1. 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.

2. 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!

3. 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

4. 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)

5. 4km swim, 180km bike, 42km run!

6. 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

7. 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%

8. Homeostasis All of our organ systems work
together to maintain Homeostasis
Homeostasis is a steady internal
state, keeps conditions in the body
constant.
Examples:
Blood Pressure (circulatory system)
Respiration Rate (respiratory system)
Body Temperature (circulatory system)
Blood Sugar (digestive and circulatory)
The brain and the adrenal system
(hormones) do most of the
regulating.

9. Homeostatic Control Mechanisms
Monitors
Senses state of system
(Brain stem receptors detect increased CO2 in the blood)
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)
Regulator
Carries out the appropriate next step to keep system at homeostasis
(Diaphragm increases depth and rate of breathing)
Monitor sales and stock of stores and report to factory manager. Based on stocks, factory manager instructs more or less of something to be made. Works increase or decrease production of certain items.

10. Homeostatic Control System
Stimulus
Deviation from set point
Response
Move system towards set point
Sensor
Constantly monitors conditions
Negative feedback (-)
Integrating Centre
Compares conditions to a set point based on a desired value
Effector
Causes changes to compensate for deviation

11. 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! es
Homework…Read p (Feedback)
Do Q 2, 3, 4, 9, 10 p348

12. 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 mechanism consists of reducing the output or activity of any organ or system back to it's normal range of functioning.
Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both are the effectors. The heart rate would decrease as the blood vessels increase in diameter. This change would result in the blood pressure to fall back to its normal range. The opposite would happen when blood pressure decreases.

14. 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.
Most controls in the body are negative.

15. Negative Feedback Loop

16. 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?

18. 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…

19. Example of Negative feedback: Blood Pressure Regulation
Negative feedback mechanism consists of reducing the output or activity of any organ or system back to it's normal range of functioning.
Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both are the effectors. The heart rate would decrease as the blood vessels increase in diameter. This change would result in the blood pressure to fall back to its normal range. The opposite would happen when blood pressure decreases.

20. 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!!!

21. 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.

22. 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.

24. Physiological Response
Thermoregulation
Stimulus
Physiological Response
Adjustment
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
What happens when the body gets too hot?
The brain senses the increase in temperature and sends a signal to hypothalamus which tells sweat glands to start sweating and blood vessels near the surface of the skin to dilate (open wide).
Evaporation of sweat cools the body – blow across the back of your hand…Now lick the back of your hand and blow across it. Your spit is evaporating (as sweat would) and it is cooling you down.
Wider blood vessels means more blood to skin surface which is cooler. Blood cools and is sent back to the core of body to help lower temperature.
What happens when the body gets too cold?
The brain senses the drop in temperature and sends a signal to the hypothalamus to do something.
The hypothalamus sends a signal to the muscles to contract rapidly and a signal to the blood vessels near the skin to constrict (become smaller in diameter).
Rapid muscle contraction builds up heat – it’s like a mini workout.
The smaller blood vessels reduces blood flow to the skin where the cold is and therefore less blood gets cooled and sent back to the core of the body.
When the body is back to normal, the process stops.

25. Tomorrow:
RAFT:
“Drugs such as ecstasy interfere with the feedback mechanism that helps maintain a constant body temperature.” Explain why these drugs are dangerous.