Homeostasis Flashcards

Question

Regulators

Answer 1

either use behavioural or metabolic mechanisms to maintain their body temperatures. The lizard basking on a rock uses heat radiated from the sun to warm its body and moves out of the sun when it is warm enough but its body temperature over the course of a day is not stable. Birds regulate body temperature at a constant level using metabolic sources of heat.

Answer 2

Can tolerate a wide temperature range

Answer 3

Can tolerate only a small range of temperatures

Answer 4

Optimal evolutionary fitness is a function of life history and peak bodily performance is often at an optimal body temperature. High temperatures are typically more deleterious to performance than lower temperatures – within the Pejus range a small increase in temperature has a large adverse effect (compare with a decrease in temperature of the same magnitude). Thermal tolerance has both low and high critical temperatures that can adversely affect survival if they are crossed.

Answer 5

Cutaneous evaporation Respiratory evaporation

Answer 6

exhibit physiological mechanisms that allow them to modify their body temperature over a long period of time

Answer 7

Animals can tolerate a wide range of environmental temperatures Different species have different thermal tolerances Often reflect differences in enzyme activity

Answer 8

Acute Chronic Evolutionary

Answer 9

Ectotherms derive heat from external sources and if they poikilothermic they will change temperature as the ambient temperature changes. This impacts on cell metabolism and body performance but changes in temperature produce an asymmetric curve around an optimal temperature. Reducing temperature slows performance and metabolic rate but small increases in temperature can have dramatic adverse effects on performance. These changes are characterized by curvilinear responses and a higher temperatures the effects can be abrupt.

Answer 10

the physical properties of molecular interactions and the metabolic rate of an animal

Answer 11

Determining the Q10 value for a response Q10 = RT/R(T-10) RT is the rate at any given body temperature R(T-10) is the rate at the temperature at a body temperature 10 °C lower the slope of the regression line on a semi-logarithmic plot.

Answer 12

Determining the Q10 value for a response Q10 = RT/R(T-10) RT is the rate at any given body temperature R(T-10) is the rate at the temperature at a body temperature 10 °C lower the slope of the regression line on a semi-logarithmic plot.

Answer 13

Metabolism Heart rate Gill ventilation

Answer 14

Temperature where 50% of the population can survive

Answer 15

Protein denaturation and coagulation- prevents eg enzyme activity

Answer 16

Protein denaturation and coagulation- prevents eg enzyme activity

Answer 17

1) Different animal may have unique metabolic pathways that are critically sensitive to temperature -May explain differences between species but diversity of habitat temperature means that variability in metabolic processes just isn’t observed 2) Small changes to amino acid sequences changes temperature sensitivity -Enzymes in icefish may be denatured at 6ºC because they different in their amino acid profile to eurythermal fish that live at higher temperatures and are denatured at 30-35ºC

Answer 18

Metabolic rate increases exponentially against temperature

Answer 19

family of proteins that are produced by cells in response to exposure to physiologically stressful conditions (temperature, UV light, and during wound healing. Perform chaperone function by stabilizing new proteins to ensure correct folding or by helping to refold proteins that were damaged by the cell stress

Answer 20

Consider a simple metabolic pathway X → Y Y → Z Q10 = 1.7 Q10 = 3.0 As temperature increases the conversion of Y → Z will be almost twice as fast as the rate that it can be converted from X Concentration of Y decreases and the production of Z decreases Y may also be important in other metabolic processes, which then slow and perhaps fail

Answer 21

Fluidity of lipids is temperature sensitive – as temperature increases they become more fluid, as it cools they can solidify High temperatures cause lipids to become less organised These changes in fluidity can affect the biochemical processes mediated by proteins embedded in the membrane

Answer 22

As temperatures decrease there is a greater risk of ice crystal formation in cells that physically damage structures Reduced temperatures may slow elements of key biochemical pathways and if the rate of reaction is too low then vital processes may be stopped If axon conduction stops then this can affect important autonomic processes, such as breathing Ironically, cold temperatures can delay death by slowing biochemical processes even after breathing or heart function have ceased.

