1. Control of digestive secretion
The three main digestive juices are
Saliva
Gastric juice
Pancreatic juice
The control of the secretion combines both hormonal and nervous co-ordination

2. Why control digestive secretion?
Waste of energy and nutrients if constantly produced
Constant secretion of gastric and pancreatic juice increases risk of self digestion
Essential that secretion is timed to be present when food is present in that area of gut

3. Control of saliva production
Entirely nervous control
Food in mouth triggers a simple reflex
Stimulus (food in the mouth)
Nerve impulse to brain
Nerve impulse via the vagus nerve to salivary glands
response (saliva secreted)
A reflex is a quick automatic response to a stimulus

4. Conditioned reflex
Conditioned stimulus (thought/smell of food)
Nerve impulse to the brain
Nerve impulse via vagus nerve to salivary glands
Response (saliva secreted)
Remember that the conditioned reflex is learned

5. Subject to copyright clearance a suitable image showing a cutaway view of a stomach could be inserted here.
e.g. one similar to that found at:

6. Control of gastric secretion
Both nervous and hormonal control
Nervous control
Stimulus food in the mouth
Nerve impulse to brain
Motor impulse via vagus nerve to gastric glands
Response gastric glands secrete ¼ gastric juice
Digestion of protein starts

7. Hormonal control of gastric secretion
Stimulus – partially digested food in the stomach
Release of hormone gastrin from the G cells in stomach wall
Response - gastric glands secrete ¾ of total gastric juice

8. Sight/smell/tasted of food Brain
nerve impulse
Sight/smell/tasted of food
Brain
Subject to copyright clearance a suitable image showing a cutaway view of a stomach could be inserted here.
e.g. one similar to that found at:
nerve impulse
Via blood
Hormone gastrin released
¼ gastric juice secreted
¾ gastric secretion
Partially digested food in stomach

9. Control of bile and pancreatic juice
Stimulus acid food in the stomach
Causes the release of 2 hormones
Secretin stimulates liver to produce bile and pancreas to produce alkaline fluid
Cholecystokinin (CCK) causes the release of bile and the pancreas to secrete enzymes

10. Secretin stimulates the
pancreas to secrete alkaline fluid
liver to make bile
g b
duodenum
liver
pancreas
Cholecystokinin stimulates the
Pancreas to produce enzymes
Gall bladder to release bile