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Animal Ecophys Third Year > Lecture 17 > Flashcards

Lecture 17 Flashcards

1
Q

What are the differences between hibernation and torpor?

A

. The duration
. The groups that undertake them
. The size of the animals that undertake them

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2
Q

How does duration differ between hibernation and torpor?

A

. Torpor is usually a physiological state that is utilised daily or over a few days
. Whereas hibernation takes place over weeks, maybe months

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3
Q

What groups undertake torpor? What is the issue with one of these groups?

A

The groups that undertake torpor include birds, mammals and maybe reptiles but if difficult because their metabolic rate is linked to that of the environment so if the environment temp changes then so does the metabolic rate.
So it is only really the birds and the mammals that undergo a regulated drop in body temp that is torpor

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4
Q

What animals does hibernation occur in?

A

Only really in mammals but one species of bird, the poorwill

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5
Q

What is the only species of bird that hibernates?

A

The poorwill

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6
Q

What sized animals are torpor and hibernation undertaken by?

A

. Torpor is usually undertaken by small animals

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7
Q

Why is torpor usually undertaken by small animals?

A

It is related to the duration of the state. So if you are changing your body temp daily then there are limits of how big you can be for those changes to take place.
Large animals change their body temp much slower than small animals do so it is not really a strategy that large animals can use

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8
Q

What are the largest animals that can undertake torpor? What is the median?

A

About 9 kilos is the largest.

The median is about 19g

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9
Q

Why type of animals is hibernation generally taken by and why?

A

Hibernation is generally taken by slightly bigger animals because to be able to withstand long periods of low metabolic rates and you need the stores and you have to be a certain size to be able to put on sufficient stores to be able to last you over the period of time and the smaller you are the less you are able to put on relative to your body size

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10
Q

What is the median mass of mammals that hibernate?

A

It is about 85g (so about 4 times that of the torpid animals)

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11
Q

Give the levels of hypometabolism in order

A
  1. Regional hypothermia (cooling of parts of the body without altering Tb)
  2. Regulated central hypothermia (e.g. nocturnal torpor)
  3. Partial hibernation (lacking either sustained consciously with incomplete metabolic depression)
  4. True hibernation
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12
Q

What is regional hypothermia?

A

Is what we see in us where certain parts of the body are cooler than the body core e.g. the skin and fingers

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13
Q

Give an example regulated central hypothermia

A

Nocturnal torpor

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14
Q

What is partial hibernation?

A

Where there is incomplete metabolic depression but there is sustained consciousness

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15
Q

What are the three definitive and coordinated physiological changes that true hibernators undergo?

A

. Thermal dormancy
. Behavioural suppression
. Metabolic inhibition

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16
Q

What is thermal dormancy? (Is one of the 3 definitive and coordinated physiological changes true hibernators undergo)

A

The ability of an animal to operate its biological functions at very low core body temperatures. (The animals essentially stop thermoregulating entirely and any functions that are undertaken by the animals have to be undertaken at those low temperatures)

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17
Q

What is behavioural suppression (one of the three definitive and coordinated physiological changes that true hibernators undergo)?

A

The cessation of activity of many muscles (they are unresponsive), which depends upon the ability of the brain to override sensory inputs and endogenous rhythms such as breathing

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18
Q

What is metabolic inhibition (one of the three definitive and coordinated physiological changes that true hibernators undergo)?

A

The ability of an animal to undergo episodic bradymetabolic changes (those vet low levels of metabolism): that is through the depression of energy related and metabolic reactions

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19
Q

What are the three most important environmental stimuli imitating hibernation?

A

. Food supply- dwindling food supply is the reason for going into that hibernating state
. Daylength- changes in daylength because that food supply of plants and other animals is linked to it
. Ta- the ambient temp changes, most of the animals we are talking about live in temperate areas and so what we are talking about is a reduction in food supply, daylength and ambient temperature

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20
Q

For any reptile or amphibian what is it’s body temperature predominantly linked to?

A

Linked to that of the environment

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21
Q

How can reptiles and amphibians control their body temperature (so some extent)?

