Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A2 BIO UNIT3 > 3.7 Homeostasis & the Kidney > Flashcards

3.7 Homeostasis & the Kidney Flashcards

1
Q

What is meant by homeostasis?

A
  • maintenance of a constant internal environment
  • body kept in dynamic equilibrium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is homeostasis controlled by?

A
  • endocrine system
  • hormones that operate by negative feedback
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define negative feedback

A
  • where a change in a system produced a second change which reverses the initial change
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain negative feedback mechanism

A
  • set point for a factor is the norm at which a system operates
  • a receptor detects the level of the factor and its deviation from the set point
  • the receptor sends instructions to a coordinator or controller
  • the coordinator communicates with one or more effectors which make responses that are corrective
  • the factor returns to normal, monitored by the receptor and the information is fed back to effectors which stop making the correction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Briefly explain how glucose concentration in blood plasma is maintained

A
  • if too high, insulin is secreted to encourage conversion of glucose to glycogen for storage
  • if too low, glucagon is secreted to break down glycogen to glucose
    —> all detected by pancreas and go to liver
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Briefly explain how body temp is maintained

A
  • if get too cold, increased respiration generates heat and the constriction of blood vessels enables the body to retain heat
  • if get too warm, blood vessels dilate and heat radiates from body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define excretion

A
  • the removal of nitrogenous metabolic waste from the body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define osmoregulation

A
  • the control of the water potential of body fluids (plasma, tissue fluid and lymph) by regulating the water content and therefore solute concentration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Equation for production of urea

A

amino acid —> alpha keto acid + ammonia —> urea

CHR.NH2.COOH —> R.CO.COOH + NH3 —> O=C(NH2)2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Draw and label a kidney

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is found in the cortex?

A

Nephrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is found in the pyramids of medulla?

A

The loop of henle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Role of renal vein and artery

A

Artery: blood to kidney
Vein: blood from kidney

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Draw and label a nephron

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe a nephron

A
  • blood filtering unit
  • afferent arteriole brings blood to nephron
  • blood carried by efferent arteriole to a capillary network and the vasa recta (capillary network around loop of henle)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What arteriole brings blood to the glomerus?

A

Afferent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is blood in the afferent arteriole under high pressure?

A
  • afferent arteriole has wider diameter than the efferent arteriole
  • the hearts contraction increases the pressure of arterial blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What 3 layers separate the blood entering the glomerus and the Bowman’s capsule?

A
  • the wall of the capillary which is a single layer of endothelial cells
  • basement membrane is an extra cellular layer of proteins, mainly collagen and glycoproteins. It has a molecular filter and selective barrier that act like a sieve between the capillary and nephron
  • the wall of the capsule is made of squamous epithelial cells called podocytes which has pedicels that wrap around the capillaries. The gaps between pedicels are filtration slits
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Components of the glomerular filtrate

A

Water, glucose, salts, urea, amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Water potential of blood flowing into efferent arteriole

A

Low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is meant by selective reabsorption?

A

The uptake of specific molecules and ions from the glomerular filtrate in the nephron back into the blood stream

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe role of PCT

A
  • longest and widest part of nephron
  • carries filtrate away from bowman’s capsule
  • blood around PCT reabsorbs all the glucose and amino acids, some urea and most of the water and sodium and chloride ions from the filtrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Features of the PCT

A
  • large SA as longest part of the nephron and there are millions of nephrons
  • cuboidal epithelial cells increase the SA with microvilli and invaginations called basal channels - short diffusion distance
  • many mitochondria to provide ATP for active transport
  • a close association with capillaries - short diffusion distance
  • tight junctions between the cells of the PCT epithelium - multi protein complexes encircle the cell and attach to it tightly to prevent molecules from diffusing to adjacent cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Briefly explain selective reabsorption from the PCT

A
  • 70% of salts in filtrate are reabsorbed into blood by active transport using membrane pumps
  • all glucose and amino acids are reabsorbed into blood by co-transport with Na+ ions
  • 90% of water in the glomerular filtrate is reabsorbed passively by osmosis as the reabsorbed ions lower the water potential
  • 50% of urea and small proteins is reabsorbed into blood by diffusion and a steep conc gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Explain the co-transport of glucose and amino acids

A
  • glucose or amino acids and 2x Na+ ions binds to a transporter protein in the cuboidal epithelial cell membrane and enter by facilitated diffusion
  • Na+ ions pumped into capillary, reducing their conc and more Na+ enters cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Define and explain secondary active transport

A
  • the coupling of movement, eg of Na+ ions, down their electrochemical gradient with the movement of another molecule, eg glucose
    —> not using energy from ATP directly but from electrochemical gradient of Na+ ions from lumen into cell, which was generated by active transport of Na+ into capillary
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What happens to the filtrate at the base of the PCT?

A

It is isotonic with the blood plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What happens if the glucose concentration in the filtrate is too high?

