Chapter 14: Bones, Muscles, and Skin Key terms: Cell, cell membrane, nucleus, cytoplasm, tissue, muscle tissue, nervous tissue, connective tissue, epithelial tissue, organ, organ system, homeostasis, stress Key concepts: what are the levels of organization within the body? What is homeostasis?

Levels of organization Levels of organization in the body consists of cells, tissues, organs, and organ systems.

Cells! Yay we already know this! Cells – basic units of structure and function in living things (memorize this statement, please, you will be happy you did for the rest of your biology-loving life)

Structure of cells Cell membranes – forms the outside boundary of the cell. Nucleus – control center that directs cells’ activities (CONTAINS GENETIC MATERIAL) Cytoplasm – material within a cell that holds organelles. Clear, jellylike substance.

Functions of cells Cells carry on processes that keep organisms alive. For example: Molecules from digested food undergo chemical reactions that release energy for the body’s activities Cells get rid of waste Cells grow and reproduce

Tissues – The next unit of organization above cells (memorize THAT, too ) Tissue – group of similar cells that perform the same function. The human body has four basic types of tissue – muscle, nervous, connective, epithelial

Muscle tissue Like the muscle cells that form it, muscle tissue can contract, or shorten. This makes parts of your body move.

Nervous tissue Nervous tissue directs and controls the process of movement. It carries electrical messages back and forth between the brain and other parts of the body.

Connective tissue Connective tissue provides support for your body and connects all its parts. Examples are bones and fat.

Organs!

Organs! An organ is a structure that is composed of different kinds of tissue. Like a tissue, and organ performs a specific job. Organs are a bit more complex though, and can contain more than 1 kind of tissue. Examples: heart, lungs, skin, brain, liver, pancreas, etc

Organ systems (yes, you should know them all) Organ system – group of organs that work together to perform a major function. Circulatory – transports material to and from cells (blood, heart, veins, arteries) Endocrine - controls processes with chemicals Digestive – breaks down food Muscular – muscles! Nervous – brain, nerves, spinal cord, Skeletal – bones Respiratory – breathing (lungs, trachea) Excretory – removes wastes

Homeostasis Homeostasis is the process by which an organism’s internal environment is kept stable in spite of changes in the external environment Example: internal body temperature

Stress Stress – the reaction of your body to potentially threatening events Endocrine system releases adrenaline, which gives you energy. Your heart beats faster, you receive more oxygen. Why? Fight or flight response 