Nuclear chain fiber

Information about Nuclear chain fiber

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A muscle spindle, with γ motor and Ia sensory fibers


A Nuclear chain fiber is a specialized sensory organ contained within a muscle. Nuclear chain fibers are intrafusal fibers which, along with nuclear bag fibers, make up the muscle spindle responsible for the detection of changes in muscle length.

There are 3-9 nuclear chain fibers per muscle spindle that are half the size of the nuclear bag fibers. Their nuclei are aligned in a chain and they excite the secondary nerve. They are static while the nuclear bag fibers are dynamic in comparison. The name "nuclear chain" refers to the structure of the central region of the fiber, where the sensory axons wrap around the intrafusal fibers.

The secondary nerve association involves an efferent and afferent pathway that measure the stress and strain placed on the muscle (usually the extrafusal fibers connected from the muscle portion to a bone). The afferent pathway resembles a spring wrapping around the nuclear chain fiber and connecting to one of its ends away from the bone. Again, depending on the stress and strain the muscles sustains, this afferent and efferent coordination will measure the "stretch of the spring" and communicate the results to the central nervous system.

Also note that a similar structure attaching one end to muscle and the other end to a tendon is known as a Golgi tendon. However, golgi tendons differ from nuclear chain and nuclear bag fibers in that they are considered in series rather than in parallel to the muscle fibers.

Innervation

As intrafusal muscle fibers, nuclear chain fibers both send afferent innvervation and receive efferent innervation. The afferent innervation is via Group II and Ia neruons. These project to the nucleus proprius in the dorsal horn of the spinal cord. Efferent innervation is via static γ nerons. Stimulation of γ neurons causes the nuclear chain to shorten along with the extrafusal muscle fibers. This shortening allows the nuclear chain fiber to be sensitive to changes in length while its corresponding muscle is flexed.

External links

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Nervous system, receptors: somatosensory system
Medial lemniscus
Spinothalamic tract
In a sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. In response to stimuli the sensory receptor initiates sensory transduction by creating graded potentials or action potentials in the same cell
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organ (Latin: organum, "instrument, tool") is a group of tissues that perform a specific function or group of functions. Usually there is a main tissue and sporadic tissues. The main tissue is the one that is unique for the specific organ.
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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Intrafusal fibers are muscle fibers that comprise the muscle spindle. These fibers are walled off from the rest of the muscle by a collagen sheath. This sheath has a spindle or "fusiform" shape, hence the name "intrafusal.
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1 to 3 nuclear bag fibres lie in the centre of each intrafusal muscle fibre of a muscle spindle. Each has a large number of nuclei concentrated in bags and they cause excitation of both the primary and secondary nerve fibres.

See also

  • nuclear chain fiber.

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Muscle structure is innervated by both sensory and motor neuron axons. The Muscle Spindle's functions are to send proprioceptive information about the muscle to the central nervous system, and to respond to muscle stretching.
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1 to 3 nuclear bag fibres lie in the centre of each intrafusal muscle fibre of a muscle spindle. Each has a large number of nuclei concentrated in bags and they cause excitation of both the primary and secondary nerve fibres.

See also

  • nuclear chain fiber.

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Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons.

They are motor neurons and generate tension, mechanical work and allow for movement by contracting.
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The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Together with the peripheral nervous system, it has a fundamental role in the control of behavior.
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The Golgi organ (also called Golgi tendon organ, neurotendinous organ or neurotendinous spindle), is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibres into the tendons of skeletal muscle.
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1 to 3 nuclear bag fibres lie in the centre of each intrafusal muscle fibre of a muscle spindle. Each has a large number of nuclei concentrated in bags and they cause excitation of both the primary and secondary nerve fibres.

See also

  • nuclear chain fiber.

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Intrafusal fibers are muscle fibers that comprise the muscle spindle. These fibers are walled off from the rest of the muscle by a collagen sheath. This sheath has a spindle or "fusiform" shape, hence the name "intrafusal.
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Afferent is an anatomical term with the following meanings:
  • Conveying towards a center, for example the afferent arterioles conveying blood towards the Bowman's capsule in the Kidney.

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Efferent can refer to:
  • Efferent nerve
  • Efferent ducts
  • Efferent arteriole
  • Efferent lymphatic vessel

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The Nucleus proprius is a layer of the spinal cord adjacent to the substantia gelatinosa. It receives non-noxious inputs from the periphery. Cells in this nucleus project to deeper laminae of the spinal cord, to the posterior column nuclei, and to other supraspinal relay centers
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The posterior horn (posterior column, posterior cornu, dorsal horn, spinal dorsal horn) of the spinal cord is the dorsal (more towards the back) grey matter of the spinal cord.
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spinal chord is a thin, tubular bundle of nerves that is an extension of the central nervous system from the brain and is enclosed in and protected by the bony vertebral column.
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Gamma motoneurons (γ-motoneurons), also called gamma motor neurons, are a component of the fusimotor system, the system by which the central nervous system controls muscle spindle sensitivity.
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Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons.

They are motor neurons and generate tension, mechanical work and allow for movement by contracting.
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nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. Prominent parts of a nervous system include neurons and nerves, which are used in coordination.
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In a sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. In response to stimuli the sensory receptor initiates sensory transduction by creating graded potentials or action potentials in the same cell
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Somatic sensation consists of the various sensory receptors that trigger the experiences labelled as touch or pressure, temperature (warm or cold), pain (including itch and tickle), and the sensations of muscle movement and joint position including posture, movement, and facial
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The medial lemniscus, also known as Reil's band or Reil's ribbon, is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus.
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A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles.
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Pacinian corpuscles are one of the four major types of mechanoreceptor, responsible for sensitivity to deep pressure touch and high frequency vibration.

Location

These corpuscles are found in mesenteries, especially the pancreas, and are often found near joints.
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Meissner's corpuscles (or tactile corpuscles) are a type of mechanoreceptor, responsible for sensitivity to light touch.

Location

They are distributed throughout the skin, but concentrated in areas especially sensitive to light touch, such as the fingertips, palms,
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Merkel nerve endings are mechanoreceptors found in the skin and mucosa of vertebrates that provide touch information to the brain. Each ending consists of a Merkel cell in close apposition with an enlarged nerve terminal.
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The Ruffini ending or Ruffini corpuscle is a class of slowly adapting mechanoreceptor thought to exist only in the glabrous dermis and subcutaneous tissue of humans. It is named after Angelo Ruffini.
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A free nerve ending (FNE) is an unspecialized, afferent nerve ending, meaning it brings information from the body's periphery to the brain. Free nerve endings are unencapsulated and have no complex sensory structures, unlike those found in Meissner's or Pacinian corpuscles.
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Location Cochlea
Function Amplify sound waves and transduce auditory information to the Brain Stem

Morphology Unique (see text)
Presynaptic connections None
Postsynaptic connections
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