Answer 23

Only species that are fixed to one location (e.g. sessile sponges or coral) lack any ability to control body temperature through some kind of behaviour Water readily conducts heat and temperature can change on short or long term time periods Simplest method of temperature control is to move to locations that are at the preferred body temperature

Answer 24

Body temperature rises as body mass increases As animals grow their surface layers become better insulators so more metabolic heat is retained and a higher body temperature can be maintained- thermal inertia

Answer 25

Behaviour Posture Increased surface area and colour to absorb sun’s radiation Shading by vegetation Short flights to increase convective heat losses Albedo- lightening in colour eg frogs

Answer 26

Reduced heart rate vasoconstriction

Answer 27

Evaporative cooling via respiration Distribution of blood

Answer 28

Changes in metabolic rate

Answer 29

Enzyme-substrate affinity depends on protein conformation, which in turn is affected by temperature Differential expression of genes that produce heat shock proteins Antifreeze proteins produced in liver and epidermis that absorbs ice crystals and prevents them growing- lowers freezing point of blood and minimises risk of ice nucleation . Accumulation of glycerol in blood lowering freezing point of lipids

Answer 30

Increased rate of heat absorption

Answer 31

Hypoxia induces gaping of the mouth that increases evaporation and cools the head

Answer 32

Temperature of pools varies from 10-31 degrees Pools can dry up

Answer 33

So in Tegula snails one species T. brunnea lives higher up the beachand is exposed to high ambient temperatures than the other species T. funebralis that lives further down the beach and is exposed for shorter periods. This choice of habitat is reflected in the differential expression of different heat shock proteins (HSP) – brunnea seems to express HSPs 38 & 70 more than funebralis. This is an evolutionary response that has allowed brunnea to live higher up the beach, which may confer other advantages to that species (e.g. reduced predation).

Answer 34

Maintain a near constant high body temperature by utilising heat generated by metabolism

Answer 35

where the metabolic rate is unaffected by ambient temperature Below a critical low ambient temperature metabolism increases because TB > TA Above a critical ambient temperature TB < TA and so metabolism increases in a similar way to poikilotherms

Answer 36

Higher metabolic rates and higher body temperatures than lower vertebrates of equivalent mass

Answer 37

Daily cycle Diurnal species = higher during day Nocturnal species = higher at night

Answer 38

Helps retain metabolic heat within the core body allowing body temperature to rise Fourier’s law of heat flow: M = C*(TB – TA) M = metabolic rate and C = thermal conductance Materials with a low thermal conductance are good insulators

Answer 39

Determined using combination of peripheral and central temperature receptors Skin receptors fire at a peak rate at particular temperatures Cold receptors only sensitive at cooler temperatures Warm receptors are deeper in dermis and only respond above 30 degrees Thermosensitive neurones in CNS- especially pre-optic area of hypothalamus

Answer 40

Microbial infection stimulates fever- high body temperature but feel cold Response to prostaglandins and thromboxanes (pyrogens) produced by white blood cells Pyrogenes stimulate release of prostaglandin E2 that interacts with neurones in the pre-optic area to re-set the balance point Higher body temperatures = faster clearances of micro-organisms

Answer 41

Changing level of insulation provided by air Reducing or increasing blood flow to the periphery Forced convection or conduction Increased or reduced evaporative cooling Increased metabolic heat production Storage of heat

Answer 42

Modify thickness of fur/feather layer in response to cold

Answer 43

Unsynchronised contraction and relaxation of skeletal muscle in high frequency rhythms to generate heat Mediated by somatic nervous system

Answer 44

Mammals have brown adipose tissue that is stimulated by sympathetic nervous system to oxidise lipids to generate heat Common in small, cold acclimatised mammals, hibernators and newborns

Answer 45

Under hot conditions, vasodilation can allow blood to be shunted to the skin and lose heat via radiation, convection, and/or conduction Under cold conditions vasoconstriction prevents blood from going to the skin and retains heat in the body core

Answer 46

Piloerection Vasodilation/vasoconstriction

Answer 47

Evaporative cooling (eg sweating, panting, gular flapping, saliva spreading)

Answer 48

Countercurrent systems prevent heat loss in limbs Respiratory turbinates

Answer 49

bony or cartilaginous structures in the nasal cavity of mammals and birds They are simple or complex swirls or branched structures that are covered with a moist epithelium Inspiration – air entering the nasal cavity is warmed as it passes over the epithelium – the turbinates cool Expiration – air leaving the body passes over the cool turbinates which are then warmed and water vapour condenses on the epithelium Birds expire air at 20ºC (core = 40ºC) saving 5% of energy expenditure

Answer 50

ball of blood capillaries located within a venous sinus that contains blood cooled by it coming from the nasal vein can selectively cool blood going into the brain to minimise high temperature thermal stress

