Identifier |
wh_ch17_p826_2 |
Title |
Walsh & Hoyt: Phasic Velocity and Tonic Position Commands to Orbital Forces that Determine Ocular Motility |
Creator |
James A. Sharpe, MD, FRCP(C) (1941-2013); Agnes Wong, MD, PhD, FRCSC |
Affiliation |
(AW) University of Toronto |
Subject |
Ocular Motor System; Ocular Motor Systems; Anatomy; Physiology; Phasic Velocity; Tonic Position Commands; Ocular Motility |
Description |
Before discussing the central organization of the different ocular motor systems, it is useful to review the nature of the mechanical properties of the orbital tissues, since passive forces must be overcome to move the eyes and, once the eyes are in position, to hold them in place. The predominant orbital forces are elasticity and viscosity. The moment of inertia of the human eye is so small relative to other tissue forces that for practical purposes it can be ignored. Viscous forces are the major hindrance to movement of the globe within the orbit. For fast eye movements, therefore, a powerful phasic contraction of the extraocular muscles is necessary to overcome viscous drag. This high-frequency phasic discharge provides a ""burst"" of neural activity that stimulates muscle contraction. The very-high-frequency burst that is required to drive the eyes at saccadic speeds is called a pulse of innervation. |
Date |
2005 |
Language |
eng |
Format |
application/pdf |
Type |
Text |
Source |
Walsh and Hoyt's Clinical Neuro-Ophthalmology, 6th Edition |
Relation is Part of |
Walsh and Hoyt's Clinical Neuro-Ophthalmology Walsh and Hoyt's Clinical Neuro-Ophthalmology |
Collection |
Neuro-Ophthalmology Virtual Education Library: Walsh and Hoyt Textbook Selections Collection: https://NOVEL.utah.edu |
Publisher |
Wolters Kluwer Health, Philadelphia |
Holding Institution |
Spencer S. Eccles Health Sciences Library, University of Utah |
Rights Management |
Copyright 2005. For further information regarding the rights to this collection, please visit: https://NOVEL.utah.edu/about/copyright |
ARK |
ark:/87278/s60039mf |
Setname |
ehsl_novel_whts |
ID |
186425 |
Reference URL |
https://collections.lib.utah.edu/ark:/87278/s60039mf |