PHYS20008 Lecture Notes - Lecture 2: Positive Feedback, Homeostasis, Brainstem
27 Jul 2018
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Lecture 1
HOMEOSTASIS:
* Homeostasis – the maintenance of a relatively stable internal environment
* homeo = “the same”, stasis = “stand or stay”
* Homeostasis is essential for the survival of each cell (so the systems can work) and
therefore the individual
* We can maintain things within a relatively narrow range (that our body is content with).
When we divert away from the range, our body senses this and makes a change to bring us
back into this range. E.g. blood pressure
* Our environment is constantly changing and our body is constantly adapting to those
changes in our environment (working to maintain homeostasis)
Basic process of homeostasis:
1. Detect changes (sensor) – sense the factor that
we are monitoring/sense a stimulus/sensory input
to monitor a stimulus
2. Message to integrator (afferent) – sensor/receptor
has to that information via the afferent pathway to
the integrating centre, which is generally the brain.
3. Controller or integrator (compare to set point) -
The integrating centre will take the signal and
interpret the signal and translate it into an output
4. Message to effector (efferent) - This translated output is sent out to the efferent
pathway to some sort of organ or gland or tissue – something
that is able to make a change to bring the parameter back into target range/set point
5. Response – return to desired range (negative feedback)
Example:
Blood pressure (stimulus) drops, and the nerve cells (sensor) sense the drop in blood
pressure and send a signal to the brain stem (integrator), The brain stem will send a signal
out causing the blood pressure to go back to normal range
Integration:
* Negative feedback – constant monitoring and adjustment – when somethings drifts out of
normal range, the body works to bring it back into the desired range
* Integration involves afferent and efferent pathways (signals sent around the body) using
hormones (endocrine) and nerves (neural – electrical signals)
Document Summary
* homeostasis the maintenance of a relatively stable internal environment. * ho(cid:373)eo = (cid:862)the sa(cid:373)e(cid:863), stasis = (cid:862)sta(cid:374)d or stay(cid:863) * homeostasis is essential for the survival of each cell (so the systems can work) and therefore the individual. * we can maintain things within a relatively narrow range (that our body is content with). When we divert away from the range, our body senses this and makes a change to bring us back into this range. * our environment is constantly changing and our body is constantly adapting to those changes in our environment (working to maintain homeostasis) * negative feedback constant monitoring and adjustment when somethings drifts out of normal range, the body works to bring it back into the desired range. * integration involves afferent and efferent pathways (signals sent around the body) using hormones (endocrine) and nerves (neural electrical signals) * specific goes from point a to point b.
