Lecture 20: Homeostasis of Temp, Water, and Food

What is homeostasis?

Maintaining a stable internal environment, balancing a set point for optimization

why is temperature stability so important for cell functioning?

cells perform biochem reactions that increase when temp is high and decrease when temp is low. they are interdependent and need to function as a unit

what is the Q10 theory?

if you raise the temp by 10 degrees, cell reaction rate is 2-3x faster. decreasing the temp by 10 degrees causes a slow down by 2-3x

what are the 4 types of heat transfer?

conduction, convection, radiation, induction

how does conduction work?

Heat is transferred due to direct contact with the environment, by solid surfaces

how does convection work

Heat is transferred through density differences (lava lamp), heat between fluid and gas, like when water boils

how does radiation work?

Heat transferred through electromagnetic waves, like when facing a bonfire vs back to a bonfire

how does changes of state transfer heat?

condensation is a net gain of heat (exothermic, surroundings absorb heat released), evaporation is a net loss of heat (endothermic, system absorbs heat to break IMF)

what is a homeotherm in biology terms?

a regulator, where the external environment does not impact the internal temp of the animal, "warm blooded"

what is a poikilotherm in biology terms?

a conformer, like a reptile or fish that have body temperatures that vary based on the environment

what do homeotherms (regulators) do when its too cold?

decrease conduction (jacket or fur)

increase heat production (faster metabolism or shiver)

avoid it (migrate south)

hibernate (metabolism slows)

what do homeotherms (regulators) do when its too hot?

avoid it (nocturnal)

fur or feathers to reflect light

evaporative heat loss (sweat, pant, lick)

What part of the hypothalamus controls body temperature (thermoregulator)?

preoptic medial nucleus

how did the chiroprobe experiment in the preoptic nucleus show balancing behavior?

double dissociation experiment, the probe controls temp, they made external and internal environments opposite and then the animal on reacted to the preoptic nucleus temp

where is water found in the body?

extracellular (37.5%)

intracellular (55%)

blood plasma (5%)

are we constantly losing water?

yes

where is water lost from when we urinate, sweat, etc?

the blood plasma

what role does the blood plasma play in water balance?

delivers water from intestine to intracellular matrix, as it is connective tissue

what is osmosis?

the movement or diffusion of water, where water levels change but not the amount of solute in each cell- tries to reach equilibrium

why does a high salt diet increase blood pressure?

through osmosis, a high salt intake causes a hypertonic solution in which water rushes out of the cells and into the blood plasma to reach equilibrium

blood plasma expands and increases pressure on the blood vessels

What is tonicity?

the concentration of solute to water in a cell, prefers isotonic solution (equilibrium)

what part of the hypothalamus detects thirst?

the lateral preoptic area

What does isotonic mean?

Right amount of water and solutes

what is a hypotonic solution?

the solution has a lower solute concentration than the cell so water moves into the cell causing plant cells to swell and animal cells to swell and burst

what is a hypertonic solution?

Solute concentration is greater than that inside the cell; cell loses water, blood plasma grows

t or f: The lateral pre-optic area in the hypothalamus is responsible for sensing one's hydration level.

true

t or f: Poikilotherms are organisms that maintain a relatively constant body temperature regardless of the temperature in the environment.

false, this is homeotherm

Why does keeping our body temperatures relatively constant matter?

to make sure biochemical processes are happening at appropriate rates