UNIT 3
UNIT TITLE: HOMEOSTASIS
Area of interaction:
Health and social
education
MYP unit question:
What advantage
or disadvantage is
it to be warm
blooded?
Summative assestment:
Exposition about the role of
homeostatic processes for
the maintenance of life.
You will make a presentation of 5-8 minutes. It will be presented
in class the 16th of april.
 You should also write down a summary of 2-3 pages (with
references in APA format) and present it the 11th of april (it
should be send to me by phidias). I will correct them and send
them to the whole class.
 It must be a creative presentation of information.
 Subjects:

•
•
› role of the hypothalamus to control body temperature
› role of sweat glands to control body temperature
› role of the skin arterioles to control body temperature
› role of shivering to control body temperature
Include one advantage and one disadvantage of being warm blooded
Criteria Evaluated: B and C
Homeostasis
A state of
balance
in the body
What is Homeostasis?
“The maintenance of a constant
environment in the body”.
Your body has many mechanisms that
keep the cells surroundings constant
even though your external environment
is changing. This is homeostasis.
Body cells work best if they have the correct...
•
•
•
•
•
Body temperature
Blood pH
Carbon dioxide concentration
Blood glucose concentration
Water balance
http://biocalaix.wordpress.com/2011/05/22/i
matges-de-cel-lules-sanguinies/red-bloodcells-sem/
The endocrine system is involved directly in
homeostatic processes…
Both, the endocrine system and nervous system are
involved in controlling the internal environment of our
bodies. The endocrine system consists of glands, which
release hormones that are transported in the blood.
http://www.webbooks.com/eLibrary/Medicine/Physio
logy/Endocrine/Endocrine.htm
http://www.faqs.org/health/Body-byDesign-V2/The-Nervous-System-Designparts-of-the-nervous-system.html
Negative feedback
http://www.phys.unsw.edu.au/biosnippets/

Occurs when feedback (from sensor to integrator)
results in a reversal of the direction of change.

An example: thermostat's response causes
temperature decrease to reverse and become a
temperature increase.

Negative feedback tends to stabilize a system.
Variable: position of body
Setpoint: directly over the
wire
Sensors: nerve receptors
(eyes, inner ears, muscle
stretch receptors, etc.)
Integrator: brain
Effectors: skeletal muscles
http://www.popcrunch.com/16-entertainerswho-died-in-the-act/philippe-petit/
High-wire artist uses negative feedback to
maintain relatively constant position on wire.
Your cells also need an exact level of glucose in
the blood.
 Excess glucose gets turned into glycogen in the
liver
 This is regulated by 2 hormones (chemicals) from
the pancreas called:
Insulin
Glucagon

http://www.medicinayprevencion.com/pancreas.htm
Responses to high blood
glucose levels
Responses to low blood
glucose levels
• Glucagon is produced in
• Insuline is produced in the
the pancreas.
pancreas.
• Glucagon stimulates liver
• Insuline stimulates the liver
cells to break glycogen
and muscle cells to
down into glucose and
absorb glucose and
release the glucose into
convert it to glycogen.
the blood.
Ypu need to search Diabetes in the
list on the left upper side, in order to
see the animations
http://www.medmovie.com/mmdatabase/mediaplayer.aspx