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Biology A2 Unit 5 > 12 Homeostasis > Flashcards

12 Homeostasis Flashcards

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0
Q

Homeostasis ensures…

A

Cells in the body are in an environment that meets their needs and allows them to function properly.

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1
Q

Define homeostasis

A

the maintenance of a constant internal environment in an organism.

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2
Q

Homeostasis ensures enzymes can work by…

A

maintaining a constant pH and temperature

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3
Q

Homeostasis regulates water potential to ensure…

A

Cells don’t shrink or burst

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4
Q

Organisms with the ability to maintain a constant internal environment are…

A

more independent of the external environment therefore

have a wider geographical range

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5
Q

Five stages in a self-regulating system

A 
Set-point
Receptor
Controller
Effecter
Feedback look
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6
Q

The set point is the…

A

desired level at week the system operates

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7
Q

The recepter

A

detects deviation from the set point

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8
Q

The controller

A

receives a signal about a change so it may send instructions to a effecter

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9
Q

the effecter

A

brings about changes needed to return the system to the set point

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10
Q

The feedback loop

A

informs the receptor of the changes to the system made by the effecter

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11
Q

Receiving information from a number of sources allows…

A

a better degree of control

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12
Q

If body temperature is too low…

A

the rate of enzyme-controlled reactions may be too slow

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13
Q

If the body temperature is too high

A

enzymes may be denatured and not function at all

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14
Q

The regulation of body temperature is…

A

thermoregulation

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15
Q

Methods of gaining heat…

A

production of heat

gain of heat from environment

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16
Q

Production of heat from…

A

metabolism of food during respiration

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17
Q

Gain heat from the environment by…

A

conduction
convection
radiation

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18
Q

Methods of losing heat

A

Evaporation of water…

Loss of heat to the environment

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19
Q

Evaporation of water to lose heat by

A

sweating

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20
Q

Loss of heat to the environment can occur by

A

Conduction
Convection
Radiation

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21
Q

Conduction:

A

Occurs in solids

Transfer of energy from particle to particle via kinetic energy

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22
Q

Convection

A

Occurs in fluids (gases and liquids)
Transfer of heat by the movement of the matter
Fluid expands + moves; carrying heat with it

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23
Q

Radiation

A

Transferred by electromagnetic waves

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24
Q

Ectotherm

A

an animal uses the environment to regulate its body temperature

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25
Q

Endotherm

A

an animal maintaining its body temperature by physiological mechanisms

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26
Q

An ectotherm’s body temperature will…

A

Fluctuate with the environment

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27
Q

Ectotherms control their body temperature by

A

adapting their behaviour to changes in the external temperature

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28
Q

Five ways an ectotherm might control their body temperature

A 
Exposing themselves to the Sun
Take shelter
Gain warmth from ground
Generate metabolic heat (minor)
Colour variation
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29
Q

An endotherm’s body temperature…

A

remains reasonably constant despite changes in the external temperature

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30
Q

The temperature range of an endotherm is a compromise between..

A

Having a high temperature for enzymes to proceed faster

And the work needed to maintain the higher temperature

31
Q

The smaller the surface area to volume ratio…

A

The easier it is to maintain a high body temperature

32
Q

The higher the surface area to volume ratio

A

The harder it is to maintain a high body temperature

33
Q

To make rapid changes in temperature, to warm up, 6 ways.

A 
Vasoconstriction
Shivering
Raising of hair
Increased metabolic rate
Decrease in sweating
Behavioural mechanisms
34
Q

Rapid responses to lose heat (4)

A

Vasodilation
Increased sweating
Lowering body hair
Behavioural mechanisms

35
Q

Vasoconstriction (3)

A

Diameter of arterioles near skin surface is made smaller.
Volume of blood reaching surface capillaries reduces.
Most blood therefore loses little heat to the environment

36
Q

Raising of hair to increase body temperature (3)

A

Hair erector muscles in skin contract
Traps a layer of insulating air next to the skin
Lowering the temperature difference, reducing heat lost

37
Q

Vasodilation (3)

A

Diameter of arterioles near skin surface increase
Warm blood passes close to skin surface capillaries
Heat from the blood is radiated away from the body

38
Q

Lowering of body hair to reduce body temperature (3)

A

Hair erector muscles relax and hair flattens
Insulating air layer thickness is reduced
More heat is lost to the environment

39
Q

Hypothalamus

A

The region of the brain that acts as the control centre for the autonomic nervous system and regulates body temperature/fluid balance

