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Weird Body Quirks
• Brain freeze
• “Ice cream headaches”
happen when something
cold touches nerves in the
roof of the mouth, triggering
blood vessels in the front of
your head to constrict -producing pain. Try this
quick pain relief trick: Press
your tongue to the roof of
your mouth to warm it up.
HOMEOSTASIS
& Control
Systems
UNIT 4
Also Known As…
If it ain’t broken, don’t waste my
valuable time & energy trying to
fix it, fool!
Learning goals . . .
• To explain the process of maintaining
homeostasis through feedback loops and their
components.
You will show your understanding by . . .
• Presenting an explanation (diagramatic, written
or kinesthetic) of thermoregulation
What happens in your body when you
do a Triathalon?
• Cell Resp increases
• Body Temp increases to 39 degrees Celsius (due to heat from
CR rxns)
• Sweat is produced to dissipate heat
• This loss of water, drops blood pressure
• Heart responds, Kidneys conserve water
• Electrolytes (salts) are lost in sweat
• Body must use hormones to keep a steady supply of glucose to
CR pathways
• Nervous systems monitors o2 levels, increasing breathing rate
if necessary
• Nervous systems also work with the circulatory system to
divert blood to essential areas (muscles, brain, heart…away
from stomach etc)
4km swim, 180km bike, 42km run!
The “Ideal Body State”
•
•
•
•
•
37 degrees
0.1% blood sugar
Blood pH 7.35
Environment doesn’t always allow for this!
Organs and body systems are constantly
adapting
Homeostasis
• Maintenance of a relatively stable
internal, fluid environment (internal
milieu) despite a changing external
environment
• Homios = Similar
Stasis = Standing Still
Temperature
37oC (98.6oF)
Blood pH
7.35
Blood sugar level
0.1%
• http://www.lionden.com/homeostasis.htm
Homeostasis
All of our organ systems work
together to maintain Homeostasis
Homeostasis is a steady internal
state, keeps conditions in the body
constant.
Examples:
1.
Blood Pressure (circulatory system)
2.
Respiration Rate (respiratory
system)
3.
Body Temperature (circulatory
system)
4.
Blood Sugar (digestive and
circulatory)
The brain and the adrenal system
(hormones) do most of the
regulating.
Homeostatic Control Mechanisms
1. Monitors
▫
▫
Senses state of system
(Brain stem receptors detect increased CO2 in the blood)
2. Coordinating Centre
▫
▫
Receives incoming info about system and decides what the next
steps should be
(Nerve cells in brain receive and send a signal to the diapragm)
3. Regulator
▫
▫
Carries out the appropriate next step to keep system at
homeostasis
(Diaphragm increases depth and rate of breathing)
Homeostatic Control System
Stimulus
Deviation from set point
Response
Move system towards set
point
Effector
Causes changes to
compensate for deviation
Negative feedback (-)
Sensor
Constantly monitors
conditions
Integrating
Centre
Compares conditions to a
set point based on a
desired value
Dynamic Equilibrium
• There will always be fluctuations in levels
• Homeostatic mechanisms ensure that all body
systems function within an acceptable range.
• Mammalian Diving Reflex
• Check out the ICEMAN!
• http://www.youtube.com/watch?v=madoDvtKE
es
• Homework…Read p344-347 (Feedback)
• Do Q 2, 3, 4, 9, 10 p348
Feedback Mechanisms/Loops
• Positive feedback - a mechanism by which an
output is enhanced
▫ Contractions in childbirth: contractions stimulate
oxytocin which stimulates more muscle
contractions
Negative feedback - a mechanism by
which an output is diminished
Any change from normal range of function is resisted in
negative feedback.
The change initiates responses that bring the function of
the organ back to its normal range.
Negative feedback loops require a Receptor, A Control
Center, and Effectors.
Blood vessels have receptors (monitors) which can
measure the resistance of blood flow against vessel
walls
The brain (control center) receives info about change in
body’s internal conditions, sends out signals via nerves
• Effectors (regulators) - the muscles, organs, and other
structures that receive signals from the control center
and respond to correct the deviation.
Negative Feedback Loop
Negative Feedback in the Home?
• Negative feedback can be likened to your
home’s heating system.
• Temperature too high…Thermometer (monitor)
senses increase in temperature.
• Signal sent to thermostat (coordinating centre)
and thermostat says we better cool it down.
• Thermostat tells air conditioner (regulator) to
start pumping in the cold air.
• Once house is cooled…system rests – why
waste the energy?
Negative feedback in the home?
• What if the temperature is too low?
• Thermometer senses that it is too cold and
sends signal to thermostat.
• Thermostat figures it is time to turn up the heat.
• Thermostat tells furnace to get going and heat
the place up.
• Once temperature is back up to normal levels,
the system rests – why waste the energy?
• Saving energy is important to any energy being
like yourself…
Example of Negative feedback: Blood
Pressure Regulation
Thermoregulation
Also known as…
Why do students complain when
the room is too hot or too cold
when their own bodies are gonna
look after them anyways!!!
Thermoregulation
• Thermoregulation is the maintaining of a stable body
temperature.
• This is necessary for the cells to function properly
because the “rock star” proteins might decide to lose it if
the room is not just right!
• The brain is the monitor and coordinating centre in this
process is the hypothalamus – a part of the brain that is
in the centre of the head and lies below the thalamus but
above the pituitary gland.
• Hypothalamus – Region of the vertebrate’s brain responsible for
coordinating many nerve and hormone functions.
Ecto Vs. Endo
• Ectotherms – Invertebrates, fish, amphibians,
reptiles...Depend on air temp to regulate body
temp.
• Endotherms – Mammals – Are able to maintain
a constant body temp regardless of
surroundings.
Thermoregulation
Stimulus
Physiological
Response
Adjustment
Decreased Enviro Temp
-Constriction of blood
vessels
-Hairs stand on end
-Shivering
Increased Enviro Temp
-Dilation of blood vessels -Heat is dissipated
of skin
-Sweating
http://www.youtube.com/watch?v=eJEXdW
HKDmg
http://www.youtube.com/watch?v=Yotp6ov
9-w0&feature=fvw
-Heat is conserved
-More heat is generated
by increased metabolism
http://www.youtube.com/watch?v=vc86u0Is
Owc&feature=related
• Tomorrow:
▫ RAFT:
“Drugs such as ecstasy
interfere with the feedback
mechanism that helps
maintain a constant body
temperature.” Explain
why these drugs are
dangerous.