Organ Systems
1. Nervous System
My nervous system gathers and processes information from my body's internal and external environment. That means that my nervous system responds to what is going on inside and outside my body. My nervous system is made up of my brain, spinal cord, and nerves. My nervous system also helps my body move around. My brain and nerves direct and tell my muscles to contract, get tight, release, and move around.
2. Cardiovascular System
My cardiovascular system transports or carries the needed materials to my body cells and also helps remove wastes that could harm me if they stayed in my body. My cardiovascular system is made up of my heart, arteries, and veins. My cardiovascular system takes nutrients that are absorbed through the small intestines and carries the nutrients to the blood so the nutrients can be carried throughout my entire body. My cardiovascular system also carries oxygen and transports food to cells.
3. Muscular System
My muscular system enables or allows my body to move. My muscular system helps move my jaw so I can break down food. My muscles absorb nutrients, help me swallow food, and the muscles in my stomach help me to churn and squeeze my food so it can be broken down into smaller particles. Muscles help me move by contracting or shortening.
4. Integumentary (Skin) System
My integumentary system helps protect my body, keep water inside, and helps me sense the external environment. It's my skin.
5. Excretory System
My excretory system helps my body remove waste such as poop and carbon dioxide. Wastes are things that will harm my body if I don't get rid of them. My excretory system also helps regulate water in the body through the use of my kidneys.
6. Skeletal System
The skeletal system supports and protects my body. My skeletal system works with muscles to help with movement. My body's skeletal system is made up of all my bones. There are about 208 bones in my body. Without a skeletal system, I would fall to the ground like slime.
7. Digestive System
My digestive system breaks down food and absorbs the broken down materials. My digestive system is made up of my liver, stomach, gall bladder, small intestine, and large intestine. My digestive system is also made up of my mouth. My digestive system processes food and gets it ready to be transported to my body's cells.
8. Respiratory System
My respiratory system gets oxygen into my body and removes carbon dioxide out of my body. My respiratory system is made of my trachea (windpipe), diaphram, and lungs.
9. Endocrine System
My endocrine system produces chemicals called hormones that help my body control many body funtions and processes. My endocrine system is made of glands, stomach, pancreas, and kidneys.
10. Immune System
My Immune system fights disease and sickness. My immune system is made up of my liver, lymph nodes (armpits), blood, and white blood cells. My white blood cells are like my own little army. They help me fight bacteria and infections. Sometimes I don't even know how hard my white blood cell army is fighting.
11. Reproductive System
My reproductive system may one day help me create offspring (children). My reproductive system also determines the characteristics that make me a male or female. If I am a girl, my reproductive system is made of ovaries, fallopian tubes, and other female parts. If I am a boy, my reproductive system is made up of testes and other male parts.

Organ systems are interdependent like a city
1. The trash handlers remove waste and the sewage workers regulate water like the excretory system.
2. The power plant breaks down materials (fuels) to provide energy just like the digestive system breaks down food to provide energy.
3. The streets and traffic transport materials like the circulatory system.
4. The police and firefighters provide protection and support like the skeletal system.
5. The hospital, dentist, and pharmacy keep the city healthy by fighting disease and illness like the Immune system.
6. The people have offspring like the reproductive system.
7. The city council processes information from inside and outside the city and send signals like the nervous system.
8. The trees absorb carbon dioxide and expel oxygen similar to how the repiratory system absorbs oxygen and expels carbon dioxide.
9. The stop ligjts, laws, rules, and signs control regular functioning in the city like the hormones in the Endocrine system.
10. The highway allows movement like the muscular system.
My body works together to help me digest food
1. My digestive system breaks down food into smaller particles to be used by my body's cells. My mouth and stomach break down food. My small intestine completes the breakdown of food and absorbs nutrients. My large intestines allows undigested food to pass out of the body as poop. My muscles move my stomach to break down food, absorb nutrients and enables digestion of food. My cardiovascular system carries the absorbed nutrients in the blood to the rest of the body.
Levels of Organization
1. Cell
Cells are the first level of organization. They are the basic unit of structure and function.
2. Tissue
Group of cells that perform the exact same function (job)
Example: My liver tissue is made of liver cells
3.Organ
A group of tissue that perform the same function
Example: My heart tissue makes up my heart organ
4. Organ System
A group of organs that work together to perform a specific function
Example: My brain, nerves, and spinal cord are organs that work together to make my
nervous system.
Feedback Mechanisms
Feedback Mechanisms
Equilibrium: balance, stable: all parts function smoothly
Homeostasis : Process by which the body's internal environment is kept stable even if the external environment is changing.
Feedback Mechanism: A signal received by the body due to change.
Negative Feedback
This feedback mechanism occurs when the body must change what it is doing in order to return to homeostasis (equilibrium).
Example: I stop eating because I feel full.
Example: My heart rate slows down after running.
Positive Feedback
Positive feedback occurs when the body must continue what it is doing.
Example: I continue eating because I’m hungry.
Example: My heart rate speeds up because I’m jogging and need more
oxygen.
Maintaining Homeostasis
Glucose (energy comes from the breakdown of glucose)
- Eating
- Insulin
Body Temperature
- Shivering
- Sweating
Water Equilibrium
- Animals - Thirst & Kidneys
- Plants - Turgor Pressure
Chemical Reactions
- Metabolism
Turgor Pressure
A feedback mechanism for water equilibrium in plants. It is the amount of pressure against the cell wall. Water moves through the cell membrane.
Negative Feedback & Homeostasis
Most control systems of the body operate via negative feedback.
Example: An increase in carbon dioxide above normal levels (not Homeostatic)
triggers a responce which send a signal to the respiratory system to
increase breathing.
Example: When receptors in the arteries sense an increase in pressure, they
signal the Cardiovascular System to decrease impulses which decreases the
amount of blood pumped, and allows the pressure to return to homeostasis.
Homeostasis is a function of the Endocrine System. Hormones are released and carried through the circulatory system, and they control the functioning of the body.
Example: The hormone insulin is released to control glucose levels in order to return the body to homeostasis.