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6. Responses > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

What is homeostasis

A

the maintenance of a constant internal environment

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2
Q

What does homeostasis regulate

A
  • PH
  • Blood glucose
  • temperature
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3
Q

Why is it important for glucose and PH and temperature levels to not be too high

A

If PH too high or low = enzymes denature
If BG high = water potential of blood decrease = water moves out of cells and die
If temp too high = enzymes denature

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4
Q

What are negative feedback loops
And what are the advantages of multiple feedback loops

A
  • mechanism that restores systems to original
  • multiple mechanisms = better control as body able to to respond in multiple ways
  • can only work within a certain range = if change is too great = cannot return to normal
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5
Q

Gylcogenesis

A

Glucose to glycogen

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6
Q

Glycogenolysis

A

Glycogen to glucose

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7
Q

Gluconeogenesis

A

Glycerol + amino acids to glucose

Forms glucose from non-carbohydrate molecules

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8
Q

What hormone is released if BG too high

A

Insulin

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9
Q

Detection and action of BG too high

A

1- High BG detected by Beta cells in pancreas / islets of langerhans
2- insulin secreted to muscles and liver
3- insulin binds to muscle cell + increase number of glucose channel proteins in cell membrane = increase glucose uptake + rate of respiration
4- insulin binds to liver cell = glucose to glycogen ( glycogenesis)

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10
Q

What hormones are released if BG to low

A

Glucagon + adrenaline

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11
Q

Detection and action of BG too low

A

1- low BG detected by Alpha cells in pancreas/ islets of Langerhans
2- glucagon secreted
3- glucagon binds to liver cells =
- glycogen to glucose
- glycerol + AA/Non-carbohydrates to glucose
4- glucagon slows down rate of respiration = less glucose used up

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12
Q

Action of adrenaline

A

1- secreted from adrenal gland in Low BG
2- binds to liver cells:
- activate glycogen to glucose
- inhibit glucose to glycogen

3- promotes glucagon secretion + inhibits insulin secretion

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13
Q

Difference between primary and secondary messengers

A

Primary = do not enter cell = bind to cell membrane + trigger action in cell (hormones)

Secondary = inside cell= activated by primary binding to membrane + cause the change ( cyclic AMP)

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14
Q

Steps in control of low blood glucose for a secondary messenger ( what happens inside cells) - complex

A

1- Glucagon/adrenaline bind to cell membrane of liver cells
2- binding activates Adenyl cyclase = converts ATP to Cyclic AMP (cAMP)
3- cAMP activates protein kinase A = results in group of reactions that cause glyconeolysis
(glycogen to glucose)

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15
Q

Action of secondary messengers in low BG (action inside cell)
- simple

A

1- hormone binds to cell
2- adrenal cyclase causes ATP to cyclic AMP
3- cAMP activates protein kinase
4- glycogen to glucose

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16
Q

What is type 1 diabetes

A
  • beta cells damaged + no longer produce insulin = BG cannot be regulated
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17
Q

What is hyperglycaemia

A
  • BG too high + nothing to counteract
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18
Q

What is the treatment for type 1 diabetes

A
  • insulin shots or pump
    Type 1 develops in childhood
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19
Q

What is type 2 diabetes

A
  • beta cells do not produce SUFFICIENT insulin = blood glucose cannot be regulated / hyperglycaemia
20
Q

Treatment for type 2 diabetes

A
  • eating healthy + exercise
    Type 2 develops in later life + is linked to obesity
21
Q

What is a way to measure glucose concentration

A

Colorimetry and Dilution Series
= identifies BG conc in urine

22
Q

Steps of colorimetry

A

1- prepare urine samples
2- prepare calibration curve = with known concentrations
3- incubate test tubes
4- use colorimeter
5- record results

23
Q

What reagent is used in colorimetry and what colour does it turn in glucose

A

Benedict’s reagent
Blue to red
In glucose

24
Q

What is osmoregulation

A

Control of water potential in blood

25
Q

Where does osmoregulation take place

A
  • kidneys/ Nephrons
  • kidneys absorb more or less water according to water potential of blood
26
Q

What are nephrons and what are the 5 key structures

A

Functional unit of kidney
1- Bowman’s capsule
2- Afferent + efferent arterioles
3- Proximal convoluted tubule
4- Loop of Henle
5- Collecting duct

27
Q

What is the bowman’s capsule

A
  • Cup-shaped beginning of tubules
  • surrounds glomerulus = network of capillaries
  • layer is made of Podocytes = specialised epithelial cells
28
Q

