Chapter 15: Homeostasis Flashcards
Why are communication systems needed in multicellular organisms
Both animals and plants must respond to their internal + external environments to survive
organisms must coordinate the function of different cells and organs to operate efficiently
What are communication systems
A nervous and hormonal system (send signals to other cells in the body)
What is cell signalling
process in which cells communicate with each other
e.g. a cell releasing a chemical (signal) that can have an effect on other cells (which responds)
How does communication occur via cell signalling ?
Nervous and hormonal systems coordinate the activities of whole organisms + this communication occurs at a cellular level
(cell signalling)
cells can transfer signals locally- between neurones at synapses
cells can transfer signals across large distances - using hormones
Define homeostasis
Homeostasis is the process in which a stable internal environment is maintained (In living organisms) allowing small fluctuations over a narrow range of conditions
Explain the process of positive feedback
a change in internal environment is detected by sensory receptors and effectors are stimulated to reinforce that change in increasing the response
E.g. release of oxytocin’s in pregnancy
Explain the process of negative feedback
a small change above regular conditions in something is detected by sensory receptors + effectors work to reinforce that change restoring conditions to their bases level
negative feedback systems work to reverse initial stimulus
What are ectotherms and how do they regulate their temperature
Ectotherms are organisms like amphibians and reptiles that cannot regulate their own body temperature (core body temp is heavily dependant on their environment)
What are behavioural responses in ectotherms that enable them to increase their body temperature
bask in the sun + orientate their bodies so that maximum surface area is exposed to the sun (to warm up)
pressing their bodies against the warm ground (conduction)
contract their muscles/ vibrate wings to increase body temperature
What are behavioural responses in ectotherms that enable them to decrease their body temperature
can press their bodies against the cool/shady earth
move into available water or mud
can shelter from the sun by seeking shade, digging burrows
orientate their bodies so that minimum surface area is exposed to the sun
minimise movements
What are some physiological responses to temperature in ectotherms
Darker colours absorb more radiation that lighter colours, lizards living in colder climates tend to be darker coloured than those living in hotter countries
