Ch10: Homeostasis Flashcards
Define homeostasis
The maintenance of internal conditions when an organisms external environment is changing
Describe how increasing temperature affects homeostasis
Thermoreceptors detect temperature change, sending an impulse to brain (control centre)
The brain compares this with a SET POINT and if this temperature exceeds (or is lower than) this point, the brain sends signals to sweat glands (EFFECTOR CELLS) to sweat
Evaporation cools the body until it reaches the set point
maintaining homeostasis
How does increasing temperature affect reaction rate
It increases kinetic energy and thus increases molecular interactions.
Increasing reaction rate until optimum temperature is reached
What do thermal response curves do?
They measure the rate of a particular reaction as temperature changes
What does Q10 mean and what is its equation?
It measures the rate of change of a reaction over a 10˚C change in temperature
Q10 = RT/R(T-10)
If Q10 =1, 2, 3, what does this mean for temperature?
1: reaction is NOT temperature sensitive
2: reaction rate doubles with each 10˚C increase
3: reaction rate triples with each 10˚C increase
What are the implications of having a wide optimum temperature?
Generalist species are able to grow and adapt to a wider range of envrionment/climates
Can plant optimal temperatures be altered? If so, how?
Yes, if they are grown in higher environmental temperature
What are the trends seen in sedentary organisms in terms of optimum temperatures? How do they maintain these temperatures?
They have a broad range of temperatures for optimisation
They maintain them through biochemical reactions
How do large, mobile organisms maintain optimum temperatures
Physiological and behavioural measures
Must balance heat gain/lose to their environment
Define thermoregulation
the control of internal body temperature via physiological or behavioural means
How do simple round worms regulate their temperatures?
Their thermoreceptors synapse directly to interneurons
They carry this signal to motor neurons, which cause the worm to move to a more suitable micro-climate
What do vertebrates use to detect temperature change?
How to do control the change? (Hint: there are 2 methods)
Peripheral nervous system:
1) Vasoconstriction: prevents heat loss + allows for conservation of heat
2) Vasodilation: allows heat to be lost (cooling)
What is the difference between Endotherms and Ectotherms?
Endotherms: organisms that can regulate their internal body temperature using their metabolic processes that generate their own heat
Ectotherms: cannot regulate their own heat + have to gain heat for thermoregulation from an external source
Difference between Homeotherm and Heterotherm?
Homeotherm: body temperatures remain relatively stable, and can be maintained
Heterotherm: unstable/unmaintainable body temperature (fluctuates regularly OR under conditions or life stages)
Describe ectothermic heterotherms and endothermic homeotherms (think of what body temp. v environmental temp. graph looks like
See Doc, 10a:
Ectothermic heterotherms: fluctuate at SAME rate as external environment temperature
Endothermic homeotherms: relatively stable body temperature, other than at extremes
Describe the regulation of homeothermic ectotherms and heterothermic endotherms:
Homeothermic ectotherms: body temperature is stable throughout their lifetime as their environment’s temperature is stable
- they have adapted to these conditions and cannot lie outside of them
Heterothermic endotherms: when these organisms live in environments with extreme fluctuations, some use TORPOR (hibernation) to survive these condtions
- they drop their body temperature to surrounding temperatures
- they use their own heat to heat up after torpor to exist in conditions that are more favourable
Define behavioural thermoregulation
adjusting activity to maintain/gain/lose heat to remain within optimum conditions
Define thermal performance curves
They show how temperature affects performance of a variable
Demonstrates a thermal tolerance breadth: determined (bounded) by critical thermal minimum/maximum (Tmin/Tmax) (where performance >0)
Define thermoneutral zone, and what happens to the body when it goes below/above this range? (In ENDOtherms)
Where the cost of maintaining optimal body temperature is minimised
Below: metabolise increases to produce heat
Above: metabolism increases to produce energy for cooling mechanisms and to DUMP heat
Define thermal conductance. What is this determined by?
rate of exchange of heat between an organism and its environment
Determined by:
- size, shape + thickness of insulation (fat, fur, scales)
- increase thermal conductance = steeper relationship between metabolism and temperature
- decrease thermal conductance = shallower relationship between metabolism and temperature
In endotherms what does thermal conductance influence? How does the size of the animals effect this?
Breadth of thermoneutral zone;
Small animals: greater thermal conductance = smaller range of thermoneutral zone
Large animals: lower thermal conductance = increases range of thermoneutral zone
Define allometry
relationship between body mass + physiological or morphometric characteristics and behaviours
When do we compare metabolic rates? (only 2 words)
At rest
What are the rest states of endotherms and ectotherms: describe the conditions
Endotherms: Basal Metabolic Rate (BMR)
- In resting state
- Post adsorptive (not digesting or feeding)
- Non-reproductive
Ectotherms: Standard Metabolic Rate (SMR)
- Resting
- Post adsorptive
- Non-reproductive
- Same environmental temperature as endotherm
Describe Max Kleiber’s law
Metabolic rate ~= Body Mass^0.75
NOTE: metabolic rate= cellular respiration
Other than Max Kleiber’s law, what other factors may affect metabolic rate?
- Metabolic rate + bodymass = function of fractal geometry: way vascular tissue supplies oxygen to all cells in the body
OR: there is a direct interplay with metabolic rate, growth and reproduction
- leads to the optimisation of phenotypes producing the scaling relationships we see
