BIOL 241 - thermoregulation

What is homeostasis?

The regulation of an internal environment in the face of changes in the external environment

What are negative feedback mechanisms

A change in factor under homeostatic control tiggers a response that opposes the change

The stimulus does what for negative feedback mechanisms?

external or internal change

A sensor does what for negative feedback mechanisms?

detects the change

A integrator does what for negative feedback mechanisms?

Compares the signal from the sensor to the "set point"

What does the effector do for negative feedback mechanisms?

A physiological or chemical response that restores the set point counters change

Temperature Regulation in a organism

• hovers around a set point, hard to make it exact

• -set point, desired Tb (body temp)

What is the sensor in temperature regulation?

Temperature detection nerves

What is the integrator in temperature regulation?

Hypothalamus

What is the effector in temperature regulation?

Muscle tissue vasculature sweat glands

Regulating the internal body temp to what range?

Ta (ambient temperature) ranges from about -50ºC to about 50ºC

What is ambient temperature (Ta)?

environmental (surroundings) temp

Effect if body temp (Tb) is too high or low?

-if too low, membranes becomes viscous, enzyme rates are low

-if too high: membranes become too fluid, enzymes denature

Body heat is generated from what?

metabolism

Heat can be exchanged with the environment by…. 4 terms

-Conduction

-convection
-Radiation
-Evaporation

Conduction is?

Direct contact (usually solid)

Convection is?

To a flowing medium (liquid or gas)

Radiation is?

Emitting/absorbing EM radiation

Evaporation is?

heat loss as solid becomes liquid -> gas

How do animals regulate body heat?

Bu changing the rate of heat gain/loss

The rate of heat exchange is called?

Conductance

Body temp regulation strategies - endotherm

Generate most body heat through metabolism

Body temp regulation strategies - ectotherm

generate most body heat from the environment

Body temp regulation strategies - homeotherm

maintain a "constant" Tb, most homeotherms are endotherms

Body temp regulation strategies - heterotherm/poikilotherm

Tb can fluctuate with Ta

What is behavioural regulation of conductance

Moving to optimize heat exchange with the environment to attain an ideal body temperature

Behavioural Regulation of Conductance - exposure defintion?

• movement into, or out of, the sun/wind

• grouping

• -dormancy

Behavioural Regulation of Conductance - migration defintion?

complete avoidance of poor environmental conditions

Dormancy- daily torpor definiton

• short reduction ( 4-8hr) in activity

• reduce HR+Tb (about 10ºC)

• saves energy in winter, small birds + mammals

Dormancy - Hibernation definition

• regulate Tb around Ta

• Large reduction in MR, saves lots of energy

• requires a lot of energy to revive

• -"awake" for 1-2 days

• lasts about 2 weeks before revival

What is Physiological Regulation of Conductance?

Making physiological adjustments to optimize heat exchange with the environment to attain an ideal body temperature

Physiological Regulation of Conductance adjustments? 8 terms

• acclimation

• blood flow

• insulation

• fur length and colour change

• sweating and panting

• cryoprotectants

• shivering thermogenesis

• non-shivering thermogenesis

What is acclimation?

• Physiological changes that occur in response to seasonal temperature changes

• massive physio changes that allow organisms to live in environment (slow changes)

• Organisms adjust their cellular conditions to work optimally in cold and warm environments

What is blood flow? - vasoconstriction

Vasoconstriction - decrease conductance

-> endotherms: when cold to retain heat

-> ectotherms: when hot to retain heat

What is blood flow? - vasodiliation

Vasodilation - increase conductance

-> endotherms: when hot to lose heat

-> ectotherms: when cold to absorb heat

What is internal and external insulation?

Insulation: decreases conductance

• internal: fat layer inside skin, thicker the layer -> slower heat loss

• -external: fur/feathers outside the skin, thicker/longer the layer -> slower conductance

What is piloerection insulation?

Contracting muscle in the skin to "fluff up" (thicken) insulation layer

Fur colouration significance?

Dark fur absorbs heat outside the insulation layer where it is lost easily

White fur absorbs heat inside the insulation layer where it is absorbed by the skin

What is sweating/panting?

heat loss due to evaporation

What are cryoprotectants?

molecule produced when cold to..

1. reduce freezing point of water

2. forces cellular water into extracellular space when the water freezes, the cells are protected

What is shivering thermogenesis?

simultaneous action of antagonistic muscles generates heat

when antagonistic muscle contracts at the same time… movement is not possible

What is non-shivering thermogenesis

Organisms have brown fat tissue that is full of special mitochondria

Won't have ATP synthase