bio 225 exam 4 thermoregulation

heat can be lost much easier

heat is retained much easier

1. physiological processes are temperature sensitive

2. few animals can live outside of 0-45°C range

3. even within this range, there are important consequences of changing temperatures

temperature quotient, a measure of thermal sensitivity of a chemical reaction or physiological process, works well for ectothermic (cold-blooded) animals

Q10 = rate at (T + 10)°C / rate at T °C

• some animals can’t live outside of a 10°C range

• response to temperatures may not be the same at all temperatures, response may not be linear

body heat = heat produced + (heat gained - heat lost) aka heat transferred

when external temperature > internal temperature

when internal temperature > external temperature

direct transfer of thermal energy of molecular motion, takes place between physical bodies that are in contact with one another

heat flux from one object to another

Q = (λ ΔT) / L

λ = 1 / conductance

the higher the insulation, the lower the conductance

the conductance of water is much greater than air (λ changes)

muscle is a better conductor and fat is a better insulator

aquatic sea mammals (not birds or fish)

a layer of fat between the skin and visceral organs, subcutaneous fat

it has a good blood supply so it can control movement of heat from outside to inside or vice versa

• internal - blubber

• external - hair, feathers, fur, air, water

thickness

mass movement of gas or fluid contributes to renewal of fluid at the boundary, accelerates heat transfer

heat transfer that takes place without direct contact, due to electromagnetic radiation

always removes heat from the body

heat flux = metabolic heat production ± conduction ± convection ± radiation - evaporation

it increases

animals living in colder climates have a smaller surface area : volume ratio to conserve heat, vice versa for hotter climates

changing posture, huddling

they decrease the surface area : volume ratio as a group, conserving heat

in terms of volume, large animals eat more, but in comparison to body mass, large animals eat less

large animals exchange heat slower than small animals

smaller extremities and large size

poikilotherm and homeotherm

animals with variable body temperatures, like polar bears

animals with stable body temperature, like humans

ectotherm and endotherm

animal’s body temperature is determined by environment, lower metabolic rate

animal’s body temperature is maintained by internally generated heat, higher metabolic rate

• most ancient but not primitive

• heat obtained from environment, body temperature depends on environmental temperature

• lower metabolic rate

• all invertebrates, fish, amphibians, reptiles

• does NOT occur in coldest environments

lifestyle is based on low energy flow, allows ectotherms to exploit adaptive zones unavailable to mammals/birds, more suited to periodic shortages in food, water, and oxygen

• more recent

• heat produced by metabolic means, physiological thermoregulation

• higher metabolic rate

• birds and mammals

thermoneutral zone, range of temperatures optimal for physiological processes, only applies to endotherms

TNZ

upper critical temperature, metabolic rate increases as animal induces a physiological response to prevent overheating

above UCT and below LCT

lower critical temperature, metabolic rate increases to increase heat production, thermogenesis

our metabolic rate goes up for active cooling (sweating)

when ambient temperature exceeds counteracting abilities of metabolic processes, metabolic rate then starts to decrease, meaning heat stroke is causing the organism to die

active cooling

thermogenesis, shivering to generate heat

body temperature varies in regions of the body

• billfish have heater organs near eyes

• tuna retain heat in red muscle

• great white sharks with countercurrent exchanger (rete mirabile, warm blood exchanges cold blood from environment, keeping muscle warm)

body temperature changes over time

• hibernating animals

• pythons after a large meal

changing body location or position, migration, adding external insulation, most important for ectotherms

optimum or “preferred” body temperature, this is temp when physiological functions are optimal, more important for ectotherms

• lizards burrow during the night, matching body temperature to burrow temperature

• lizards bask in the sun during the day, increasing body temperature and metabolic rate

• during the day, lizards go back and forth between sun and shade, all to maintain preferred temperature

seasonal mass movement to avoid unfavorable conditions

ectothermic animals reduce issues from increased viscosity by changing cell membrane composition

it increases the viscosity

a shorter chain length allows for more fluidity, molecules can cross membranes easier

more unsaturated phospholipids increase fluidity, molecules can cross membranes easier

more polar head groups increase fluidity and make molecules cross membranes easier

cholesterol in cell membranes increases in cold temperatures

increased cholesterol content in cell membrane increases fluidity and makes molecules cross membrane easier

• in-situ modification (in place) - phospholipids change when already in cell membrane

• de novo modification (from new) - new phospholipids made in smooth ER

only one, if both are unsaturated and have a “kink”, they will interfere with each other

• there is a heat shock protein called Hsp70, bound to a heat shock factor (HSF) under unstressed conditions

• under heat stress, this complex dissociates

• Hsp70 binds to denatured protein

• HSF trimerizes, triggers transcription and translation to make more Hsp70

changes in metabolic machinery that allow some ectotherms to have optimal metabolic rates in different temps

enzymes with same catalytic function work optimally at different temperatures

alters body reflectance, increases/decreases heat absorption

large fish use rete mirable to increase the core body temperature

some animals allow their tissues to freeze but keep the core unfrozen

• ice nucleus - particle acts as nucleus for formation of ice crystal in atmosphere

1. cryoprotectant — increases intracellular solute concentration to decrease freezing point of water

2. antifreeze macromolecules — production of proteins decrease freezing point and disrupt ice crystal formation

it occurs for 1-2 days, temperature drops dramatically

a state of regulated hypothermia, lasting several days/weeks that allows animals to conserve energy in the winter; two types are obligate and facultative

a state of dormancy similar to hibernation, animals that estivate spend the summer inactive to avoid harmful effects of the season, some estivate to conserve energy when food/water supply is low

type of fat cell, important for small mammals, rich in mitochondria giving it brown color

white adipocytes have few mitochondria with one big lipid droplet, while brown adipocytes have many mitochondria, many small lipid droplets, and are vascularized

responsible for non-shivering thermogenesis (babies can’t shiver), located around core organs

reside in WAT, similar to WAT/BAT, store energy and dissipate energy to hear at low temps

• norepinephrine stimulates BAT hyperplasia (more) and hypertrophy (bigger)

• BAT makes thermogenin (UCP1)

• thermogenin activates UCP, uncoupling the activity of the ETC from ATP synthase so that the energy of oxidation is dissipated as heat instead of used for ATP synthesis

ATP is used to couple and uncouple actin and myosin, but no contraction occurs, generating heat instead, unique to mammals and birds, muscles are rapidly depleted and exhausted (short period of time)

• sweating

• panting

• saliva spreading

• vasodilation

many rodents spread saliva on body surfaces to increase heat loss via evaporation

dilation of peripheral blood vessels to lose heat via increased convection

via evaporative cooling

it raises the heat of vaporization, causes greater heat loss than evaporation of pure water

it decreases to minimize ionic and osmotic problems

in the hypothalamus (which is in the brain)

1. the golgi apparatus

they’re made in the smooth ER and packaged in the golgi apparatus

4. conduction of heat AND behavioral mechanisms

3. both will cool at the same rate

notice that you’re ignoring metabolic rate, ignore differences due ectothermy/endothermy