HOMEOSTASISUNIT 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)

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•See page 324

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.

Three Components of Control

1. Monitors ▫ (Brain stem receptors detect increased

CO2 in the blood)2. Coordinating Centre

▫ (Nerve cells in brain receive and send a signal to the diapragm)

3. Regulator▫ (Diagragm increases depth and rate of

breathing)

Dynamic Equilibrium•There will always be fluctuations in levels•Homeostatic mechanisms ensure that all

body systems function within an acceptable range.

•Mammalian Diving Reflex (P. 340)•Check out the ICEMAN!•http://www.youtube.com/watch?

v=madoDvtKEes•Homework…Read P335-336 (Feedback)•Do Q 1-5 P. 337•Read P338-341 – Thermoregulation!

Feedback Mechanisms

•Negative – Prevent small changes from becoming too large (i.e. A thermostat)

•Most controls in the body are negative feedback

•Positive – amplify small effects (i.e. Oxytocin and childbirth)

Thermoregulation

•Maintenance of body temperature within a range that enables cells to function efficiently

•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