1. HOMEOSTASIS
UNIT 4

2. 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)

3. 4km swim, 180km bike, 42km run!

4. 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

5. 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.

6. Three Components of Control
Monitors
(Brain stem receptors detect increased CO2 in the blood)
Coordinating Centre
(Nerve cells in brain receive and send a signal to the diapragm)
Regulator
(Diagragm increases depth and rate of breathing)

7. 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! es
Homework…Read P (Feedback)
Do Q 1-5 P. 337
Read P – Thermoregulation!

8. 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)

9. 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.

10. 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.

12. 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