Logan Steele
The human body is made up of over 600 muscles, which help us do everything from moving our bodies to keeping us alive. In 1826, Charles Bell introduced the idea of muscle sense, which refers to our ability to perceive the position and movement of our body segments without visual aid. Muscle sense, or kinaesthesia, is made possible by sensory receptors located in skeletal muscle, including the Golgi tendon organ and the muscle spindle. These receptors play an important role in movement control and can detect the length of muscles, joint angle, and force. Muscle sense is not limited to humans and is essential for the motor coordination of many mobile animals.
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What You'll Learn
Muscle sense is also known as kinaesthesia
Muscle sense, or the ability to feel movements of the limbs and body, is also known as kinaesthesia. It is a remarkable ability that allows humans to perceive the position and movement of their body segments without visual aid.
The term "muscle sense" was first introduced by Charles Bell in 1826, who described it as a physiologic feedback mechanism. Bell suggested that commands are carried from the brain to the muscles, and the muscles then report back to the brain on their condition. In 1880, Henry Charlton Bastian proposed the term "kinaesthesia" instead of "muscle sense", acknowledging that some of the information sent back to the brain comes from sources other than the muscles.
Kinaesthesia is mediated by proprioceptors, a type of sensory receptor located within muscles, tendons, and joints. Most vertebrates possess three types of proprioceptors: muscle spindles, Golgi tendon organs, and joint receptors. These proprioceptors detect distinct kinesthetic parameters such as joint position, movement, and load. The information gathered by these receptors is transmitted to the central nervous system, where it is integrated with data from other sensory systems, such as the visual and vestibular systems. This integration creates an overall representation of body position, movement, and acceleration.
The role of muscle receptors in kinaesthesia has been studied through various techniques, including skin and joint anaesthesia, muscle vibration, and the disengagement of muscles from joints. These studies have shown that muscle receptors are crucial for the detection of passive movements and the sense of limb position and movement.
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Muscle sense is mediated by proprioceptors
Muscle sense, or kinaesthesia, is the ability to perceive the position and movement of body segments without visual aid. It was first described by Charles Bell in 1826, who posited that commands are carried from the brain to the muscles, and reports on the muscle's condition are sent back to the brain.
Proprioception is the sense that mediates muscle sense. Proprioceptors are a type of sensory receptor located within muscles, tendons, and joints. They are distributed throughout an animal's body and are essential for motor coordination. 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. These proprioceptors detect distinct kinesthetic parameters, such as joint position, movement, and load.
The proprioceptive sense is believed to be composed of information from sensory neurons located in the inner ear and in the stretch receptors located in the muscles and joint-supporting ligaments. Proprioceptors can form reflex circuits with motor neurons to provide rapid feedback about body and limb position. For example, in the stretch reflex, stretch across a muscle is detected by a sensory receptor, which activates a motor neuron to induce muscle contraction and oppose the stretch.
In humans, there is a distinction between conscious proprioception and nonconscious proprioception. Conscious proprioception is communicated by the dorsal column-medial lemniscus pathway to the cerebrum, while nonconscious proprioception is communicated via the dorsal spinocerebellar tract and ventral spinocerebellar tract to the cerebellum. Nonconscious proprioception can be observed in the human proprioceptive reflex, or righting reflex, where the person cocks their head back to level their eyes with the horizon when the body tilts.
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Muscle sense is essential for motor coordination
Muscle sense, or proprioception, is the ability to perceive the position and movement of body segments without visual aid. It is essential for motor coordination as it helps the body maintain posture and balance, especially during locomotion. Proprioceptors, a type of sensory receptor located within muscles, tendons, and joints, detect distinct kinesthetic parameters such as joint position, movement, and load. This information is transmitted to the central nervous system, where it is integrated with data from other sensory systems like the visual and vestibular systems to form an overall representation of body position, movement, and acceleration.
In the case of humans, there is a distinction between conscious and nonconscious proprioception. Conscious proprioception is communicated via the dorsal column-medial lemniscus pathway to the cerebrum, while nonconscious proprioception is communicated via the dorsal spinocerebellar tract and ventral spinocerebellar tract to the cerebellum. Nonconscious proprioception can be observed in the human righting reflex, where an individual cocks their head back to level their eyes with the horizon when their body tilts. This reflex is present even in infants once they gain control of their neck muscles.
Proprioceptors can form reflex circuits with motor neurons to provide rapid feedback about body and limb position, which is crucial for maintaining posture and balance. For example, the stretch reflex involves a sensory receptor, such as a muscle spindle or chordotonal neuron, detecting stretch across a muscle and activating a motor neuron to induce muscle contraction and oppose the stretch. During locomotion, sensory neurons can reverse their activity when stretched to promote movement rather than oppose it.
