Exam 4- Intro to GI and Swallowing

Question 1

What are the 4 functions of the GI tract?

Answer 1

Boundary (between external and internal environments), musculature, digestion, and absorption

Question 2

Absorption in the GI tract occurs via what 3 processes?

Answer 2

Diffusion, carrier transport, endocytosis

Question 3

Oral and anal events are regulated by what portion of the nervous system?

Answer 3

Somatic nerves via skeletal muscle

Question 4

The mid-esophagus to internal anal sphincter are controlled by what portion of the NS?

Answer 4

ANS via visceral smooth muscle (enteric nervous system)

Question 5

In addition to absorption of nutrients, what must also be reabsorpted to prevent imbalances?

Answer 5

7-8 L of GI secretions

Question 6

What 6 processes move food through the GI tract (start to finish)?

Answer 6

Ingestion, mechanical digestion, propulsion, chemical digestion, absorption, defecation

Question 7

What are the layers of the GI tract from serosal to luminal side?

Answer 7

Serosa, longitudinal muscle, myenteric plexus, circular muscle, submucosa, submucosal plexus, mucosa

Question 8

What are the 3 layers of the mucosa from outside to inside?

Answer 8

Muscularis mucosae, lamina propria, epithelium

Question 9

What is the outer most layer of the GI tract that continues to the mesentery?

Answer 9

Serosa

Question 10

What 2 layers of the GI tract are part of the enteric nervous system (ENS)?

Answer 10

Submucosal plexus and myenteric plexus

Question 11

What layer of the GI tract is composed of collagen, elastin, glands, and blood vessels?

Answer 11

Submucosa

Question 12

Auerbach’s is aka?

Meissner’s is aka?

Answer 12

Auerbach’s = Myenteric plexus

Meissner’s = Submucosal plexus

Question 13

What layer of the mucosa changes the shape of the epithelial layer?

Answer 13

Muscularis mucosae

Question 14

Which layer of the mucosa is mostly connective tissue but also contains some blood and lymph vessels?

Answer 14

Lamina propria

Question 15

Which layer of the mucosa is responsible for absorptive and secretory functions?

Answer 15

Epithelial cells

Question 16

What effect does venous drainage from the GI tract into the portal vein have on the liver?

Answer 16

Perfuses the liver

Question 17

Venous drainage from the pancreas stomach, sm & lg. intestine empties into where?

Answer 17

Portal vein

Question 18

What does parallel organization of splanchnic circulation allow for?

Answer 18

Regulation of flow to individual organs

Question 19

What does series organization of splanchnic circulation allow for?

Answer 19

Liver is exposed to all absorbed substances

Question 20

What is the pathway of nerve transmission in the GI tract? (4 steps)

Answer 20

Chemo/ mechanoreceptors → afferent nerves → submucosal/ myenteric plexuses → CNS (via ANS)

Question 21

The ENS does NOT require what in order to carry out most functions?

Answer 21

ANS input (it is self-contained)

Question 22

What does the myenteric (Auerbach’s) plexus innervate?

Answer 22

Longitudinal and circular smooth muscle layers

Question 23

Which plexus if primarily concerned with control of gut movements?

Answer 23

Myenteric (Auerbach’s) plexus

Question 24

What does the submucosal (Meissner’s) plexus intervate? (3)

Answer 24

Glandular epithelium, intestinal endocrine cells, and submucosal blood vessel

Question 25

What plexus is primarily concerned w/ control of intestinal secretion?

Answer 25

Submucosal plexus

Question 26

SNS stimulation via what nerves innervates from the esophagus to the proximal colon?

Answer 26

Celiac ganglia

Question 27

SNS stimulation via what nerves innervates the distal colon and rectum?

Answer 27

Superior and inferior mesenteric ganglia

Question 28

PNS stimualtion via what nerve innervates from the esophagus to the proximal colon?

Answer 28

Vagus nerve

Question 29

PNS stimulation via what nerves innervates the distal colon and rectum?

Answer 29

Sacral → pelvic nerve

Question 30

What effect does SNS release of NE on intramural plexuses, vascular smooth muscle, and secretory cells have?

Answer 30

Inhibitory effect

Question 31

What are the differences between SNS and PNS innervation of the gut?

