Term
| What are the stages of motility through the alimentary tract? |
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Definition
| chewing and swallowing, esophageal motility, gastric motility, small intestinal motility, and large intestinal motility |
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Term
| Define: hunger, appetite. |
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Definition
1. the intrinsic desire for food
2. the amount of food a person preferentially seeks |
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Term
| Which nerve innervates the jaw for the process of chewing? What part of the CNS controls chewing? |
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Definition
1. CN V
2. reticular areas in the brain stem taste centers and areas of the hypothalamus, amygdala, and cerebral cortex near the sensory areas from taste and smell can all cause chewing, in addition to regular somatic action |
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Term
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Definition
| 1. the presence of a bolus of food in the mouth initiates reflex inhibition of the muscles of mastication, which lowers the jaw, causes stretching and a reflex contraction in response to the stretching, hence the chewing reflex |
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Term
| What is the purpose of chewing? |
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Definition
| to increase the surface area of the food, to aid in the ability of digestive enzymes to degrade the food, and to prevent excoriation of the linings of the alimentary tract |
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Term
| What are the stages of swallowing? Which are voluntary and which are involuntary? |
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Definition
a. voluntary - voluntary
b. pharyngeal - involuntary
c. esophageal - involuntary |
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Term
| What does the voluntary stage of swallowing consist of? |
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Definition
| the tongue rises to the top of the mouth and moves backwards, pushing the bolus of food into the esophagus; when this action is initiated, the epiglottis switches to cover the larynx, to prevent food from going into the trachea, making way for the food to enter the esophagus |
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Term
| What does the pharyngeal stage of swallowing consist of? |
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Definition
| the soft palate is pulled superiorly, preventing food from getting into the nasal cavities; the palatopharyngeal folds are pulled medially form a slit through which food must pass, preventing large undigested food from passing; the vocal cords are strongly approximated and the larynx is pulled upward and anteriorly to cause the epiglottis to cover the larynx; the upward movement of the larynx also opens up the esophagus and the upper esophageal sphincter relaxes, allowing food to easily enter the esophagus; the upper wall of the pharynx then contracts, propelling food into the esophagus via an initiated peristaltic action |
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Term
| How is the pharyngeal stage of swallowing initiated? What is the nervous involvement of the pharyngeal stage? |
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Definition
| 1. a ring of tactile sensory areas around the pharyngeal opening send impulses through the trigeminal and glossopharyngeal nerves into the swallowing center in the medulla oblongata to initiate the peristalsis and inhibit breathing during swallowing |
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Term
| What does the esophageal stage of swallowing consist of? |
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Definition
| primary peristalsis, involving peristaltic waves traveling down the esophagus, pushing the food toward the stomach; if those waves do not push all the food into the stomach, secondary peristaltic waves will be stimulated to do so |
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Term
| How is the esophageal stage of swallowing initiated? |
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Definition
| primary peristalsis is a continuation of the distension -> inferior relaxation & superior contraction axis that begins in the pharyngeal stage; secondary peristalsis is initiated with continued distension of the esophagus, resulting in afferent feedback through the CN X nerves and efferent response through the CN IX and X nerves as well as reseponse through the myenteric plexus (the latter of which can function on its own, if need be) |
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Term
| What is the muscular difference between the upper and low esophagus? |
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Definition
| the upper 1/3 of the esophagus is striated and therefore somewhat under voluntary control; this means that is the vagus nerve is cut, the upper esophagus cannot intiate swallowing; the lower 2/3 of the esophagus is smooth muscle |
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Term
| What is another name for the upper esophageal sphincter? The lower esophageal sphincter? |
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Definition
1. the pharyngoesophageal sphincter
2. the gastroesophageal sphincter |
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Term
| What is dysphagia? What can cause it? What does it cause? |
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Definition
1. difficulty swallowing
2. anesthesia, stroke, cranial nerve damage, or muscular diseases (such as myasthenia gravis, polio, or botulism)
3. uncoordinated UES and pharyngeal contractions, which can cause aspiration |
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Term
| What is GERD? What causes it? What can it cause? |
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Definition
1. gastroesophageal reflux disease; aka heartburn
2. backwash of acid, pepsin, and bile into the esophagus; affects 1 in 10 people