A
  • cannot absorb all the glucose
  • too few transport molecules in the membrane to absorb it
  • glucose pass through loop of henle and is lost in urine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What might cause the glucose conc of urine to be too high?

A
  • the pancreas secreting too little insulin (type I diabetes)
  • the response of liver cells to insulin is reduced because insulin receptors in surface membranes are damaged (type II diabetes and gestational diabetes)
30
Q

% of water reabsorbed by PCT and collecting duct

A
  • 90% of water filtered at Bowman’s capsule is reabsorbed into PCT
  • 5% reabsorbed from collecting duct
31
Q

Describe the role of the ascending limb in water reabsorption

A
  • walls are impermeable to water
  • actively transport sodium and chloride ions out of the filtrate in the tubule into the tissue fluid in the medulla
  • loops of henle collectively concentrate salts in the tissue fluid which has a low water potential
32
Q

Describe the role of the descending limb in water reabsorption

A
  • walls are permeable to water and slightly permeable to sodium and chloride ions
  • as filtrate flows down the limb, water diffuses out by osmosis into tissue fluid of medulla which has low water potential
  • water moves into the vasa recta (capillaries surrounding nephron)
  • some Na+ and Cl- also diffuses in
33
Q

Describe the counter current mechanism

A
  • 2 limbs work side by side with filtrate flowing in opposite directions which enables the maximum concentration and the apex of the loop
34
Q

How do birds and reptiles remove their nitrogenous waste?

A
  • Uric acid
  • expensive process but lightweight needed to fly
35
Q

How do fish remove their nitrogenous waste?

A
  • Ammonia diffuse through gills into freshwater
  • freshwater dilutes it
36
Q

Define antidiuretic hormone

A
  • hormone produced in the hypothalamus and secreted by posterior pituitary gland
  • increases the permeability of the cells of the distal convulatesd tubule and collecting duct to water, increasing water absorption
37
Q

Define diuresis and anti-diuretic

A
  • production of large volumes of dilute urine
  • production of a small volume of concentrated urine
38
Q

What can cause the water potential of the blood to fall?

A
  • ingestion of large quantities of salts
  • reduced water intake
  • sweating
39
Q

Describe how ADH gets produced and what it does

A
  • reduced water potential detected by osmoreceptors in the hypothalamus
  • secretory granules carry ADH along axons from the hypothalamus to posterior pituitary gland
  • increases permeability of cell walls so me water absorbed into medulla
  • water water to blood in capillaries
  • water potential restored to normal
40
Q

Describe the ADH mechanism of action

A
  • ADH binds to membrane receptors on cells of CD and DCT
  • adenyl cyclase catalyses the production of cyclic AMP, the second messenger
  • vesicles containing aqua porins move and use with the cell membrane
  • aquaporins now in the membrane allow the water molecules to move in single file into the cell down a water potential gradient

—> when Intracellular cyclic AMP levels fall, the aquaporins are removed from the cell membrane and they accumulate again in vesicles

41
Q

What happens if the kidneys fail?

A
  • urea builds up to toxic concentrations and body fluids increase in volume and are diluted, compromising metabolic reactions
42
Q

What are the causes of kidney failure?

A
  • diabetes: high glucose concentration in plasma results in the glomeruli losing protein into the filtrate, triggering scarring in a condition called glomerulosclerosis
  • high blood pressure: damage to capillaries of glomerulus prevents ultrafiltration
  • autoimmune disease
  • infection
  • crushing injuries
43
Q

Describe treatments when both kidneys are compromised

A
  • reduce intake of certain nutrients (mainly protein) to reduce urea production
  • drugs to regulate BP
    —> angiotensin converting enzyme (ACE) inhibits and angiotensin receptor blockers (ARB) reduce impact of angiotensin, a hormone which constricts blood vessels thus increasing BP
    —> calcium channel blockers dilate blood vessels
    —> beta blockers reduce effect of Adrenalin
  • control of conc of potassium and calcium ions
    —> high potassium treated with glucose and insulin - can lead to arrhythmias so intravenous calcium added too
    —> high calcium in blood is correlated with risk of heart disease, kidney stones, and osteoporosis - treated with biophosphonates which decrease activity of osteoclasts so calcium accumulates in bone instead
  • dialysis to artificially filter blood
    —> fluid has same water potential as blood but low ion conc and no urea
    —> inorganic ions, water, and urea diffuse out of blood
    —> no glucose leaves
  • kidney transplant
44
Q

Describe haemodialysis

A
  • use of dialysis machine to artificially filter blood
  • blood taken from artery in arm and ran through selectively permeable tubing
  • counter current to maintain diffusion gradients
  • anticoagulant added to thin blood and stop clotting
45
Q

Describe continuous ambulatory peritoneal dialysis

A
  • allows patient to walk and live normal life whilst dialysis operates
  • drains fluid through catheter in abdomen
  • uses peritoneum lining body cavity as has rich supply of capillaries
  • happens 4x a day
  • retention of liquid is common and K+ ions accumulate in blood so must drink v little and avoid foods rich in potassium
46
Q

Describe kidney transplants and the challenges

A
  • donors may be living or suffered a brain stem or circulatory death
  • ABO blood groups and HLA must be compatible
  • dialysis still required initially if kidney came from dead donor
  • placed in lower abdomen
  • renal artery and vein attached to iliac artery and vein
  • circulation restored when gos pink, and when urine is seen emerging the ureter is attached to the bladder
  • must take immunosuppressants for rest of life - increased risk of cancer
  • patients vulnerable to infection
  • could result in long term antibiotic use - antibiotic resistance
47
Q

What is transamination?