A

Through behavioural and physiological means (but ultimately they are linked to the external temperature)

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22
Q

What happens to reptiles and amphibians when the temperature drops?

A

Their metabolic rate also drops

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23
Q

How do most reptiles and amphibians spend winter?

A

In a torpid state (due to a reduction in temperature)

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24
Q

Some do some species of tortoise and snakes spend their winter?

A

There is some evidence that some species hibernate

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25
Q

Some species of tortoise are forgot to hibernate, what evidence is there for this?

A

. Lay down fat reserves
. Burrow below depth of frost
. Metabolic inhibition
. High atrial pCO2- start reducing the rates in which they breath which means that the CO2 is not released so it is kept within the cardiovascular system so you get this high atrial pCO2
. Respiratory acidosis- implicated in metabolic depression (the high atrial pCO2 causes the respiratory acidosis and is why there is this metabolic inhibition

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26
Q

Why do you think/ what is the potential evidence that some species of snakes hibernate?

A 
. Retreat to hibernacula 
. Store lipids in fat bodies and glycogen in the liver 
. Survival appears to be dependant on:
- lipid reserves 
- resistance to desiccation
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27
Q

Describe the hibernation of the Golden-mangled ground squirrel

A

. Body temp in summer (like most mammals) remains fairly constant
. Then comes into hibernating state, body temp declines and stays at a low level of about 4/5 degrees
. Stays at a low level from about October to April
. Peaks in body temp that are reasonably regular (all hibernating animals show these) which are periodic arousal periods
. So find that animals are stopping their low body temp and their temp increases
. Then become active for a small period and then go back into their hibernating state

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28
Q

Describe the arousal of hibernating animals (when? What happens etc)

A

. Periodic- every few weeks or so
. Energetically expensive- because the animals are going from about 5 degrees up to 37 degrees so have to increase their body temp and then decrease it again
. Triggers unknown
. Reversal of respiratory acidosis- animals start breathing again at a faster rate, getting rid of that CO2 that has built up in the blood. So, the metabolism is no longer being inhibited so that causes an increase in thermogenesis
. Animal warms up
. Increased protein synthesis- this may be a clue as to why they are taking these periodically expensive arousals

29
Q

How many hypotheses are there for the reasons for the periodic arousal in hibernating animals?

A

3

30
Q

Explain the pros and cons of the hypothesis ‘hibernating is an exaggerated form of sleep’

A

. No pros
. Cons:
Wouldn’t evolution processes have selected for continuous hibernation period. Know this hypothesis is wrong because Hibernation isn’t similar to torpor never mind sleep but if it were wouldn’t evolution have selected for continuous hibernation, why have those arousal periods there would be no reason for it because evolution would have gotten rid of them so there must be some other reason for these arousal periods

31
Q

Explain the pros and cons of the hypothesis ‘response of depletion of energy stores and build-up of metabolic wastes’ for the reason for the periodic arousal in hibernating animals

A

Pros: ok for those that have food stores
Cons: maladaptive for those relying on fat stores. So this one is that they wake up to replenish energy stores and get rid of metabolic rate and that’s ok if you are an animal that has energy/ food stores but those that are reliant on fat stores would mean that waking up and warming up would use those fat stores at a much faster rate, so it is unlikely unless there are two separate forms of hibernation then this is unlikely.

32
Q

Explain the issues with the hypothesis that ‘replenish body water’ is the reason for the periodic arousal from in hibernating animals

A

Not much evidence to suggest that these animals go out and look for water during these periods of arousal

33
Q

Since all three hypotheses for why there is periodic arousal in hibernating animals have a lot of cons what is the likely reason for it? (Does not mean it is the reason as we don’t know the trigger yet)

A

So, the likely hood is that it is to repair tissue and possibly tto defend off disease organisms as well.
Probably it is that they need to repair tissues, they have a metabolic rate less than 1% of their normothermic level, so any tissue damage is going to be taking place at a very slow rate but it still needs to be undertaken, so come out, repair tissues and then go back into their hibernating state

34
Q

Whether it not they are coming out of hibernation at the arousal phase or at the end of hibernation entirely they have to reheat so increase their thermogenesis. What are the mechanisms of reheating/ what are the ways they can do that?

