thermal physiology

Samantha bruce
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lectures 8 and 9

Samantha bruce
Created by Samantha bruce 2 months ago
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Question Answer
pros and cons of living on land air less dense than water means that land dwellers require more support air less viscous than water- quicker movement and acceleration more oxygen available on land diffusion rate 300000 times greater on land there is no access to salts apart from obtained through diet water harder to obtain and loss is inevitable
what is the definition of thermal strategy combination of behavioural, biochemical and physiological responses that ensure the Tb is within acceptable limits
what is the definition of ectotherm environment greatly determines body temperature
what is the definition of endotherm generation of internal heat
what is the definition of heterotherm only heat the parts of the body that cannot maintain high core temperature continuously
what is the definition of homeotherm stable body temperature
what is the definition of poikilotherm variable body temperature
what is the definition of eurytherm tolerates wide ranges of temperatures
what is the definition of steotherm tolerates a narrow range of temperatures
name the ways that temperature regulation can be dealt with biochemical physiological behavioural
describe the biochemical effect that can take place in temperature regulation -temperature alters the chemical reaction and enzyme kinetics -Q10 temperature coefficient is a measure of the the rate of change of a biochemical reaction as a consequence of altering the temperature by 10c
discuss the short term enzyme adaptations that can occur -change the effective concentration of an enzyme -alter rate limiting enzyme concentration -change the structure and therefore catalytic efficiency -phosphorylation to active forms -inhibitors and activators -change in the intracellular environment pH, ion levels -energy for the reaction controlled -hormone control
discuss long term enzyme adaptations -use if different allozyms in different populations temperature specific works best at the temperature that the species is usually found e.g. enzymes of warmer adapted species more thermostable than cold species use different isozymes within one animal - genetic loci for 2 or 3 different versions works best at different times during the year and these can be turned on and off as appropriate -->differential protein expression when in different conditions
what are heat shock proteins -heat shock, pH shift or hypoxia, leads to increased expression of HSPs to protect the cell by stabilizing unfolded proteins giving the cell time to repair or re-synthesize damaged proteins. this is a cellular cascade that leads to changes in gene expression of HSPs; particularly HSP90, HSP27 and HSP 70 families
describe lipid viscosity at differing temperatures low temperatures = increased viscosity and membranes become more rigid--> too rigid for functional purpose high temperatures= membrane is too fluid
discuss the adaptation that could take place to prevent temperature affecting membrane stability homeoviscous adatations (HVA) to prevent the membrane becoming too rigid at cold temperatures unsaturated lipids may be inserted as this prevents the fatty acid tails being packed too tightly
name 4 routes of thermal exchange radiation conduction convection evaporation
describe thermal exchange through radiation transfer of heat from a warmer object to a cooler one in the form of electromagnetic waves e.g. the sun
describe thermal exchange through conduction transfer of heat from a warmer to a cooler object by direct contact
describe thermal exchange through convection transfer of heat by air currents
describe thermal exchange through evaporation conversion of a liquid such as heat into a gaseous vapour
how might body temperature be regulated in a changing environment avoidance of the problem tolerance of the problem regulation to cope with the problem
temperature regulation of aquatic species relative to their environment -these are usually the same temperature as the environment they are in as water is stable and fairly conductive -->it would be too difficult and energy consuming to maintain a temperature difference -convective heat transfer rapid so few have Tb above Ta; with exception of a few marine mammals and birds
where can heat gain come from increased conduction from the environment increased radiation from the environment in endotherms- metabolic heat production --> this is really expensive and is typically only used as a last resort
methods of gaining external heat - basking in the sun -looking for warmer microhabitats -vertical migration in aquatic systems and body adaptions e.g. darks skin is employed by many organisms to allow them to warm up quicker --> marine iguanas
methods of generating internal heat physical activity increases metabolic rate and in turn increases heat
how is internal heat retained vasoconstriction- regulating the blood flow near the skin large bodies- small surface to volume ratio
how is heat lost when necessary vasodilation evaporation behaviour adaptation - such that contact with the hot surfaces is limited
how can respiration be controlled to control body temp spiracle control one way ventilation in some insects (in thorax and out abdomen)as air flows through this systems some exhaled water recondenses in abdomen e.g. the condensing sub-elytra chambers of a desert beetle that produces water that can be taken up by the insect
ways that body temp can be controlled behaviourally -plants and burrows can provide microclimates that can be exploited -burrowing allows for a constant environment, and releives the pressure of UV limitation of burrowing- build up of naturally produced gases such as ammonia must move between burrows and external to maintain temperature
migration this is not common with ectotherms but there are some examples e.g. desert locust migration and monarch butterfly migration can take more than one generation
endotherms large size higher mitchochondrial density die to higher heat production better internal heat distribution systems
what are the requirements of an ectotherm- -plentiful food and water supply insulation to control heat loss this allows for sustained locomotion, expansion of daily activities into night time higher digestion rates habitat expansion
what strategy of temperature regulation is burrowing avoidance
name low heat conducting structure and what their purpose is fat blubber fur feathers
how may blood flow to blubber be controlled, why? when the absent temperature is cold and the organism has no need for heat loss- peripheral flow to blubber halted by shunting--> preventing heat loss shunt route is open when the animal is hot, the shunt route is closed and leaves only the bypass route o the blubber where their can be heat loos to the surroundings
in what animals is countercurrent exchange common, why? ectotherms especially marine animals that have flippers warm arterial blood running near the cold venous blood -->this warms the cold blood and helps to maintain the core temperature selective cooling sections where the extremities are particularly cool
what is the function of long cold noses animals in high temperatures brain cooling cools that blood travelling to the brain to maintain the core temperature expired cool air moves towards the brain, condenses to water and cools the vessels heading to brain
what is the purpose of panting and sweating cooling short repetitive breaths that pass over the hot moist tongue this is under neuronal control and can be deactivated and active at will sweating is under neural control come from 2 glands- eccrine (where there is no hair present) apocrine glands where there is hair
name a disadvantage of sweating water and salt loss air cooling is more useful
name the system used to cool the brain in medium/large desert animals carotid rete system
carotid rete system cooler blood that returns from the face (especially the long cold nose) forms a sinus that runs that runs close to hot blood in carotid artery acts as a heat exchanger cools carotid as it ascends to the brain
name 3 ways that an endotherm to increase heat moving about- muscular locomotor activity involuntary muscular activity - shivering thermogenesis chemical means cycling between enzymes producing nonshivering thermogenesis
discribe shivering thermogenesis short repetitive contractions of agonistic muscles with no net movement that generates heat ==>shivering
what is non shivering thermogenesis - mediated by brown adipose tissues found in small mammals and young children forms around the core organs localised to the core uses the proteins gradient within mitochondria under hormonal control -->epinephrin
name a behavioural mechanism to deal with heat hypometabolism during periods of sleeping or resting large number of mammals and bird enter extended periods of hypometabolism and hypothermia 2 forms hibernation and torpor
what would lead an organisms to undergo a period of torpor changing physical environment e.g. extreme temperatures, drought, shortened day lengths inadequate food fasting reduced metabolic rate
what is typically lowered during torpor heart rate body temperature physical activity
what should be considered during torpor that it is a balance between the energy that is saved during the torpor and energy required to exit torpor
examples of torpor Siberian hamster -faces severe winter conditions very cold (-40) and low food supply bouts of torpor reduce body temperature from 37 to 12-15for between 4 and 8 hours large decrease in metabolic rate