90 Questions
What initiates the basic electrical rhythm (BER) in the gastrointestinal tract?
Interstitial cells of Cajal
Where are the cells of Cajal located in the stomach and small intestine?
Outer circular muscle layer near the myenteric plexus
What is the role of spike potentials superimposed on the depolarizing portions of the BER waves?
Increase muscle tension
What ion is responsible for the depolarizing portion of spike potentials in the gastrointestinal tract?
Ca2+ influx
In what part of the gastrointestinal tract does the BER rarely cause muscle contraction?
Esophagus
Which region of the gastrointestinal tract exhibits a descending gradient in pacemaker frequency?
Small intestine
What happens to gastric secretion, bile flow, and pancreatic secretion during each MMC?
They increase
What occurs when a meal is ingested in relation to motilin secretion and MMC?
Motilin secretion is suppressed
What is the role of erythromycin in gastrointestinal motility?
It binds to motilin receptors
What triggers receptive relaxation in the stomach?
Vagal stimulation
How does the stomach accommodate food upon entry?
Through receptive relaxation
What initiates peristaltic waves in the stomach after food entry?
Gastric BER control
What is the primary function of the colon in relation to fluid absorption?
Convert isotonic chyme to semiliquid feces
What is the role of the ileocecal valve in the digestive process?
Act as a barrier to prevent reflux into the relatively sterile ileum
What happens when peristaltic waves reach the ileocecal valve?
The valve opens briefly to allow some ileal chyme to enter the cecum
Which reflex is responsible for increasing passage through the ileocecal valve when food leaves the stomach?
Gastro-ileal reflex
What is a common feature between segmentation contractions in the colon and small intestine?
They mix and expose contents to mucosa for absorption
What is the function of antiperistalsis occasionally seen in the colon?
Reverse direction of movement in specific cases
What is the main physiological mechanism through which fats, carbohydrates, and acid in the duodenum inhibit gastric acid and pepsin secretion?
Neural and hormonal mechanisms
Which hormone has been identified as possibly being the messenger involved in inhibiting gastric acid and pepsin secretion in the duodenum?
Peptide YY
What is the role of CCK in gut motility?
Inhibitor of gastric emptying
What initiates the process of vomiting?
Salivation and sensation of nausea
Why does the glottis close during vomiting?
To prevent aspiration of vomitus into the trachea
Which region of the brain contains the 'vomiting center' responsible for controlling different components of the vomiting act?
Reticular formation of the medulla
What initiates the defecation reflex?
Rectal distension
How does the frequency of the wave in the colon change along its length?
Increases from the ileocecal valve to the sigmoid colon
How long does it take for the first remnants of a meal to reach the terminal part of the colon?
12 hours
What percentage of small colored beads fed with a meal are typically recovered in the stool after 72 hours?
70%
What does monitoring a pill containing sensors and a miniature radio transmitter allow observation of within the gastrointestinal tract?
Transit time, pressure fluctuations, and pH changes
What type of contraction occurs exclusively in the colon?
Mass action contraction
What is the function of motilin during the MMC?
Promotes peristalsis and spike potentials
How does erythromycin impact gastrointestinal motility?
Binds to motilin receptors
What initiates peristalsis in the lower portion of the stomach?
Intrinsic reflexes
Which compound may have therapeutic value in patients with decreased gastrointestinal motility?
Erythromycin derivatives
What occurs in the stomach during receptive relaxation?
Accommodation of food without pressure increase
Which process is suppressed during a meal ingestion?
Peristalsis and MMC
What initiates the basic electrical rhythm (BER) in the gastrointestinal tract?
Interstitial cells of Cajal
What ions are responsible for the depolarizing and repolarizing portions of spike potentials in the gastrointestinal tract?
K+ and Ca2+
Where are the cells of Cajal primarily located in the stomach and small intestine?
Outer circular muscle layer near myenteric plexus
What role do neurotransmitters play in affecting the BER in the gastrointestinal tract?
Enhance BER frequency
What is the main function of spike potentials superimposed on the BER waves in the gastrointestinal tract?
Increase muscle tension
What effect does the location of interstitial cells of Cajal have on pacemaker frequency in the gastrointestinal tract?
Descending gradient in pacemaker frequency
What is the primary function of peptide YY in the gastrointestinal system?
Inhibiting gastric acid and pepsin secretion
Which of the following statements about vomiting is true?
Vomiting involves the closure of the glottis to protect the lungs
What is the role of CCK in relation to gastric emptying?
Inhibiting gastric emptying
Which of the following does NOT occur during the process of vomiting?
