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Mechanisms for regulation of
saliva secretion
- Influence of local
incitement
- The food mechanically
irritates the surface of glandular cells and
causes saliva secretion. The presence of
smooth objects in oral cavity (e.g. pebble)
results in substantial hypersalivation while
rough objects cause weaker salivation and
maybe even stop it.
- Chemical irritation,
specially the taste of sour, results in
abundant hypersalivation, often as high as
5 ml per minute or 8 to 20 times more than
the basal saliva secretion.
- Nervous regulation of
saliva secretion
- Submandibular and subligual
glands are controlled by neural impulses
from upper salivary nucleuses and parotid
gland by impulses from lower salivary
nucleuses. Those nucleuses are situated
close to the border of medulla oblongata and
pons and they are stimulated by receptors
for taste and touch of the tongue and other
areas of oral cavity.
- Salivation can be
stimulated or inhibited by impulses coming
to salivation centers from higher centers of
the central nervous system. For example,
salivation intensifies when someone smells
or eats the food he likes. The center for
appetite in the brain regulating this is
located very close to parasymphatic
nucleuses in frontal hypothalamus and
activity of that area is to a large extent a
reaction to impulses coming from the center
for taste and smell, located in almond
nucleuses in cortex.
The role of autonomous
nervous system - parasymphatic stimulation
Stimulation of
parasymphatic nearly always intensifies
gland secretion. Stimulation of symphaticus,
by itself, has a slight effect on secretion.
However, weak parasymphatic stimulation
often results in reduced secretion due to
vasoconstriction and poorer blood supply.
Hormonal regulation of
salivation
Certain hormones,
above all aldosteron, estrogen and
progesterone, play an important role in
salivation and composition of saliva .
Excessive
secretion of aldosteron brings about
increased reabsorption of Na and Cl while
the secretion of K increases; thus, the
concentration of NaCl in saliva is reduced
and the concentration of K is increased.
Stimulation by
estrogens intensifies the secretion of
saliva with the larger quantity of water,
Na and Cl. Increased concentration of NaCl
in saliva leads to its crystallization.
Progesterone causes decrease in quantity of
saliva, its water share and concentration of
Na and Cl.
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