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Flashcards in HOMEOSTASIS Deck (71):
1

What is homeostasis?

- Maintenance of relatively constant internal enviro. within small tolerance limits, optimum zone, despite changes external + internal enviro.
- Increase/decrease = mechanisms act to restore optimum state

2

Why do body levels need to be maintained within limit?

CO2: When dissolved in water ➡️ carbonic acid, lowering pH + affected enzyme activity

3

What is steady state control system?

SR MERF

Stimulus: Change in enviro.
Receptor: Detect change
Modulator: Control centre
- Processes info from receptor
- Sends info effector
Effector: Carries out response (muscles / gland)
Response: Counteracts stimulus
Feedback: Original stimulus changed

4

What are the internal conditions controlled?

- CO2
- Oxygen
- Temp.
- Salts
- H2O
- pH
- Glucose

5

What is vasoconstriction?

- When cold, blood vessels constrict
- Reduce blood flow near skin
- Reduce heat loss

6

What is vasodilation?

- When too hot
- Blood vessels dilate
- Allow more blood to flow near surface of skin
- Heat is lost

7

Thermoregulation of body in hot temperatures?

S - ⬆️ temp of blood
R - thermorecept. detect change
M - hypothalamus compares change to optimum temp, processes info from receptor
E - R
>sweat glands >⬆️ sweat production
>blood vessels >vasodilation
>skeletal muscle >seek shade
>thyroid >⬇️ thyroxine, ⬇️ MR
F- ⬇️ temp of blood

8

Thermoregulation of body in cold temps?

S - ⬇️ temp of blood
R - thermorecept. detect change
M - hypothalamus compares change to optimum temp, processes info from receptor
E - R
>blood vessels >vasoconstriction
>skeletal muscle >shivering/seek warmth
>thyroid >⬆️ thyroxine, ⬆️MR
F- ⬆️ temp of blood

9

How does sweat cool you down?

- Excrete water your sweat glands
- Releases kinetic energy (heat) - evaporates
- Resulting in cooling down

10

What is the stimulus response model in which change in external and internal environment conditions is detected and responses occur?

Steady state controls system - process of SR MERF

11

Advantages + disadvantages of ectotherm?

Advantage:
- little energy required
- feed less often

Disadvantage:
- restricted geographic range
- inactive in cold + night

12

Advantages + disadvantages of endotherm?

Advantage:
- body temp. constant
- active at any temp
- 24 hrs/day
- any geographic region

Disadvantage:
- large energy requirement
- need insulation +\or cooling mechanism

13

What are some of the physiological adaptations in hot environments?

- sweating/panting
- coat thinning
- vasodilation
- decrease metabolic rate

14

What are some of the structural adaptations in hot environments?

- Insulting fur
- Large SA:vol
- Large extremities to aid heat loss

15

What are some of the behavioural adaptations in hot environments?

- Burrowing in heat of day
- Decrease physical activity / movement in heat
- Standing or lying in shade
- Increase SA for radiation - flapping ears

16

What are some of the physiological adaptations in cold environments?

- Increased metabolic rate
- Shivering
- Pilo-erection
- Vasoconstriction
- Hibernation

17

What are some of the structural adaptations in cold environments?

- Insulating fur
- Insulating fat
- Small SA:vol

18

What are some of the behavioural adaptations in cold environments?

- Huddling/clusters
- Staying in burrows
- Basking in sun
- Migration

19

What is ectotherm?

- Body heat external enviro.
- Regulate temp. through behaviour

20

What is endotherm?

- Body heat metabolic activity - internal
EG birds, mammals

21

What is 3 types of nitrogenous waste?

- Ammonia
- Urea
- Uric acid

22

What is nitrogenous waste?

- Produced as a result of breakdown of a.a - process known as deamination
- Results in production of ammonia, urea or uric acid

23

Ammonia?

- Extremely toxic, very soluble + energy inexpensive to produce
- Needs to be excreted very dilute (hypotonic) urine so only aquatic vertebrates like fish which have large water supply - ammonia waste
- Produce soft shelled eggs in water so ammonia produced by embryo can diffuse into enviro.

24

Urea?

- Mod. soluble, mildly toxic (100,000 less ammonia)
- Excreted as hypertonic (mammals) / isotonic (amphibians) solution due to mod. toxicity
- Allow mammals internal development, as foetal urea can be passed across placenta
- Involves water loss in urine, mammals restricted to enviros. water availability
- High energy expenditure in producing + concentrating in urine restricts use to high metabolic organisms (mammals)

25

Uric acid?

