Digestion 9 Regulation of saliva secretions

This is purely neural

the control of salivary secretion depends on reflex nerve impulses that involve:

afferent limbs

medullar salivatory nuclei

efferent limb consisting of the parasympathetic and sympathetic secretomotor and vascular nerves

both parasympathetic and sympathetic stimulation increases saliva secretion

parasympathetic activity evokes a copious secretion relatively poor in protein and marked vasodilatation in the salivary gland

sympathetic activity evokes sparse but protein-rich saliva

the primary stimulus for salivation is taste

sour taste induces the greatest amount of saliva secretion by the salivary glands

afferent input is carried to the superior and inferior salivatory nuclei in the medulla via the facial (VII) and glossopharyngeal (IX) nerves

input from other senses, such as smell and sight are also integrated in the salivatory nuclei

parasympathetic efferent pathways for the sublingual and submandibular glands are from the facial nerve via the submandibular ganglion and for the parotid gland from the glossopharyngeal nerve via the otic ganglion

these pathways regulate fluid secretion by releasing

acetylcholine (ACh) at the surface of the salivary gland acinar

cells

macromolecule secretion is regulated by norepinephrine release from sympathetic nerves

sympathetic post ganglionic pathways are from the cervical ganglion of the sympathetic chain

higher brain centers control salivation by sending neurons to the salivatory nuclei

parasympathetic nerves of the salivary gland may also release peptides (substance P and Vasoactive Intestinal Polypeptide (VIP), neurokinin A, neuropeptide P) and NO as cotransmitters of acetylcholine

ACh triggers saliva secretion via the IP3 pathway whiles