Chapter 35

What role does histamine play in gastrointestinal function? A. It is a powerful stimulant of gastric acid secretion. B. It helps in the digestion of cholesterol. C. It emulsifies fatty substances. D. It assists in protein digestion.

A. It is a powerful stimulant of gastric acid secretion. Histamine causes parietal cells to produce large amounts of gastric secretions. Cholesterol is digested by pancreatic esterase. Bile salts emulsify the fatty substances. Pepsin is neutralized in the duodenum, and pancreatic trypsin, chymotrypsin, and carboxypeptidase take over protein digestion.

What gastrointestinal alteration is increased with aging? (Select all that apply.) A. Peristalsis B. Constipation C. Taste sensation D. Hiatal herniation E. Esophageal mobility

B. Constipation D. Hiatal herniation Transient time for intestinal contents to pass through the gastrointestinal tract is decreased resulting in increased risk for constipation. The incidence of hiatal hernia is increased. As a person ages, gastrointestinal muscle strength and movement decrease, leading to reduced peristalsis and decreased gastrointestinal motility throughout the system. Elderly people experience a decline in taste. This decline is as a result of both an increase in the sensation threshold for all four tastes and a decrease in the number of papillae. A condition called presbyesophagus, in which esophageal motility is slowed or disorganized, may develop in older adults.

Which statement is true related to the affect the sympathetic and parasympathetic nervous systems have on the activity of the intrinsic nervous system? A. Both systems can increase its activity. B. Sympathetic stimulation decreases its activity. C. Parasympathetic stimulation decreases its activity. D. Neither system affects the activity of the intrinsic nervous system.

B. Sympathetic stimulation decreases its activity. Sympathetic stimulation decreases the activity of the intrinsic nervous system. Only parasympathetic stimulation stimulates the intrinsic nervous system.

The function of cholecystokinin is that it A. increases stomach motility. B. is responsible for fat digestion and absorption. C. plays an important role in carbohydrate metabolism. D. prevents reflux of stomach contents into the esophagus.

B. is responsible for fat digestion and absorption. Cholecystokinin, which is secreted by the mucosa of the jejunum in response to the entry of fatty substances, plays an important role in fat digestion and absorption. Gastrin, which is secreted by specialized endocrine cells (G cells) of the stomach mucosa in response to food entry, increases stomach motility and is the primary mediator of gastric acid secretion. The digestive enzyme contained in saliva, salivary amylase (also called ptyalin), initiates carbohydrate digestion by breaking down polysaccharides (also called starch) into the simpler molecular structures of dextrin and maltose. Secretin, which is produced by the mucosa of the duodenum in response to the entry of acidic gastric juice from the stomach, stimulates pancreatic fluid and bicarbonate secretion, with the effect of neutralizing the acidity of intestinal contents.

Which specialized cell in the stomach produce a substance needed for adequate intestinal absorption of vitamin B12? A. Chief B. Mucus C. Parietal D. Gastrin

C. Parietal Parietal cells produce hydrochloric acid and a substance called intrinsic factor, which is needed for adequate intestinal absorption of vitamin B12. Chief cells produce pepsinogen, the inactive form of the enzyme pepsin. Mucous cells produce an alkaline mucus that serves to shield the stomach wall and neutralize the acidity in the immediate area of the lining. Gastrin cells are located in the antral epithelium and have surface microvilli that monitor intragastric pH.

How and where are water and electrolytes absorbed? A. Primarily in the small intestine as a result of osmosis B. In the gastric mucosa caused by the hormone gastrin C. In the small intestine, stimulated by the chime D. In the mouth, as a result of the saliva

A. Primarily in the small intestine as a result of osmosis Absorption of water occurs passively by osmosis, which occurs mainly in the small intestine and to a lesser extent from the colon. Factors that may affect the rate at which the stomach empties include the degree of distention of the gastric wall and release of the hormone gastrin in response to certain types of food in the stomach. A hormone called GIP, which is released from the upper portion of the small intestine in response to fat in chyme, as well as to carbohydrates, is known to inhibit gastric motility under some conditions. As the food is manipulated and broken down in the mouth, it is moistened by saliva and it initiates carbohydrate digestion.

Sympathetic innervation inhibits gastrointestinal (GI) motility by A. secreting norepinephrine. B. secreting epinephrine. C. accelerating the motility of the GI tract. D. transmitting information to the GI tract.

A. secreting norepinephrine. Sympathetic nerve endings in the GI tract secrete norepinephrine, which promotes the inhibitory effect on the GI tract. Epinephrine accelerates the functioning of the GI tract. Parasympathetic stimulation increases its activity. The central nervous system through its autonomic division transmits information.

Nutrients are propelled through the gastrointestinal tract by a process known as A. emptying. B. peristalsis. C. contraction. D. spike potentials.

B. peristalsis. The basic propulsive movement of the gastrointestinal tract is peristalsis. Gastric emptying refers to the rate the stomach empties. The electrical activity occurring in the smooth muscle of the gut gives rise to tonic contractions and rhythmic contractions, both of which occur in most types of smooth muscle. In general, most contraction in the GI tract occurs in response to spike potentials.

The muscular activity involved in the digestive and absorptive function of the GI tract include which of the following? (Select all that apply.) A. Chewing B. Swallowing C. Colonic movements D. Mixing movements E. Propulsive movements

D. Mixing movements E. Propulsive movements In different portions of the GI tract, mixing movements and propulsive movements serve different functions to achieve proper digestion and absorption of nutrients. Mixing movements that serve to keep the intestinal contents thoroughly mixed on a constant basis are caused by either peristaltic contractions or local constrictive contractions of small segments of the gut wall. The basic propulsive movement of the GI tract is peristalsis. Nutrients are propelled by the slow advancement of circular constriction that squeezes the materials in front of the constricted area forward. The entry of solid food into the mouth results in the action of chewing, an important first step in the process of nutrient digestion; the process of moving the food around in the mouth and mixing it with saliva. Swallowing is the transport of material from the mouth to the stomach. Colonic movements are the major type of motility in the large intestine.