The ______ system consists of a group of organs that work together to perform certain tasks.

Organ systems often work together to do complicated tasks. For example, after a large meal is eaten, several organ systems work together to help the digestive system Overview of the Digestive System The digestive system, which extends from the mouth to the anus, is responsible for receiving food, breaking it down into nutrients (a process called digestion), absorbing the nutrients into... read more obtain more blood to perform its functions. The digestive system enlists the aid of the cardiovascular system Biology of the Heart The heart and blood vessels constitute the cardiovascular (circulatory) system. The heart pumps the blood to the lungs so it can pick up oxygen and then pumps oxygen-rich blood to the body.... read more and the nervous system Overview of the Nervous System The nervous system has two distinct parts: the central nervous system (the brain and spinal cord) and the peripheral nervous system (the nerves outside the brain and spinal cord). The basic... read more . Blood vessels of the digestive system widen to transport more blood. Nerve impulses are sent to the brain, notifying it of the increased digestive activity. The digestive system even directly stimulates the heart through nerve impulses and chemicals released into the bloodstream. The heart responds by pumping more blood. The brain responds by perceiving less hunger, more fullness, and less interest in vigorous physical (musculoskeletal system) activity, which preserves more blood to be used by the digestive system instead of by skeletal muscles.

Homeostasis is the term used to describe how the body maintains its normal composition and functions. Because organ systems communicate with each other, the body is able to maintain stable amounts of internal fluids and substances. Also, the organs neither underwork nor overwork, and each organ facilitates the functions of every other organ.

Communications to maintain homeostasis occur by means of the autonomic nervous system and the endocrine system. Special chemicals called transmitters carry out the communications.

*Levels of Organization*

CELLS: LEVEL ONE Within a multicellular organism there is a division of labor.  Division of labor means that the work of keeping the organism alive is divided among the different parts of the body.  Each part has a specific job to do.  And as each part does its special job, it works in harmony with all the other parts. The arrangement of specialized parts within a living thing is sometimes referred to as levels of organization.  Cells, of course, are the first level of organization.

TISSUES: LEVEL TWO In any multicellular organism, cells rarely work alone.  Cells that are similar in structure  and function are usually joined together to form tissues.  Tissues are the second level of organization. Bone cells in your body from bone tissue, a strong sokid tissue that gives you shape and support.  Blood cells in your body are part of blood tissue, a liquid tissue responsible for transporting food and oxygen throughout the body.

ORGANS: LEVEL THREE Tissues are further organized in organs, the third level of organization in living things.  Organs are groups of different tissues that work together.  Your heart, for example, is an organ made up of muscle tissue, blood tissue, and nerve tissue.  You are probably familiar with the names of many of the body organs.  The brain, stomach, kidneys, and skin are some examples.

ORGAN SYSTEMS: LEVEL FOUR Like cells and tissues, organs seldom work alone.  They "cooperate" with one another and form specific organ systems.  Organ systems are the fourth level of organization in living things.  An organ system is a group of organs working together to perform a specific function for the organism.

ORGANISMS: LEVEL FIVE You are an organism.  Dogs, trees, and butter cups are also organisms.  Even a unicellular bacterium is an organism.  An organism is an entire living thing that carries our all the basic life fuctions.  The organism is the fifth level of organization. Cells, tissues, organs, organ systems organisms--each level of organization interacts with every other level.  The smooth fuctioning of a complex organism is the result of all it various parts working together.

Return to Worksheet Menu

*All content on this page came from a website with the following address:
  http://www.ssanpete.k12.ut.us/EMS/staff/Staff/Bishop/Bishop-7/cells/lvlsorg.htm. 

I previously used this site, but it is now not accessible.  This information comes from a printed copy of the site made before the site went down.  I will be happy to relink to this site when and if it becomes available in the future.