Table 3-1.Functions of the autonomic nervous system
Lessens tonus of ciliary muscles so the eyes
may accommodate to see distant objects.
Quickens and strengthens the action of the
Contracts blood vessels of the skin and viscera
so that more blood goes to the skeletal and
cardiac muscles where it is needed for fight
Relaxes gastrointestinal tract and bladder.
Decreases secretions of the gastrointestinal
Increases secretion of sweat glands.
Causes contraction of sphincters to prevent
emptying of bowels or bladder.
Contracts ciliary muscles so the eyes may
accommodate to see objects near at hand.
Slows the action of the heart.
Dilates blood vessels (except cardiac).
Increases contraction of gastrointestinal tract
and muscle tone of the bladder.
Increases secretions of gastrointestinal glands.
No action on sweat glands.
Relaxes sphincters so that waste matter can be
ocular muscles, eyelids, conjunctival, and lacrimal
Structure of The Eye
The eye is a hollow ball, or globe, which con-
sists of various tissues that perform specific func-
tions. The globe, or eyeball, is composed of three
layers (fig. 3-45).
OUTER LAYER.The outer layer of the eye
is called the sclera. It is the tough, fibrous, pro-
tective portion of the globe, commonly called the
white of the eye. Anteriorly, the outer layer is
transparent and is called the cornea, or the win-
dow of the eye. It permits light to enter the globe.
The exposed sclera is covered with a mucous mem-
brane, the conjunctival, which is a continuation
of the inner lining of the eyelids. The lacrimal
gland produces tears that constantly wash the
front part of the eye and the conjunctival. The tear
gland secretions that do not evaporate flow
Figure 3-45.Cross section of the eye.