Characteristics of Life

Characteristics of Life

• Movement• Responsivene

ss• 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.

HomeostasisBecause 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• Photopupillary reflex test• “Dolls Eyes” test • Ice water test• Corneal reflex test• Response to pain test• Gag reflex test• Apnea test