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Stretch reflex

Structures

The stretch reflex is accomplished through several different structures. In the muscle, there are muscle spindles, whose extrafusal muscle fibers lie parallel to the muscle and sense changes in length and velocity. The afferent sensory neuron is the structure that carries the signal from the muscle to the spinal cord. It carries this action potential to the dorsal root ganglion of the spinal cord. The efferent sensory neuron is the structure that carries the signal from the spinal cord back to the muscle. It carries the action potential from the ventral root of the spinal cord to the muscle down the alpha motor neuron[1]. This synapsis on the first structure discussed, the extrafusal fibers of the muscle spindle.


Clinical Significance

The knee jerk reflex is an example of the stretch reflex and it is used to determine the sensitivity of the stretch reflex. Reflexes can be tested as part of a neurological examination. To test the reflex, the muscle should be in a neutral position. The patient should flex the muscle being tested for the clinician to locate the tendon. After the muscle is relaxed, the clinician strikes the tendon. The response should be contraction of the muscle. If this is the knee jerk reflex, the clinician should observe a kick. The clinician rates the response.


The patellar tendon reflex is an example of the stretch reflex.

Spinal Control

Spinal control of the stretch reflex means the signal travels between the muscle and spinal cord. The signal returns to the muscle from the same spinal cord segment as where it entered the spinal cord. This is the shortest distance for a reflex signal to travel, thus creating a fast response. These responses are often referred to short latency stretch reflexes. An example of a short latency stretch reflex is the withdrawal reflex.

Supraspinal Control

Supraspinal control of the stretch reflex means the signal travels above the spinal cord before traveling back down to the same segment it entered the spinal cord from. The responses from these pathways are often termed medium or long latency stretch reflexes, because the time course is longer due to distance it needs to travel.

Clinical significance

Include the following citation for grading the responses: [2] Include the following citation for the clasp-knife response: [3]


Trying to make things bold.

Make edits to an article here?

  1. ^ Dolbow, James; Bordoni, Bruno (2019), "Neuroanatomy, Spinal Cord Myotatic Reflex", StatPearls, StatPearls Publishing, PMID 31869093, retrieved 2019-12-30
  2. ^ "StatPearls". 2019. PMID 31082072. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ Ashby P, Mailis A, Hunter J (1987). "The evaluation of "spasticity"". Can J Neurol Sci. 14 (3 Suppl): 497–500. doi:10.1017/s0317167100037987. PMID 3315151.{{cite journal}}: CS1 maint: multiple names: authors list (link)