Characteristics of Life
Characteristics of Life
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Movement
Responsiveness
Growth
Reproduction
Respiration
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Absorption
Circulation
Digestion
Assimilation
Excretion
Factors necessary to maintain life
• Water
• Food
• Oxygen
• Heat
• Pressure
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.
Homeostasis
Because these properties
affect the chemical
reactions that keep us alive,
we have built-in
physiological mechanisms
to maintain them at
desirable levels.
Homeostatic Mechanism
Components
• Receptors:
Provide information
about specific
conditions in the
internal environment.
Homeostatic Mechanism
Components
• Set Point:
Tells where a particular
value should be.
Homeostatic Mechanism
Components
• Effectors:
Cause responses that
alter conditions in the
internal environment.
POSITIVE AND NEGATIVE FEEDBACK
• When a change
occurs in the body,
there are two general
ways that the body
can respond:
Homeostatic Mechanisms
• Negative Feedback Mechanism
–Shuts off or reduces the
output of a system to
prevent sudden severe
changes in the body.
Homeostatic Mechanisms
Homeostatic Mechanisms
Examples:
• Regulation of Glucose levels in
the blood
• Maintenance of Blood-oxygen
levels
• Temperature regulation
• Fluid Regulation
Temperature Regulation
Temperature Regulation
Homeostatic Mechanisms
• Positive Feedback Mechanism
Enhances/exaggerates
the output of an activity
to accelerate its output
Positive feedback
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
Brain Death
Who determines brain death?
• More than one doctor
determines brain death.
• The doctor must be a
neurologist.
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!
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”.
Brainstem
Brainstem Tests
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Photopupillary reflex test
“Dolls Eyes” test
Ice water test
Corneal reflex test
Response to pain test
Gag reflex test
Apnea test