Tonic vibration reflex

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Tonic vibration reflex is a sustained contraction of a muscle subjected to vibration. This reflex is caused by vibratory activation of muscle spindles — muscle receptors sensitive to stretch.

Muscle contractile soft tissue of animals

Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system via peristalsis.

Tonic vibration reflex is evoked by placing a vibrator — which in this case is typically an electrical motor with an eccentric load on its shaft — on a muscle's tendon. 30–100  Hz vibration activates receptors of the skin, tendons and, most importantly, muscle spindles. Muscle spindle discharges are sent to the spinal cord through afferent nerve fibers, where they activate monosynaptic and polysynaptic reflex arcs, causing the muscle to contract.

A vibrator is a mechanical device to generate vibrations. The vibration is often generated by an electric motor with an unbalanced mass on its driveshaft.

Afferent nerve fiber

Afferent nerve fibers refer to axonal projections that arrive at a particular region ; as opposed to efferent projections that exit the region. These terms have a slightly different meaning in the context of the peripheral nervous system (PNS) and central nervous system (CNS).

A reflex, or reflex action, is an involuntary and nearly instantaneous movement in response to a stimulus. A reflex is made possible by neural pathways called reflex arcs which can act on an impulse before that impulse reaches the brain. The reflex is then an automatic response to a stimulus that does not receive or need conscious thought.

The effects of sustained vibratory stimulation on muscle contraction, posture and kinesthetic perceptions are much more complex than merely contraction of the muscle being vibrated.

Perception organization, identification, and interpretation of sensory information in order to represent and understand the environment

Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information, or the environment.

Russian scientists Victor Gurfinkel, Mikhail Lebedev, Andrew Polyakov and Yuri Levick used vibratory stimulation to study human posture control and spectral characteristics of electromyographic (EMG) activity.

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Skeletal muscle one of three major muscle types

Skeletal muscle is one of three major muscle types, the others being cardiac muscle and smooth muscle. It is a form of striated muscle tissue, which is under the voluntary control of the somatic nervous system. Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons.

Muscle spindle specialized innervated muscle structure involved in the reflex action and in proprioception

Muscle spindles are stretch receptors within the body of a muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be processed by the brain as proprioception. The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, by activating motor neurons via the stretch reflex to resist muscle stretch.

Reflex arc

A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain. However, the brain will receive the sensory input while the reflex is being carried out and the analysis of the signal takes place after the reflex action.

A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. Normally there are four main types in glabrous, or hairless, mammalian skin: lamellar corpuscles, tactile corpuscles, Merkel nerve endings, and bulbous corpuscles. There are also mechanoreceptors in hairy skin, and the hair cells in thoreceptors of primates like rhesus monkeys and other mammals are similar to those of humans and also studied even in early 20th century anatomically and neurophysiologically.

Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord, and are associated in two ways with an alpha motor neuron.

Patellar reflex

The patellar reflex or knee-jerk (myotatic) (monosynaptic) is a stretch reflex which tests the L2, L3, and L4 segments of the spinal cord.

Tensor tympani muscle muscle in the inner ear

The tensor tympani is a muscle within the ear, located in the bony canal above the osseous portion of the auditory tube. Its role is to damp loud sounds, such as those produced from chewing, shouting, or thunder. Because its reaction time is not fast enough, the muscle cannot protect against hearing damage caused by sudden loud sounds, like explosions or gunshots.

Gamma motor neuron

A gamma motor neuron, also called gamma motoneuron, is a type of lower motor neuron that takes part in the process of muscle contraction, and represents about 30% of fibers going to the muscle. Like alpha motor neurons, their cell bodies are located in the anterior grey column of the spinal cord. They receive input from the reticular formation of the pons in the brainstem. Their axons are smaller than those of the alpha motor neurons, with a diameter of only 5 μm. Unlike the alpha motor neurons, gamma motor neurons do not directly adjust the lengthening or shortening of muscles. However, their role is important in keeping muscle spindles taut, thereby allowing the continued firing of alpha neurons, leading to muscle contraction. These neurons also play a role in adjusting the sensitivity of muscle spindles.

Soleus muscle

In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg. It runs from just below the knee to the heel, and is involved in standing and walking. It is closely connected to the gastrocnemius muscle and some anatomists consider them to be a single muscle, the triceps surae. Its name is derived from the Latin word "solea", meaning "sandal".

The gastrocnemius muscle is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a two joint muscle. The muscle is named via Latin, from Greek γαστήρ (gaster) "belly or stomach" and κνήμη (knḗmē) "leg"; meaning "stomach of leg".

First described by German neurologist Oskar Kohnstamm (1871–1917) in 1915, Kohnstamm's phenomenon is a sustained involuntary contraction of a muscle after a prolonged voluntary contraction. The simplest demonstration, sometimes called "the floating arms experiment", is to have a subject press the arms against a door frame or wall for about thirty seconds, and then step away. The arm will involuntarily rise.

The stretch reflex is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length.

The Golgi tendon reflex is a normal component of the reflex arc of the peripheral nervous system. In a Golgi tendon reflex, skeletal muscle contraction causes the antagonist muscle to simultaneously lengthen and relax. This reflex is also called the inverse myotatic reflex, because it is the inverse of the stretch reflex. Though muscle tension is increasing during the contraction, alpha motor neurons in the spinal cord supplying the muscle are inhibited. However, antagonistic muscles are activated.

Locomotor effects of shoes

Locomotor effects of shoes are the way in which the physical characteristics or components of shoes influence the locomotion neuromechanics of a person. Depending on the characteristics of the shoes, the effects are various, ranging from alteration in balance and posture, muscle activity of different muscles as measured by electromyography (EMG), and the impact force. There are many different types of shoes that exist, such as running, walking, loafers, high heels, sandals, slippers, work boots, dress shoes, and many more. However, a typical shoe will be composed of an insole, midsole, outsole, and heels, if any. In an unshod condition, where one is without any shoes, the locomotor effects are primarily observed in the heel strike patterns and resulting impact forces generated on the ground.

Spinal locomotion

Spinal locomotion results from intricate dynamic interactions between a central program in lower thoracolumbar spine and proprioceptive feedback from body in the absence of central control by brain as in complete spinal cord injury (SCI). Following SCI, the spinal circuitry below the lesion site does not become silent rather it continues to maintain active and functional neuronal properties although in a modified manner.

Neuromechanics

As originally proposed by Enoka, neuromechanics is a field of study that combines concepts from biomechanics and neurophysiology to study human movement. Neuromechanics examines the combined roles of the skeletal, muscular, and nervous systems and how they interact to produce the motion required to complete a motor task.

Cutaneous reflex in human locomotion

Cutaneous, or skin reflexes, are activated by skin receptors and play a valuable role in locomotion, providing quick responses to unexpected environmental challenges. They have been shown to be important in responses to obstacles or stumbling, in preparing for visually challenging terrain, and for assistance in making adjustments when instability is introduced. In addition to the role in normal locomotion, cutaneous reflexes are being studied for their potential in enhancing rehabilitation therapy (physiotherapy) for people with gait abnormalities.

Golgi tendon organ

The Golgi tendon organ (GTO) is a proprioceptive sensory receptor organ that senses changes in muscle tension. It lies at the origins and insertion of skeletal muscle fibers into the tendons of skeletal muscle. It provides the sensory component of the Golgi tendon reflex.

References

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