The kidneys Flashcards
1
Q
State the parts of a nephron
A
- glomerulus
- bowman’s capsule
- proximal convoluted tubule
- descending limb of loop of Henle
- ascending limb of loop of Henle
- distal convoluted tubule
- collecting duct
2
Q
Where do the collecting ducts of the nephrons lead to?
A
- lead to the ureter which travel to the bladder where urea can be stored
- it is then excreted out via the urethra
3
Q
Describe selective reabsorption in the proximal convoluted tubule
A
- The sodium potassium pump on cells lining the PCT actively pump Na+ ions out of these cells
- this causes Na+ ions to diffuse down their concentration gradient from the fluid in PCT to cells lining it
- Na+ ions can only diffuse with a cotransporter protein which either cotransports glucose or amino acid sir ions with the sodium ions.
- these molecules then diffuse out of the cells lining the PCT via facilitated diffusing using protein channel
- increased water potential so water also moved into blood via osmosis down water potential gradient.
- PCT is where majority of the water is retained
4
Q
What happens during selective reabsorption in the loop of Henle?
A
- in the ascending limb, at the bottom sodium and chloride ions passively diffuse out into tissue fluid but at the top they are actively pumped out.
- decreased water potential in tissue fluid because increased ion concentration
- urea also diffuses out of PCT and collecting duct to further decrease water potential
- ascending limb is impermeable you water
- water moves down water potential gradient from the descending limb to tissue fluid
5
Q
What is the function of the distal convoluted tubule?
A
- maintains the pH of blood
- maintains salt levels
- actively transports sodium into tissue fluid
- controlled by aldosterone hormone
6
Q
What is osmoregulation?
A
- maintenance of water potential in the blood via negative feedback mechanisms
7
Q
Where is the anti diuretic hormone produced and where does it travel to?
A
- it is produced by the neurosecretory cells in the hypothalamus when the osmoreceptors, which is also in the hypothalamus, detect a change in water potential levels
- when water potential is very low, it causes osmoreceptors to shrink and release the hormone ADH
- ADH travels to prosterier pituitary gland where it is stored
8
Q
Which parts of the nephron does the hormone ADH affect?
A
- distal convoluted tubule
- collecting duct
9
Q
What does ADH do?
A
- ADH is a peptide hormone so it binds to receptors on the cells lining the collective duct
- this activates the phosphorylase enzymes
- this cause vesicles containing small fragments of the cell surface membrane to move towards the cell surface membrane and fuse
- aquaporins inserted so more water can diffuse out faster
10
Q
What needs to be done to actually solve the issue of low water potential in blood?
A
- you need to actually drink water because the kidneys can only minimise the effect but not actually solve the problem
11
Q
Why do desert animals have longer loops of Henle?
A
- they have less access to water
- longer ascending limb means more sodium and chloride ions can be pumped to tissue fluid of medulla
- water potential of medulla tissue fluid would be lowered more
- more water will diffuse out of descending limb via osmosis
12
Q
what is the difference between urea and urine/
A
- urea is produced by the deamination of amino acids
- urine is the fluid produced by the kidneys
13
Q
what are the nitrogenous waste excreted by the kidneys?
A
- urea produced by deamination and then the ornithine cycle
- uric acid which is from the deamination of purines(adenine and guanine)
- creatine formed form muscle metabolism
14
Q
Why can fish excrete ammonia?
A
- freshwater fish usually excrete ammonia and have no need to produce urea because ammonia is highly soluble and so can dissolve in the surrounding water and can easily get diluted to safe levels
15
Q
Why does urea not need a lot of water for it to be excreted out of the body?
A
- it isn’t as toxic as ammonia
16
Q
what is included in the three part filter of ultrafiltration?
A
- capillaries which contain fenestrations between the endothelial cells
- basement membrane which consists of collagen and glycoproteins
- podocytes which contain finger like projections that wrap around the capillaries of the glomerulus
17
Q
Describe the process of ultrafiltration
A
- due to the high hydrostatic pressure, molecules that are small enough are passed through the fenestrations of the capillaries
- blood cells and platelets remain in the blood as they are too big to pass the capillary fenestrations
- proteins that can pass through fenestrations are repelled by the negatively charged basement membrane which is made of collagen and glycoproteins as proteins are also negatively charged
- podocytes with finger like extensions that giev space for the filtrate to pass through
- any substance with a molecular weight of less than or equal to 69000 can pass the basement membrane
18
Q
Where is most of the water retained?
