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Homeostasis in the Human Body

A brief overview of some components of homeostasis

Shay Bytheway

on 3 January 2014

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Transcript of Homeostasis in the Human Body

The Excretory System
The excretory system uses the
to maintain homeostasis by:

Filtering water and salt from the blood
Regulating the body's water content
Eliminating toxic by-products from the body
Regulating ion concentrations
Feedback Mechanisms
Homeostasis is maintained using
positive or negative

feedback mechanisms
. In the endocrine system, most glands are under negative feedback influence.
Some Control Mechanisms Involved in Homeoestasis
: A
in/on an organ that detect changes in external conditions (such as
nerve endings
on the skin).

Coordinating Center
: (
brain stem
) Receives and interprets information from a
sends it to the designated

: (G
) Carries out the appropriate response to restore the homeostatic balance.

Negative Feedback Loops
: Where a change in environment triggers a control mechanism to respond accordingly (this is covered in more detail shortly).
Homeostasis in
the Human Body

- The
Pituitary gland
(endocrine) releases
anti diuretic hormone (ADH)
to encourage more
water re absorption
by the kidneys (excretory) when the body needs to keep water within it.

- The hormone
is released by the
adrenal glands
(endocrine) to
aid blood pressure regulation

- The enzyme
is released to activate hormone
(endocrine) to
increase blood pressure

- The excretory system is responsible for a buffer reaction that creates more
bicarbonate (base)
and excretes

in urine to

pH balance
in the body.
Positive Feedback Mechanisms
Although most endocrine glands use negative feedback to induce a response, some use positive feedback instead.
Positive feedback mechanisms
control events that do not require constant adjustment, and instead of attempting to maintain hormone levels within narrow ranges, it promotes deviation from the normal value.
is the body's ability
to maintain a constant internal
environment, despite external
changes. To the right is an
overview of how homeostasis

Navigate through the mobile by
using the left and right arrow
buttons when finished reading.

Using these control mechanisms, the body systems are able to communicate and respond to one another to maintain a homeostatic balance.
How is the excretory system related
to others in homeostasis?
Excretory System
works with the
Endocrine System
by using hormones to regulate homeostasis:
The Endocrine System
The endocrine system uses chemical messengers called
to make regulatory changes in the body. It is composed of
that release these hormones into the blood stream, which delivers them to their target cells. The release of these hormones increases or decreases the target cell's activity, therefore maintaining homeostasis in the body. The image at the right shows the glands of the endocrine system.
The endocrine system is the body's main way of maintaining homeostasis. The
pituitary gland
is the "master gland" of the endocrine system as it controls most other glands in this system. It works in conjunction with the
of the nervous system; the hypothalamus sends a message to the pituitary, and the pituitary gland then releases the necessary hormone(s) or sends a signal to the appropriate gland to do so.
Negative feedback
is similar to a thermostat in a house. When the temperature reaches a certain degree, the heat turns on/off. This is to save energy, and the same goes for the body.
A homeostatic example of this would be
calcium level regulation
- if it is detected that there is too little calcium in the blood,
parathyroid hormone
(which regulates blood-calcium levels) is released to stimulate calcium to be released from the bones. This feedback loop is shown to the left.
An example of positive feedback mechanisms can be seen in child birth. The hormone
is released to increase the effectiveness of uterine contractions during labor. When the baby is in the birth canal, oxytocin is released which then stimulates stronger contractions (this is positive feedback) to help aid in the delivery of the baby. When the baby is delivered, oxytocin production ends.
Homeostasis is a complex and intricate system that we are only just beginning to understand. The topics covered in this presentation are merely scratching the surface of homeostasis - there are other systems involved in homeostatic maintenance, the hormones involved in the endocrine system are vast, and the interconnection of it all makes us appreciate these unconscious processes!
In Conclusion
Homeostasis Examples
Unconsciously, the body maintains its own stable environment according to internal and external changes.

Some examples of this are:

Body temperature

Blood-glucose and blood-calcium levels

White blood cell production in times of infection

Blood pressure regulation

pH regulation

Water regulation
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