Digestive System Regulation Quiz

PDF page 1096: In reaction to the smell, sight, or thought of food, like that shown in Figure 25.21, the first response is that of salivation. The salivary glands secrete more saliva in response to stimulation by the autonomic nervous system triggered by the food in preparation for digestion. Simultaneously, the stomach begins to produce hydrochloric acid to digest the food. Recall that the peristaltic movements of the esophagus and other organs of the digestive tract are under the control of the brain. The brain prepares these muscles for movement as well. When the stomach is full, the part of the brain that detects satiety signals fullness. There are three overlapping phases of gastric control—the cephalic phase, the gastric phase, and the intestinal phase—each requires many enzymes and is under neural control as well.

PDF page 1097: stomach. (credit: Kelly Bailey) Digestive Phases The response to food begins even before food enters the mouth. The first phase of ingestion, called the cephalic phase, is controlled by the neural response to the stimulus provided by food. All aspects—such as sight, sense, and smell—trigger the neural responses resulting in salivation and secretion of gastric juices. The gastric and salivary secretion in the cephalic phase can also take place due to the thought of food. Right now, if you think about a piece of chocolate or a crispy potato chip, the increase in salivation is a cephalic phase response to the thought. The central nervous system prepares the stomach to receive food. The gastric phase begins once the food arrives in the stomach. It builds on the stimulation provided during the cephalic phase. Gastric acids and enzymes process the ingested materials. The gastric phase is stimulated by (1) distension of the stomach, (2) a decrease in the pH of the gastric contents, and (3) the presence of undigested material. This phase consists of local, hormonal, and neural responses. These responses stimulate secretions and powerful contractions. The intestinal phase begins when chyme enters the small intestine triggering digestive secretions. This phase controls the rate of gastric emptying. In addition to gastric emptying, when chyme enters the small intestine, it triggers other hormonal and neural events that coordinate the activities of the intestinal tract, pancreas, liver, and gallbladder.

PDF page 1099: alimentary canal tubular digestive system with a mouth and anus aminopeptidase protease that breaks down peptides to single amino acids; secreted by the brush border of small intestine anus exit point for waste material bile digestive juice produced by the liver; important for digestion of lipids bolus mass of food resulting from chewing action and wetting by saliva carboxypeptidase protease that breaks down peptides to single amino acids; secreted by the brush border of the small intestine carnivore animal that consumes animal flesh cephalic phase first phase of digestion, controlled by the neural response to the stimulus provided by food cholecystokinin hormone that stimulates the contraction of the gallbladder to release bile chylomicron small lipid globule chyme mixture of partially digested food and stomach juices chymotrypsin pancreatic protease digestion mechanical and chemical break down of food into small organic fragments dipeptidase protease that breaks down peptides to single amino acids; secreted by the brush border of small intestine duodenum first part of the small intestine where a large part of digestion of carbohydrates and fats occurs elastase pancreatic protease endocrine system system that controls the response of the various glands in the body and the release of hormones at the appropriate times esophagus tubular organ that connects the mouth to the stomach essential nutrient nutrient that cannot be synthesized by the body; it must be obtained from food gallbladder organ that stores and concentrates bile gastric inhibitory peptide hormone secreted by the small intestine in the presence of fatty acids and sugars; it also inhibits acid production and peristalsis in order to slow down the rate at which food enters the small intestine

PDF page 1104: a. when food is smelled

PDF page 1104: b. when food reaches the stomach

PDF page 1104: c. when chyme enters the small intestines

PDF page 1097: stomach. (credit: Kelly Bailey) Digestive Phases The response to food begins even before food enters the mouth. The first phase of ingestion, called the cephalic phase, is controlled by the neural response to the stimulus provided by food. All aspects—such as sight, sense, and smell—trigger the neural responses resulting in salivation and secretion of gastric juices. The gastric and salivary secretion in the cephalic phase can also take place due to the thought of food. Right now, if you think about a piece of chocolate or a crispy potato chip, the increase in salivation is a cephalic phase response to the thought. The central nervous system prepares the stomach to receive food. The gastric phase begins once the food arrives in the stomach. It builds on the stimulation provided during the cephalic phase. Gastric acids and enzymes process the ingested materials. The gastric phase is stimulated by (1) distension of the stomach, (2) a decrease in the pH of the gastric contents, and (3) the presence of undigested material. This phase consists of local, hormonal, and neural responses. These responses stimulate secretions and powerful contractions. The intestinal phase begins when chyme enters the small intestine triggering digestive secretions. This phase controls the rate of gastric emptying. In addition to gastric emptying, when chyme enters the small intestine, it triggers other hormonal and neural events that coordinate the activities of the intestinal tract, pancreas, liver, and gallbladder.

PDF page 1099: gastrin hormone which stimulates hydrochloric acid secretion in the stomach gastrovascular cavity digestive system consisting of a single opening gizzard muscular organ that grinds food herbivore animal that consumes strictly plant diet ileum last part of the small intestine; connects the small intestine to the large intestine; important for absorption of B-12 ingestion act of taking in food intestinal phase third digestive phase; begins when chyme enters the small intestine triggering digestive secretions and

PDF page 1097: The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.

PDF page 1099: gastrin hormone which stimulates hydrochloric acid secretion in the stomach gastrovascular cavity digestive system consisting of a single opening gizzard muscular organ that grinds food herbivore animal that consumes strictly plant diet ileum last part of the small intestine; connects the small intestine to the large intestine; important for absorption of B-12 ingestion act of taking in food intestinal phase third digestive phase; begins when chyme enters the small intestine triggering digestive secretions and

PDF page 1097: The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.