A

An enzyme catalysed reaction that transfers an amino group to an alpha keto acid, making an amino acid

48
Q

Explain the effect of a large loss of blood from the body on the filtration rate

A
  • loss of blood pressure due to blood loss
  • therefore less filtrate formed as pressure for ultrafiltration cannot be maintained
49
Q

Why is a protein controlled diet recommended for those with kidney disease

A
  • protein contain amino acids, ammonia in urea
  • large vols of urea cannot be removed
50
Q

Why is a low salt intake recommended for kidney disease

A
  • reduced amount of salt needing to be removed
  • high salt causes high blood pressure and fluid retention
51
Q

Movement of glucose and amino acids in SR

A
  • Co-transport with Na+
  • glucose down electrochemical gradient via electrochemical gradient
  • facilitated diffusion
52
Q

Why does sodium and glucose absorption improve water reabsorption?

A
  • more sodium and glucose absorbed into blood
  • therefore more in glomerular filtrate
  • more Na+ diffuses into PCT due to higher conc gradient
  • more glucose is transported
  • lower water potential results in increased reabsorption by osmosis
53
Q

Benefit of removing waste via uric acid

A

Requires less water for disposal, therefore water can be conserved

54
Q

Which type of molecule in blood is responsible for maintaining blood osmotic pressure?

A

Protein

55
Q

How does the contraction of circular muscles in the afferent arteriole prevent changes in hydrostatic pressure in the glomerus?

A
  • circular muscles contract, lumen decreases
  • less difference between A+E arteriole
  • therefore decreased pressure
56
Q

What would happen if arterial blood pressure increased and the kidneys feedback system did not work?

A
  • damage to kidney and capillaries
  • more filtration occurs
57
Q

How would a low protein diet affect the rate at which glomerular filtrate is formed?

A
  • less protein in blood so increased water potential
  • overall pressure increases and more filtrate is produced
58
Q

Describe how changes in the afferent and efferent arterioles could increase the pressure forming the filtrate

A
  • dilate the afferent to make wider
  • constrict efferent to make narrower
  • increases hydrostatic pressure
59
Q

Suggest two reasons why proteins are not usually reabsorbed back into blood stream

A
  • too big to go through
  • no specific proteins for their transport
60
Q

Why do fish convert waste to urea when in dried out mud?

A
  • ammonia is more toxic than urea so needs to be diluted ie by water
  • when in mud the fish needs to conserve water
  • urea enables conservation and reduced toxicity for storage
61
Q

Possible effects of kidney failure

A
  • fatigue/dizziness
  • blood in urine
  • nausea
  • decreased volume urine
62
Q

Suggest why heart disease or loss of large volumes of blood can lead to kidney failure

A
  • blood cannot reach kidney in high enough pressures to enable ultrafiltration
63
Q

Explain fistula formation

A
  • high blood pressure
  • veins don’t have thick muscular wall to withstand the high pressures
64
Q

Why does dialysis use counter current?

A

Diffusion gradient maintained along entire length

65
Q

Advantage to animals excreting urine with high urea concentrations

A
  • conserves water
  • reduces risk of dehydration
  • enables them to survive in terrestrial life
66
Q

How does urine concentration change during space flight?

A
  • concentration increases
  • lower intake of water and lower percentage in urine
67
Q

Why are astronauts given high levels of salts when they return to earth?

A

To restore normal salt levels in blood

68
Q

Explain why urea and glucose have a renal:plasma ratio of 1 in the Bowman’s capsule

A
  • same concentration in plasma and filtrate
  • forced into bowman’s capsule from the glomerulus through gaps as they’re small molecules
69
Q

Why does the renal:plasma ratio of urea increase in the PCT

A
  • concentration urea increases as water is reabsorbed into the capillaries whilst urea remains in filtrate
    (as seen by increase 1 to 1.7)
70
Q

Describe the role of the nephron and collecting duct in achieving increase urea concentrations

A
  • water reabsorbed from filtrate
  • les urea is reabsorbed
  • sodium reabsorbed by PCT so water is also reabsorbed
  • active transport of Na+ out of loop of henle
  • water reabsorbed from filtrate in descending limb
  • lower water potential of medulla
  • therefore water reabsorbed in CD/DCT

A2 BIO UNIT3 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions