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A2 Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

what is homeostasis

A

the maintenance of the internal environment within an optimum range

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2
Q

changes to the water potential of the blood and tissue fluids cause cells to

A

shrink and expands as a result of water leaving or entering by osmosis

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3
Q

what is negative feedback

A

a change is counteracted to return back to normal

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4
Q

what is positive feedback

A

change is amplified so level moves further away from normal

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5
Q

what happens to enzyme activity when temperature falls below optimum range

A

enzyme activity decreases and causes rate of important reactions to slow down

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6
Q

in terms of bonds and enzymes what happens when body temperature rises above optimum range

A

enzymes denature at higher temperature causes the hydrogen bonds that maintain enzyme structure to break this alters active site so the enzyme can no longer catalyse reactions

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7
Q

in terms of respiration what will happens if the blood glucose levels are too low

A

respiration will slow and the amount of ATP will fall

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8
Q

how does carbohydrates affect blood glucose level

A

causes an increase In blood glucose concentration

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9
Q

which organ maintains the blood glucose levels

A

pancreas

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10
Q

how does exercise cause a decrease in blood glucose concentration (glucose)

A

glucose is being used in respiration to power muscle contractions

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11
Q

what occurs if there is a fall in blood glucose concentration (5M)

A

stimulus is detected by receptors
alpha cells in pancreas will secrete glucagon
glucagon will cause liver cells to convert glycogen into glucose
which raises BGC which is circulated back to the pancreas reducing alpha cell stimulation therefore reducing glucose production

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12
Q

what occurs if there is a rise in blood glucose concentration

A

insulin will be produced from beta cells in pancreas
insulin increases uptake of glucose by cells and its conversion to glycogen and fat
the fall in BGC reduced insulin production

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13
Q

what is glycogenesis

A

when BGC too high

glucose —->glycogen

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14
Q

glycogenolysis

A

BGC too low

glycogen—->glucose

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15
Q

glyconeogenesis

A

BGC too low

glycerol+amino acid. —–> glucose

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16
Q

what hormone do beta cells secrete when there is high blood glucose concentration

A

insulin

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17
Q

where are the beta cells located

A

islet of langerhans

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18
Q

in terms of insulin, enzymes, muscle cells, respiration explain how insulin lowers blood glucose concentration

A

insulin binds to the receptors in the muscle cell
causes a change in the tertiary structure of the glucose allowing more glucose into cells by facilitated diffusion
activation of the enzymes that convert glucose to glycogen and fat
the rate uptake of glucose by muscle cells increase
rate of respiration in muscle cells increase

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19
Q

what is the importance of insulin (2M)

A

lowering BGC

maintaining an optimum blood water potential

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20
Q

what do alpha cells detect

A

fall in BGC

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21
Q

what do alpha cells secrete when detecting a fall in blood glucose concentration

A

hormone glucagon

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22
Q

does glucagon increase or decrease blood glucose concentration

A

increases BGC

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23
Q

if blood glucose concentration were not increased by glucagon how would this affect respiration

A

there would not be enough glucose available for respiration then there would be energy for survival

24
Q

is adrenaline secreted at low or high blood glucose concentration

A

low BGC

25
Q

where is adrenaline secreted

A

adrenal gland

26
Q

how does adrenaline raise blood glucose concentration

A

by attaching to protein receptors on the cell-surface membrane of target cells
activating enzymes that causes the breakdown of glycogen to glucose in the liver

27
Q

what is osmoregulation

A

control of water potential in the blood

28
Q

what occurs if the blood water potential is too high(3M)

A

more water may be lost by excretion to return normal water potential levels
the blood reabsorbs less water from kidney
urine is more dilute water potential in blood decreases

29
Q

what occurs if the blood WATER potential is too low

A

less water lost by excretion the blood reabsorbs more water from kidney
urine is more concentrated and water potential in blood increases

30
Q

the first step of filtration of the blood to form urine takes place in the bowmans capsule this produces a

A

glomerular filtrate

31
Q

blood flows into the glomerulus through which arteriole

A

afferent arteriole

32
Q

is the afferent arteriole much wider or narrower than the efferent arteriole and how does this affect the blood pressure in capillaries

