Page 372 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

A. Visual field (right eye) B. Visual pathway and visual field deficits

Nose Temple Visual field
Left Right

Blind spot
Visual Field, Visual Pathway
90° 60° 30° 104°
a

b Optic nerve
C. Successive color contrast
Explained on p. 354 a b
Optic chiasm
c Optic tract
c
Superior Plate 12.25
colliculi
Lateral
geniculate
d body
d Optic radiation
Secondary
visual cortex
(V 2 , etc.)
Primary
visual cortex (V 1 , etc.)

Color, high-resolution stationary shapes, mo- the hypothalamus, which is responsible for cir-
vement, and stereoscopic depth are processed cadian rhythms (! p. 334).
in some subcortical visual pathways, and from The pupillary reflex is induced by sudden
V 1 onward in separate information channels. exposure of the retina to light (! p. 350). The
These individual aspects must be integrated to signal is relayed to the pretectal region; from
achieve visual perception. In diurnally active here, a parasympathetic signal flows via the
primates like humans, over half of the cortex is Edinger–Westphal nucleus, the ciliary gan-
involved in processing visual information. On a glion and the oculomotor nerve, and induces
simplified scale, the parietal cortex analyzes narrowing of the pupils (miosis) within less
the “where” and involves motor systems, and than 1 s. Since both pupils respond simul-
the temporal cortex takes care of the “what” of taneously even if the light stimulus is uni-
visual input comparing it with memory. lateral, this is called a consensual light response.
Axons of the optic tract (especially those of Meiosis also occurs when the eyes adjust for
M and γ cells) also project to subcortical re- near vision (near-vision response ! p. 360).
gions of the brain such as the pretectal region, The corneal reflex protects the eye. An ob-
which regulates the diameter of the pupils (see ject touching the cornea (afferent: trigeminal
below); the superior colliculi (! B), which are nerve) or approaching the eye (afferent: optic 359
involved in oculomotor function (! p. 360); nerve) results in reflex closure of the eyelids.
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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