5.1 Communication And Homeostasis Flashcards
Why do we need a communication system
- multicellular organisms need to maintains a suitable temp + ph = so cells need to communicate w eachother to respond to changes in internal + external environment + coordinate activities of diff organs
Neuronal system
Faster, short lasting
Hormonal system
Slower, longer lasting
Stimulus
Change in environment
How do the internal environment change
New toxins and build up of waste products
Good communication system
- cover the whole body
- Enable cells to communicate w eachother
- Specific + fast communication
- Both short term + long term responses
Homeostasis
maintaining a constant internal environment, despite changes in the external or internal environment
What does homeostasis allow?
Allows us to maintain our blood temp, glucose levels etc in a narrow range
How does homeostasis work
Stimulus—> detected by sensory receptors—> sent to communication pathway (neuronal or hormonal)—> goes to effector—> response
Negative feedback
- reverse the change and bring back the condition to optimum
Negative feedback example
Positive feedback
Initial change occurs and body increases the change
Example of positive feedback
if body temp rises the body will increase the temp further
Example of usually negative feedback but sometimes positive
cervix dilating during labour in response to the hormone oxytocin, the more oxytocin the more the cervix dilates which allows the baby to come out.
Ectotherms
organisms that rely on external sources of heat to maintain body temperature
What do ectotherms do if they’re too cold
may move into sunny area, lie on warm surface, expose a large SA of skin towards the sun
What do ectotherms do when they’re too hot
may move out of the sun, move underground, reduce the body surface exposed to the sun
Examples of ectotherms
Snakes, locust, lizards
Advantages of ectotherm temp control
less food used for respiration so don’t need much food, more energy in body used towards growth, can survive a long period without food
Disadvantage of temp control in ectotherms
less active when temp is colder = more at risk of predators, can’t live anywhere in the world they’d have to live where the temperature suits them
Endotherms
use internally generated heat (generated from respiration) to maintain steady body temperature regardless
of environment.
Endotherms when hot
- liver = sweat glands secrete sweat bc heat energy is used to evaporate sweat
- hairs would be flat
- vasodilation = arteries dilate so more blood flows = more heat energy released by skin
- gas exchange increases so heat from lungs can come out
Endotherms when it’s cold
- exothermic reactions that release heat to keep warm
- Vasoconstriction = arteries contract so less blood flows near surface of skin = less heat energy released by skin
- muscles contract less so less heat released
- skin = less sweat secreted
- hairs and feathers stand up to trap heat
- gas exchange system: less panting + gas exchange so less heat is lost
Advantage of temp control in endotherms
- can maintain a stable body temp despite the external temperature
- can remain active even when the temperatures are low = less prone to being attacked by predators
- can live in colder parts of the world
Disadvantages of temp control in endotherms
- most of our energy is used to keep our body warm so we need more food
- less energy used towards growth compared to an ectotherm
- we can overheat in hot weathers
Thermoregulatory centre
Detects core temp
Peripheral receptors
monitor the temperature on the outside and any changes would be sent to the thermoregulatory centre in the hypothalamus
What are the two types of response used by endotherms to regulate body temperature?
Physiological and behavioural
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