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| Control of Digestion |
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| Digestion is actually carried out by enzymes but the secretion of these enzymes is controlled by the nervous system and endocrine system. |
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| Nervous control of digestion |
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| There are receptors in the wall of the alimentary canal that send reflexes to the brain through sensory neurons. The brain then sends motor impulses through the motor neurons to the target glands or cells. The nervous control of digestion takes place in the following ways- |
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| 1) The secretion of saliva is controlled by two types of reflexes - unconditioned and conditioned. |
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| The taste buds on the tongue stimulate receptors that communicate with the brain through the sensory neurons. The brain in turn stimulates the salivary glands to secrete saliva by the motor nerves. This is called unconditioned reflex. |
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| Conditioned reflexes were demonstrated by Pavlov. He showed that by ringing a bell every time the dog was served food this made the dog associate the sound of the bell with food. Then when the bell was rung even without the food, the dog salivated. These reflexes are called conditioned reflexes. For e.g., watering of mouth at the thought of our favourite food. |
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| 2) The gastric glands are stimulated by two types of nerve impulses. One set of impulses comes from the mouth in response to the presence of food or swallowing. The other set of impulses come from the stomach wall receptors in response to the stretching of the stomach wall, on receiving food. |
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| 3) The gastric glands are inhibited by the nerve impulses in response to the passage of acidified chyme into the duodenum. The receptors are present in the duodenal wall. |
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| 4) The presence of acidified chyme in the duodenum also triggers another reflex from the duodenal wall to the brain that slows down the release of chyme into the intestine. |
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