Communication in the human body takes many forms. Our nervous system communicates with our organs and tissues using electrical signals. Endocrine glands secrete chemical messengers called hormones that travel through the blood to a target and bring about change. Our special senses and our skeletal and muscular systems allow us to move, gesture and speak, to communicate our ideas, and to interact with the world around us. A breakdown in communication would disrupt the body’s overall homeostasis or internal balance. In this unit, students will explore the concept of communication as it applies to everyday life, machines and technology, and as it applies to their own body. In the next lesson, students will explore how the brain sends and receives electrical signals and how electricity is generated and propagated through human systems. In the third lesson, students will examine chemical communication in the human body. Students will investigate the components of the endocrine system, the mechanisms of hormone action and the regulatory power of feedback. They will show, using a feedback loop, how the body uses chemicals to maintain healthy blood sugar levels. Finally, students will explore how the body communicates with the outside world by examining the structure of an eye and completing an eye dissection. They will investigate the many aspects of visual perception by completing station exercises and by interpreting results for tests in visual acuity, depth perception, peripheral vision, color vision, accommodation, optical illusions, and afterimages. Students will use an eye model to investigate the function of the lens in the eye and will use this model to explore the power of corrective lenses.