Nuclear bag fiber

From WikiMD's Wellness Encyclopedia


General Information
Latin fibra nuclearis sacci
Greek
TA98
TA2
FMA
Details
System Muscular system
Artery
Vein
Nerve
Lymphatic drainage
Precursor Mesoderm
Function Detects changes in muscle length
Identifiers
Clinical significance
Notes


Nuclear bag fibers are specialized muscle fibers found within the muscle spindle, a sensory receptor located in skeletal muscles. These fibers play a crucial role in the proprioception system by detecting changes in muscle length and the rate of that change.

Structure[edit | edit source]

Nuclear bag fibers are characterized by a central region where the nuclei are clustered together, giving them a "bag-like" appearance. This is in contrast to nuclear chain fibers, where the nuclei are arranged in a linear chain. The central region of the nuclear bag fiber is non-contractile, while the ends are contractile and attach to the extrafusal muscle fibers.

Function[edit | edit source]

The primary function of nuclear bag fibers is to sense dynamic changes in muscle length. They are innervated by afferent nerve fibers, specifically the Ia afferent fibers, which are sensitive to the rate of change of muscle length. This allows the central nervous system to receive information about the speed and extent of muscle stretch, contributing to the stretch reflex and maintaining muscle tone.

Types[edit | edit source]

There are two types of nuclear bag fibers:

  • Bag1 fibers: Sensitive to dynamic changes in muscle length.
  • Bag2 fibers: Sensitive to static changes in muscle length.

Clinical significance[edit | edit source]

Dysfunction in the muscle spindle, including nuclear bag fibers, can lead to impaired proprioception and muscle control. This can be observed in various neuromuscular disorders and conditions affecting the nervous system.

See also[edit | edit source]

References[edit | edit source]

Eric R.,

 Principles of Neural Science, 
  
 McGraw-Hill, 
 2013, 
  
  
 ISBN 978-0071390118,

Matthews, P.B.C.,

 The response of de-efferented muscle spindle receptors to stretching at different velocities, 
 The Journal of Physiology, 
 1963, 
 Vol. 168(Issue: 3), 
 pp. 660–678, 
 DOI: 10.1113/jphysiol.1963.sp007196,
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