A
- proximal convoluted tubule
19
Q
what is reabsorbed during selective reabsorption?
A
- all of the vitamins, hormones, glucose and amino acids
- most of the sodium chloride and water is reabsorbed as well
- sodium ions are actively pumped while chloride ions and water follow down concentration gradients
- a significant amount of urea is reabsorbed too because the concentration of urea is higher in the filtrate that in the blood but enough urea is still being removed by the body that it isn’t toxic
20
Q
state three ways in which the cells lining the cells of the proximal convoluted tubule is adapted for selective reabsorption?
A
- has a lot of mitochondria as ATP is required for active transport needed by sodium potassium pumps
- has microvilli which provides a large surface area for cotransporter proteins
- the cells are also tightly packed meaning no fluid can pass between the cells and all substances reabsorbed must enter the cells lining the PCT
21
Q
describe a positive pregnancy result?
A
- hCG is small enough to pass from the blood to the filtrate
- human chorionic gonadotrophin hormone binds to its complementary mobile antibodies
- this hormone antibody/hormone complex travels down the strip
- once it reaches the first window, it binds to its specific immobilised antibodies as they are complementary to the complex
- the highly concentrated complex will show a coloured line due to the die attached to the mobile antibodies
- the excess unbound mobile antibodies will bind to its specific immobile antibodies in the control zone
- two coloured lines will result in a positive result
22
Q
why is it that when hCG is present, the strip where the urine touches isn’t shown blue?
A
- the blue line appears when there is a high concentration in one place
23
Q
where are podocytes found?
A
- bowman’s capsule
24
Q
how will the composition of blood change if the kidney has failed and substances remain in blood?
A
- higher urea concentration
- more water
- more creatine
- more ions and salts
25
how will the composition of the blood change if kindey has failed and bigger substances can pass to the kidney?
- less plasma proteins
- less glucose
- less water
- less ions and salts
26
Why is it important that they donor kidney matches the tissue of patient as much as possible?
- because the immune system would recognise the foreign antigens on the donated kidney cells and the lymphocytes and macrophages would attack them, causing rejection
- immunosuppressant drugs would be needed to supress the immune system from rejecting the kidney tissue
- size also has to be considered because for example, a child's kidney would be way too small
27
Where is ADH made and where is it stored?
- it is made in the hypothalamus by neurosecretory cells
- it is stored and released in the prosterior pituitary gland when osmoreceptors detect a change in the water potential of the blood and send an impulse to the prosterior pituitary gland
28
What causes the pituitary gland to release stored ADH?
- A decrease in the water potential of blood causes osmoreceptors to shrink and this sends an impulse travels to the prosterior pituitary gland, causing ADH to be released into the blood
29
what potential side effects could be caused by steroids?
- infertility
- depression
- liver damage
- heart attack
30
why should steroids not be permitted in sport?
- it gives them an unfair advantage
- there may be side effects
- it helps them train for longer as it helps build more muscle mass
- it doesn't reflect the athlete's natural talent
31
what is the difference between secretion and excretion?
- excretion is the removal of metabolic waste from the body
| - secretion is releasing useful products into the body from glands or ducts
32
what are the similarities between excretion and secretion?
- they both require ATP
- they are both involved in homeostasis
- they both require molecules crossing a membrane
33
what is the actual filter of the three part filter?
- the basement membrane
34
what precautions can be taken to avoid dehydration in diabetes insipidus?
- drink plenty of water
- take desmopressin drugs
- reduce salt content in diet
35
why aren't all excess amino acids deaminated?
- some undergo transamination
36
what is the purpose of transamination?
- sometimes, the body doesn't have the right balance of amino acids to match its requirements
37
why is it important that ammonia is converted to urea via the ornithine cycle?
- urea is less toxic
- it is less soluble so it doesn't require large amounts of water to excrete
- water potential can be maintained
- body won't face dehydration
38
why can freshwater fish excrete ammonia?
- as ammonia more soluble than urea, it can be rapidly excreted before it reaches a concentration where it is toxic
39
what is uric acid?
deamination of purines
40
give two macromolecules that form nitrogenous waste when broken down?
- proteins
| - nucleic acids
41
Why do birds and insects excrete uric acid?
- its solubility is very low so doesn't require a lot of water to excrete
- these animals are prone to water loss so it is important that they conserve water
