5.1 communication and homeostasis Flashcards
define cell signalling
the way in which cell communicate with each other
what will a good communication system be able to do
cover the whole body
enable cells to communicate with each other
enable specific communication
enable rapid communication
enable both short and long-term responses
define homeostasis
maintaining a constant internal environment despite changes in external and internal facots
define negative feedback
the mechanism that reverses a change bringing the system back to the optimum
define positive feedback
the mechanism that increases a change taking the system further away from the optimum
define ectotherm
an organism that relies on external sources of heat to maintain body temperature
define endotherm
an organism that uses heat from metabolic reactions to maintain body temperature
what do ectotherms do if they aren’t warm enough
move into a sunny area
lie on a warm surface
expose a larger surface area to the sun
what do ectotherms do if they are too hot
move out of the sun
move underground
reduce body surface exposed to the sun
what are some examples of ectotherms and what are their behavioural adaptations
snakes bask in the sun
lizards use burrows and crevices
horned lizards can change their shape by contracting and expanding their ribcage
What are some advantages of ectotherms
less of their food is used in respiration
more of the energy from food can be converted into growth
they can survive long periods without food
what are some disadvantage’s of ectotherms
they are less active in cooler temperatures so this makes them more vulnerable to predators
define exergonic
release of energy in the form of heat
what are some organs that contain physiological adaptations to maintain body temperature in endotherms
skin
gaseous exchange system
liver
skeletal muscles
blood vessels
What is the skins response if it is too hot
sweat glands secrete fluid to be evaporated of the skin by using blood as the latent heat of vaporisation
hairs and feathers lie flat to reduce insulation
vasodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated from the body
What is the response of the gaseous exchange system if it is too hot
panting to evaporate water from the surface of the lungs and airways and uses blood as the latent heat of vaporisation
What is the response of the liver if it is too hot
less respiration takes place so less energy from food is converted to heat
What is the response of the skeletal muscles if it is too hot
less contractions means less heat is released
What is the response of the blood vessels if it is too hot
vasodilation to direct blood to the extremities so that more heat can be lost
what are the advantages of endothermy
maintains a fairly constant body temperature
remain active even when temperatures are low
inhabitance of colder habitats
what are the disadvantages of endothermy
may overheat in hot weather
need more food
use a significant part of their energy intake on maintaining body temperature
What part of the brain regulates homeostatic responses
the hypothalamus
what is the role of the periphery receptors
the thermoregulatory centre in the hypothalamus monitors blood temperature
However if the extremities begin to be too hot or too cold they send signals to the brain for behavioural adaptations such as going in the shade to occur
What is the role of the hypothalamus in control of temperature regulation
Temperature receptors in the hypothalamus detect changes in the temperature and then send impulses
the neuronal system transmits impulses for rapid responses and the hormonal system is used for a long-term response