A

. Shivering- increase the muscle activity and that will not do any work per say/ so not moving around but your muscles will be contracting and relaxing producing heat
. Activity will increase the muscle activity which will increase temperature
. Non-shivering thermogenesis- ability to produce heat that does not come from muscle activity

35
Q

How does non-shivering thermogenesis occur to in mammals?

A

Occurs to the:
. Liver
. Brown adipose tissue- special tissue found in mammals
. BMR- can be thought of as a mech Idm for the animal to produce heat without shivering

36
Q

How does non-shivering thermogenesis occur to in birds?

A

. Liver activity so the metabolic rate of the liver can increase, obvs the liver is not a muscle so it is not shivering so therefore it is non-shivering thermogenesis
. BMR- changes in animals depending on the time of the year (was discussed in earlier lecture referring to seals), and that might be related to the requirement for increased thermogenesis

37
Q

How does brown adipose tissue differ from normal fat deposits?

A

Contains lipid droplets and very little blood supply- is a fat store

38
Q

Why is brown adipose tissue brown?

A

Because it has a very dense capillary network- lots of blood vessels, lots of blood supply, very small cells and because of that it looks brown

39
Q

What is brown adipose tissue common in?

A

Young mammals, particularly found around some of the key organs- the heart, vertebral column and the kidneys

40
Q

How does brown adipose tissue differ from normal fat deposits?

A

Because it contains lipid droplets, there also a large number of mitochondria in those cells as well, also has nervous innovation

41
Q

What is brown adipose tissues only found in?

A

Mammals

42
Q

What does brown adipose tissue work as/ do?

A

As a heat producing tissue so if the animal gets cold then there is a release of noradrenaline which causes the fat to be released so there is a rapid lipolysis and release of free fatty acids and coenzyme A and it is these free fatty acids and of acyl coenzyme A that is used by the mitochondria in the brown adipose tissue and within the brown adipose tissue there is a protein called UCP1 it was found in brown adipose tissue because brown adipose tissue is a thermal organ/ tissue.

43
Q

What does UCP1 do in adipose tissue and what is the acyl coenzyme A released by the lipolysis do to it?

A

It binds to purine nucleotides.
The acyl coenzyme A that is released also dislodges these purine nucleotides from UCP1 and causes the mitochondria respiration to become uncouple

44
Q

How do bears spend their winter/ why?

A

. Dormancy rather than hibernation
. Lack of food supply that causes the dormancy
. Hyperplasia during summer and autumn
. Retreat to dens when food supply is reduced
. Torpor is very shallow- ‘heavy sleep’ or ‘Carnivorean lethargy’
. Due to animals bulk the microclimate within the den is relatively warm and humid
. Reduction in body temp is only slight
. Reduction in water loss by not defecting or urinating and by reducing respiratory water loss because they are reducing the rate in which they are breathing because they are dormant/ not moving

45
Q

Why do bears not defecate while in torpor?

A

Because they are not eating so they are not needing to get rid of nitrogenous waste products because they are mainly using fat that doesn’t have a nitrogenous component to it, so don’t need to produce urine

46
Q

Why is hyperphagia during summer and autumn helpful?

A

Considerable fat reserves

47
Q

What interesting physiological problems does that fact that bears do not defecate or urinate during ‘hibernation’ pose?

A

. hibernating bears gradually switch to lipid metabolism
. low protein metabolism means no need to produce large volumes of urine
. Small amounts of urine are produced yet the bears have only small volumes in their bladders
. Bladder is a site of water and nitrogen reabsorption- the nitrogen being disposed of metabolically

48
Q

How does urine volume (ml.d^-1) change before and during hibernation in brown bears?

A

Before: 1872
After: 107

49
Q

How does the total N2 (g.d^-1) change before and during hibernation in brown bears?

A

Before: 15.5
During: 3.5

50
Q

How does the amount of uric acid (mg.d^-1) differ before and during hibernation in brown bears?

