Write observations as you watch The following video link will provide more information about some of the specialized cells of the human body and how they function: http://www.youtube.com/watch?v=I8uXewS9dJU. 4:25

Levels of Organization 7.3.1 Summarize the levels of organization within the human body (including cells, tissues, organs, and systems).

Life is organized into 5 levels: Cells Tissues Organs Organ systems Organisms

There are 5 Levels of Organization in Multicellular Organisms: 1. Cells 2. Tissues 3. Organs 4. Organ Systems 5. Organisms 6. Population 7. Ecosystem

the CELL The cell is the basic unit of structure and function of a living thing. Cells are specialized by size and shape for the job they do The amoeba above is made of only one cell and it must perform all the jobs of the organism.

Do cells work together? Cells, like these nerve cells, do not work in isolation. To send orders from your brain to your legs, for example, signals pass through many nerve cells. These cells work together to perform a similar function. Just as muscle cells work together, bone cells and many other cells do as well. A group of similar cells that work together is known as a tissue.

Tissues A group of specialized cells that work together to perform the same function. There are four basic types of tissue in the human body:

Human Body Tissues

Your body has four main types of tissue: nervous tissue epithelial tissue connective tissue muscle tissue

Tissues Nervous tissue – carries impulses back and forth to the brain from the body

Nervous tissue Made up of nerve cells that sense stimuli and transmit signals. Nervous tissue is found in nerves, the spinal cord, and the brain.

Three types of muscle tissue Muscle tissue – (cardiac, smooth, skeletal) contract and shorten, making body parts move. Skeletal Cardiac Smooth

3. Epithelial tissue – covers the surfaces of the body, inside (as lining and /or covering of internal organs) and outside (as layer of skin)

4. Connective tissue – connects all parts of the body and provides support (for example tendons, ligaments, cartilage).

Groups of tissues form organs A single tissue alone cannot do all the jobs that are needed to keep an organism alive and healthy. After tissues, organs are the next level of organization of the human body. An organ is a structure that consists of two or more types of tissues that work together to do the same job.

Examples of human organs include: brain heart lungs skin kidneys Human organs are organized into organ systems. An organ system is a group of organs that work together to carry out a complex overall function. Each organ of the system does part of the larger job.

You can watch overviews of the human organ systems and their functions at the links below. http://www.youtube.com/watch?v=po8D290YF9o http://www.youtube.com/watch?v=SSqwRkDLyH4 http://www.youtube.com/watch?v=KidJ-2H0nyY

GROUPS OF ORGANS FORM ORGAN SYSTEMS Organs that work together form an organ system, which is an essential part of allowing an organism to function correctly. For instance, together, your heart, blood, and blood vessels form your cardiovascular or circulatory system.

Organisms Sum of all cells, tissues, organs and organ systems makes an organism.

Review Questions: 1. What are the different types of specialized cells? 2. What type of organisms have specialized cells? 3. What are the four types of tissue found in humans? 4. Name the main organ systems in humans. 5. How might two different organ systems depend on each other to function?

Maintaining Homeostasis The process in which organ systems work to maintain a stable internal environment is called homeostasis. Keeping a stable internal environment requires constant adjustments. Here are just three of the many ways that human organ systems help the body maintain homeostasis:

1. Respiratory system: A high concentration of carbon dioxide in the blood triggers faster breathing. The lungs exhale more frequently, which removes carbon dioxide from the body more quickly.

2. Excretory system: A low level of water in the blood triggers retention of water by the kidneys. The kidneys produce more concentrated urine, so less water is lost from the body.

3. Endocrine system: A high concentration of sugar in the blood triggers secretion of insulin by an endocrine gland called the pancreas. Insulin is a hormone that helps cells absorb sugar from the blood.

Failure of Homeostasis Many homeostatic mechanisms work continuously to maintain stable conditions in the human body. Sometimes, however, the mechanisms fail. When they do, cells may not get everything they need, or toxic wastes may accumulate in the body. If homeostasis is not restored, the imbalance may lead to disease or even death.

Review Questions 1. What are the different types of specialized cells? 2. What type of organisms have specialized cells? 3. What are the four types of tissue found in humans? 4. Name the main organ systems in humans. 5. Explain how homeostasis helps living things. 6. What is one way a person might affect their body’s ability to maintain homeostasis? 7. How might two different organ systems depend on each other to function?

The four different tissue types work together in the heart as they do in the other organs.

End of Lecture

Population A group of the same type of organisms all living together in the same place.

Ecosystem Populations living together in one area.

All the ecosystems around the world make up the biosphere.