Do all of your cells do the same thing? Give a few examples.

There are nearly a hundred trillion cells that make up the human body. Every cell is an independent unit and an interdependent part of a larger community. All the body systems work together so the body functions properly.

An organism is a living thing made of a group of organs systems. Organ systems are living things made of a group of organs that contribute to a specific function within the body. Organs are living things made of tissues that work together to perform a specific, complex function. Tissues are living things made of a group of cells with similar structures and functions. Cells are the smallest unit of life.

Different tissue types work together within organs: Muscle tissue (most abundant): controls internal movements of materials (ex: blood, food) Epithelial tissue: closely packed cells covering the surface of the body and line internal organs (ex: inside chambers of heart, glands) Connective tissue: holds organs in place and binds different parts of the body together (ex: tendons, ligaments) Nervous tissue: receives messages from the body’s external and internal environments, analyzes the data, and directs response (ex: controls heart beat)

The eleven organ systems of the human body work together to maintain homeostasis. 1. Nervous7. Integumentary 2. Respiratory 8. Digestive 3. Excretory9. Skeletal 4. Muscular10. Circulatory 5. Endocrine11. Reproductive 6. Lymphatic Try to identify as many systems as possible on picture… What are some organs in each system?

Nervous SystemIntegumentary SystemSkeletal SystemMuscular SystemCirculatory System Section 35-1 Figure 35-2 Human Organ Systems Part I

Respiratory SystemDigestive SystemExcretory System Endocrine SystemReproductive SystemLymphatic System Section 35-1 Figure 35-2 Human Organ Systems Part 2

Nervous: coordinates the body’s response to change in the internal and external environments. Integumentary: serves as a barrier against infection and injury, helps to regulate body temperature, provides protection against UV radiation from the sun Respiratory: provides oxygen needed for cellular respiration and removes excess carbon dioxide from the body Digestive: converts foods into simpler molecules that can be used by the cells of the body, absorbs food Excretory: eliminates waste products of metabolism from the body, maintains homeostasis Skeletal: supports the body, protects internal organs, allows movement, stores mineral reserves, provides a site for blood cell formation

Muscular: works with skeletal system to produce voluntary movement, helps to circulate blood and move food through the digestive system Circulatory: brings oxygen, nutrients, and hormones to cells, fights infection, regulates body temperature Endocrine: controls growth, development, metabolism, and reproduction Reproductive: produces reproductive cells (in females, nurtures and protects developing embryo Lymphatic: helps protect the body from disease, collects fluid lost from blood vessels and returns the fluid to the circulatory system

While walking along a dusty path, you begin to cough. As you continue your walk, a small insect comes flying toward you. You blink and then duck so that it misses you. These actions are just a few examples of homeostasis. Homeostasis is the process by which organisms keep internal conditions relatively constant despite changes in their external environments. 1. List three other examples of homeostasis that occur in organisms. 2. Why is homeostasis important to an organism? Interest Grabber

Your organ systems are working together constantly trying to maintain a controlled, stable internal environment. Remember: Your cells need a constant supply of nutrients and oxygen at a stable temperature for cellular respiration, and then the waste products need to be removed.

Heating system turns on Thermostat senses temperature change and switches on heating system Thermostat senses temperature change and switches off heating system Room temperature decreases Feedback Inhibition

The process by which the product of a system shuts down the system or limits its operation. When the system is switched on, it produces a product that changes the internal environment = “feedback” When the change (feedback) is detected, it shuts down the system = “inhibition” This system is usually automatic and very stable.

Biological systems achieve homeostasis through feedback inhibition. All that is needed is a system that regulates some aspects of the cellular environment, and the system responds to feedback by switching on or off as needed.

Body temperature remains stable with a balance of heat production and heat loss. The hypothalamus in your brain contains nerve cells that monitor skin temperature and core temperature. If core temperature drops, the hypothalamus produces chemical signals throughout the body to speed up activities producing heat. When the nerve cells detect a temperature rise, the feedback inhibits the production of the chemical signals and prevents the temperature from rising too high. If you’re very cold, your hypothalamus releases chemical signals for your muscles to shiver involuntarily, producing heat until your body temperature reaches normal again. If you’re too warm, your hypothalamus slows down cellular activities, making you feel tired/sluggish and you sweat, which cools your body surface by evaporation, until you reach a normal temperature again.