The role of muscle sense in movement control has been explored through studies investigating the attenuation of muscular sense during human movement. These studies have found that muscular sense is attenuated during active hand movements compared to passive movements, indicating a potential role for both peripheral and central sources in this process. The results suggest that cutaneous receptors may play a significant role in gating muscle receptor signals to the brain during movement.
In conclusion, muscle sense is essential for motor coordination as it provides the body with information about its position, movement, and acceleration, enabling the maintenance of posture and balance during locomotion. The integration of proprioceptive signals with other sensory systems allows for the coordination of body movements and the adaptation of gait patterns.
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Muscle sense is impaired during human movement
Muscle sense, or kinaesthesia, is the ability to perceive the position and movement of body segments without visual aid. It is mediated by proprioceptors, a type of sensory receptor located within muscles, tendons, and joints. These proprioceptors can form reflex circuits with motor neurons to provide rapid feedback about body and limb position, which is essential for motor coordination.
However, muscle sense can be impaired during human movement. This impairment is known as sensory attenuation, and it has been observed during cyclic stretching of the skin on the dorsum of the hand and prior to wrist flexion movements. The attenuation is believed to be caused by a combination of signals from peripheral receptors excited by movement and central sources. During active hand movements, muscle sense was significantly attenuated compared to kinaematically similar passive movements.
The source of sensory attenuation has been investigated, and evidence suggests that both peripheral and central structures play a role. Peripheral receptors, such as cutaneous receptors, are active during movements of the fingers and contribute to the gating of muscle receptor signals to the brain. Centrally mediated effects may also contribute to the attenuation of muscle sense during movement.
Impairment of muscle sense can have several consequences. Temporary loss or impairment of proprioception, for example, can lead to a disruption in an individual's sense of limb location. This can result in experiences such as needing to look down at one's limbs to be sure they are still there or falling down while walking when attention is focused on something other than the act of walking.
Furthermore, defects in the proprioceptive system can lead to ataxia, a neurological disorder characterized by impaired coordination and balance. To test for impairments in muscle sense, specific tests can be performed, such as dorsal placement of the feet or crossing of the limbs, which are commonly used in animal models.
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Muscle sense is related to muscle spindle receptors
The concept of "muscle sense" was first introduced by Charles Bell in 1826. He described it as the ability to feel movements of the limbs and body, or more specifically, the ability to perceive the position and movement of body segments without visual aid. This ability, known as kinaesthesia, is now understood to be mediated by proprioceptors, a type of sensory receptor located within muscles, tendons, and joints. These proprioceptors form reflex circuits with motor neurons to provide rapid feedback about body and limb position, allowing for the flexible maintenance of posture and balance during locomotion.
Muscle spindles, also known as stretch receptors, are a type of proprioceptor that is embedded in skeletal muscles. They are small sensory organs with an elongated shape and are involved in proprioception. Muscle spindles are the most frequently found sense organs in skeletal muscles and are present in almost every muscle. They consist of several intrafusal muscle fibres that are enclosed in a sheath of connective tissue. The sensory endings of primary (group Ia) and secondary (group II) afferent fibres coil around the non-contractile central portions of these intrafusal fibres.
The primary function of muscle spindles is to sense how much and how fast a muscle is lengthened or shortened. When a muscle is stretched, the change in length is transmitted to the spindles and their intrafusal fibres, which are subsequently stretched. This information is then relayed to the central nervous system (CNS), allowing it to compute the position and movement of our limbs in space. This is crucial for motor control, maintaining posture, and achieving a stable gait. The CNS also uses this information to regulate muscle contraction by activating motor neurons via the stretch reflex to resist further muscle stretch.
The role of muscle spindles in sensorimotor control is not yet fully understood, particularly in the context of naturalistic active movement. However, it is known that muscle spindles have their own motor supply in the form of gamma motor ('fusimotor') neurons, which can alter the firing rate and stretch-sensitivity of the afferent fibres. Additionally, muscle spindles have been shown to respond to force-related variables, particularly in relaxed muscles.
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Frequently asked questions
Muscle sense, or kinaesthesia, is the ability to perceive the position and movement of our body segments without the aid of vision.
The idea of muscle sense was first introduced by Charles Bell in 1826, who suggested that commands are carried from the brain to the muscles, and reports on the muscle's condition are sent back to the brain. Later, in 1880, Henry Charlton Bastian suggested the term "kinaesthesia" instead of "muscle sense" as some of the information sent back to the brain comes from other sources.
Muscle sense is mediated by proprioceptors, which are located within muscles, tendons, and joints. The three basic types of proprioceptors are muscle spindles, Golgi tendon organs, and joint receptors. These receptors play an important role in movement control and provide rapid feedback about body and limb position.
