Homeostasis Flashcards
What do homeostatic systems do? What do they involve?
They detect a change and respond by negative feedback
They involve receptors, a communication system and effectors
What is homeostasis
The maintenance of a constant internal environment
Why does homeostasis involve more than 1 negative feedback mechanism
Having more than 1 gives more control over changes in the internal environment. Having multiple mechanisms means you can actively increase or decrease a level so it returns to normal
What would happen if you only had one negative feedback mechanism
All you could do is turn it on or turn it off. You would only be able to actively change a level in one direction so it returns to normal. Only one mechanism means a slower response and less control
What does a positive feedback mechanism do
Amplify a change from the normal level. The effectors respond to further increase the level away from the normal level
what are positive feedback mechanisms useful for? Example.
To rapidly activate something. Eg blood clot after injury…
Platelets activated, release chemical which triggers more platelets to be activated, and so on
Platelets very quickly form blood clot at injury site
Process ends with negative feedback when body detects the blood clot has been formed
Why isn’t positive feedback involved in homeostasis
Because it doesn’t keep your internal environment constant
Examples of ectotherms
Reptiles
Fish
Examples of endotherms
Mammals
Birds
How do ectotherms control their body temp
They can’t control their body temp internally, instead control their temp by changing their behaviour (eg reptiles laying in sun)
Their internal temp depends on the external temp
Their activity level depends on the external temp, they’re more active at higher temps
Have a variable metabolic rate and generate little heat themselves
How do endotherms control their body temp
Control temp internally by homeostasis. Can also control their temp by behaviour (eg finding shade)
Their internal temp is less affected by external temp, they can be active at any temp
Their activity level is largely independent of external temp, can be active at any temp
Have a constantly high metabolic rate, generate lots of heat from metabolic reactions
Body temp in mammals is maintained at a constant level by a part of the brain called the…
hypothalamus
What is the hypothalamus and what is its role
A part of the brain which maintains body temp at a constant level in mammals
How does the hypothalamus work
It receives info from both internal and external temp from thermoreceptors
Info about internal temp comes from thermoreceptors in the hypothalamus that detect blood temp
Info about the external temp comes from thermoreceptors in the skin which detect skin temp
Thermoreceptors send impulses along sensory neurones to hypothalamus, which sends impulses along motor neurones to effectors (muscle and glands)
The neurones are part of the autonomic nervous system, so is done unconsciously
The effectors restore body temp back to normal
What does FSH do
Stimulates the development of follicles in the ovaries. Stimulates the follicles to produce oestrogen
What is a follicle
An egg and its surrounding protective cells. Developed in the ovary
What is ovulation
The release of an egg
