Sherrington’s Law

Sherrington’s Law of Reciprocal Innervation

Whenever an agonist receives an impulse to contract, an equivalent inhibitory

impulse is sent to its antagonist, which relaxes and actually lengthens

• Agonist Muscles

− AKA prime mover

− On contracting it automatically is checked and controlled by the opposing simultaneous

contraction of another muscle

• Antagonist Muscles

− An agent that acts in physiological opposition

− A muscle that contracts and limits the action of an agonist with which it is paired

Important Concepts to Understand

• Synergistic Muscles

− Two muscles moving the eye in the same direction

• Yolk Muscles

− AKA Contralateral Synergists

− Pair of muscles producing conjugate ocular movements

Important Concepts to Understand

Right Eye Left Eye Movement Position of Gaze

Lateral Rectus Medial Rectus Move the globe to the right Dextroversion

Medial Rectus Lateral Rectus Move the globe to the left Laevoversion

Superior Rectus Inferior Oblique Move the globe upward Dextroelevation

Inferior Oblique Superior Rectus Move the globe upward Laevoelevation

Superior Oblique Inferior Rectus Move the globe downward Laevodepression

Inferior Rectus Superior Oblique Move the globe downward Dextrodepression

Paired Agonist Muscles

Eye movements previously mentioned visible via motility test

Physiologically and clinically important because it explains why

strabismus occurs due to paralysis of extraocular muscle

Importance of Sherrington’s Law

• Measure electrical potential changes within a muscle based on muscle fibre contraction indicating overall neuromuscular activity

Electromyography (EMG)

• Uses:

− Strabismus

− Patients with Duane’s Syndrome

Sherrington’s Law – Clinical Use

Duane’s Syndrome

• Not only applicable to EOM

• It applies to all striated muscles of the body

Something to Take Home

• http://www.cybersight.org/bins/content_page.asp?cid=735-2858-4397-4404-4654-4704-4707

• http://www.vestib.com/EOM-muscles-movements.html

• http://onlinelibrary.wiley.com/doi/10.1111/j.1442-9071.1982.tb01632.x/pdf

• http://www.authorstream.com/Presentation/optom.rawaa-513087-4th-lecture/

• https://books.google.gy/books?id=DN60U5yZkyQC&pg=PA63&lpg=PA63&dq=sherrington+law+muscles&source=bl&ots=_bIrlBf7_d&sig=mpcXewinO1L7NwpY6B84Q4h3tS0&hl=en&sa=X&ved=0CCEQ6AEwAjgKahUKEwiRgp2h8tzIAhXHGh4KHSheDNc#v=onepage&q=sherrington%20law%20muscles&f=false

Reference