Opening of the lower esophageal sphincter
What triggers the sensation of nausea before vomiting occurs?
Impulses from the vestibular nuclei
Which part of the brain contains the 'vomiting center' that controls different components of the vomiting act?
Medulla reticular formation
What is the main purpose of slowing motility in the colon?
To facilitate absorption of water, Na+, and minerals
What is the function of the ileocecal valve in relation to the colon and ileum?
Restricts passage of commensal bacteria from the ileum to the colon
What physiological mechanism facilitates absorption in the colon?
Segmentation contractions
What initiates the gastro-ileal reflex leading to an increased flow through the ileocecal valve?
Exit of food from the stomach
What type of waves propel the contents of the colon towards the rectum?
Strong peristaltic waves
Which segmental contractions promote mixing and absorption in the colon?
Segmentation contractions
What type of contraction occurs exclusively in the colon?
Mass action contraction
What initiates the defecation reflex?
Rectal distension
Which part of the colon has the highest frequency of contraction waves per minute?
Sigmoid colon
What is the average transit time for the first remnants of a meal to reach the terminal part of the colon?
12 hours
How long does it typically take for total recovery of small colored beads fed with a meal in the stool?
1 week
What allows observation of transit time, pressure fluctuations, and pH changes in the gastrointestinal tract?
Using sensors within a pill
What is the main purpose of segmentation in the intestines?
To mix chyme with digestive juices
Which neurotransmitter is responsible for producing relaxation ahead of the stimulus in the intestines?
Nitric oxide (NO)
What describes the motility pattern related to peristalsis that retards movement of intestinal contents?
Segmentation
Which neurotransmitter activates sensory neurons that activate the myenteric plexus?
Serotonin
What is the primary function of cholinergic neurons passing in a retrograde direction in the myenteric plexus?
Produce smooth muscle contraction behind the bolus
Which type of contraction occurs routinely in the setting of segmentation in the intestines?
Retrograde movement of chyme
What is the primary function of motilin during the MMC?
Clearing stomach and small intestine of luminal contents
What triggers receptive relaxation in the stomach?
Movement of the pharynx and esophagus
Which compound may have therapeutic value in patients with decreased gastrointestinal motility?
Erythromycin
What effect does a meal ingestion have on secretion of motilin and the MMC?
Suppresses motilin secretion and abolishes MMC
What initiates peristaltic waves in the stomach after food entry?
BER controlled waves
What is the role of the ileocecal valve in the digestive process?
Controlling passage from small intestine to colon
What is the primary function of peptide YY in the gastrointestinal system?
Inhibiting gastric acid and pepsin secretion
Which part of the brain contains the 'vomiting center' responsible for controlling different components of the vomiting act?
Reticular formation of the medulla
What initiates the process of vomiting?
Irritation of upper gastrointestinal tract mucosa
Why does the glottis close during vomiting?
To prevent aspiration into the trachea
What is an example of central regulation of gut motility functions?
Vomiting
Which messenger is probably involved in inhibiting gastric acid and pepsin secretion and gastric motility in the duodenum?
Peptide YY
Which area of the brain is responsible for initiating vomiting in response to certain chemical agents?
Area Postrema
What type of receptors in the small intestine trigger impulses that lead to vomiting?
5-HT3 receptors
What is the role of ondansetron and haloperidol in treating vomiting?
Act as effective antiemetic agents
Which of the following is a condition where lesions of the area postrema decrease vomiting?
Radiation sickness
What is the primary function of serotonin (5-HT) released from enterochromaffin cells in the small intestine?
Trigger impulses for vomiting
In which part of the brain are dopamine D2 receptors and 5-HT3 receptors primarily located?
Area Postrema
What is the function of peristalsis in the small intestine?
To propel intestinal contents towards the large intestines
Which muscle contractions are initiated by focal increases in Ca2+ influx in the small intestine?
Segmentation contractions
What is the main function of the colon in relation to meal residues?
To serve as a reservoir for undigested residues
What is the average frequency of BER cycles/min in the distal ileum of the small intestine?
8 cycles/min
How do segmentation contractions in the small intestine affect chyme?
Increase exposure of chyme to the mucosal surface
What is the impact of tonic contractions on transit time in the small intestine?
Tonic contractions slow down transit time
Test your knowledge on the neural and hormonal mechanisms involved in inhibiting gastric acid and pepsin secretion, as well as gastric motility in the presence of fats, carbohydrates, and acid in the duodenum. Explore the role of peptide YY and CCK in inhibiting gastric emptying, and understand the central regulation of gut motility functions, including the process of vomiting.
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