3. can lead to stricture of the esophagus (scar tissue), asthma/aspiration, chronic sinus infection (if the reflux goes into the throat), and/or Barrett's esophagus (high turnover of esophageal cells that can lead to cancer) |
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Term
| What is achalasia? What causes it? What can it cause? |
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Definition
1. a disorder of the esophagus in which the LES fails to relax, causing the LES pressure to rise; organized peristaltic contractions may be absent
2. a neurological problem with the ENS
3. over time, the esophagus can significantly distend, causing megaesophagus; this can lead to esophageal ulceration, rupture, and death |
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Term
| What are symptoms of achalasia? How is it treated? |
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Definition
1. difficulty swallowing liquids and solids, regurgitation of undigested food, weight loss, halitosis, excessive belching, and heartburn
2. anti-spasmotic drugs can relax the smooth muscle, a pneumatic dilator (stiff balloon) can open the LES if needed, or surgical myotomy can remove the problem muscle |
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Term
| What are the steps of gastric motility? What areas of the stomach do these steps occur at? |
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Definition
1. relaxation to accommodate food, mixing food with gastric juice, and propelling chyme into duodenum
2. orad area, caudad area, and caudad area respectively |
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Term
| What are the anatomical parts of the stomach? |
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Definition
| the body or orad, comprising the superior 2/3 of the stomach, and the antrum or caudad area, comprising the inferior 1/3 of the stomach |
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Term
| What does the receptive relaxation step of gastric motility consist of? |
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Definition
| as food entering the stomach from the esophagus, it stretches the walls of the stomach, carrying an afferent impulse through the vagus nerve to the brain stem, then back through the vagus nerve to the stomach, causing release of VIP, causing relaxation of the stomach walls; this can occur until the stomach is distended enough to accommodate 0.8-1.5 L of food |
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Term
| How does distension of the stomach affect the alimentary tract? |
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Definition
| it causes the vagovagal reflex in the stomach, increases CCK levels, causing a decrease in gastric emptying, and causes the release of gastrin in the stomach, which can also stimulate the ileosphincter to open, allowing the duodenum to make room for more food |
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Term
| What does the mixing step in gastric motility consist of? |
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Definition
| secretion of digestive juices by gastric glands and weak peristaltic waves called constrictor or mixing waves to mix the food and digestive juices |
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Term
| What causes the mixing waves in the stomach? |
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Definition
| the basic electrical rhythm that consists of spontaneously occurring slow waves; these mixing waves are stronger toward the antrum |
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Term
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Definition
| when mixing waves become particularly strong, they cause a peristaltic action potential and a constrictor ring forms that pushes the majority of the stomach contents toward the pylorus, however, the pylorus does not relax and often constricts, meaning the majority of the stomach contents are forced back through the constrictor ring into the body of the stomach, as a more forceful mixing action |
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Term
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Definition
| mixed and partially digested food; food is called chyme when it reaches and is mixed by the stomach |
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Term
| What are hunger contractions? |
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Definition
| powerful contractions of the stomach smooth muscle that occur when the stomach is empty (usually for 12-24 hours); the contractions can become so strong as to be painful and be called hunger pangs; these are strongest in young people with high GI tonus and become stronger with low blood sugar and with greater amount of time without food reaching the stomach, peaking at 3-4 days |
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Term
| What conditions favor stomach emptying? |
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Definition
| increased orad tone, forceful perstaltic contractions, decreased tone of the pylorus, and absence of segmental contractions in the intestine |
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Term
| What inhibits gastric emptying? How does it inhibit gastric emptying? |
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Definition
1. activation of intestinal mucosa receptors and via the following in the duodenum: high or low osmolarity, acid, fat, protein, and/or irritation
2. activation of the receptors trigger enterogastric reflexes causing relaxation of the orad stomach, decreased force of peristaltic contractions, and segmentation contractions in the intestine |
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Term
| What are the mechanisms of the enterogastric reflexes for the following: fats, proteins and acid |
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Definition
1. CCK release increases gastric distensibility, which decreases gastric emptying
2. same as fats
3. decreases gastric emptying via intrinsic neural reflex |
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Term
| What effect does fluidity of chyme in the stomach have on gastric emptying? |
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Definition
