Question

Describe the intrinsic and extrinsic controls of the digestive system. How do mechanoreceptors and chemoreceptors inform the nervous controls about the state of the alimentary canal? Describe how they control the cephalic, gastric, and intestinal phases of stomach’s action.

Answer 1

There are many intrinsic and extrinsic factors which control the digestive system, and, in most cases, these are the nerves. The two types of nerves which control the digestive system are the extrinsic and intrinsic nerves where the extrinsic nerves are those which control and helps in connecting the digestive organs from the system to the brain and spinal cord. The extrinsic nerves help in release of chemicals which helps in contraction or relaxation of the GI tract muscles. The intrinsic nerves are present within the GI tract and they help in stretching the walls of organs present in the GI tract which helps in movement of the food and digestive juice release. The intrinsic system or reflex helps in stimulating the gastric mucosa which activates the sensory afferent and then the efferent signal is passed to cells of stomach or smooth muscles of gut and helps with contraction or relaxation of gut. The extrinsic reflexes are those where the afferent signal is passed from gut to spinal cord or brain stem and goes back into gut.

The GI tract is regulated with a group of regulatory mechanisms which includes mechanoreceptors, chemoreceptors, and the intrinsic and extrinsic controls. The receptors are present in the GI system and it helps in responding to factors like stretch along with change in pH and osmolarity and also associate with process of digestion. The mechanoreceptors are stretch receptors which are present in the membranes and muscle of digestive system and as soon as they receive stretch through expansion or contraction of smooth muscles, they send the signal to the brain and the nerves helps in causing the relaxation or contraction. When it comes to the chemoreceptors, they detect the presence of digestive juice which can activate or inhibit the digestive glands and hence they helps in sending the message to the nervous system which helps in stimulating the muscles to move and mix the lumen content.