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Homeostasis and negative feedback
Descrição
Mapa Mental sobre Homeostasis and negative feedback, criado por hannahdrane em 08-04-2014.
Mapa Mental por
hannahdrane
, atualizado more than 1 year ago
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hannahdrane
aproximadamente 10 anos atrás
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Resumo de Recurso
Homeostasis and negative feedback
Keeping the internal environment constant despite external changes
Body temperature
Blood glucose concentration
Blood salt concentration
Water potential of the blood
Blood pressure
Carbon dioxide concentration
Negative feedback
In order to maintain a constant internal environment a number of processes must occur
Any change of the internal environment must be detected
The change must be signalled to other cells
There must be a response that reverses the change
For negative feedback to work effectively there must be a complex arrangement of structures that are all coordinated through cell signalling
Sensory receptors
These are internal and monitor change in the body
If they detect change then they are stimulated to send a message
E.g. temperature receptors or glucose concentration receptors
A communication system
Acts by signalling between cells
Used to transmit a message from the receptor cells to effector cells
The message may or may not pass through a coordination centre such as the brain
E.g. the nervous system or hormonal system
Effector cells
These cells will bring about a response that reverses the change detected by receptor cells
E.g. liver cells or muscle cells
Positive feedback
Less common than negative feedback
The response is to increase the original change
Destabilises the system and is usually dangerous
E.g. when the body gets too cold, the enzymes become less active, and reactions slow causing less heat to be released - cooling the body further
The end of pregnancy is an example of beneficial positive feedback
As the cervix begins to stretch the change is signalled to anterior pituitary gland
Stimulates it to secrete the hormone oxytocin
Oxytocin increases uterine contractions, which stretch the cervix even more
Once the cervix is fully dilated the baby can be born
The meaning of constant
The conditions will never remain perfectly constant
There will be some variation about the mean or optimum condition
As long as the variation is not too great then the conditions will remain acceptable
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