digestive 2

Question 1

the digestive secretions and contractions must be controlled such that they provide optimal conditions for

Answer 1

digestion and absorption

Question 2

the GI control systems regulate conditions

Answer 2

in the lumen of the tract (rather than in the ECF)

Question 3

the GI control reflexes are governed by

Answer 3

volume and composition of contents of the lumen (rather than the nutritional state of the body)

Question 4

most of the receptors (that initiate GI reflexes) are located

Answer 4

in the wall of the GI tract itself

Question 5

the receptors located in the wall of the GI tract respond to:

Answer 5

distention of the lumen wall, the osmolarity or acidity or the chyme, or the products of digestion (amino acids, fatty acids, monosaccharides, etc)

Question 6

the reflexes (from receptors located in the wall of the GI tract) are triggered by the activation of these mechano-, osmo-, and chemoreceptors in the lumen wall, and influence:

Answer 6

the muscles in the GI tract wall and the exocrine glands that secrete into its lumen

Question 7

the GI tract reflexes, like any negative feeback reflex, prevent large changes in the variables that initiate them. this prevention of change maintains the optimal luminal conditions for

Answer 7

digestion and absorption

Question 8

GI tract has its own local nervous system, the ____ nervous system, in the form of the ____ and ____ nerve plexuses

Answer 8

enteric

myenteric and submucosal

Question 9

sympathetic neurons are mainly

Answer 9

postganglionic

Question 10

parasympathetic neurons are mainly

Answer 10

preganglionic

Question 11

the neruons of the myenteric plexus and submucosal plexus synapse with each other, with the GI tract muscles, glands, and epithelial cells, so that stimulation at one point can

Answer 11

lead to impulses that go both up and down the tract

Question 12

neural reflexes within the tract can act ____ of the CNS

Answer 12

independently

Question 13

sympathetic and parasympathetic neurons synpase with neurons of both plexuses, allowing

Answer 13

CNA influence on GI tract motility and secretions

Question 14

transmitters released by enteric neurons include

Answer 14

norepinephrine, acetylcholine, nitric oxide, ATP and several neuropeptides

Question 15

a few reflexes are initiated by stimuli (such as ____ , ____ or the ____ or ____ of food) that are outside the GI tract

Answer 15

hunger, emotions, sight or smell

Question 16

the hormone-secreting cells of the GI tract are cells scattered throughout

Answer 16

the tracts mucosal epithelium (rather than beging clustered into discreted organs)

Question 17

the luminal surface of hormone-secreting cells of the GI tract are exposed to and stimluated by

Answer 17

some chemical in the chyme, causing hormone release into the blood from the cell’s other surface

Question 18

the released hormone diffuses into blood capillaries, thus these hormones reach their target cells mainly via the

Answer 18

circulation

Question 19

hormones secreted from the GI tract that participate in homronal regulation of GI control reflexes include ____ from the stomach, and ____ and ____ from the SI

Answer 19

gastrin

secretin and cholecystokinin

Question 20

function of cholecystokinin (CKK)

Answer 20

keeps fat content of duodenum as close to zero as possible

Question 21

chewing (mastication) occurs via ____ muscles and is regulated by ____ neurons

Answer 21

skeletal

somatic motor

Question 22

the pressure of food against the palate, tongue, and gums reflexively activates

Answer 22

rhythmic contractions (and inhibits the muscles holding the jaw closed)

Question 23

sailva is secreted by

Answer 23

parotid glands (x2)

submandibular glands (x2)

sublingual glands (x2)

Question 24

unlike with most organs, both ____ and ____ input to the salivary glands ____ secretion, with ____ input being more potent

Answer 24

sympathetic and parasympathetic

stimulate

parasympathetic

Question 25

the control reflex for saliva secretion are initiated by various stimuli including

Answer 25

sight of food, smell of food, mechanoreceptors in the mouth that detect pressure, and chemo/taste receptors in the mouth, especially ones that detect acids

