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Homeostasis ­ the maintenance of a steady
internal state in the body almost regardless of
changes in either the external or the internal
Changes in the body are detected by a sensor
This send a message to an effector which
either works to reverse the change or
increase it.…read more

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Feedback systems
A change in conditions is registered by receptors.
Effectors are stimulated to restore the equilibrium.
If the concentration goes up, the effectors bring it down
Positive: Effectors work to increase the effect which
has triggered the response.
Communication may be by hormones or nerve
There is often a small overshoot or undershoot as a
feedback system corrects.…read more

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Normal level
Fall to a Rise to a higher
lower level level
Receptor ·If communication is
Detects change hormonal, the Detects change
effectors are the
Communication by: various target of the Communication by:
1.Hormones hormones 1.Hormones
2.Nervous system via ·If communication is 2.Nervous system via
coordination centre nervous, the effectors coordination centre
are muscles or glands
Effector Effector
Carries out response Carries out response
which brings out which brings out
corrective change corrective change
Rise to normal Fall to normal
level level
Normal level…read more

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Changing cardiac output
Cardiac output = cardiac volume x heart rate
(dm3) (beats min-1)
The volume of blood pumped The number of heart
at each heartbeat beats per minute
The cardiac volume
can increase by
more efficient
contraction of the
ventricles.…read more

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Effect of Exercise
When a fit athlete anticipates exercise:
The heart rate begins to increase before
exercise begins.
The cardiac volume increases more slowly.
Cardiac output increases.…read more

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