Topic 8: Thermoregulation Flashcards
Homeostasis
regulation of internal environment in the face of changes in the external environment (dynamic process)
What parameters must organisms control for homeostasis?
- pH
- temperature
- O2/Co2
- heart rate
- solutes
- water (volume and pressure of cells & blood plasma)
- osmoregulation
Negative Feedback Mechanisms
a change in a variable under homeostatic control triggers a response that OPPOSES the change
Sensor
detects environmental conditions
Integrator
analyzes sign from signal; compares conditions to the set point & activates effector
Effector
causes a physiological change that opposes the deviation from the set point
Role of sensor in temperature regulation
detects temp. in skin
What is the integrator in temperature regulation
hypothalamus
What is the effector in temperature regulation?
muscle tissue, vasculature, sweat glands
Positive Feedback Mechanisms
change in a variable under homeostatic control triggers a response that AMPLIFIES the change
Thermoregulation
regulating internal body temperature
- this has huge impact on energy budgets
Ta
ambient temperature
Tb
body temperature
Body heat
generated by metabolism
can be exchanged with environment
regulated by changing rate of heat gain/loss
The rate of heat exchange is called
conductance
4 ways heat can be exchanged with the environment is:
conduction
convection
evaporation
radiation
What is the adaptation for heat retention?
low conductance
What is the adaptation for heat loss?
high conductance
How do ectotherms primarily regulate Tb?
using behaviour
When temperature rises above thermal neutral zone, homeothermic endotherms risk entering state of _______________
hyperthermia
Animals _______ have to spend energy to maintain body temperature during hibernation
do
____________ have a broader range of temperatures
endotherms
Homeotherms
maintain constant Tb independant of Ta
Heterotherms
Tb fluctuates with Ta (ie. seasonal changes)
Endotherm
uses metabolism to generate body heat (internal heat generation)
Ectotherm
aquires body heat from environment (external heat source)
4 Behavioural Regulation of Conductance:
- in an attempt to optimize heat exchange w/ the environment to attain an ideal body temperature:
exposure
grouping
dormancy
migration
9 Physiological Regulation of Conductance:
- in an attempt to optimize heat exchange w/ the environment to attain an ideal body temperature:
membrane acclimation
blood flow
insulation
fur length & colour
sweating/panting
cryoprotectants
ice-nucleating agents
shivering thermogenesis
non-shivering thermogenesis
Exposure:
moving in/out of sun/wind or increasing/decreasing surface area
Grouping
huddling together to share radiation
Dormancy
Daily torpor & hibernation or winter sleep
Hibernation
usually lasts 2 weeks
Tb is regulated close to Ta
massive decrease in MR
non-shivering thermogenesis occurs when organism wakes up for 1-2 days
Migration
complete avoidance of poor environmental conditions
Membrane Acclimation
- organisms adjust cellular conditions to work optimally in cold & warm environments
- membrane viscosity is affected by temperature
- different conformation decreases the enzyme’s optimum temperature
- increase in enzyme concentration counters lower activity
- phospholipid change level of saturation
- accumulation of changes in every cell acclimates the entire organism
Blood Flow
vasodilation & vasoconstriction
Vasoconstriction occurs when there is __________ conductance with the environment
decreasedV
Vasodilation occurs when there is _________________ conductance with the environment
increased
Endotherms ________ when cold to retain heat
vasoconstrict
Endotherms ___________ when hot to release heat
vasodilate
Ectotherms __________ when hot to retain heat
vasoconstrict
Ectotherms ___________ when cold to increase heat gained from environment
vasodilate
Insulation
fat/blubber, fur/feathers, piloerection
Fat/blubber provides _____ insulation to __________________________
internal; slow heat transfer
Fur/feathers provide _____ insulation to ____________________-
external; slow heat transfer
piloerection is the _________ of feathers/fur __________ the rate of heat transfer by ___________ thickness of insulation layers
fluffing; decreases; increases
Fur length & colour
thicker fur provides better insulation
white fur: allows light to reach the skin
black fur: absorbs light and generates heat outside of the insulation layer
black skin: absorbs light and generates heat inside insulation layer
Best combination of fur and skin colour for best insulation is:
white fur and black skin
Sweating/panting allows ___________ through _____________
heat loss; evapouration
Cyroprotectants are __________ produced to ______________
molecules (glucose/glycerol); lower freezing point
Ice-nucleating Agents are ______________________ that prevents ______ from forming
antifreeze proteins; ice
Shivering thermogenesis is the:
simultaneous action of antagonistic muscles that generates heat without causing movement
Non-shivering thermogenesis:
special fat tissue (brown fat) is loaded with special mitochondira
- instead of using the PMF for ATP synthase, it is used to generate heat:
- electrons released are sent to UCP1 instead of ATP synthase that releases more energy as heat
Non-shivering thermogenesis raises ____ for ___________
Tb; newborns, those recovering from torpor. hibernation, or winter sleep
Thermal neutral zone
the range of temperatures where the metabolic rate of an organism is at its minimum, and the organism does not need to expend energy to maintain its body temperature
what happens to homeothermic endotherm when the Tb is below thermal neutral zone?
endotherm increases metabolic rate to generate more body heat and maintain its Tb
what happens to homeothermic endotherms when Tb is above thermal neutral zone?
endotherms must dissipate excess heat produced by their metabolism through behavioural and physiological regulation methods of conductance: this may involve vasodilation, panting, or sweating.
Effect of high conductance
increases rate of heat exchange from body to environment to increase heat loss through behavioural and physiological regulation methods
Effect of low conductance
decreases rate of heat exchange from body to environment to increase heat retention through behavioural and physiological regulation methods
