Characteristics of Life

Characteristics of Life Movement Responsiveness Growth Reproduction Respiration 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. Receives information from internal and external environment

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

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

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. reverse the direction of change. Because this tends to keep things constant, it allows us to maintain homeostasis.

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

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

Temperature Regulation

Temperature Regulation

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.

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 “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