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Biology Unit 3 > Homeostasis and the kidney > Flashcards

Homeostasis and the kidney Flashcards

1
Q

homeostasis definition

A

the maintenance/control of an internal environment at a constant/set point by negative feedback

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2
Q

what internal factors may change due to changes in our activity or external environment

A
  • core body temp
  • pH
  • blood glucose conc
  • blood solute potential
  • water potential
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3
Q

describe dynamic equilibrium

A

constant changes occur, but corrective mechanisms bring the internal environmental conditions back towards a set point

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4
Q

what does negative feedback do

A

restores conditions back to their set point when there is a deviation

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5
Q

describe the negative feedback loop

A
  • receptor detects a deviation from set point in internal environment
  • receptor sends instructions to co-ordinator
  • co-ordinator communicates with effectors which make corrective responses
  • factor returns to normal (set point)
  • receptor feeds info back to effectors which stop making the correction
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6
Q

examples of effectors

A

muscle or gland

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7
Q

positive feedback

A

effector increases change (causes further movement away from the norm)

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8
Q

4 excretory organs

A
  1. lungs
  2. kidneys
  3. skin
  4. liver
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9
Q

2 functions of the kidney and brief descriptions of them

A

excretion = removal of nitrogenous waste from body
osmoregulation = control of water potential of the body’s fluids

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10
Q

what happens in the medulla

A

reabsorption of water

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11
Q

what happens in the cortex

A

ultrafiltration and selective reabsorption

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12
Q

how is urea formed

A
  • excess aa’s deaminated in liver
  • amino group removed and converted into ammonia and then to urea
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13
Q

what is the nephron?

A

functional unit of the kidney which filters blood

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14
Q

what is the vasa recta?

A

a capillary network surrounding the loop of Henle

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15
Q

what is ultrafiltration?

A

filtration under high pressure

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16
Q

Blood enters capillaries of glomerulus from afferent arteriole and leaves via efferent. Blood has high hydrostatic pressure because :

A
  1. heart’s contraction increases pressure of arterial blood
  2. afferent has wider diameter than efferent
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17
Q

what does the glomerular filtrate contain?

A

water, glucose, salts, urea, aa’s

18
Q

how do SMALL molecules and ions enter Bowman’s capsule and tubule as filtrate?

A
  • through 3 filtration layers
  • high hydrostatic pressure forces molecules through :
    *fenestrations of endothelial cells
    *selective molecular filter of basement membrane
    *filtration slits of pedicels into Bowman’s space
19
Q

3 layers separating the blood in glomerulus from the space inside Bowman’s capsules

A
  • capillary walls
  • basement membrane
  • podocytes = squamous epithelial cell layer of Bowman’s capsule wall
20
Q

capillary cell walls purpose in blood filtration

A

have tiny pores/fenestrations between cells which allow solute to pass to basement membrane

21
Q

basement membrane purpose in blood filtration

A

selective molecular filtrate

22
Q

podocytes purpose in blood filtration

A

have extensions = pedicels which wrap round a capillary, pulling it closer to basement membrane
- gaps between pedicels = filtration slits

23
Q

where and by what processes does selective reabsorption happen?

A

proximal convoluted tubule in cortex
facilitated diffusion & active transport and osmosis & co-transport

24
Q

what is selective reabsorption?

A

useful substances (glucose, aa’s, salts) are reabsorbed from glomerular filtrate back into bloodstream

25
Q

5 adaptations to the cells lining the wall of PCT

A
  1. microvilli = increase SA
  2. lots of mitochondria = produce ATP for AT
  3. tight junctions between cells = prevent molecules from diffusing between cells
  4. basal channels = increase SA at the basement membrane
  5. cells are closely associated with blood capillaires of vasa recta
26
Q

how does selective reabsorption happen?

A
  • nephrom closely associated with vasa recta
  • reabsorbed substances pass from PCT into blood plasma in vasa recta capillaries
27
Q

where does reabsorption of water happen?

A

loop of Henle

28
Q

descending and ascending limb of loop of Henle : which is permeable and which is impermeable to water?

A

descending = permeable to water
ascending = impermeable to water

29
Q

what happens in the descending limb of the loop of Henle during reabsorption of water?

A
  • water leaves filtrate and enters blood by osmosis
  • Na+ & Cl- diffuse into descending limb from medulla
30
Q

where does the filtrate reach its maximum concentration?

A

apex of the loop of Henle

31
Q

what happens in the ascending limb of the loop of Henle during reabsorption of water?

A
  • initially Na+ & Cl- leaves ascending limb by FD
  • as conc of solutes decrease AT takes over
32
Q

filtrate in the limbs of the loop of Henle flow in opposite directions there fore it is a :

A

counter current multiplier

33
Q

long loops of Henle

A
  • higher conc of solutes at the apex
  • animals adapted to dry environments e.g camels
34
Q

short loops of Henle

A

animals adapted to fresh water environment e.g otters

35
Q

osmoregulation = (x2)

A
  • the control of body fluid water potential by negative feedback
  • under hormonal control
36
Q

what causes a decrease in blood plasma water potential?

A
  • low water intake
  • high intake of solutes
  • sweating
37
Q

osmoregulation process

A
  1. osmoreceptors in hypothalamus detect decrease in blood plasma WP
  2. signal sent to posterior lobe of pituitary galnd (co-ordinator) which releases ADH into bloodstream
  3. ADH carried to kidneys and binds to receptor proteins on wall of collecting duct and DCT (effectors)
  4. aquaporins added to cell membs of effectors –> allow more H2O to be reabsorbed
    => WP in blood increases back to set point
  5. info fed back to hypothalamus and less ADH produced
38
Q

ADH (antidiuretic hormone) purpose

A

increases permeability of collecting duct and distal covoluted tubule cells to water

39
Q

what happens if more ADH is secreted

A

more H2O reabsorbed by osmosis => urine produced is more conc, less volume

40
Q

where is ADH produced and secreted

A

hypothalamus, posterior lobe of pituitary gland

41
Q

process of ADH increasing the permeability of cell membranes to water

A
  • ADH binds to ADH receptor proteins in cell membrane
  • causes vesicles containing aquaporins to fuse with cell memb
  • increases permeability of cell memb to water => more H2O is reabsorbed into blood of vasa recta capillaries

Biology Unit 3 (4 decks)

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