Homeostasis
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Homeostasis
Homeostasis is the maintenance of a
dynamic consistency of the body’s internal
environment.
Normal functional activities of the cell depend
on the internal environment being maintained
within very limited normal range. The
chemical content, volume, temperature, and
pressure of the fluid must stay the same,
regardless of external conditions, so that the
cell can function properly.
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Homeostasis
If the conditions in the fluid deviate from
normal, mechanisms respond to restore
conditions to normal. If the mechanisms
are unsuccessful, the cell malfunctions and
dies.
This leads to illness or disease and if,
homeostasis is not restored, eventually to
death of the individual.
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Or when Mr. B asks his
wife to buy a new big
screen TV 
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Homeostasis
Stable operating conditions in the
internal environment
Three components interact
RECEPTOR
(e.g., free
nerve ending
in the skin)
Regulator
(such as
the brain)
EFFECTOR
(a muscle
or a gland)
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Homeostasis
Homeostasis is achieved by the regulatory
mechanisms of the body, which operate mainly
through “negative feedback” loops,
counteracting the deviation from the ‘set-point’
value.
Negative feedback mechanisms inhibit a
change or deviation from normal
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Homeostasis: Negative Feedback
(continued)
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Homeostasis: Positive Feedback
Positive feedback mechanisms stimulate or amplify
changes.
Why is positive feedback mechanism beneficial ?
– Because it quickly terminates a process that, if allowed to
continue for a prolonged period, might be detrimental.
– The events in the birth of a baby and the formation of a
blood clot are examples of positive feedback.
– Production of oxytocin amplifies uterine contraction to help
give birth to a baby
– Fever ... Infection signals onset of a fever that rises higher
and higher to kill infection. At 45 degrees celsius, the fever
kills
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Body Systems hard at work
Kidneys
– managing and filtering wastes
Stomach / Intestines – obtaining nutrients
Heart / Lungs
– providing oxygen and removing
carbon dioxide waste
Testes / Ovaries
– supplying sex hormones for
reproduction
Liver
– filtering wastes
Pancreas
– secreting insulin for blood
sugar
And the list goes on and on and on…
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