Triceps reflex

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The triceps reflex, a deep tendon reflex, is a reflex as it elicits involuntary contraction of the triceps brachii muscle. It is initiated by the Cervical (of the neck region) spinal nerve 7 nerve root (the small segment of the nerve that emerges from the spinal cord).^[1] The reflex is tested as part of the neurological examination to assess the sensory and motor pathways within the C7 and C8 spinal nerves.

Contents 1 Testing 2 Reflex arc 3 Test indicators 4 Absence of reflex 5 Notes 6 References 7 See also 8 External links

[edit] Testing

The test is performed by tapping the tendon^{[note 1]} with the sharp end of a reflex hammer while the forearm is hanging loose at a right angle to the arm. A sudden contraction of the triceps muscle causes extension^{[note 2]}, and indicates a normal reflex.^[2][3]

[edit] Reflex arc

The arc involves the stretch receptors in the triceps tendon, from where the information travels through the C7 nerve root to the spinal cord, and the motor signal for contraction returns back through the radial nerve.^{[note 3]}

[edit] Test indicators

• Normal: There are no problems detected.
• Absence of a reflex (areflexia): If no reflex is elicited then it is essential to try again with reinforcement, with the patient clenching his or her teeth just as the reflex hammer strikes.
• Hyper-reflexia (a response far larger than considered normal): Indicates a potential upper motor neurone lesion.

[edit] Absence of reflex

An absence of reflex can be an indicator of several medical conditions: Myopathy, neuropathy, spondylosis, sensory nerve disease, neuritis, potential lower motor neurone lesion, or poliomyelitis.^[4]

Other medical problems that may cause irregular reflexes include Hyperthyroidism.

[edit] Notes

1. ^ A tendon is a strip or sheet of connective tissue that transmits the force generated by the contraction of muscle to the bone by attaching with it. Thus, in simple words, a tendon attaches a muscle to a bone
2. ^ A straightening at the elbow joint) of the forearm
3. ^ A reflex arc is the path in the nervous system through which the sensory information (stimulation—sudden stretching of the triceps tendon in this case) travels to the spinal cord in form of an action potential through a sensory neuron, and comes in contact with a motor neuron at a synapse, which also carries an action potential back to the muscle of origin and results in its (triceps's) contraction. Note that the contact between the sensory and motor neurons does not require immediate involvement of the brain making it involuntary, though the sensation of stretch (as the hammer hits the skin and tendon beneath) and contraction of the muscle are both sent to the brain making the subject aware of the entire testing procedure.

[edit] References

[edit] See also

• Reflex arc
• Reflex
• Golgi tendon organ

[edit] External links

• Illustration of reflex testing

v • d • e Nervous system physiology: neurophysiology - reflex Cranial nerve midbrain: Pupillary light reflex - Accommodation reflex pons/medulla: Jaw jerk reflex - Corneal reflex - Caloric reflex test/Vestibulo-ocular reflex - Gag reflex Tendon reflexes upper limb: Biceps reflex - Brachioradialis reflex - Extensor digitorum reflex - Triceps reflex lower limb: Patellar reflex - Ankle jerk reflex - Plantar reflex Primitive reflexes Galant - Grasp - Moro - Rooting - Stepping - Sucking - Tonic neck Other Baroreflex - Acoustic reflex - H-reflex - Oculocardiac reflex - Stretch reflex - Startle reaction