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Equine Special Senses - Horse Anatomy (view source)
Revision as of 16:57, 22 November 2012
, 16:57, 22 November 2012→Vision
Cone cells function better in higher intensities of light (photopic vision). Most cone cells are found concentrated in the '''fovea'''. The fovea is the region of the retina where the retinal layers are parted, allowing light to fall directly onto the cone cells. Cone cells provide greater visual acuity, as each cone synapses with a single interneuron, meaning that the visual signal is not amplified, therefore is more distinct. Cone cells respond to light in the same way as rod cells. The only difference is that the pigment present in cone cells is '''iodopsin''', as opposed to rhodopsin. Retinene that is bound to opsin within the iodopsin is stimulated in the presence of light to undergo structural change to form trans-retinene.
Cone cells function better in higher intensities of light (photopic vision). Most cone cells are found concentrated in the '''fovea'''. The fovea is the region of the retina where the retinal layers are parted, allowing light to fall directly onto the cone cells. Cone cells provide greater visual acuity, as each cone synapses with a single interneuron, meaning that the visual signal is not amplified, therefore is more distinct. Cone cells respond to light in the same way as rod cells. The only difference is that the pigment present in cone cells is '''iodopsin''', as opposed to rhodopsin. Retinene that is bound to opsin within the iodopsin is stimulated in the presence of light to undergo structural change to form trans-retinene.
====Eye Movements====
*Saccades: the rapid, involuntary eye movements that occur in both eyes simultaneously when changing the point of fixation. Can be up to 400°/s.
*Smooth pursuit movements, up to 30°/s.
*Vergence, which is limited by lens accommodation.
*Vestibular, up to 30°/s - 'Nystagmus': rhythmic, oscillating motions of the eye.
====Determination of Distance====
*Parallax: eyes see objects from slightly different aspects.
*Head movement: exaggerates the parallax effect
*Vergence: the brain detects the degree to which eyes must cross.
*Overlay: determination of which objects lie in front of which.
===Autonomic Innervation of the Eye===
'''Parasympathetic innervation''' to the eye is supplied by the oculomotor nerve ([[Equine Cranial Nerves - Horse Anatomy#Oculomotor Nerve (III)|CN III]]). When parasympathetic innervation is predominant, it acts upon the circular muscles of the iris, causing '''constriction of the pupil'''.
'''Sympathetic innervation''' to the eye is via the '''cranial cervical ganglion'''. When sympathetic innervation is predominant, it acts upon the radial muscles of the iris, causing '''dilation of the pupil'''.
==Ear==
==Ear==