It was previously believed that pain was simply the overloading of pressure receptors, but research in the first half of the 20th century indicated that pain is a distinct phenomenon that intertwines with all of the other senses, including touch.
12.
Motion sickness is the result of a conflict between messages delivered to the brain, with one signal coming from the inner ear that controls balance and a disparate signal coming from the eyes and pressure receptors of the skin and joints.
13.
As a result of increased vascular resistance, blood pressure rises throughout exercise and stimulates baroreceptors in the carotid arteries and aortic arch . These pressure receptors are important since they regulate arterial blood pressure around an elevated systemic pressure during exercise .
14.
Both the pulp and periodontal ligament have nociceptors ( pain receptors ), but the pulp lacks proprioceptors ( motion or position receptors ) and mechanoreceptors ( mechanical pressure receptors ) . whereas pain from the periodontal ligament will typically be well localized, although not always.
15.
In microgravity environments, these constant signals are absent : the otolith organs in the inner ear are sensitive to linear acceleration and no longer perceive a downwards bias; muscles are no longer required to contract to maintain posture, and pressure receptors in the feet and ankles no longer signal the direction of " down ".
