Page 16 - LN-NEURAL CONTROL & COORDINATION

aqueous chamber, which contains a thin watery fluid called aqueous humour.

(ii) Vitreous Humour The space between the lens and retina is called the
vitreous chamber, which is filled with a transparent get called the vitreous
humour.
Mechanism of Vision
In human eyes, the vision is called binocular vision (i.e., both the eyes can be
focused on a common object).
(i) Retina receives light rays (in visible wavelength) through the cornea and lens
generate impulses in rods and cones.

(ii) The photosensitive compounds (photopigments) in the human eye are
composed of opsin (a protein) and retinal (an aldehyde of vitamin-A).
(iii) The received light induces dissociation of the retinal from opsin resulting in
changes in the structures of the opsin. This causes the changes in the
permeability of membrane.
As a result, the potential differences are generated in the photoreceptor cells.
This produces a signal that generates action potential in the ganglion cells

through the bipolar cells.
(iv) These impulses (action potentials) are transmitted by the optic nerves to
the visual cortex of the brain.
(v) In brain, neural impulses are analysed and the image formed on the retina
is recognised (based on earlier
memory and experience).
Common Diseases
(i) Cataract This is a eye disease generally occur in older people (above 60

years). Lens becomes opaque due to disease or ageing. It leads to blindness. It
can be corrected by wearing suitable glasses or by replacing the defective lens
with a normal lens from a donor.
(ii) Myopia (near or short sightedness) It occurs due to convexity of lens or
longer eye ball, which results in an image of distant objects being formed in
front of the retina, and can be corrected by wearing spectables or concave

lenses.
(iii) Hypermetropia (far or long sightedness.) The image of nearer object
becomes blurred. It is due to image being formed beyond the retina due to eye
ball being short or lens being flattened. It can be corrected by wearing convex
or convergent lenses.
(iv) Presbiopia It generally occurs after 40 years. The loss of elasticity in the eye
lens occurs so that near objects (written or printed words) are not correcdy
visible. It can be correct’d by convex/bifocal lenses.
Ear

Ears are a pair of statiocoustic organs meant for both sensory functions, i.e.,