Module 5.1 Flashcards
communication and homeostasis
why are communication systems needed
animals and plants need to respond to changes in their internal and external environment
coordinate the activities or different organs
threats from changing external environments
temperature (enzymes and activity)
seasons e.g. fur colour for camouflage
appearance of predator
moving from burrow to sunlight
Threats from changing internal environment
using up products and creating by products which could be toxic
e.g. carbon dioxide makes fluid acidic (enzymes)
why is coordinating the activities or different organs important
organs perform specific functions that may effect other organs e.g. blood monitoring in the brain
how do cells communicate
cell signalling
neuronal system (uses neurones)
hormonal system (uses blood)
what is homeostasis
maintaining a constant internal environment despite changes in internal and external factors
what is negative feedback
the mechanism that reverses a change bringing the system back within a set limit/ optimum
what is positive feedback
the mechanism that increases a change taking the system further away from the set limit
mechanism of homeostasis
stimulus
receptor
communication pathway (cell signalling)
effector
response
what are receptors
sensory receptors monitor changes in the external environment
other receptors monitor the internal environment
When a change is detected they are stimulated to send a message to an effector
What are effectors
cells which bring about a response to the change in environment
what are endotherm
control their own body temperature within very strict limits independent of external temperatures
What are ectotherms
not able to control their body temperature as effectively so rely on external sources of heat
body temperature fluctuates with external temperature
how is temperature controlled in ectotherms
behavioural responses
examples of temperature control in ectotherms
too cool:
move into sunny area
lie on warm surface
expose larger surface area to the sun
too warm:
move out of the sun
move underground
reduce surface area exposed to sun
advantages of ectothermy
do not need to use up energy to keep warm so:
less food used on respiration
more energy and nutrients used on growth
need to find less food
survive for long time without food
disadvantages of ectothermy
less active in cool temperatures so:
at risk from predators when cold
cannot take advantage of available food while cold
how endotherms control temperature
physiological and behavioural responses
heat receptors in endotherms
peripheral temperature receptors in the skin
the hypothalamus
role of the hypothalamus
transmits neuronal and hormonal messages to cause physiological changes
ectotherms heat effectors
skin
muscles
skin responses
more/less sweat
hair and feather lie flat/stand up
vasodilation/vasoconstriction of arterioles near skin surface
muscles response
less contractions
spontaneous muscles contractions
endotherms behavioural responses
hide away / lie in sun
orient body towards/away from sun
inactivity/activity
spread limbs out/curl into ball
wet skin/remain dry
