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Biology A2 Unit 5 > 12 Homeostasis > Flashcards

12 Homeostasis Flashcards

(77 cards)

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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
Ectotherm
an animal uses the environment to regulate its body temperature
25
Endotherm
an animal maintaining its body temperature by physiological mechanisms
26
An ectotherm's body temperature will...
Fluctuate with the environment
27
Ectotherms control their body temperature by
adapting their behaviour to changes in the external temperature
28
Five ways an ectotherm might control their body temperature
``` Exposing themselves to the Sun Take shelter Gain warmth from ground Generate metabolic heat (minor) Colour variation ```
29
An endotherm's body temperature...
remains reasonably constant despite changes in the external temperature
30
The temperature range of an endotherm is a compromise between..
Having a high temperature for enzymes to proceed faster | And the work needed to maintain the higher temperature
31
The smaller the surface area to volume ratio...
The easier it is to maintain a high body temperature
32
The higher the surface area to volume ratio
The harder it is to maintain a high body temperature
33
To make rapid changes in temperature, to warm up, 6 ways.
``` Vasoconstriction Shivering Raising of hair Increased metabolic rate Decrease in sweating Behavioural mechanisms ```
34
Rapid responses to lose heat (4)
Vasodilation Increased sweating Lowering body hair Behavioural mechanisms
35
Vasoconstriction (3)
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
Raising of hair to increase body temperature (3)
Hair erector muscles in skin contract Traps a layer of insulating air next to the skin Lowering the temperature difference, reducing heat lost
37
Vasodilation (3)
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
Lowering of body hair to reduce body temperature (3)
Hair erector muscles relax and hair flattens Insulating air layer thickness is reduced More heat is lost to the environment
39
Hypothalamus
The region of the brain that acts as the control centre for the autonomic nervous system and regulates body temperature/fluid balance
40
Autonomic nervous system
Part of the nervous system controlling muscles and glands that is not under voluntary control
41
The thermoregulatory centre of the hypothalamus has two parts...
Heat gain centre | Heat loss centre
42
Heat gain centre...
Activated by a fall in blood temperature | Controls mechanisms to increase body temperature
43
Heat loss centre...
Activated by a rise in blood temperature | Controls mechanisms to decrease body temperature
44
Two ways temperature is measured...
Hypothalamus monitors blood temperature | Skin thermoreceptors send impulses to hypothalamus
45
Two principle coordinating systems...
``` Nervous system (rapid) Hormonal system (slower) ```
46
Hormones are (3)
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
Second messenger model (5)
- 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
Pancreas produces
Enzymes: protease, amylase, lipase Hormones: insulin, glucagon
49
Groups of hormone producing cells in the pancreas
islets of Langerhans
50
Cells in islets of Langerhans, two types
alpha cells | beta cells
51
alpha cells of the islets of Langerhans;
larger and produce glucagon
52
beta cells of the islets of Langerhans
smaller and produce insulin
53
If blood glucose level falls too low...
cells will be deprived of energy and die, especially brain cells
54
If blood glucose levels are too high
The water potential of the cell is lowered | Causing osmotic problems that may result in dehydration
55
Three sources of blood glucose
Directly from the diet From the breakdown of glycogen (glycogenolysis) Gluconeogenesis
56
Glycogenolysis
splitting of glycogen into glucose
57
Gluconeogenesis
formation of new glucose from sources other than carbohydrates
58
Beta cells in the islets of Langerhans detect a rise in blood glucose levels and...
secrete insulin directly into the blood plasma
59
Insulin combines with glycoprotein receptors and... (3)
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
Changing the tertiary structure of glucose transport proteins...
causes them to change shape and open, allowing more glucose into the cells
61
Four ways blood glucose is lowered by insulin
- absorbed faster into cells especially muscles - respiration rate increased - conversion into glycogen (glycogenesis) - conversion into fat
62
alpha cells in islets of Langerhans detect a fall in blood glucose,
secreting glucahon into the blood plasma
63
Glucagon binds to receptors in the...
liver
64
Liver cells respond to glucagon by.. (2)
- activating enzyme to concert glycogen into glucose | - increasing gluconeogeneis (conversion of amino acids and glycerol into glucose)
65
Adrenaline is produced by...
the adrenal glands in times of excitement/stress
66
Adrenaline raises the blood glucose level by (2)
- activating an enzyme that breaks glycogen into glucose in the liver - inactivating an enzyme that synthesises glycogen from glucose
67
Insulin ... the blood glucose level
lowerse
68
Glucagon ... the blood glucose level
increases
69
A person affected by diabetes...
cannot metabolise carbohydrate (especially glucose) properly
70
Symptoms of diabetes (7)
high blood glucose, glucose in urine increases thirst/hunger, need to urinate excessively tiredness, weight loss, blurred vision
71
Type 1 diabetes is insulin...
dependent
72
Type 2 diabetes is insulin...
independent
73
Affect on cells in the liver with type 1 diabetes
Body's immune system attacks the beta cells
74
In type 2 diabetes, (2)
glycoprotein receptors lose their responsiveness OR | there is an inadequate supply of insulin
75
Type 1 diabetes is controlled by
injections of insulin
76
Insulin must be injected as...
it is a protein and would be digested before it could be effective

Biology A2 Unit 5 (7 decks)

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