Cephalic phase
Encyclopedia
The cephalic phase of gastric secretion occurs even before food enters the stomach
, especially while it is being eaten. It results from the sight, smell, thought, or taste of food, and the greater the appetite
, the more intense is the stimulation
. Neurogenic signals that cause the cephalic phase of gastric secretion originate from the cerebral cortex
and in the appetite centers of the amygdala
and hypothalamus
.They are transmitted through the dorsal motor nuclei of the vagi and then through the vagus nerve
to the stomach. This phase of secretion normally accounts for about 20 percent of the gastric secretion associated with eating a meal.
This enhanced secretory activity brought on by the thought or sight of food is a conditioned reflex. It only occurs when we like or want food. When appetite is depressed this part of the cephalic reflex is inhibited.
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, especially while it is being eaten. It results from the sight, smell, thought, or taste of food, and the greater the appetite
Appetite
The appetite is the desire to eat food, felt as hunger. Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain. Decreased desire to eat is...
, the more intense is the stimulation
Stimulation
Stimulation is the action of various agents on nerves, muscles, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity.The word...
. Neurogenic signals that cause the cephalic phase of gastric secretion originate from the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
and in the appetite centers of the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
and hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
.They are transmitted through the dorsal motor nuclei of the vagi and then through the vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
to the stomach. This phase of secretion normally accounts for about 20 percent of the gastric secretion associated with eating a meal.
This enhanced secretory activity brought on by the thought or sight of food is a conditioned reflex. It only occurs when we like or want food. When appetite is depressed this part of the cephalic reflex is inhibited.