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16 homeostasis Flashcards

1
Q

define homeostasis

A

the maintenance of a constant internal environment

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2
Q

what does homeostasis ensure for cells in the body?

A

that they are in a stable environment that meets their needs and allows them to function normally despite any external or internal changes

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3
Q

what factors affect enzyme activity?

A

temperature
pH
inhibitors
activators
substrate concentration

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4
Q

why is it important to maintain a constant internal environment? (refer to enzymes)

A

makes sure enzyme controlled biological reactions take place at a constant/optimum rate

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5
Q

organisms that control their own internal environment are more…

A

independent of their environment

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6
Q

what does organisms being more independent of their environments lead to?

A
  1. greater geographical range so can colonise more habitats and ecosystems
  2. greater chance of finding food/shelter/mates
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7
Q

what must happen to all muscles for homeostasis to be achieved?

A

muscles have to be coordinated

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8
Q

what are the 5 control mechanisms?

A
  1. set point
  2. receptor
  3. controller
  4. effector
  5. feedback loop
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9
Q

define negative feedback

A

when there is an change from the set point, the opposite effect is instigated

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10
Q

what type of mechanism does the blood glucose regulation use?

A

negative feedback mechanism

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11
Q

what system does the blood glucose regulation involve?

A

endocrine system

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12
Q

what similarities do the hormones involved in the blood glucose regulation have?

A
  1. produced by glands and secreted into the blood
  2. carried in blood plasma to target cells
  3. complementary receptors only found on target cell
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13
Q

blood glucose concentration is strictly controlled within the range of…

A

80-100 mg 100cm^-3

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14
Q

what is the word for very low levels of glucose?

A

hypoglycaemia

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15
Q

what is the word for very high levels of glucose?

A

hyperglycaemia

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16
Q

what des hypoglycaemia mean?

A

vey low levels of glucose

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17
Q

what does hyperglycaemia mean?

A

very high levels of glucose

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18
Q

hyper and hypoglycaemia can both be…

A

fatal

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19
Q

what does the pancreas do?

A

controls glucose levels

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20
Q

what are the 4 reactions called during blood glucose concentration?

A

glycogenesis
glycogenolysis
gluconeogenesis
glycolysis

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21
Q

what is glycogenesis?

A

alpha glucose -> glycogen

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22
Q

what is glycogenolysis?

A

pyruvate + glycerol + amino acids -> glucose

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23
Q

what is gluconeogenesis?

A

glycogen -> alpha glucose

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24
Q

what is glycolysis?

A

glucose -> pyruvate + glycerol + amino acids

25
Q

what are the 2 types of hormones involved in blood glucose regulation?

A

insulin
glucagon

26
Q

what are the two types of cells in the blood glucose regulation?

A

alpha cells and beta cells

27
Q

which cell secretes glucagon and which secretes insulin?

A

alpha cells secrete glucagon
beta cells secrete insulin

28
Q

what is the aim of insulin?

A

to reduce blood glucose levels

29
Q

hat is the aim of glucagon?

A

to increase blood glucose levels

30
Q

where are alpha and beta cells located?

A

in the pancreas

31
Q

explain how insulin reduces blood glucose levels

A
  1. insulin binds to complementary receptors on cell surface of target cell
  2. this regulates the addition of glucose carrier proteins in the membrane of target cells
  3. insulin activates enzymes to stimulate glycogenesis- decreasing blood glucose
32
Q

explain how glucagon decreases blood glucose levels

A
  1. glucagon binds to complementary receptor on surface membrane on target cells
  2. activates enzymes involved in glycogenolysis and gluconeogenesis
33
Q

what 2 processes create glucose?

A

gluconeogenesis
glycogenolysis

34
Q

what 2 processes hydrolyse glucose?

A

glycolysis and glycogenesis

35
Q

what does adrenaline do regarding blood glucose levels ?

A

increases blood glucose levels

36
Q

explain the second messenger model regarding hormones and blood glucose concentration

A
  1. adrenaline and glucagon bind to complementary receptors on target cell (first messenger)
  2. hormone receptor complex formed causing receptor to change structure
  3. adenylate cyclase activated
  4. cAMP produced (secondary messenger)
  5. activates protein kinase in cell
  6. activates glycogenolysis and gluconeogenesis
37
Q

what is diabetes caused by?