| increased fluidity causes increased gastric emptying, because food must be in liquid form to be evacuated |
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Term
| What effect does the presence of fat, acid, hypertonic solution, or distension in the duodenum have on gastric emptying? |
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Definition
| all of these factors initiate the enterogastric reflex or triggers the release of enterogastrones (secretin and CCK); this causes gastric motility and emptying to be inhibited until the duodenum can deal with the food it already has |
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Term
| How do emotions affect gastric emptying? How about intense pain? |
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Definition
1. it alters autonomic balance, which can stimulate or inhibits motility and emptying, depending on what state the emotions are in
2. increases sympathetic activity, which inhibits motility and emptying |
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Term
| How are inhibitory impulses transmitted from the duodenum to the stomach? |
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Definition
a. through the ENS
b. through extrinsic nerves through the prevertebral sympathetic ganglia and then back through inhibitory nerve fibers to the stomach
3. through vagus nerves to the brain stem to inhibit normal excitatory impulses to the stomach |
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Term
| What hormones in the stomach encourage gastric emptying? |
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Definition
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Term
| What hormones in the duodenum inhibit gastric emptying and where are they released? Which is the most powerful? |
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Definition
1. a. CCK, in the jejunum
b. secretin, in the duodenum
c. gastric inhibitory peptide (GIP), in the duodenum
2. CCK |
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Term
| What type of movement follow a meal? What do they involve? |
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Definition
a. peristalsis - a propulsive movement
b. segmentation - a mixing movement |
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Term
| What is notable about the slow wave frequency throughout the small intestine? What is it limited by? |
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Definition
1. the slow wave frequency is greater in the duodenum, less in the jejunum, and less still in the ileum
2. slow wave frequency
NOTE: spike potentials are required for contractions in the small intestine |
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Term
| How quickly do small intestine peristaltic waves travel? |
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Definition
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Term
| What is the gastroenteric reflex? |
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Definition
| distension of the stomach causes increased peristaltic activity in the small intestine via the myenteric plexus |
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Term
| Which hormones cause enhanced peristaltic activity in the small intestine? Which hormones inhibit peristaltic activity? |
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Definition
1. gastrin, CCK, insulin, motilin, and serotonin
2. secretin and glucagon |
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Term
| What are MMCs? What do they do? How are they mediated? |
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Definition
1. migrating motility complexes; periods of intense contractions in the intestines
2. they sweep out undigested residue toward the colon to maintain low bacterial counts in the upper intestine
3. by motilin and the ENS |
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Term
| What reflexes are contributing factors to spike potentials in the small intestine? |
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Definition
a. the peristaltic reflex - mediated by the ENS
b. the intestino-intestinal reflex - severe distension inhibits bowel movements through extrinsic nerves
c. gastroileal reflex - meal stimulates the ileocecal sphincter to relax and ileal peristalsis to increase, via the extrinisic nerves |
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Term
| What effect does the PNS input have on small intestine motility? How about SNS input? |
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Definition
1. stimulation
2. inhibition |
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Term
| How do the following hormones affect small intestine motility: epinephrine, motilin, serotonin, prostaglandin? |
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Definition
1. inhibits motility
2. mediates MMCs
3. stimulates motility in large quantities
4. stimulates motility in large quantities |
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Term
| What is peristaltic rush? |
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Definition
| serious irritation (such as in infectious diarrhea) stimulates strong and rapid peristalsis to sweep the small intestine clear of the irritating chyme |
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Term
| What is the purpose of mucosal and villous contractions? How are they initiated? |
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Definition
1. they cause folds to appear in the intestinal mucosa and cause the villous to move around to absorb and move fat through their lymph lacteals
2. via the submucosal nerve plexus |
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Term
| What is unique about the ileocecal junction? How are its functions regulated? |
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Definition
it has valvular function, to prevent backflow into the small intestine, and sphincter function, to regulate movement of ileal contents into the large intestine
2. the former is regulated mechanically while the latter is regulated via ENS and extrinsic nerves |
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Term
