This lesson will move on to the organ systems. It'll start with the one that the instructor finds most interesting—the nervous system. You'll learn how it's organized, its different jobs, and the structures that make thinking, feeling, and moving possible. You'll also learn how the nervous system works when you think you're in danger or you've suddenly been affected by physical pain. You'll use your knowledge about chemistry in this chapter, too, as this chapter talks about how nervous impulses are transmitted. Finally, this lesson will talk about some disorders of the nervous system—what causes them and their effects.

Your bones have several functions, and some aren't so obvious. For example, did you know that red blood cells are made in your bones? Or that bones store minerals that are essential for the function of your nerves and muscles? This lesson on the skeletal system will explore the structure and function of bones, and then it'll talk about different types of joints and the amazing structure of your spinal column. You'll learn about some common disorders of this system and what you can do to keep your bones strong.

Like the skeletal system, the muscular system is crucial for movement, but it has other functions, too. This lesson will discuss them in detail. Muscles are also a lot more complicated than they appear, so this lesson will spend some time talking about both the structures that you can see and the structures that you can't see without a microscope. This lesson will go over some of the specific muscles in the body and how they work together to perform specific movements. You'll also learn why even simple movements involve chemical reactions and a close coordination between this system and the nervous system. The last chapter will look at several common injuries to different parts of the muscular system.

Lesson 7 will focus on the respiratory system. As you're probably aware, it's the group of organs that allow you to get that crucial substance—oxygen—to all the cells in your body. But your respiratory system has some other functions that will be touched in this lesson. You'll learn about the anatomy of your respiratory organs and which muscles are crucial for breathing. You'll also become aware of the differences between ventilation, external respiration, internal respiration, and cellular respiration. And this lesson will talk about some illnesses that could affect your respiratory system, compromising your ability to breathe.

There's so much to learn about the circulatory system! Lesson 8 will explore the composition of blood, the various blood cells, and the different kinds of blood vessels in your body. Of course, the heart is a crucial part of the circulatory system, so this lesson will talk about its chambers, valves, coronary vessels, and electrical system. You'll learn how blood travels around the body and its important functions. This lesson will spend some time on two of the most common health problems people experience—high blood pressure and coronary artery disease. You'll finish this lesson knowing the importance of taking care of this organ system.

In this very interesting lesson, you'll learn all about the disease-fighting ability of your body. Did you know that your body is constantly bombarded with germs that want to make you sick? Lesson 9 will talk about that, as well as some of the many ways your body fights back to keep you well. The human body also has a system of vessels (similar to blood vessels) called the lymphatic system. This lesson will talk about its disease-fighting role as well as some of its other functions. You'll learn about some of the other organs in your body that are involved in the battle against disease. At the end this lesson will talk about different ways the body's disease-fighting ability can be compromised and why sometimes the body turns on its own cells.

Lesson 10 will take a close look at two different organ systems—the integumentary system (the skin) and the urinary system. Both of these systems work to get rid of waste products that would kill you if they were allowed to build up in your body. You'll learn, too, how important these two systems are in maintaining homeostasis. This lesson will spend quite a bit of time on the structure of these two systems. People are often surprised to learn how complex even the skin can be. And the structures of the urinary system, particularly the kidneys, are quite amazing. At the end of this lesson, you'll learn about kidney failure and the challenges of dialysis and kidney transplantation.

You'll never think about food the same way again after this lesson on the digestive system! Just writing about it made the instructor want to be a bit more careful about what she eats. You'll learn about all the different structures involved with converting food into the chemicals your bodies need to grow, repair tissues, and carry on all the functions of life. This lesson will also discuss the role of the three main types of foods and the importance of many different vitamins and minerals. When you finish this lesson, you'll understand the value of eating a variety of foods and how good food choices will enhance your health. This lesson will spend some time discussing two common digestive disorders, and then it'll talk about one of the most common kinds of cancer—colon cancer.