1. Characteristics of Life

2. Characteristics of Life
Movement
Responsiveness
Growth
Reproduction
Respiration
Absorption
Circulation
Digestion
Assimilation
Excretion

3. Factors necessary to maintain life
Water
Food
Oxygen
Heat
Pressure

4. homeostasis Maintenance of a stable internal environment.
The body’s concentrations of water, nutrients, oxygen, carbon dioxide, and ions, as well as body temperature and blood pressure must be maintained for organ systems to function properly.

5. Homeostasis
Because these properties affect the chemical reactions that keep us alive, we have built-in physiological mechanisms to maintain them at desirable levels.

6. Homeostatic Mechanism Components
Receptors:
Provide information about specific conditions in the internal environment.
Receives information from internal and external environment

7. Homeostatic Mechanism Components
Set Point:
Tells where a particular value should be. 
Control Center -contains set point,
-recieves info from receptor
-sends message to effector
-hypothalmus of brain

8. Homeostatic Mechanism Components
Effectors:
Cause responses that alter conditions in the internal environment.
Effector act to bring body back to set point
-muscles or glands

9. POSITIVE AND NEGATIVE FEEDBACK
When a change occurs in the body, there are two general ways that the body can respond:

10. Homeostatic Mechanisms
Negative Feedback Mechanism
Shuts off or reduces the output of a system to prevent sudden severe changes in the body.
reverse the direction of change. Because this tends to keep things constant, it allows us to maintain homeostasis.

11. Homeostatic Mechanisms
Receptors control center effectors
Temp sensors Brain (hypothalmus) Blood vessels
on skin Setpoint:98.6F muscles

12. Homeostatic Mechanisms
Examples:
Regulation of Glucose levels in the blood
Maintenance of Blood-oxygen levels
Temperature regulation
Fluid Regulation
Regulation of Glucose levels in the blood: insulin
Maintenance of Blood-oxygen levels deeper breathing
Temperature regulation sweating, shivering
Fluid regulation thirst

13. Temperature Regulation

14. Temperature Regulation

15. Homeostatic Mechanisms
Positive Feedback Mechanism
Enhances/exaggerates
the output of an activity
to accelerate its output
Positive Feedback Mechanism
Same activity increases
Examples: lactation
clotting
childbirth
de-stabilizing effect, so it does not result in homeostasis. Positive feedback is used in certain situations where rapid change is desirable.

16. Positive feedback

17. Factors that can disrupt homeostasis
The following factors can disrupt homeostasis, leading to serious health effects and possibly death.
Chronic stress
Poor diet
Disease
Injury

18. Brain Death

19. Who determines brain death?
More than one doctor determines brain death.
The doctor must be a neurologist.

20. What are they trying to prove?
They are trying to prove that you are ALIVE! If they cannot prove you are alive than you must be DEAD!

21. Brain Functions
If normal brain functions are missing the neurologist tests for electrical activity in the brain using an EEG.
If there is no electrical activity the neurologist will perform the brainstem tests to determine “brain death”.

22. Brainstem

23. Brainstem Tests “Dolls Eyes” test Ice water test Corneal reflex test
Photopupillary reflex test
“Dolls Eyes” test
Ice water test
Corneal reflex test
Response to pain test
Gag reflex test
Apnea test