Saliva I & II

• What are the two stages of saliva formation?

  Primary secretion and modification
• What do acinar cells secrete in the first stage of saliva formation?

  A NaCl rich fluid called primary saliva
• How does the ionic composition of primary saliva compare to plasma?

  It is similar to that of plasma
• What happens to primary saliva as it passes through the duct system?

  It undergoes selective reabsorption and secretion
• What ions are reabsorbed from primary saliva in the duct system?

  Na+ and Cl- ions
• What ions are secreted into primary saliva during modification?

  K+ and HCO3- ions
• What is the final composition of saliva after modification?

  It is hypotonic
• How does the final saliva compare to primary saliva in terms of salt concentration?

  It has a lower salt concentration
• What do small ducts within salivary glands lead to?

  Larger ducts that empty into the oral cavity
• What is the first step in the movement of ions and water into acinar cells?

  Transport of Cl- into the lumen
• How is Na+ transported into the lumen of acinar cells?

  Via tight junctions to neutralize charge
• What role does water play in the lumen of acinar cells?

  It is transported via tight junctions and aquaporins
• What happens to synthesized polypeptide proteins in acinar cells?

  They are packaged into secretory granules
• What triggers the release of secretory granules in acinar cells?

  An appropriate stimulus
• What is the nature of primary acinar fluid?

  Isotonic or slightly hypertonic
• Where does major modification of primary acinar fluid occur?

  In the striated duct
• What is the consequence of electrolyte reabsorption and secretion during saliva modification?

  A hypotonic final saliva is produced
• What regulates salivary secretion?

  Nervous mechanisms and reflexes
• What are the two types of salivary reflexes?

  Unconditioned reflex and conditioned reflex
• What triggers the unconditioned reflex for saliva secretion?

  Presence of any substance in the mouth
• Why is the unconditioned reflex also called an inborn reflex?

  It is present since birth
• What triggers the conditioned reflex for saliva secretion?

  Sight, smell, or thought of food
• What is the role of chemoreceptors and pressure receptors in salivary reflexes?

  They initiate impulses to the salivary center
• Where is the salivary center located?

  In the medulla of the brain
• What type of nerve system controls saliva production?

  Autonomic nervous system
• What are the two types of nerves that control salivary secretion?

  Parasympathetic and sympathetic nerves
• What type of saliva does the parasympathetic nerve supply produce?

  Watery, serous saliva
• When is the parasympathetic nerve supply most active?

  During the day while eating
• What type of saliva does the sympathetic nerve supply produce?

  Thicker, mucous saliva
• When is the sympathetic nerve supply activated?

  During fear, stress, or exercise
• What are the two pathways involved in saliva secretion regulation?

  Phospholipase C pathway and adenyl cyclase pathway
• What neurotransmitter binds to muscarinic cholinergic receptors?

  Acetylcholine
• What neurotransmitter binds to α-adrenergic receptors?

  Norepinephrine
• What does the phospholipase C pathway activate?

  Regulatory enzymes like phospholipase C
• What is the effect of increased [Ca2+] inside the cell?

  It opens Cl- and K+ channels
• What does the osmotic gradient created by [Cl-] do?

  It draws Na+ and water into the lumen
• What is the role of the Na+/K+/2Cl- co-transporter?

  It maintains intracellular ionic balance
• What happens to Na+ during active secretion?

  It is driven out via Na+/K+ exchanger
• What does the apical Cl- channel also transport?

  Bicarbonate (HCO3-)
• What restores intracellular pH after HCO3- secretion?

  Na+/H+ exchanger