Answer 51

Cold adapted mammals have wider thermal neutral zones and flatter responses of metabolic rate to cold temperatures

Answer 52

many large moths and other insects have insulated (hairy) thoraxes and can rapidly contract their flight muscles without flapping their wings. This generates metabolic heat and raises muscle temperature and efficiency. This allows them to warm the muscles preferentially and so fly on relatively cold days. The graph shows that these moths respond to colder air temperatures in a similar way to full homeotherms and can maintain high thoracic temperatures (aided by the insulation). A similar system is often seen in very active, large oceanic fish, such as tuna. There are counter-current blood systems that retain heat the heat generated by muscle contraction within the muscles rather than it being sent to the skin where it would be lost. This increases muscle temperature and efficiency

Answer 53

caused by prolonged exposure to extreme cold Lewis-Hunting reaction helps prevent this by having cycles of vasoconstriction and vasodilation to protect the extremities

Answer 54

leatherback turtles. These are amongst the largest of all modern reptiles and yet regularly visit cold seas. They are able to maintain a stable, relatively high temperature because of their large size, subcutaneous blubber and a counter-current heat exchanger in their flippers. They have different behaviours according to the water temperature, which they seem to use to ‘dump’ excessive metabolic heat generated during swimming.

Answer 55

Nasal cavity

Answer 56

family of proteins produced by cells that are produced in response to physiological stressors (not just temperature). They serve to bind with other proteins in such a way to ensure that the protein configuration (shape) is maintained at temperatures where it could be changed and so not function. Peptide strands that combine to form 3D proteins are held together by the HSPs.

Answer 57

Lose water freely through cutaneous evaporation Cannot produce hypertonic urine Have limited tolerance to high temperatures Not found in deserts?

Answer 58

Extended periods of time laying dormant

Answer 59

Nocturnal behaviour

Answer 60

change in physiology often in relation to high temperatures (but not always). Many frogs that perform this feat create cocoons from their shed skin that they use to minimise water loss whilst they are in a burrow Sandy soils – substrate remains friable and there is massive increase in water potential after rains Heavier clay soils – substrate is denser and goes hard when dry Cocoon formation can be a plastic response depending on water potential of soil Amphibians can absorb water from the soil if osmotic balance is correct but process is complicated by water potentials of different soils

Answer 61

Aestivating amphibians can accumulate molecules to increase osmotic pressure of body fluids Urea is retained within tissues to reduce need to urinate and lose electrolytes

Answer 62

Drops to 20-25% of SMR by 2-4 weeks of aestivation then remains stable Extends survival time when using endogenous energy stores (lipids)

Answer 63

Bury themselves in wet mud Aestivation for 4-5 months Metabolic depression Timing activity to coolest part of day

Answer 64

Sequential expression of different categories of genes reflected severity of stress. Regardless of acclimation temperature, mild stress = gene encoding heat shock protein 70 (HSP70) upregulated Higher temperatures = the gene encoding the proteolytic protein ubiquitin (UBIQ) was upregulated Extreme stress = a gene encoding cyclin-dependent kinase inhibitor 1B (CDKN1B) a protein involved in cell cycle arrest and apoptosis was upregulated

Answer 65

Desert larks 43% lower basal metabolic rate and 27% lower total evaporative water loss

Answer 66

Cold-acclimated birds use cutaneous water loss less than hot-acclimated doves, which rely less on respiratory water losses for cooling when challenged with high temperatures. example of phenotypic plasticity in response to short-term acclimation

Answer 67

1) Greater difference between body and air temperature so “dry” heat loss is increased 2) Stored heat in body can be dissipated at other times when air temperatures are reduced 3) Increased Tb in thermoneutral zone reduces evaporative water loss

Answer 68

Evaporation via respiratory surfaces, the skin (cutaneous) or the cloaca Some birds can use cloacal evaporation as part of their thermoregulation response to temperature stress

Answer 69

Sandgrouse (Pteroclididae) nest 50 km away from watering holes – reduced predation Chicks potentially deprived of water but resolved by soaking of breast feathers by adults flying to drink

Answer 70

Largest bill relative to body size of all birds Used as controllable heat radiator that regulates heat distribution by modifying blood flow

Answer 71

1) Increase thermal conductance to facilitate heat loss by conduction and convection 2) evaporative heat loss 3) Heat storage