- Insoluble, non toxic, complex molecule energy expensive to produce
- Excreted w/out loss water, allowing birds + reptiles live dry areas
- Bc insoluble, does not allow birds + reptiles internal development young, low toxicity + insolubility means can be stored hard shelled dry eggs during development
- Allows birds to fly bc don't have to carry heavy water with nitro. waste

26

What is process of counter current heat exchange?

1. Veins + artery touching
2. Arterial blood loses heat venous blood
3. Cooler arterial blood = less difference between foot temp. + extern enviro temp
Lower rate heat loss - 15°C/5°C
4. Foot temp just above freezing
5. Venous blood returning to core heated by arterial blood
6. Venous blood almost back to core temp
Little energy required to reheat it

27

What is counter current heat exchange?

System used by organisms in cold climates to minimise heat loss + keep extremities warm

28

What organisms use counter current heat exchange?

- Penguins + feet
- Grey whale + tongue
- Bottlenose dolphin + fin

29

How is water gained and loss?

Gain: food, metabolism, drink
Loss: lungs, skin, kidneys, poo

30

What is excretion?

- Removal waste products of metabolism
- Urine

31

What is urine?

Produce by kidneys + composed water, urea, uric acid, ions
Substances reabs. kidneys:
- 99% H2O
- all glucose + a.a
- most salts + urea

32

What are some of the factors that affect water gain and loss?

Enviro: availability water
Structural: SA:vol, skin, scales, gills
Physiological: kidneys, large intestine

33

What is ADH?

- Anti diuretic hormone
- Decrease urine production

34

SRMERF for low H2O?

S- low H2O in blood
R- osmoreceptor in hypothalamus
M- hypothalamus
E- posterior lobe of pituitary secretes ADH
R- collecting ducts more permeable (H2O absorption)
F- increase H2O in blood

35

SRMERF for high H2O?

S- high H2O in blood
R- osmoreceptor
M- hypothalamus
E- posterior lobe pituitary stop ADH
R- collecting ducts less permeable (decrease H2O absorption)
F- decrease H2O in blood

36

What is pilo-erection?

- When cold small muscles in hair follicle erect/stand up
- Creates pocket of air near skin surface, heated by body temp
- Acts as insulation

37

What is isotonic?

2 solutions same concen. dissolved ions

38

What is hypotonic and hypertonic?

2 solutions with diff. ion concen.
- hypo: lower concen.
- hyper: higher concen.

39

What is an osmoregulator?

Specialised mechanism regulate internal water + solute concen. despite concen. changes in exter. enviro.

40

What is a osmocomformer?

Internal solute concen. changes w/ concen. solutes in exter. enviro.

41

What is marine organism osmoconformer?

- Body fluid composition varies w/ water surrounding them
- Intertidal species tolerate large variations - starfish, jellyfish, worms, molluscs

42

What is marine osmoregulator?

Regulate salt + water levels

43

What are some of the marine organisms that are osmoregulators?

- Bony fish
- Cartilaginous organisms - sharks + rays
- Marine mammals
- Marine birds

44

What is freshwater osmoregulator?

Water moves into cell by osmosis

45

How does osmoregulator work for fresh water organisms?

AMOEBA: contractible vacuoles collect + expel excess water
INVERTEBRATES: nephridial organs (like kidney nephron)
MAMMALS: reabsorption through kidneys

46

What is the way that fish osmoregulate?

- Large amounts of dilute urine
~ high infiltration rate in kidneys
~ large no. glomeruli
- Active uptake of salts through gills
- Preventing water entering body cells water only enters blood + excreted
- Scales / mucus layer

47

What is plant water balance?

Gain:
- root hair cells - increase SA

Loss:
- evaporation
- transpiration through stomata

48

What is transpiration?

Evaporation/loss water from leaves/ surface of leaves
- Helps keep leaves cool
- Transport of minerals
- Dissolving gases
- Guard cells control water + gas exchange

49

What are guard cells?

- Become flaccid or turgid according to pressure within cell
- Either side of stomata
- Cell wall thickens next to pore
- Becomes turgid, thin walls stretches more + thickens ➡️ bow out (opens) to allow gas exchange to occur
- Becomes flaccid when loses water + begins to close up, reduces gas exchange

50

Factors affecting transportation rate?

