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 SystemsUNIT 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)
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
• http://www.lionden.com/homeostasis.htm
Temperature 37oC (98.6oF)
Blood pH 7.35
Blood sugar level 0.1%
HomeostasisAll of our organ systems worktogether to maintain Homeostasis
Homeostasis is a steady internalstate, keeps conditions in the bodyconstant.
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 Mechanisms1. 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
StimulusDeviation from set point
SensorConstantly monitors
conditions
Integrating Centre
Compares conditions to a set point based on a
desired value
EffectorCauses changes to
compensate for deviation
ResponseMove system towards set
point
Negative feedback (-)
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=madoDvtKEes•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 diminishedAny 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 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…
ThermoregulationAlso 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.
ThermoregulationStimulus Physiological
ResponseAdjustment
Decreased Enviro Temp
-Constriction of blood vessels-Hairs stand on end-Shivering
-Heat is conserved-More heat is generated by increased metabolism
Increased Enviro Temp
-Dilation of blood vessels of skin-Sweating
-Heat is dissipated
http://www.youtube.com/watch?v=Yotp6ov9-w0&feature=fvw
http://www.youtube.com/watch?v=eJEXdWHKDmg http://www.youtube.com/watch?
v=vc86u0IsOwc&feature=related