When the muscles contract or are stretched they cause the MRO to change its firing pattern, providing information to the nervous system regarding the relative position of the abdominal segments. There are two kinds of MROs. Tonic MROs respond to chronic stretch with continuous firing and habituate slowly. Phasic MROs respond to rapid changes in posture, but habituate quickly when the posture is maintained for more than a few moments. Some animal possess specialised sensory cells that enable them to detect changes in the electromagnetic field around them.
Some snakes hunt their prey using body heat.
Sound is a c ompression wave which travels away from the source as a series of high pressure peaks separated by troughs of low pressure. The stimulus energy is mechanical - the oscillations of high and low pressure impart energy to the sensory structures evolved to detect sound. These sensory cells are usually connected to a tympanum, or eardrum, which is free to vibrate in response to changes in air pressure. The eardrum is often backed by an air-filled space so that the difference in pressure between the two sides of the membrane is sufficient to cause the membrane to deflect inwards or outwards. These deflections are then transmitted to the receptor cell, which responds with a receptor potential.