Afferent and efferent arterioles

A

Afferent = blood flow into glomerlus
Efferent = blood flow out of glomerulus

Afferent is wider = causes high blood pressure in capillaries

29
Q

Proximal convoluted tubule (PCT)

A
  • site of selective re-absorption
    -after Glomelar filtrate produced in bowman’s capsule= glucose + water reabsorbed through PCT
30
Q

Loop of Henle

A

Produces a low water potential + high solute/Na+ conc in medulla of kidney
2 parts:
Ascending limb= impermeable to water
Descending limb = permeable to water
“Down below all to go”

31
Q

Collecting duct

A

Water reabsorbed into blood via collecting duct
- amount of water reabsorbed depend on water potential of blood
Eg: low water potential = more water absorbed

32
Q

What is the first stage of osmoregualtion

A

Formation of glomelar filtrate
- takes place in bowman’s capsule

33
Q

Stages in formation Glomelar filtrate

A

1- pressure filtration - capillary entering is wider than capillary leaving glomerlus = High BP = Fluid forced out of capillary
2- fluid forced out pores in capillary epithelial cells
3- small molecules filter through the pores whereas large molecules cannot fit
4- Podocytes - inner layer of bowman’s capsule = finger like projections
- substance passes from blood = to bowman’s capsule
This is glomelar filtrate

34
Q

Stages of selective reabsorption in proximal convoluted tubule (long)

A

1- Na+ actively transported from PCT epithelial cells to blood
2- Conc of Na+ decrease in epithelial cells
3- Na+ diffuse with glucose + other small molecules in glomelar filtrate to epithelial cells via Co-transport
4- conc in epithelial cellsincrease = diffusion into capillary/blood
(The blood pressure is high = substances in blood carried away fast = maintains diffusion gradient
5- movement of glucose + S molecules into blood lowers water potential in blood + increases it in PCT= water moves into blood by osmosis
6- substances not selectively re absorbed = excreted as waste (Urine)

35
Q

Stages of selective reabsorption in proximal convoluted tubule (simple)

A

1- active transport by Na-K pump
2- diffusion with Co-transport proteins of S molecules + Na+
3- reabsorption of small molecules by diffusion
4- reabsorption of water by osmosis

36
Q

What are podocytes

A

Epithelial cells of bowman’s capsule
Specialised finger like projections that increase Surface area of bowman’s capsule = gaps between the podocytes allows substances to pass through

37
Q

Action of water reabsorption in loop of henle

A

1- Na+ actively transported out of Top of ascending limb into tissue fluid of Medulla
2- Na+ diffuse from bottom of ascending limb to medulla = overall effect of decrease in water potential in medulla + increase in Na+ conc
3- descending limb is permeable to water = water in tubule/limb diffuse out by osmosis due to low water P
4- Water that moves into Medulla re absorbed into blood

38
Q

Overall idea of reabsorption of water

A
  • overall effect of ascending + descending limb = create low water potential in tissue fluid of Medulla + surrounding collecting duct
  • water in collecting duct diffuse out via osmosis = water reabsorbed by bloodstream
39
Q

What does the volume of water reabsorbed into blood depend on

A

Permeability of collecting duct

40
Q

What does the permeability of collecting duct depend on

A

Water potential of blood
- if water potential is high + collecting duct less permeable = less water reabsorbed
- If water potential is low = collecting duct more permeable = more water reabsorbed

41
Q

What does ADH influence in osmoregualtion

A
  • affect’s permeability of PCT + collecting duct
    = controls how much water is reabsorbed
42
Q

Secretion and action of ADH

A

1- Osmoreceptors in hypothalamus (area of brain) shrink or swell depending on blood water potential
2- if water P is low = osmoreceptor cells shrink = detected by Posterior pituitary gland
3- ADH released
4- ADH bind to receptors on PCT + collecting duct = vesicles with aquaporins fuse with cell membrane

(Aquaporins are protein channels for water , more channels = permeability increase = more water reabsorbed

43
Q

ADH effect on urine concentration

A

More ADH = more water Reabsorbed + less water In urine = urine is more concentrated

44
Q

What happens to substance in collecting duct + PCT that is not reabsorbed

A

Collecting duct connect to Ureter
- Ureter carries urine/ left over molecules to bladder to wait to be excreted (weeing)

45
Q

What’s the basement membrane

A

In between the pores in capillary of glomerulus and podocytes of bowman’s capsule
The basement membrane acts as a filter = stops large protein molecules from getting through

6. Responses (6 decks)

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