40
Q

Autonomic nervous system

A

Part of the nervous system controlling muscles and glands that is not under voluntary control

41
Q

The thermoregulatory centre of the hypothalamus has two parts…

A

Heat gain centre

Heat loss centre

42
Q

Heat gain centre…

A

Activated by a fall in blood temperature

Controls mechanisms to increase body temperature

43
Q

Heat loss centre…

A

Activated by a rise in blood temperature

Controls mechanisms to decrease body temperature

44
Q

Two ways temperature is measured…

A

Hypothalamus monitors blood temperature

Skin thermoreceptors send impulses to hypothalamus

45
Q

Two principle coordinating systems…

A 
Nervous system (rapid)
Hormonal system (slower)
46
Q

Hormones are (3)

A

Produced by glands secreting into the blood
Carried in plasma to where they will act (target cells)
Effective in small quantities with widespread/longlasting effects

47
Q

Second messenger model (5)

A
  • Hormone is first messenger. Binds to specific receptors on membranes to form hormone-receptor complex.
  • H-R complex activates an enzyme to produce a chemical for 2nd messenger.
  • Second messenger causes chemical changes, producing response.
  • For adrenaline, this is conversion of glycogen to glucose
48
Q

Pancreas produces

A

Enzymes: protease, amylase, lipase
Hormones: insulin, glucagon

49
Q

Groups of hormone producing cells in the pancreas

A

islets of Langerhans

50
Q

Cells in islets of Langerhans, two types

A

alpha cells

beta cells

51
Q

alpha cells of the islets of Langerhans;

A

larger and produce glucagon

52
Q

beta cells of the islets of Langerhans

A

smaller and produce insulin

53
Q

If blood glucose level falls too low…

A

cells will be deprived of energy and die, especially brain cells

54
Q

If blood glucose levels are too high

A

The water potential of the cell is lowered

Causing osmotic problems that may result in dehydration

55
Q

Three sources of blood glucose

A

Directly from the diet
From the breakdown of glycogen (glycogenolysis)
Gluconeogenesis

56
Q

Glycogenolysis

A

splitting of glycogen into glucose

57
Q

Gluconeogenesis

A

formation of new glucose from sources other than carbohydrates

58
Q

Beta cells in the islets of Langerhans detect a rise in blood glucose levels and…

A

secrete insulin directly into the blood plasma

59
Q

Insulin combines with glycoprotein receptors and… (3)

A

changes the tertiary structure of glucose transport proteins
increases the number of cell-surface carrier molecules
activates conversion of glucose into glycogen and fat

60
Q

Changing the tertiary structure of glucose transport proteins…

A

causes them to change shape and open, allowing more glucose into the cells

61
Q

Four ways blood glucose is lowered by insulin

A
  • absorbed faster into cells especially muscles
  • respiration rate increased
  • conversion into glycogen (glycogenesis)
  • conversion into fat
62
Q

alpha cells in islets of Langerhans detect a fall in blood glucose,

A

secreting glucahon into the blood plasma

63
Q

Glucagon binds to receptors in the…

A

liver

64
Q

Liver cells respond to glucagon by.. (2)

A
  • activating enzyme to concert glycogen into glucose

- increasing gluconeogeneis (conversion of amino acids and glycerol into glucose)

65
Q

Adrenaline is produced by…

A

the adrenal glands in times of excitement/stress

66
Q

Adrenaline raises the blood glucose level by (2)

A
  • activating an enzyme that breaks glycogen into glucose in the liver
  • inactivating an enzyme that synthesises glycogen from glucose
67
Q

Insulin … the blood glucose level

A

lowerse

68
Q

Glucagon … the blood glucose level

A

increases

69
Q

A person affected by diabetes…

A

cannot metabolise carbohydrate (especially glucose) properly

70
Q

Symptoms of diabetes (7)

A

high blood glucose, glucose in urine
increases thirst/hunger, need to urinate excessively
tiredness, weight loss, blurred vision

71
Q

Type 1 diabetes is insulin…

A

dependent

72
Q

Type 2 diabetes is insulin…

A

independent

73
Q

Affect on cells in the liver with type 1 diabetes

A

Body’s immune system attacks the beta cells

74
Q

In type 2 diabetes, (2)

A

glycoprotein receptors lose their responsiveness OR

there is an inadequate supply of insulin

75
Q

Type 1 diabetes is controlled by

A

injections of insulin

76
Q

Insulin must be injected as…

A

it is a protein and would be digested before it could be effective

Biology A2 Unit 5 (7 decks)

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