A

failure of glucose homeostasis

38
Q

describe type I diabetes

A
  • insulin dependent
  • insulin deficiency due to autoimmune killing beta cells
39
Q

describe type II diabetes

A
  • non-insulin dependent
  • insulin is produced but receptors are unresponsive so insulin has no effect
40
Q

what happens after a meal fin both types of diabetes after a meal?

A

very high blood glucose level after a meal
active transport pumps into the proximal convoluted tubule of the kidney
kidney can’t re absorb so glucose is excreted in urine

41
Q

what are the symptoms of diabetes?

A
  1. high thirst
  2. large volume of urine
  3. poor vision
  4. tiredness
  5. muscle wasting
42
Q

why do people with diabetes experience these 5 symptoms?

A
  1. high thirst - osmosis of water from cells to blood
  2. large volume of urine- excess water in blood
  3. poor vision- osmotic loss of water from eye
  4. tiredness- loss of glucose
  5. muscle wasting- gluconeogenesis
43
Q

what an diabetes be treated with?

A

injection of insulin or careful diet

44
Q

describe the structure of a kidney

A

fibrous capsule
cortex
renal medulla
renal pelvis
ureter
renal artery
renal vein

45
Q

what is osmoregulation?

A

homeostatic control of water potential in blood

46
Q

which cells detect a fall in water potential in the blood?

A

osmoreceptor cells

47
Q

where are osmoreceptor cells located ?

A

hypothalamus

48
Q

what happens when osmoreceptor cells detect a fall in water potential in the blood?

A
  1. anti diuretic hormone secreted into capillaries of posterior pituitary gland
  2. ADH travels to kidneys and increases permeability of DCT and collecting duct
  3. causes vesicles bound with aquaporin to fuse with cell surface membranes of DCT and collecting duct
49
Q

give stages of the re absorption of water in the loop of henle

A
  1. ultrafiltration
  2. reabsorption
  3. loop of henle
  4. DCT
  5. collecting duct
50
Q

what is the structure of a cortex in the kidney?

A

glomerulus
bowmans capsule
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct

51
Q

describe how ultrafiltration produces glomerular filtrate

A
  1. higher than normal hydrostatic pressure
  2. urea/amino acids/ions pass through basement membrane
  3. protein too large to pass through
  4. travels through pores and podocytes
52
Q

how is urea removed from the blood?

A
  1. hydrostatic pressure causes ultrafiltration at bowman’s capsule
  2. passes through basement membrane due to small size of urea molecule
53
Q

describe reabsorption of glucose and water by the PCT

A
  1. PCT has high SA due to microvilli and contain lots of mitochondria for ATP for active transport
  2. sodium ions actively transported out of the PCT into blood
  3. allowing sodium ions from filtrate to move into surrounding cells via facilitated diffusion and CO TRANSPORT
  4. allowing useful molecules to be absorbed back into the blood
54
Q

which limp of the loop of henle is narrow and which is wider and what does this mean?

A

descending is narrow- highly permeable to water
ascending is wider- impermeable to water

55
Q

describe what happens at the loop of henle

A
  1. sodium ions actively transported out of the ascending limb and re enter the descending limb
  2. lowers water potential between two limbs
  3. water leaves descending limb by osmosis
  4. no water leaves ascending limb
56
Q

where does the water that has been moved out of the descending limb by osmosis move into?

A

capillaries

57
Q

what is the role of the distal convoluted tubule?

A

to make final adjustments to the water and slats that are reabsorbed

58
Q

is the collecting duct permeable or impermeable to water?

A

permeable so water moves out by osmosis as countercurrent gradient ensures a water potential gradient

59
Q

how does ADH cause movement of water into the collecting duct?

A
  1. causes aquaporins to be inserted into the collecting duct wall
  2. water enters cell through aquaporins by osmosis down a water potential gradient
  3. to capillary via tissue fluid

biology (23 decks)

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