Question 26

salivary reflexes can be modified by input from other brain regions (e.g. appetite area of the ____ ) to the ____ ____ in the brainstem

Answer 26

hypothalamus

salivatory nuclei

Question 27

salivary secretion flowchart:

eyes, smell receptors, taste buds, mouth mechanoreceptors → sensory neurons in ____ nerves from receptors to brain → ____ ____ in brainstem → ____ neurons in facial and ____ nerves → increased saliva secretion from salivary glands

Answer 27

eyes, smell receptors, taste buds, mouth mechanoreceptors → sensory neurons in cranial nerves from receptors to brain → salivatory nuclei in brainstem → parasympathetic neurons in facial and glossopharyngeal nerves → increased saliva secretion from salivary glands

Question 28

pressure receptors in the pharynx wall are stimulated by food forced into the pharynx/posterior oral cavity, and sends sensory impulses to the swallowing center in the

Answer 28

medulla oblongata

Question 29

swallowing center’s output:

1. includes both impulses in somatic neurons to ____ muscles and in autonomic neurons to ____ muscles
2. inhibits respirations and closes the ____ ( which is further protected when food pushes the ____ back to cover the glottis) ; these actions are very temporary
3. elevates the soft palate to prevent food from:
4. relaxes the
5. causes ____ waves of the muscle contraction (skeletal muscles in the upper 1/3 and smooth muscle in the lower 2/3 of the esophagus) that force food toward the stomach
6. opens the

Answer 29

1. skeletal smooth
2. glottis epiglottis
3. entering the nose
4. upper esophageal sphincter
5. peristaltic
6. lower esophageal spincter

Question 30

if a food bolus does not reach the stomach, the resulting distension of the esophageal wall stimulates

Answer 30

sensory receptors that initiate reflexes resulting in repeated contractile waves called secondary peristalsis

Question 31

if the lowe esophageal spincter is unable to prevent stomach contents from splashing into the esophagus, what happens

Answer 31

gastroesophageal reflux (“heart burn”)

Question 32

the mucosal epithelium in the stomach, is a single cell layer that invaginates into the mucosa to form many tubular glands, they are:

Answer 32

gastric (oxyntic) glands

pyloric glands

Question 33

gastic (oxyntic) glands secrete

Answer 33

1. hydrochloric acid and intrinsic factor (from parietal, or oxyntic cells)
2. pepsinogen (from chief cells or peptic cells)
3. mucus (from mucous neck cells)

Question 34

a parietal cell contains

Answer 34

invaginations of the luminal membrane called canaliculi

Question 35

pyloric glands secrete

Answer 35

1. mucus (for protection)
2. gastrin (is secreted into the blood)

Question 36

HCl secretion from gastric (oxyntic) glands:

on the luminal border:

1. H⁺ (derived from the breakdown of water) is pumped:
2. the K⁺ then leaks:

on the basolateral border:

1. Cl^- is exchanged for:
2. the Cl^- then diffuses:

Answer 36

on the luminal border:

1. out of the cell and into the stomach lumen by an ATP-using active transport carrier (which is a countertransporter that pumps H⁺ out and K⁺ into the cells)
2. back into the lumen through ion channels

on the basolateral border:

1. biocarbonate ions (with Cl^- moving into the cell and HCO₃^- out) by a non-energy using countertransporter
2. out of the parietal cell and into the stomach lumen via ion channels

Question 37

acid secretion into the stomach lumen is increased by messengers ( ____ , ____ , and the paracrine ____ ) that act on parietal cells to stimulate the insertion, into the luminal membrane, of additional H⁺/K⁺ energy-using cotransporter proteins

Answer 37

acetylcholine, gastrin, and histamine

Question 38

acid secretion is decreased by the messenger ____ , a paracrine acting on the parietal cells

Answer 38

somatostatin

Question 39

histiine is released from ____ cells and in addition to its own direct actions on parietal cells to stimulate acid secretion, it potentiates the actions on parietal cells of ____ and ____

Answer 39

enterochromaffin-like (ECL)

acetylcholine and gastrin