Educational video describing the anatomy of the tensor fasciae latae muscle. Become a friend on facebook: http://www.facebook.com/drebraheim. Follow me on twitter: https://twitter.com/#!/DrEbraheim_UTMC. 1  Education. 2  Standard YouTube License.
The specific cause of body aches (myalgia) are the interleukins, which are primarily produced by the macrophages. These interleukins cause pain, body aches, hypersensitivity of the nerves, etc. Some of the interleukins (such as IL-2) cause the fever seen during the flu, and probably the headaches. Since these interleukins are produced in response many different kinds of bacterial and viral infections, symptoms such as fever, myalgia, and headaches can be seen in infections by many different etiologic agents.
This causes pain, nausea and muscle tightness in the chest -- hence the feeling that your heart is heavy, or those sharp pains when you see your crush with someone else. So essentially, your brain sends a message to a nerve. The nerve responds by making your muscles tighten in your chest. It feels like your heart is heavier, or that you're in pain, or both. When you stop being sad, your brain stops sending the message.