Kinesthetic inputs

Abstract

Kinesthesia is the sensory system which tells you what is being done to your body and what your body is doing. Kinesthesia and proprioception are synonymous. The main kinesthetic sensations are those of position and movement of the body parts with respect to each other and of muscle force and effort. These sensations derive from sensory receptors in the muscle, skin, and joints and from central signals related to motor output. The sensory receptors in the muscle are the muscle spindles and Golgi tendon organs. The muscle spindle primary endings are sensitive to the velocity and extent of muscle stretch, whereas muscle spindle secondary endings give a less dynamic signal of muscle length. The tendon organs signal muscle force. The skin receptors that are important for kinesthesia signal stretch of the skin, and joint receptors are sensitive to stretch of the joint capsule and ligaments. Signals from muscle spindles and skin and joint receptors combine together to provide perceptions of joint movement and position. During voluntary actions, it is likely that they are interpreted along with central signals (or corollary discharges) related to the production of movements. Signals from tendon organs and corollary discharge related to the strength of muscle activation provide sensations of muscle force. While kinesthetic sensations give information on what the body is doing, these sensations can also be used to judge some of the properties of objects with which the body interacts. For example, kinesthesia can be used to judge objects' heaviness or stiffness. In addition, inputs from vision, touch, and the vestibular apparatus must be combined with kinesthetic signals to allow us to interpret the environment. For example, perception of the direction of a visual object requires knowledge of the direction of gaze as well as the position of the object in the visual field. Finally, proprioceptive sensory signals are critical for the control of movement. They are closely incorporated into the control of movement at all levels of the nervous system. They act in multiple reflex pathways and also have conscious influences. Without afferent proprioceptive signals, the control of movement becomes almost impossible.