Many invertebrates, such as insects, also possess three basic proprioceptor types with analogous functional properties: chordotonal neurons, campaniform sensilla, and hair plates. Most vertebrates possess three basic types of proprioceptors: muscle spindles, which are embedded in skeletal muscles, Golgi tendon organs, which lie at the interface of muscles and tendons, and joint receptors, which are low-threshold mechanoreceptors embedded in joint capsules. Proprioception is mediated by mechanically sensitive proprioceptor neurons distributed throughout an animal's body. This control comes from the cerebellum, the part of the brain affecting balance.
This is seen even in infants as soon as they gain control of their neck muscles. A non-conscious reaction is seen in the human proprioceptive reflex, or righting reflex-in the event that the body tilts in any direction, the person will cock their head back to level the eyes against the horizon.Non-conscious proprioception is communicated primarily via the dorsal spinocerebellar tract and ventral spinocerebellar tract, to the cerebellum.Conscious proprioception is communicated by the dorsal column-medial lemniscus pathway to the cerebrum.In humans, a distinction is made between conscious proprioception and non-conscious proprioception: During locomotion, sensory neurons can reverse their activity when stretched, to promote rather than oppose movement. For example, consider the stretch reflex, in which stretch across a muscle is detected by a sensory receptor (e.g., muscle spindle, chordotonal neurons), which activates a motor neuron to induce muscle contraction and oppose the stretch. These mechanosensory circuits are important for flexibly maintaining posture and balance, especially during locomotion. Proprioceptors can form reflex circuits with motor neurons to provide rapid feedback about body and limb position. The sense of proprioception is ubiquitous across mobile animals and is essential for the motor coordination of the body. Invertebrates use hair plates to accomplish this a row of bristles located along joints detect when the limb moves. These proprioceptors are activated when the joint is at a threshold, usually at the extremes of joint position. In vertebrates, this is accomplished by Ruffini endings and Pacinian corpuscles. Ī third role for proprioceptors is to determine when a joint is at a specific position. These proprioceptors are active when a limb experiences resistance. Similarly, invertebrates have a mechanism to determine limb load: the Campaniform sensilla. These proprioceptors are activated at given muscle forces, which indicate the resistance that muscle is experiencing. To determine the load on a limb, vertebrates use sensory neurons in the Golgi tendon organs: type Ib afferents. There is a similar division of encoding in invertebrates different subgroups of neurons of the Chordotonal organ encode limb position and velocity. These two types of sensory neurons compose muscle spindles. In vertebrates, limb velocity and movement (muscle length and the rate of change) are encoded by one group of sensory neurons ( Type Ia sensory fiber) and another type encode static muscle length ( Group II neurons). In many animals, sensory feedback from proprioceptors is essential for stabilizing body posture and coordinating body movement. Proprioceptive signals are transmitted to the central nervous system, where they are integrated with information from other sensory systems, such as the visual system and the vestibular system, to create an overall representation of body position, movement, and acceleration. Although all mobile animals possess proprioceptors, the structure of the sensory organs can vary across species. Most animals possess multiple subtypes of proprioceptors, which detect distinct kinematic parameters, such as joint position, movement, and load. Proprioception is mediated by proprioceptors, mechanosensory neurons located within muscles, tendons, and joints. It is sometimes described as the "sixth sense". Proprioception ( / ˌ p r oʊ p r i oʊ ˈ s ɛ p ʃ ən, - p r i ə-/ PROH-pree-o- SEP-shən), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. Schematics and images of limb proprioceptors in mammals and insects
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