Answer 72

Endurers – generally larger mammals Avoiders – generally smaller mammals

Answer 73

allow body temperature to rise In camels (Camelus dromedarius) heats storage depends on hydration status Above 40°C there is an increase in the normal daily amplitude in body temperature fluctuation from 2 to 6°C Heat gain in dehydrated camels is reduced but stored heat is greater Metabolic depression – reduced food intake or mediated by reduced levels of circulating thyroid hormone

Answer 74

Reduced levels of thyroid hormone

Answer 75

generally smaller mammals that avoid high daytime temperatures but if they are active in the day they adopt hyperthermy to store heat. aestivation Brought on food restriction, water restriction (or both) Affects water losses Body temperature tracks ambient temperature and oxygen consumption depressed

Answer 76

ears that can be infused with blood that increases the surface area for heat loss from the blood via radiation or convection but the air temperature has to be cooler than the body for this to work.

Answer 77

inhabit seasonally ephemeral water holes in wet-dry tropics of Australia Dig burrows in river bank and stay 3-4 months 13% loss in body mass – no evidence of metabolic depression Decrease in water loss from 40 to 9.3 mL kg-1 d-1 Size water pools in body decreased as body mass decreased Cloacal urine osmolality, [K+], [Mg2+] all increased Burrow was an adequate refuge and crocodiles can survive several months without access to water

Answer 78

Marine teleosts – body fluids freezing point is -0.8°C Polar oceans temperature is -1.8°C Produce antifreeze proteins in liver and epidermis that adsorb to ice crystals and prevent them growing Lowers freezing point of blood and minimise risk of ice nucleation Also accumulation of glycerol in the blood

Answer 79

Winter dormancy Aquatic – bottom of water bodies that often freeze at surface Water has lower O2 capacity than air Ice prevent air breathing so need to use skin or gills – aerobic activity leads to hypoxia Metabolic depression due to Q10 effect and hypoxia – lower rates of energy reserves Deep snow preclude photosynthetic production of oxygen in water Tadpoles more tolerant to hypoxia

Answer 80

Lack antifreeze to depress the equilibrium freezing point of bodily fluids Turtles remove active nucleating agents from bodily fluids (including bladder and gut) Integument becomes a highly efficient barrier to the penetration of ice into body compartments from frozen soil. Absence of a nucleating agent for ice crystals - bodily fluids remain in a supercooled, liquid state Physiological challenges - increased reliance on anaerobic metabolism Circulatory system is inhibited and then caused to shut down by declining temperature. Alterations in acid/base status resulting from the accumulation of lactic acid may limit survival by supercooled turtles Sublethal accumulations of lactate may affect behavior of turtles after the ground thaws in the spring

Answer 81

Size matters – Compared to large species small birds have: Higher metabolic rates High surface area to volume ratio Less insulation Low temperatures lead to increased metabolic rate to increase heat production and maintain high body temperature

Answer 82

Colder it gets – larger the body size so high latitude species should be bigger Global patterns of body size in birds driven by interactions between the physiological demands of the environment, resource availability, species richness and taxonomic turnover among lineages

Answer 83

In order to ensure high body temperatures are maintained birds have to adjust their basal metabolic rate to counter increased loss of heat at cold temperatures Fourier’s equation: Metabolic rate = C x (Tb – Ta) Where: C = thermal conductance of the body, Tb = body temperature and Ta = air temperature. Shivering Non-shivering thermogenesis Digestion Activity

Answer 84

Involuntary isotonic trembling of skeletal muscle that generates heat Commences below critical low threshold – BMR cannot keep Tb stable Muscles have to fatigue-resistant and most muscle fibres are not involved Can increase BMR 5-fold (other physical activity = 15-20x BMR) May be required for long period of time – titmice and the Goldcrest may need to shiver for days

Answer 85

Involuntary heat production without muscle contraction Found in mammals but perhaps not birds Normally proton (H+) gradient across inner mitochondrial membrane used to generate ATP Uncoupling protein (UCP) diverts protons into mitochondrial matrix so metabolic heat production is preserved UCP activated by cold-exposure Process confined to Brown Adipose tissue – high levels of UCP1 Birds do not have this system but do have avUCP – exact nature of mechanism is unknown

Answer 86

Unavoidable heat production during digestion Tawny owl – two feeding peaks (dusk & dawn) Unavoidable heat production during digestion dependent on energy intake ~60% of thermoregulatory cost Pigeons store food in crop and delay digestion until nightfall – contributes to heat generation

Answer 87

Food caching Select roost site to minimise exposure to cold and wind Roost communally – huddling together increases effective body mass Emperor penguin incubation

Answer 88

Time inactive with depressed metabolic rate It is also characterised by a periodic return to normal metabolic rates and processes. It is a physiological response rather than a simple response to a lower ambient temperature as seen in amphibians and reptiles.