A

Before: 543
During: 133

51
Q

How does the amount of NH3 (mEq.d^-1) Differ before and during hibernation in brown bears?

A

Before: 12.2
During: 6.1

52
Q

How does the amount of creatine (g.d^-1) differ before and during hibernation in brown bears?

A

Before: 2.78
During: 2.46

53
Q

What are the strategies of of animals living in deserts?

A

. Evaders
. Evaporators
. Endurers

54
Q

What is the definition of a desert?

A

It is related to its aridity so it is related to how little water falls/ is available not the temp as you have some cold deserts not just hot

55
Q

What are the problems of deserts for animals?

A
  • restricted water intake

- need to reduce water losses as there is very little water

56
Q

How to animals is desert environments gain water (well animals in general)?

A 
. Drinking 
. Uptake via body surfaces 
- from water- contained in food 
- from air 
. Metabolic water production
57
Q

How do animals in deserts lose heat (well animals in general)?

A 
. Evaporation 
- body surfaces
- respiration 
. Faeces 
. Urine 
. Specialised secretions
58
Q

Explain water exchanges in terrestrial animals

A

. Water losses must be balance by water gains
. Air leaving lungs will be 100% humid
. Water losses are reduced by a variety of mechanisms e.g. reducing temp o the exhaled air
(. Desert animals better at reducing water loss)

59
Q

When it comes to water intake what can marine birds and reptiles do that other animals can’t? How/ why can they do this?

A

Can drink seawater- excrete using saltglands

60
Q

How do desert animals deal with increased water loss?

A

. Impermeability- to stop water losses
. Tolerance to water loss- can survive up to 48% in some desert roads
. Concentration of excretory products- very hyperosmotis urine, so changing to uric acid

61
Q

What is the water balance (losses and gains) of the Marriam’s kangaroo rat?

A

Losses
. Evaporation 75%
. Urine 25%
. Faeces 5%

Gains
. Oxidation water 90%
. Free water in food 10%
. Drinking 0%

62
Q

What is the problem with any terrestrial animal and their breath and why does it have to be this way? How does it work?

A

They have to make their breath moist, as the air that they take in is going to have a low water content but they need to increase that to 100% humidity in order for diffusion to take place. So air that goes in has a low water content, in the lungs it goes up to 100% humidity and is warmed up, so when the animal breaths out it is obviously breathing out air that is 100% humid so they have to put water into the air, so every breath these animals take is realising water into the environment

63
Q

There are a number of different strategies for desert animals; evaders, evaporators and endurers what is it linked to?

A

Body mass

64
Q

Describe the desert animals that use the endurers strategy (give examples of some)

A

. Large endothermic animals e.g. Dromedary, oryx, ostrich, Rhea

65
Q

There are a number of different strategies for desert animals; evaders, evaporators and endurers what is it linked to?

A

Body mass

66
Q

Describe the desert animals that use the endurers strategy (give examples of some)

A

. Large endothermic animals e.g. Dromedary, oryx, ostrich, Rhea

67
Q

Describe the desert animals (with examples) that use the evaporators strategy

A

. Medium sized animals
. Birds, dogs, cats, small antelopes, foxes, sheep, goat, humans
. Dependent on a reasonable water supply
. Use panting or sweating (preferable panting as it is more controllable)
. Use of carotid rete system (mammals) or ophthalmic rete (birds) for selective brain cooling
. Ability to tolerate hypothermia
. Produce hyperosmotic urine
. Migrate to follow patchy water sources

68
Q

Describe the desert animals (with examples) that use the evaders strategy

A

. Soft bodied invertebrates
. Insects, spiders and scorpions
. Vertebrates ectothermic evaders- desert amphibians e.g. tiger salamander and spadefoot toads, and reptiles
. Small vertebrates endotherms, mainly rodents e.g. antelope squirrel

69
Q

What is Q10?

A

Is an indicator of the temperature sensitivity of a physiological process caused by an increase by 10 degrees C

Animal Ecophys Third Year (17 decks)

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