Ch. 14.1 Notes

Body Organization and Homeostasis

• The levels of organization in the human body consist of cells, tissues, organs, and organ systems.

• The smallest unit is the cell.• Cell < Tissue < Organ < Organ System

Cells

• The cell is the basic unit of structure and function in a living thing.

• Complex organisms are composed of many cells.

• The human body contains about 100 trillion cells.

• Cells are so tiny, you need a microscope to see them.

Structures of Cells

• The cell membrane forms the outside boundary of the cell.

• The nucleus controls the cell and contains DNA.

• The fluid a between the cell membrane and the nucleus is the cytoplasm.

Functions of Cells

• Cells carry on the processes that keep organisms alive.

• Cells also grow and reproduce through Mitosis and Meiosis.

• They also get rid of waste products that result from their activities.

Tissues

• A tissue is a group of similar cells that perform the same function.

• The human body contains four basic types of tissue:

• 1. muscle tissue• 2. nervous tissue• 3. connective tissue• 4. epithelial tissue

Muscle Tissue

• Like the muscle cells that form it, Muscle tissue contract, or shorten.

• This characteristic allows for your body to move!

Nervous Tissue

• Nervous tissue directs and controls the process of movement.

• Nervous tissue sends out electrical messages back and forth between the brain and other parts of the body.

• It’s like the “wiring” of your body.

Connective Tissue

• Connective tissue provides support for your body and connects all the parts.

• It includes bones and fat cells.

Epithelial Tissue

• The surfaces of your body, inside and out, are covered by epithelial tissue.

• Epithelial tissue = skin cells• It also lines the digestive tissue (your stomach,

intestines, etc.)

Organs and Organ Systems

• An organ is a structure composed of different kinds of tissues.– Stomach, heart, brain, lungs,

etc.• Like tissue, an organ has a

specific job. • However, the job of an organ

is very complex. It normally does multiple things.

Organ Systems

• Each organ in your body is part of an organ system, which is a group of organs that work together to perform major function.

• We will talk about 8 organ systems:– Circulatory -- Endocrine – Digestive -- Muscular– Nervous -- Excretory– Skeletal -- Respiratory

Circulatory System

• Transports materials to and from cells.– Heart– Veins, arteries– Blood cells

Digestive System

• Breaks down food and absorbs nutrients.– Mouth, stomach, small and large intestine, colon

Nervous System

• Detects information from the environment and controls body functions.– Brain, spinal cord, nerves

Skeletal System

• Supports and protects the body.– Bones, skull, ribs, etc.

Endocrine System

• Controls many body processes by means of chemicals.– Liver, kidney, thyroid, “glands”

Muscular System

• Enables movement of the body and internal organs.– Biceps, heart, stomach, thigh, calf

Excretory System

• Removes waste (poop, etc.).– Blood cells, kidneys, bladder, colon

Respiratory System

• Takes in oxygen and eliminates carbon dioxide.– Lungs, mouth, nose

Homeostasis

• The process by which an organism’s internal environment is kept stable in spite of changes in the external environment.– “To stay the same”– Sweat to keep cool– Shiver to keep warm– Drink water to stay hydrated

Stress and Homeostasis

• Sometimes, things happen to disrupt homeostasis.

• Stress is the reaction of your body to potentially threatening, challenging, or disruptive events.

• Playing sports causes “stress” on your body. To maintain homeostasis while playing basketball (stress), you sweat to keep cool.