 Hello everybody, so today we're going to talk about how cells communicate with each other. And I'm definitely a fan of communication. So I thought, oh, I'll go onto Wikimedia and see if I can find a picture of someone communicating something. And I learned that there is an entire category of images in Wikimedia that the title is People with Handheld Megaphones. Who would ever need this picture, like ever? But that picture is so awesome, I can hardly stand it, so I just had to include it as the beginning of today's lecture on how cells communicate with each other. I'm going to draw your brain just to set some context. Keep your focus on me, I know that guy with his handheld megaphone is really awesome. But I want you to think for a second about our pathways that we talked about in anatomy. When you learned anatomy, you learned a whole bunch of structural components to neural pathways. And our structural components included like a sensory receptor that receives information and then an afferent pathway which is usually some sort of nerve that takes that information to the central nervous system where it's processed in some part of the brain, usually some kind of integrator. The message goes back out through an efferent pathway which is another nerve effector which is something that does something. The central nervous system as the integrator and what we'll learn here in this class is that the central nervous system is an important integrator and the endocrine system also plays a role in integrating that information coming in and out from the environment. But that, all those anatomical structures that are carrying information around, those really in the end are made up of cells. And physio is how do those cells deliver that information? How? How does it happen? Does the light stimulate an electrical message that travels to the occipital lobe of the brain? How does that happen? Well, that's what we're going to look at in this entire course. There are a few communication mechanisms or communication tools that we have to look at in more detail in order to move to the very next lecture which is on the endocrine system and the nervous system. That's where we're headed next to our big integrators. And how are they going to communicate information out to the rest of the body so that they can coordinate body systems so that body systems can maintain homeostasis? So this lecture is going to give you some tools, some strategies or some techniques that you can put into your toolbox that will enable communication in various places. And then we're going to look at, okay, what if you add this in? What if you add this in? What happens if we have this receptor over here in this strategy? So let's look at strategies first. Let's start out with looking at four different types of communication between body parts, between cells, between organ systems in the human body.