736568
Beschreibung
Mindmap von hannahdrane, aktualisiert more than 1 year ago
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Erstellt von hannahdrane
vor etwa 10 Jahre
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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
- Body temperature
- 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
- There must be a response that reverses the change
- The change must be signalled to other cells
- Any change of the internal
environment must be detected
- 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
- These are internal and
monitor change in the body
- 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
- Acts by signalling between cells
- Effector cells
- These cells will bring about a response that
reverses the change detected by receptor cells
- E.g. liver cells or muscle cells
- These cells will bring about a response that
reverses the change detected by receptor cells
- Sensory receptors
- In order to maintain a constant internal
environment a number of processes must
occur
- 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
- 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
- Once the cervix is fully dilated the
baby can be born
- Oxytocin increases uterine contractions, which stretch
the cervix even more
- Stimulates it to secrete the hormone oxytocin
- As the cervix begins to stretch the change is signalled
to anterior pituitary gland
- Less common than negative feedback
- 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
- The conditions will never remain perfectly
constant
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