PDF page 1100: controlling the rate of gastric emptying jejunum second part of the small intestine lactase enzyme that breaks down lactose into glucose and galactose large intestine digestive system organ that reabsorbs water from undigested material and processes waste matter lipase enzyme that chemically breaks down lipids liver organ that produces bile for digestion and processes vitamins and lipids maltase enzyme that breaks down maltose into glucose mineral inorganic, elemental molecule that carries out important roles in the body monogastric digestive system that consists of a single-chambered stomach omnivore animal that consumes both plants and animals pancreas gland that secretes digestive juices pepsin enzyme found in the stomach whose main role is protein digestion pepsinogen inactive form of pepsin peristalsis wave-like movements of muscle tissue proventriculus glandular part of a bird’s stomach rectum area of the body where feces is stored until elimination roughage component of food that is low in energy and high in fiber ruminant animal with a stomach divided into four compartments salivary amylase enzyme found in saliva, which converts carbohydrates to maltose secretin hormone which stimulates sodium bicarbonate secretion in the small intestine small intestine organ where digestion of protein, fats, and carbohydrates is completed somatostatin hormone released to stop acid secretion when the stomach is empty sphincter band of muscle that controls movement of materials throughout the digestive tract stomach saclike organ containing acidic digestive juices sucrase enzyme that breaks down sucrose into glucose and fructose trypsin pancreatic protease that breaks down protein villi folds on the inner surface of the small intestine whose role is to increase absorption area vitamin organic substance necessary in small amounts to sustain life

PDF page 1097: The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.

PDF page 1097: The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.

PDF page 1100: controlling the rate of gastric emptying jejunum second part of the small intestine lactase enzyme that breaks down lactose into glucose and galactose large intestine digestive system organ that reabsorbs water from undigested material and processes waste matter lipase enzyme that chemically breaks down lipids liver organ that produces bile for digestion and processes vitamins and lipids maltase enzyme that breaks down maltose into glucose mineral inorganic, elemental molecule that carries out important roles in the body monogastric digestive system that consists of a single-chambered stomach omnivore animal that consumes both plants and animals pancreas gland that secretes digestive juices pepsin enzyme found in the stomach whose main role is protein digestion pepsinogen inactive form of pepsin peristalsis wave-like movements of muscle tissue proventriculus glandular part of a bird’s stomach rectum area of the body where feces is stored until elimination roughage component of food that is low in energy and high in fiber ruminant animal with a stomach divided into four compartments salivary amylase enzyme found in saliva, which converts carbohydrates to maltose secretin hormone which stimulates sodium bicarbonate secretion in the small intestine small intestine organ where digestion of protein, fats, and carbohydrates is completed somatostatin hormone released to stop acid secretion when the stomach is empty sphincter band of muscle that controls movement of materials throughout the digestive tract stomach saclike organ containing acidic digestive juices sucrase enzyme that breaks down sucrose into glucose and fructose trypsin pancreatic protease that breaks down protein villi folds on the inner surface of the small intestine whose role is to increase absorption area vitamin organic substance necessary in small amounts to sustain life

PDF page 1097: The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.

PDF page 1099: alimentary canal tubular digestive system with a mouth and anus aminopeptidase protease that breaks down peptides to single amino acids; secreted by the brush border of small intestine anus exit point for waste material bile digestive juice produced by the liver; important for digestion of lipids bolus mass of food resulting from chewing action and wetting by saliva carboxypeptidase protease that breaks down peptides to single amino acids; secreted by the brush border of the small intestine carnivore animal that consumes animal flesh cephalic phase first phase of digestion, controlled by the neural response to the stimulus provided by food cholecystokinin hormone that stimulates the contraction of the gallbladder to release bile chylomicron small lipid globule chyme mixture of partially digested food and stomach juices chymotrypsin pancreatic protease digestion mechanical and chemical break down of food into small organic fragments dipeptidase protease that breaks down peptides to single amino acids; secreted by the brush border of small intestine duodenum first part of the small intestine where a large part of digestion of carbohydrates and fats occurs elastase pancreatic protease endocrine system system that controls the response of the various glands in the body and the release of hormones at the appropriate times esophagus tubular organ that connects the mouth to the stomach essential nutrient nutrient that cannot be synthesized by the body; it must be obtained from food gallbladder organ that stores and concentrates bile gastric inhibitory peptide hormone secreted by the small intestine in the presence of fatty acids and sugars; it also inhibits acid production and peristalsis in order to slow down the rate at which food enters the small intestine

PDF page 1097: The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.

PDF page 1096: In reaction to the smell, sight, or thought of food, like that shown in Figure 25.21, the first response is that of salivation. The salivary glands secrete more saliva in response to stimulation by the autonomic nervous system triggered by the food in preparation for digestion. Simultaneously, the stomach begins to produce hydrochloric acid to digest the food. Recall that the peristaltic movements of the esophagus and other organs of the digestive tract are under the control of the brain. The brain prepares these muscles for movement as well. When the stomach is full, the part of the brain that detects satiety signals fullness. There are three overlapping phases of gastric control—the cephalic phase, the gastric phase, and the intestinal phase—each requires many enzymes and is under neural control as well.

PDF page 1096: The concepts presented in this module are not within the scope for AP other than to note that the brain houses the control center for the sensation of hunger and satiety (fullness). The functions of the digestive system are regulated through neural and hormonal responses. In the chapter that discusses the endocrine system, we explore in detail the role of the endocrine system in maintaining homeostasis, including the normal functioning of the digestive system. The brain is the control center for the sensation of hunger and satiety. The functions of the digestive system are regulated through neural and hormonal responses.

PDF page 1101: The brain and the endocrine system control digestive processes. The brain controls the responses of hunger and satiety. The endocrine system controls the release of hormones and enzymes required for digestion of food in the digestive tract.