homeostasis - lorenowicz.weebly.com · homeostasis • different organs are involved with the...
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HOMEOSTASIS• The term homeostasis refers to the body’s
attempt to adjust to a fluctuating external environment…
» Homeostasis = the process by which a constant internal environment is maintained despite changes in the external environment
In Greek, ‘homois’ means “similar” and ‘stasis’ means “standing still”!
Homeostasis is also referred to as DYNAMIC EQUILIBRIUM!
Thursday, July 14, 2011
HOMEOSTASIS• Our body has several preferred homeostatic
values for life:Body Temperature = 37oC
Blood Sugar level = 0.1% glucose
Blood pH Level = 7.35
Blood pressure = 120/80 mmHg
In order to maintain these values, the body makes use of various control systems which must monitor, coordinate and regulate these
values!
Thursday, July 14, 2011
HOMEOSTASIS• Different organs are involved with the
regulation of different systems:
Kidneys maintain H2O
balance!
Hypothalamus regulates temperature and changes osmotic pressure!Pancreas regulates
blood sugar!
Blood distributes heat throughout the body!
Skeletal muscle contracts and releases heat!
Thursday, July 14, 2011
HOMEOSTASIS• A homeostatic control system must have 3
functional components!
» 1. MONITOR – special sensors (located within organs) that send a signal to the coordinating center once an organ begins to operate outside its normal limits.
» 2. COORDINATING CENTER – a processing center that will process the information from the monitor and relay the appropriate response to the regulator.
» 3. REGULATOR – will take an action in order to help restore values to normal.
Thursday, July 14, 2011
HOMEOSTASISLet’s look at the example of heating a house!
Which component is the MONITOR, COORDINATING CENTER and REGULATOR?
COORDINATING CENTER!
MONITOR!
REGULATOR!
Thursday, July 14, 2011
HOMEOSTASIS• In the example of heating your house, the furnace
(regulator) can be turned on if the house gets too cold and turned off if the house gets too warm
» This is referred to as a NEGATIVE FEEDBACK SYSTEM!!!!!!
Negative Feedback = a process by which a change in the variable being monitored triggers the control mechanism to counteract any further change in the same direction.
Thursday, July 14, 2011
HOMEOSTASIS• Most homeostatic mechanisms in animals (humans
too) operate on the principle of negative feedback!
Common examples include BODY TEMPERATURE regulation and BLOOD SUGAR levels!
Thursday, July 14, 2011
Thursday, July 14, 2011
Thursday, July 14, 2011
HOMEOSTASIS• While negative feedback loops are far more
prevalent in animals, the opposite is also possible, a POSITIVE FEEDBACK LOOP.
» POSITIVE FEEDBACK = a process by which a small effect is amplified!
Whereas negative feedback loops are designed to resist change, positive feedback loops REINFORCE the
change!!!!
Thursday, July 14, 2011
HOMEOSTASIS• A good example of positive feedback in
humans is the birthing process!!!!
Thursday, July 14, 2011
HOMEOSTASIS• In the case of positive feedback, once the
event in question is accomplished, the feedback system stops!
– Ie: once a baby is born, uterine contractions cease as does the release of oxytocin!
Thursday, July 14, 2011