the collectinf duct to water
- more aquaporines
Explain how chlroide ions are selectivley reabsorbed (2)
- facilitated diffusion
- down a concentration gradient
Describe how water is selectivley reabsorbed (3)
- osmosis
- high wter potential to low water potential
- patially permebale membrane
Describe how sodium ions are selectivley reabsorbed (3)
- facilitted diffusion into cell from glomerular filtrate
- sodium potassium pump
- ATP used
Describe how glucose and aino acids are selectivley reabsorbed (3)
- facilitated diffusion
- glucose and amino acids diffuse with sodium ions
- glucose and amino acids diffuse fand glucose activley transported from PCT cell into blood
Suggest why the sodium chloride nd glucose improve water reabsorpetion by the kidneys (3)
- more sodium and glucose absorbed from gut into blood
- more glucose and sodium ions in glomerular filtrate
- more sodium ions diffuse into PCT higher gradient
- more glucose co transported
- lower water potential - more water reabsrobed by osmosis
- reference to loop of Henle/collecting ducts
State two variable whcih would need to be considered when comparing results form a numbeer of people who have drunk similar volumes of water (2)
- age
- sex
- activity levels
- diey
- previous fluid intakr
- mass
- external temperature
- normal kidney function
Explain how high hydrostatic pressure is achieed in the glomerlus (1)
affrent arteriole is wider than effernet arteriole
Suggest which type of organic molecule in the blood is responsible for mainintaining the blood osmotic pressure (1)
