bio 225 exam 4 thermoregulation

w24 duan thermoregulation

what do long limbs allow for in hot climates?

heat can be lost much easier

what do short limbs and round bodies allow for in cold climates?

heat is retained much easier

what are 3 things to consider for thermoregulation?

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

what is Q10?

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

what is the equation for Q10?

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

what are some problems with using Q10?

• 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

what is an equation for body heat?

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

when is heat transfer positive?

when external temperature > internal temperature

when is heat transfer negative?

when internal temperature > external temperature

what is conduction?

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

what is fourier’s law?

heat flux from one object to another

Q = (λ ΔT) / L

what is thermal resistance or insulation? (λ)

λ = 1 / conductance

what is the relationship between insulation and conductance?

the higher the insulation, the lower the conductance

what is true about water conduction?

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

what is true about muscle and fat regarding conduction/insulation?

muscle is a better conductor and fat is a better insulator

what are the only mammals that have blubber?

aquatic sea mammals (not birds or fish)

what is blubber?

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

what is unique about blubber compared to our subcutaneous fat?

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

what are common insulators?

• internal - blubber

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

what does effectiveness of insulation depend on?

thickness

what is convection?

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

what is radiation?

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

what is evaporation?

always removes heat from the body

what is the equation for heat flux?

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

as animal size increases, what happens to their surface area?

it increases

how is the surface area : volume ratio related to temperature/climate?

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

what is a behavioral mechanism to gain heat?

changing posture, huddling

why do animals huddle when it’s cold?

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

how do metabolic requirements (amount of food needed) change between large and small animals?

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

how does speed of heat exchange compare between large and small animals?

large animals exchange heat slower than small animals

what are traits that animals in cold climates tend to have?

smaller extremities and large size

what are two categories regarding relative stability of body temperature?

poikilotherm and homeotherm

what is a poikilotherm?

animals with variable body temperatures, like polar bears

what is a homeotherm?

animals with stable body temperature, like humans

what are two categories regarding source of thermal energy?

ectotherm and endotherm

what is an ectotherm?

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

what is an endotherm?

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

describe ectothermy

• 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

what are some advantages of ectothermy?

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

describe endothermy

• more recent

• heat produced by metabolic means, physiological thermoregulation

• higher metabolic rate

• birds and mammals

what is TNZ?

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

when is metabolic rate minimal in homeotherms?

TNZ

what is UCT?

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

when does metabolic rate increase in homeotherms?

above UCT and below LCT

what is LCT?

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

what do we (humans) do when the ambient temperature exceeds our UCT?

our metabolic rate goes up for active cooling (sweating)

when does onset of hyperthermia begin?

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

what do homeotherms do when the ambient temperature exceeds UCT?

active cooling

what do homeotherms do when the ambient temperature exceeds LCT?

thermogenesis, shivering to generate heat

describe regional heterotherms

body temperature varies in regions of the body

what are some examples of regional heterotherms?

• 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)

describe temporal heterotherms

body temperature changes over time

what are some examples of temporal heterotherms?

• hibernating animals

• pythons after a large meal

what are some behavioral mechanisms to regulate body temperature?

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

what is the preferred body temperature?

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

describe the example of lizards behaviorally thermoregulating

• 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

what is migration?

seasonal mass movement to avoid unfavorable conditions

what is homeoviscous adaptation (HVA)?

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

how does the cold affect viscosity of membranes?

it increases the viscosity

how does fatty acid chain length contribute to HVA?

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

how does saturation contribute to HVA?

more unsaturated phospholipids increase fluidity, molecules can cross membranes easier

how do phospholipid classes contribute to HVA?

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

how do cold temperatures affect cholesterol content in cell membranes?

cholesterol in cell membranes increases in cold temperatures

how does cholesterol contribute to HVA?

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

how can phospholipids change for HVA?

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

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

can one or both phospholipid tails be unsaturated?

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

what is the heat shock response?

• 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

how do ectotherms use metabolic compensation?

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

how do isoenzymes work?

enzymes with same catalytic function work optimally at different temperatures

how do ectotherms use color change?

alters body reflectance, increases/decreases heat absorption

how do ectotherms use a countercurrent heat exchanger?

large fish use rete mirable to increase the core body temperature

what is freeze tolerance?

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

how does freeze avoidance occur?

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

what is dormancy?

it occurs for 1-2 days, temperature drops dramatically

what is hibernation?

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

what is estivation?

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

what is brown adipose tissue?

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

how do white and brown adipocytes differ?

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

why is BAT important for newborns?

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

what are beige adipocytes?

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

how does BAT cause nonshivering thermogenesis?

• 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

describe shivering thermogenesis

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)

what are mechanisms to lose body heat?

• sweating

• panting

• saliva spreading

• vasodilation

what is saliva spreading?

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

what is vasodilation?

dilation of peripheral blood vessels to lose heat via increased convection

how does sweat reduce body temperature?

via evaporative cooling

what is the purpose of NaCl in sweat?

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

how does amount of NaCl in sweat change during long periods of heat exposure?

it decreases to minimize ionic and osmotic problems

where is the thermostat located?

in the hypothalamus (which is in the brain)

De novo membrane remodeling in order to change the lipid consistency of the plasma membrane occurs where?

1. the golgi apparatus

2. in the membrane

3. the RER

4. lysosomes

1. the golgi apparatus

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

A lizard regulates its body temperature throughout the day by __________.

1. employing isozymes

2. conduction of heat

3. behavioral mechanisms

4. conduction of heat AND behavioral mechanisms

5. employing isozymes AND conduction of heat

4. conduction of heat AND behavioral mechanisms

Not considering the contribution of metabolic rate, which animal a rat or a lizard, (assuming they are the same size and same shape) will cool faster in cold water?

1. the rat

2. the lizard

3. both will cool at the same rate

4. rat will keep the body temp, while the lizard will cool to the water temp

3. both will cool at the same rate

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