Answer 89

Facultative body temperature reduction And drop in basal metabolic rate

Answer 90

Small mammals – problem of large surface area to volume ratio Aggregate together in burrows – combined body mass when huddled improves heat retention and presence of animals can raise temperatures above that of the soil and ambient air Burrow system under insulating layer of snow Build nests for insulation Hoard food

Answer 91

Large size = high thermal inertia Medium to large mammals can increase cold tolerance Acclimation of reindeer (Rangifer) allows the critical minimum air temperature for an increase in BMR to drop to -50°C from -30°C in the summer Increase in insulation though thicker pelts – thicker underpelt produced by re-activation of secondary hair follicles dormant during summer

Answer 92

Insulation via blubber in pinnipeds, sirenians & cetaceans More effective than fur for deep dives or long-term submersion – pressure forces insulating air layer out Regional heterothermy – counter-current heat exchanger for limbs Useful in aquatic habitats (cetaceans) and terrestrial habitats (cold-acclimatized wolves [Canis lupus]) Decrease body size – requires less energy Increase metabolic rate

Answer 93

Migration allow body temperature to fall close to ambient “Hibernation” is a commonly used term for a period of dormancy during unfavourable climatic conditions. Physiological process by which a homeothermic animal decreases its metabolic rate and allows its body temperature to drop to close that of the prevailing ambient air Long-term hibernation – a form of controlled hypothermia Observed in six orders of mammals: rodents (edible dormouse Glis glis and common dormouse Muscardinus avellanarius), bats, carnivores, insectivores (hedgehogs Erinaceus europaeus), marsupials & monotremes Individuals seek refuge in a hibernaculum

Answer 94

rodents (edible dormouse Glis glis and common dormouse Muscardinus avellanarius), bats, carnivores, insectivores (hedgehogs Erinaceus europaeus), marsupials & monotremes

Answer 95

Involves periodic arousals where the metabolism returns to normal animals become inactive with a decrease in heart rate, respiration and other bodily functions Characterised by times when the individual is aroused and becomes active, albeit temporarily – reason for this is unknown Hibernating mammals retain brown fat (NST) as adults- non-shivering thermogenesis Lipids – particularly triacylglycerols are deposited in adipocytes in months leading up to hibernation Temperature affects fluidity of long-chain FAs – polyunsaturated FAs (PUFAs) remain more chemically accessible at low temperatures than saturated fatty acids (SFAs)

Answer 96

Most hibernating species body mass < 5kg Beneficial effects on reduced metabolic rate decline with increasing body mass (bears are an exception)

Answer 97

Fat is deposited during the autumn months and during winter badgers remain underground in their setts – this will be warmer than the outside. They effectively sleep and allow a drop in body temperature as their metabolic rate slows. However, this physiological state is not the same as that observed in species that exhibit true hibernation. They wake up on a regular basis and will be active for relatively long periods during winter.

Answer 98

Produce antifreeze proteins in liver and epidermis that adsorb to ice crystals and prevent them growing Lowers freezing point of blood and minimise risk of ice nucleation

Answer 99

Japanese macaques (Macaca fuscata) will bathe in hot springs during winter unless they are being fed Dominant females and offspring bathe more

Answer 100

counter-current heat exchanger for limbs Useful in aquatic habitats (cetaceans) and terrestrial habitats (cold-acclimatized wolves [Canis lupus]) Decrease body size – requires less energy Increase metabolic rate caudal rete mirabile reduce heat loss

Answer 101

most mammals the distance travelled is proportional to body mass with the exception of bats, which are small in size but highly mobile and can migrate great distances (see graph).

Answer 102

most mammals the distance travelled is proportional to body mass with the exception of bats, which are small in size but highly mobile and can migrate great distances (see graph).

Answer 103

most mammals the distance travelled is proportional to body mass with the exception of bats, which are small in size but highly mobile and can migrate great distances (see graph).

Homeostasis Flashcards

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