Levels of Organization and Homeostasis

Structural Levels of Organization

I. Chemical level (Atoms): All matter, living and non-living is composed of the smallest particles called atoms.

– There are 98 naturally occurring atoms in the universe.

– 96% of the human body is made of only four:

Carbon, Hydorgen, Oxygen and Nitrogen

65-75% of body mass is water!

Structural Levels of Organization

Atoms may react together to form ions and molecules– Ions such as H+, Na+, Ca+, K+, Fe++, Mg++, Cl-– Molecules such as H2CO3, H2O, O2

– Large molecules or Macromolecules, provide structural foundation for the body include

CarbohydratesFats (lipids)ProteinsAnd Nucleic acids (DNA and RNA)

Levels of Organization In Multicellular Organisms:

I. Individual cells: Like the bricks that a building is constructed, cells are the building blocks of all living things.

Function of cells related to structure

Muscle cells are long Bone cells are hard Nerve cells are branched Covering cells are flat Structure and function change with age

(Thymus disappears, bones become brittle…)

Sizes and Shapes

Size and shape depends on function Nerve cells: are long and may have the

length of several feet (from muscles of the foot to the brain)

Levels of Organization II. Tissue Level: Tissues are a

group of cells similar in structure and function containing similar intercellular fluid and organelles

There are Four Primary types of tissues and each has several subtypes.

– Connective: Tissue that connects one tissue to another

– Epithelial: Tissue that covers and protects.

– Muscle: Specialized for movement

– Nervous: Tissue that receives, sends, processes and stores information.

Levels of Organization

III: Organ Level: Organs are two or more tissues put together in a specific pattern to carry out a particular job.

Levels of Organization IV. System Level: Several organs working together

to carry out larger body process.– There are 11 systems in the human body:

– Integumentary– Skeletal– Muscular– Nervous– Endocrine– Cardiovascular– Lymphatic– Respiratory– Digestive– Urinary– Reproductive

Sizes and Shapes

Blood cells – are flat for gas exchange

Levels of Organization

V. Organism Level: The entire body’s collection of all systems

Criteria for Life

Responds to stimuli- Excitable Ingest food- eats Digest food- metabolize food to get energy Excrete- get rid of wastes and unused food Secretion- makes and uses them (saliva, digestive

enzymes…) Reproduce- repair, grow, continue the species Movement- of materials within cells, through the

environment

Homeostasis: The Balance Of Life

Nearly constant internal state The body normally maintains in function such

as composition of body fluids, temperature, and levels of acid and bases (like the thermostat in a house)

Homeostasis and Negative feedback

Refers to a mechanism that reverses a response back to a normal state.

Example: When salt concentration rises above normal after a meal, Kidneys increase the rate of removing salt by excreting it in the urine.

Homeostasis and Positive feedback

Refers to a change from the normal state to promote the change even further.

Unlike negative feedback, positive feedback does not restore the body functions back to normal.

In some cases, can lead to a “vicious circle” of continuing deterioration.

Some positive feedbacks that operate under normal conditions.

Example: Uterine contraction during child birth- progressive stronger contractions until child is passed completely through the birth canal.

Health and Disease

Disruption of homeostasis Can vary from minor to grave and even fatal. Task of the physician is to identify these

imbalances (diseases) at an early stage so that effective actions may be taken.

Health is restored when homeostasis is brought back to balance.

Classification of Disease

Diseases may be classified into groups that share similar development

Infectious –– Viral: diseases caused by viruses such as

Measles, Mumps, Rubella, Influenza– Bacterial: diseases caused by single celled

organisms.

Classification of Disease

Congenital: arise sometime before birth. – Can be inherited (Down’s Syndrome) or – caused by disease causing agent that crosses the placental barrier

(German measles).

Immunological: Body’s defense system (initiated by other infections) respond by causing destruction of the body’s own tissues,

– strep throat - may cause heart defects, – measles - may cause deafness and or blindess.

Classification of Disease

Metabolic Diseases: Disease that affect the body’s use of energy. Diabetes is an example. The body cannot use glucose sugar properly.

Neoplastic Diseases: Loss of control of normal cell growth and reproduction. Cells become abnormal and develop into tumors that threaten normal activity of tissues and organs. cancer arises in this manner.