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Biology A Level Unit 3 > Homeostasis and the Kidney > Flashcards

Homeostasis and the Kidney Flashcards

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1
Q

homeostasis

A

maintenance of a constant internal environment around a set point/norm (pH, temp, glucose conc, solute potential)

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2
Q

negative feedback

A

change in a system occurs causing a second chance to counteract first change

set point - input - receptor - co-ordinator - effectors - output

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3
Q

positive feedback

A

effector increases change, moves further from norm (set point)

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4
Q

cortex

A

c shaped

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5
Q

medulla

A

middle layer

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6
Q

pelvis

A

p shaped

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7
Q

nephron labels

A

venal artery, afferent arteriole, glomerulus, efferent arteriole, Bowman’s capsule, proximal convoluted tubule, distal convoluted tubule, collecting duct, loop of Henlé, vasa recta (capillary network), venal vein

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8
Q

kidney functions

A

excretion - removal of nitrogenous waste

osmoregulation - control water content of blood

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9
Q

ultrafiltration

A 
Bowman's capsule
blood enters glomerulus and passes through 3 layers
endothelium - pores (fenestrae) allow most molecules through (no blood cells)
basement membrane ("molecular sieve") allows small molecules through (no large proteins)
podocyte cells - filtration slits between pedicels allow most molecules through
glomerular filtrate ends up in Bowman's capsule before moving into PCT
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10
Q

selective reabsorption

A

reabsorb glucose + amino acids (active transport using Na+), mineral ions (active transport), water (osmosis), proteins + urea (facilitated diffusion)

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11
Q

adaptations of PCT

A

large number per kidney + long + microvilli + infolding of basal membrane (“basal channels”) - increased surface area for reabsorption
mitochondria in cuboidal epithelial cells provide ATP for active transport of glucose + Na+ ions

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12
Q

loop of Henlé + reabsorption of water

A

active transport of Na+ + Cl- out of ascending limb
low water potential in medulla
water leaves descending limb by osmosis
water reabsorbed into vasa recta by osmosis
Na+ + Cl- ions diffuse into descending limb
water leaves collecting duct by osmosis
water reabsorbed in vasa recta

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13
Q

osmoregulation definition

A

control of water content + solute composition of body fluids

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14
Q

osmoregulation steps

A

stimulus - water potential decrease in blood
receptor + co-ordinator - osmoreceptors in hypothalamus detect change, hypothalamus stimulates posterior lobe of pituitary gland
effector - posterior lobe of pituitary gland secretes more ADH into blood which binds to DCT + collecting duct (makes more permeable to water)
response - reabsorption of water into blood producing smaller + higher volume + higher concentration urine

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15
Q

ADH how it works

A

causes aquapprins to become incorporated within cytoplasm of cell surface membranes of cells that form collecting duct + DCT walls

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16
Q

effects of kidney failure

A

toxic levels of urea in body

body fluids increase in volume + diluted by metabolic reactions

17
Q

potential treatments of kidney failure

A

lower protein diet
drugs to reduce blood pressure/blood potassium + calcium levels
dialysis
transplant

18
Q

excretion

A

excess amino acids (from protein in diet) broken down by deanimation in liver

19
Q

loop of Henlé length

A

depends on availability of water in an animals natural environment

20
Q

long loop of Henlé

A

more ions pumped into medulla from ascending limb, lower water potential, more water leaves collecting duct by osmosis and reabsorbed into blood

21
Q

long loops for animals in arid dry habitat

A

more water reabsorbed before urine excreted

can live off ‘metabolic water’

22
Q

short loops for animals in aquatic habitat

A

live in areas with more than enough drinking water, no need for lots of water to be reabsorbed

23
Q

how toxic is ammonia

A

highly

24
Q

how toxic is urea

A

fairly

25
Q

how toxic is uric acid

A

virtually non-toxic

26
Q

how soluble is ammonia

A

extremely

27
Q

how soluble is urea

A

fairly

28
Q

how soluble is uric acid

A

almost insoluble

29
Q

how much energy required to produce ammonia

A

little energy (easily produced - first breakdown product of deanimation)

30
Q

how much energy needed to produce urea

A

moderate amount (relatively easy to produce)

31
Q

how much energy needed to produce uric acid

A

lots of energy

32
Q

organisms that excrete ammonia

A

aquatic organisms
fish
reptiles
insects

33
Q

organisms that excrete urea

A

mammals

e.g.humans

34
Q

organisms that excrete uric acid

A

terrestrial insects

birds

Biology A Level Unit 3 (8 decks)

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