communication and homeostasis

multicellular meaning

many cells that have a range of tissues and organs performing different functions

how do single celled organisms communicate

they can communicate through cell signalling

why do multicellular organisms need communication systems

to coordniate the activites of different organs using cell signalling to maintain optimum conditions for cells

what is signal transduction

when cells turn external stimuli into fuctional responses

happens when the stimuli binfd to the receptor

homeostasis

maintenance of a stable internal environment

why do conditions need to be kept stable

optimum conditions for enzymes and cells, so that metabolic conditions stay the same

allows organisms to be independent of fluctuating external conditions

what is negative feedback

a process that brings about a reversal change in internal conditions to maintain an optimum conditions

positive feedback

when a deviation from the set limit triggers a response to increase the deviation further

give some examples of positive feedback

childbirth ( oxytocin causes babies head to push on cervix, which causes more oxytocin to be produced)

frost bite

blood clotting

thermoregulation definition

maintance of core body temperatures in animals

conduction

the transfer of energy bu physical contact between bodies (interaction between adjacent particles)

convection

energy transfered between an organisms and the environment by water/ air contacing the surface

radiation

transfer of electromagnestic energy between two objects

evaporation

conversion of water from liquid to gas

metablosim

chemical reactions inside the cells

what is an ectotherm

they rely on external sources of heat to maintain core body temp

body temp is mainly regulated by behaivour

give examples of thermoregulatory behavoirs

• snake basking in the sun

• horned lizard basking with ribcage

• shovel nosed lizard body raising

• burrowing skink

• worker bee flapping at hive entrance

name an example of an ectotherm that also thermoregulates by physiological changes

Namaqua chameleon

what is an endotherm

use internal sources of heat to maintain core body temp

thermoregulate by physiological mechanisms (use homeotasis) and by altering behavoir

what are the recpetors on the skin called that detect a temperature change called

peripheral thermal receptors

what part of the brain coordinates the impuleses detected by the stimuli

hypothalamus

examples of behavourial responses in endotherms

• huddiling in penguins

• humans wrapping up warm

• cheetas in shade

• desert mouse making burrows

• elephans fanning

examples of physiological responses in endotherms

• piloerection (hairs on skin sticking up )

• vasodilation ( arterioles near skin surface dialte, increasing blood flow to capillaries, more heat radiates off skin surface)

• vasoconstriction (opp)

anatomical adaptations in endotherms

• ear surface area changes in desert foxes

• blubber in seals

• streamline shape in humpback wales

how does coutercurrent flow help canadian geese

• warm arterial blood flowinf to the feet runs alongside cold venoules bloodflowing back to the body core

• transfers heat betwwn them

• kepping the body warm while allowing the feet to stay cool

• preventin excess heat loss to the cold ground or water