| What affect does pressure in the ileum have on the ileocecal sphincter? Chemical irritation in the ileum? Pressure in the colon? Chemical irritation in the colon? |
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Definition
1. relaxes the sphincter and excites peristalsis
2. relaxes the sphincter and excites peristalsis
3. excites the sphincter and inhibits peristalsis
4. excites the sphincter and inhibits peristalsis |
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Term
| What are the primary functions of the large intestine? |
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Definition
| fluid/electrolyte absorption, storage of fecal material, and propulsion of fecal material to the anus |
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Term
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Definition
| areas of unstimulated large intestine that bulge out as a result of strong circular muscle constrictions |
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Term
| What is the consistency of the material in the ascending colon? Transverse colon? Descending colon? Sigmoid colon? |
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Definition
1. fluid
2. mush
3. semi-solid
4. solid |
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Term
| What is the name of the longitudinal muscle in the large intestine? |
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Definition
| teneae coli (there are three groups of it) |
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Term
| What is the PSNS input to the proximal colon? The distal colon? The rectum and anus? The SNS input to the proximal colon? The distal colon? The rectum and anus? |
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Definition
1. vagus
2. pelvic nerves S2-4
3. pelvis nerves S2-4
4. T10-L2 via celiac ganglia and submucosal ganglia
5. T10-L2 via the inferior mesenteric ganglia
6. T10-L2 via the hypogastric plexus, except the external anal sphincter, which is voluntary and innervated by the pudendal nerves |
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Term
| What are mass movements? Where does it occur? When do they occur? What causes them? |
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Definition
1. powerful propulsive contractions of the large intestine to force feces into the rectum to stimulate the defecate reflex
2. it usually occurs in the transverse colon or later, since chyme in the ascending colon usually does not yet have sufficiently hard consistency/enough fluid absorbed
3. after meals (especially breakfast, since it is the first after a while of not eating and a lot of PSNS activity)
4. gastrocolic reflex (distension of the stomach) and duodenocolic reflex (distension of the duodenum) |
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Term
| Neurologically, what controls defecation/the need for defecation? |
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Definition
| the intrinsic reflex, the spinal cord reflex, and higher brain centers |
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Term
| How does the the intrinsic reflex stimulate defecation? |
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Definition
| distension of the rectal wall stimulates the myenteric plexus to initiate propulsive contractions that force feces to the rectum, at which point the myenteric plexus stimulates the internal anal sphincter to relax; if the external sphincter relaxes too, defecation occurs |
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Term
| How does the spinal cord reflex stimulate defecation? |
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Definition
| stimulation of nerve endings in the rectum causes signals to be sent into the sacral spinal cord via PSNS nerves; efferent signals through the pelvic nerves then enhance propulsive peristalsis as well as actions in the Val Salva maneuver to cause defecation |
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Term
| How do the higher brain centers stimulate defecation? |
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Definition
| the spinal cord reflex can be initiated by consciously initiating the Val Salva maneuver (holding breath, closing glottis, and contracting abdominal muscles to defecate); this will push feces at least into the rectum, which will then initiate the spinal cord reflex to assist in defecation |
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Term
| What method of defecation is most important in patients with spinal cord injuries? |
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Definition
| the spinal cord reflex, if the spinal injury is superior to that level; although there will be no higher brain control, the defecation reflex can be externally initiated by digital stimulation |
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Term
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Definition
| upper esophageal sphincter, lower esophageal sphincter, pyloric sphincter, ileocecal valve/sphincter, internal anal sphincter, and external anal sphincter |
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Term
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Definition
| peristaltic reflex, enterogastric reflex, gastroileal reflex, intestino-intestinal reflex, gastrocolic reflex, duodenocolic reflex, and defecation reflex |
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Term
| What bacterial infections are likely to cause peristaltic rush? |
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Definition
| E. Coli, Staph. Aureus, V. Cholera, Shigella, Yersinia, Typhus, Claustridium perferingens, and Claustridium difficile |
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Term
Mention defining characteristics of the following infections: V. Cholera, Shigella, Yersinia, Typhus, Claustridium perferingens, and Claustridium difficile?
Which are self-limiting infections? |
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Definition
1. "rice stool"
2. blood stool
3. bloody stool and it mostly affects kids
4. Peyer's patch infection
5. can cause gangrene in skin infection, but only diarrhea in GI infection
6. hospital-acquired infection
7. Claustridium perferingens and difficile |
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