Chapter 3

Chapter summary

The body senses provide information about surfaces in direct contact with the skin (somatosensation), the position and movement of body parts (proprioception and kinesthesis), pain (nociception), and the position and movement of the body relative to the outside world including our sense of balance (vestibular sense).

Somatosensation is based on eight different types of receptor distributed throughout the body whose responses are conveyed to the brain to create a sensory map of the body in cortex. Our ability to discriminate small differences in tactile stimulation varies in different regions of the body in a way that closely reflects the distortion of the cortical map.

The vestibular sense involves responses from hair cells in the vestibular organs, which are displaced during head movements. Separate neural structures within each organ signal angular or linear acceleration of the head through space. Several centres in the brain receive vestibular signals and control reflexive movements of the eyes, head, neck, and limbs to cope with bodily motion and the effects of gravity.

Mismatches between vestibular information and visual information often induce various illusions of body motion and sensations of motion sickness; feelings of disorientation, dizziness, and nausea.