Introduction to
P 334-340
Core Temperature
• Humans have a normal temperature
of around 36.2 to 37.2 degrees
Celsius
• Body temperature goes above
normal temperature then likely
suffering from an infection and your
body had to raise its temperature to
fight off the infection.
• If your body goes below this range it
indicates hypothermia. Therefore if
left untreated it could lead to cell
damage and possibly death.
http://news.bbc.co.uk/2/shared/spl/hi/health/03/travel
_health/diseases/html/sars.stm
http://asimplebutimpossibletask.blogspot.com/
What is Homeostasis?
http://balancewines.wordpress.com/2009/12/
• The body’s attempt to
maintain “normal” levels
within your body
• Homeostasis is often
referred to as a dynamic
equilibrium- which is a
mechanism to ensure that
all body systems function
within an acceptable
range to sustain life.
Homeostatic control systems
• 3 components:
– Monitor
– Coordinating centre
– Regulator
• Monitor sends a signal to
the coordinating centre
that the normal levels
have changed. The
coordinating centre then
messages the regulator
which helps restore
normal balance.
Monitor
Change in
balance
Normal
balance
Coordinating
centre
Regulator
Homeostasis
Example: household thermostat
• Room temperature is set to 22
degrees Celsius. When the
temperature falls below the
“normal” temperature of 22
degrees, the thermostat
recognizes change in “normal”
temperature and switches on the
furnace. When the thermometer
detects a temperature above the
“normal”, the thermostat switches
off the furnace.
http://gasfurnaceprices.co.cc/
Homeostasis
Example: household thermostat
MonitorThermometer
Detects decrease in
temperature
Furnace turns off
Thermostat detects temperature
increases over “normal”
Coordinating centre- Thermostat
switches on furnace
Regulator- Furnace
Whole control system is called a negative
feedback system
Negative feedback
• Process by which a mechanism is activated to restore
conditions to their original state
• It ensures that small changes don’t become too large.
• Why is a thermostat a negative feedback system?
Negative Feedback
Example: Thermoregulation
• The maintenance of body
temperature within a range that
enables cells to function efficiently
–Heat Stress
–Cold Stress
Negative Feedback
Example: Thermoregulation
Heat stress
• Thermoreceptors detect an
increase in body
temperature
• Hypothalamus signals to the
sweat glands to initiate
sweating.
• Evaporation of the sweat off
the skin causes cooling.
http://flairforthedramatic.mlblogs.com/archives/2008/09/of_all_times_to_start_w
inning.html
Negative Feedback
Example: Thermoregulation
Heat Stress
http://www.pgbeautygroomingscience.com/functionsof-the-dermis.html
• The hypothalamus also sends
message to blood vessels in the
skin causing them to dilate.
• Dilation allows for more blood
flow to the skin.
• Heat from the blood is lost to the
skin so blood can return to core of
your body & cool the internal
organs.
Negative Feedback
Example: Thermoregulation
Heat Stress
• Monitor: thermoreceptors
• Coordinating centre: hypothalamus turns on
cooling system
• Regulator: skin blood vessels dilate and sweat
glands initiate sweating
• Result: body temperature decreases;
hypothalamus turns off cooling system
Negative Feedback
Example: Thermoregulation
Cold stress
• Thermoreceptors message the
hypothalamus
• Hypothalamus sends a message via
the nerves to:
o Arterioles of the skin cause smooth
muscles to contract, constricting arterioles
& limiting blood flow =reduced heat loss
from the skin and retains heat in the body.
o Smooth muscle contract that surrounds
the hair follicles in your skin causing the
hair to “stand on end” trapping warm air.
o Skeletal muscle to contract causing
shivering and increasing your metabolism
to make heat.
http://www.clarian.org/ADAM/doc/HealthIllustratedE
ncyclopedia/2/19194.htm
Negative Feedback
Example: Thermoregulation
Cold stress
• Monitor: Thermoreceptors
• Coordinating centre: Hypothalamus
• Regulator: skin blood vessels constrict and
skeletal muscles contract
• Result: body temperature increases and
hypothalamus turns off.
http://www.pgbeautygroomingscience.com/functions-of-the-dermis.html