The body produces various physiological signals. The accessibility to these signals is important because
(1) they can be internal (blood pressure)
(2) they may emanate from the body (infrared radiation)
(3) they may be derived from a tissue sample (blood or tissue biopsy)
All physiological signals can be grouped into the following categories –
(4)dimensions( for example : imaging)
(5)displacement (such as velocity, force, andacceleration)
(8) chemical concentration and composition.