A

afferent arteriole is much wider

blood pressure in capillaries is very high

33
Q

after the glomerular filtrate has been produced in the bowmans capsule which two substances are reabsorbed into the bloodstream and through which tube

A

glucose and water

through the PCT

34
Q

does the loop of henle produce a low or high water potential

A

low water potenial

35
Q

is the ascending limb impermeable or permeable to water

A

impermeable

36
Q

is the descending limb impermeable or permeable to water

A

permeable

37
Q

when Na ions are actively pumped out of the ascending limb where are they pumped into and how does this affect water potential

A

into the medulla

decreasing water potential

38
Q

what is the effect of the descending and ascending limb in terms of concentration and water potential

A

creates a high solute concentration

low water potential in tissue fluid

39
Q

what effect does a high solute concentration and water potential in tissue fluid have on collecting duct

A

water inside the collecting duct to diffuse into the surrounding tissue fluid by osmosis
water is then reabsorbed into the blood stream

40
Q

what does ADH control

A

controls osmoregulation

41
Q

how does ADH affect permeability on the distal convoluted tubule and collecting duct

A

influences permeability

controls how much water is reabsorbed from the kidney into the blood

42
Q

when ADH bind….

A

vesicles containing aquaporins fuse with cells membrane
aquaporins are proteins channels for water
aquaporins increase permeability of the distal convoluted tube and collecting duct
more water is then reabsorbed into the blood by osmosis

43
Q

how ultrafiltration occurs in a glomerulus

A

high blood/ hydrostatic pressure
water, glucose, ions, urea through small gaps/pores in capillary endothelium
and through capillary basement membrane

44
Q

the thicker medulla will lead to a longer or shorter loop of henle

A

longer loop of henle

45
Q

how ultrafiltration produces a glomerular filtrate

A

high blood pressure/ hydrostatic pressure
small molecules pass through basement membranes
proteins too large to go through so stay behind
presence of pores in the capillaries

46
Q

some desert mammals have long loop of henle and secrete large amounts of ADH explain how these two features are adaptation to living in desert conditions

A

For loop of henle:
Sodium/chloride ions absorbed from filtrate in ascending limb
gradient established in medulla
For ADH:
act on collecting duct/ distal convoluted tubule
make cells more permeable

47
Q

location of osmoreceptors in the body

A

hypothalamus

48
Q

describe how the secretion of ADH affect urine produced in kidneys

A

membrane
aquaporins are proteins channels for water
aquaporins increase permeability of the distal convoluted tube and collecting duct
more water is then reabsorbed into the blood by osmosis
making the urine more concentrated and in smaller volume

49
Q

explain the role of the loop of henle in the absorption of water from the filtrate

A

in the ascending limb sodium ion actively transported
ascending limb impermeable to water
in descending limb sodium ion diffuse in
descending limb permeable to water so water moves out
low water potential In the medulla
the longer the loop of henle the lower the water potential in the medulla
water leaves collecting duct by osmosis sown water potential gradient

50
Q

role of ADH in the production of concentrated urine

A

when water potential of blood is too low
detected by receptors in the hypothalamus
pituitary secretes more ADH
ADH increases permeability
opens channels for water in the distal convoluted tubule
more water reabsorbed by osmosis down the water potential gradient

51
Q

in a diabetic person lack on insulin will lead to reduced….

A

uptake of glucose by cells/liver/muscles

reduced conversion of glucose to glycogen

52
Q

two substances that will be present in the glomerular filtrate

A

urea

amino acids

53
Q

two ways in which the cells of the proximal convoluted tubule are adapted to reabsorption

A

microvilli provide large SA
carrier protein in membrane for active transport
channel protein for facilitated diffusion
many mitochondria for active transport

54
Q

how urea is removed from the blood

A

high hydrostatic pressure causes ultrafiltration at bowman’s capsule through basement membrane enabled by small size urea molecules

55
Q

how urea is concentrated in the filtrate

A

reabsorption of water by osmosis at proximal convoluted tubule
active transport if ions/ glucose creates gradient

56
Q

where does ultrafiltration occur

A

bowman’s capsule

57
Q

part of the brain which acts as the coordinator in the control of water

A

hypothalamus

A2 Biology (5 decks)

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