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)

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

• 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 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

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

•Tomorrow:▫ RAFT: “Drugs such as ecstasy

interfere with the feedback mechanism that helps maintain a constant body temperature.” Explain why these drugs are dangerous.