The body has mechanisms to alter or maintain blood pressure and blood flow. There are sensors that sense blood pressure in the walls of the arteries... My WebMD Sign In, Sign Up
Perhaps while we're not watching, the denizens of Dark Shadows carry-on, caught in another inter-dimensional wing of Collinwood. If you peer out the corner of your eye, you may catch a glimmer of this shadowy activity, perhaps in Dark Shadows Collection 14, or Dark Shadows Collection 22.
Shadows are formed when an opaque object is placed in the path of light rays. An object through which no light can pass is known as opaque. One such example is your body. Since light cannot pass through your body, it forms a dark region. This dark region where the light cannot reach is known as a shadow. Opaque objects form clear dark shadows. A transparent object does not make any shadow as light passes straight through it. Translucent objects create faint shadows as light is able to pass only partially through them.