- Temp
- Wind
- SA
- Humidity
- Soil water

51

What is xenophyte and halophyte?

Xenophyte: dry habitat
Halophyte: salty habitat

52

What are properties of xenophyte plant?

- Thick waxy cuticle
- Reduced no. stomata
- Low SA
- Stomata in pits, grooves or depressions, lower surface
- Lead surface covered in hairs, trap humidity
- Reflect light
- Small narrow leaves
- Leaves roll, curl or fold

53

What are properties of halophyte plant when reducing water loss?

- Reduce no. + size leaves
- Few stomata
- Silver hairs
- Waxy cuticle

54

What are properties of halophyte plants when removing salt?

- Salt gland (bladders)
- Increased growth
- Dropping leaves + bark
- Returning salt to roots
- Active transport to remove salt (into vacuoles)

55

How does plant maintain their temp? Gain + losing heat?

Gain heat:
- large leaves
- dark colour
- high SA:vol
Reducing heat again:
- small leaves
- light colour
- low SA:vol
- reflective cuticle

56

How does bony fish osmoregulate?

- Lose water (osmosis)
- Drink salt water + excrete excess salt through gills

57

How does cartilaginous organisms osmoregulate?

- Sharks + rays
- Maintain high urea levels similar to salt levels in sea water
- Reduce water loss
- Sharks: secrete salt from salt glands in rectum

58

How do marine mammals osmoregulate?

Kidney produce urine high urea + salt

59

How do marine birds osmoregulate?

- Ingest high levels salt food + water
- Countercurrent heat blood flow remove large amount of salt
- Excess salt excreted through nasal gland

60

What is the role of high metabolic rate for organisms in cold climates?

- Metab. role in releasing energy + increasing body temp
- Increased metab. rate may temporarily compensate for excessive heat loss

61

What are the 4 ways of transferring heat?

- Radiation
- Conduction
- Convection
- Evaporation

62

What is radiation?

- No physical contact
- Waves of energy
- Sun

63

What is conduction?

- Contact
- Pass from one molecule to other

64

What is convection?

- Cool air + warm body heated ➡️ expands
- Becomes less dense + rises

65

What is evaporation?

- Water - 100 degrees
- Large amount of heat

66

How do fresh water fish maintain salt/water balance?

PROBLEM 1: Gain water/body fluids dilute - swell. As water moves via osmosis from region of low salt concen. in surrounding to high salt concen. in body water
SOLUTION 1: Large volume of urine

PROBLEM 2: Lose salt. As salt moves from region of high salt concen. in body to region of low salt concen. outside body via DIFFUSION
SOLUTION 2: Dilute urine. ACTIVE TRANSPORT salts absorbed across gills

67

How do marine fish maintain salt/water balance?

PROBLEM 1: Water loss ➡️ dehydration. Water moves from low salt region in body ➡️ high salt region out via OSMOSIS
SOLUTION 1: Small urine volume

PROBLEM 2: Gain salt via DIFFUSION from region of high salt outside body ➡️ low salt inside body
SOLUTION 2: Concen. urine. ACTIVE TRANSPORT across gills to remove salt

68

SA:vol: How do small animals temperature control? What's ideal SA:vol ratio for small organisms?

EG MOUSE
Small organisms = large SA:vol
- Lose heat easily, move fast, high MR
~ turpor, curling, huddling behaviour

69

SA:vol: How do large animals temperature control? What's ideal SA:vol ratio for large organisms?

EG ELEPHANT
Large organisms = small SA:vol
- Lose heat slowly, move slowly
~ low MR, SA extensions to increase SA exchange - large ears

70

What is SA:vol ratio of organisms in colder climates? Why?

COLDER CLIMATE SPECIES ARE LARGER (LARGE VOL:SA)... TO REDUCE SA:VOL RATIO + THEREFORE HEAT LOSS

71

Adaptations that leaves may have that limit which limit excessive water loss? Indicate briefly.

Long narrow leaves: reduce SA exposed to sun's heat
Reduced # stomata: less stomata = less water loss
Recessed stomata: creates humid microenviro slows water loss through evap from stomata
Stomata leaf underside: reduce rate of evap from upper surface
Hairs on leaf: reflect sun heat + temp + rate evap
Thick waxy cuticle: reflect sun + keep moisture in