Answer 31

SNS ouput synapse @ ganglia → POSTsynaptic → GI plexuses vs PNS output (pre-synaptic) → GI plexuses

Question 32

What is the largest endocrine organ in the body?

Answer 32

GI tract (15+ hormone secreting cells)

Question 33

What do GI peptides regulate? (3)

Answer 33

Smooth muscle, secretion of fluid/enzymes, growth of GI cells

Question 34

GI peptides fall into what 3 categories?

Answer 34

Hormones, paracrines, neurocrines

Question 35

Where are GI hormones released from?

Answer 35

Endocrine cells (disperesed throughout GI tract)

Question 36

What are the 4 known GI hormones?

Answer 36

Gastrin, Cholecystokinin (CCK), Secretin, Gastric inhibitory peptide

Question 37

What cells release gastrin?

Answer 37

Gastric G cells

Question 38

What cells release CCK?

Answer 38

Duodenal and jejunal I cells

Question 39

What cells release secretin?

Answer 39

Duodenal S cells

Question 40

What cells release gastric inhibitory peptide (GIP)?

Answer 40

Duodenal and jejunal K cells

Question 41

What stimulate secretion of gastin? (3)

Answer 41

Small peptides/ AAs, stomach distension, vagal stimulation

Question 42

What stimulate secretion of CCK? (2)

Answer 42

Small peptides and AA, fatty acids

Question 43

What stimulate secretion of secretin? (2)

Answer 43

H+ in the duodenum, fatty acids in duodenum

Question 44

What stimulate secretion of GIP? (3)

Answer 44

Fatty acids, AAs, oral glucose

Question 45

What hormone ↑ gastric H+ secretion and stimulates growth of gastric mucosa?

Answer 45

Gastrin

Question 46

What 2 hormones ↑ pancreatic HCO3- secretion?

Answer 46

CCK and Secretin

Question 47

What 2 hormones ↓ gastic H+ secretion?

Answer 47

Secretin and GIP

Question 48

What hormone stimulates contraction of the gallbladder and relaxation of the sphincter of Oddi?

Answer 48

CCK

Question 49

What hormones increases insulin secretion from pancreatice B cells?

Answer 49

GIP (why we are able to reactive so quickly to oral glucose)

Question 50

What hormones inhibits trophic effects of gastrin on gastric mucosa?

Answer 50

Secretin

Question 51

What hormone ↑ biliary HCO3- secretion?

Answer 51

Secretin

Question 52

What hormones inhibit gastric emptying?

Answer 52

CCK, secretin, GIP

Question 53

What hormone stimulates growth of the exocrine pancreas and gallbladder?

Answer 53

CCK

Question 54

Paracrine are carried via what to target cells? (2)

Answer 54

Capillaries or diffusion

Question 55

What are the 2 GI paracrines?

Answer 55

Somatostatin and histamine

Question 56

What hormone is released from D cells and inhibits release of all gut hormones?

Answer 56

Somatostatin

Question 57

What hormone is a non-peptide paracrine?

Answer 57

Histamine

Question 58

Neurocrines are synthesized in neurons and released in response to what?

Answer 58

Action potential

Question 59

What are the main GI neurocrines? (4)

Answer 59

Acetylcholine, norepinephrine, vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP) (others: enkephalins, neuropeptide Y, substance P)

Question 60

What neurocrine increases salivary, gastric and pancreatic secretions, relaxes sphincters, and increases contraction of wall smooth muscle?

Answer 60

Acetylcholine (PNS - cholinergic neurons)

Question 61

What neurocrine causes increased salivary secretion, sphincter contraction and relaxation of wall smooth muscle?

Answer 61

Norepinephrine (SNS - adrenergic neurons)

Question 62

What neurocrine caues relaxation of smooth muscle and increases GI secretions (intestinal and pancreatic)?

Answer 62

Vasoactive intestinal peptide (VIP) (PNS, ENS - neurons of enteric NS)

Question 63

What neurocrine increases gastrin secretion?

Answer 63

Gastrin-releasing peptide (GRP) (PNS)

Question 64

Does NO released from the neurons of the enteric NS result in relaxation or contraction of smooth muscle?

Answer 64

Relaxation

Question 65

GRP is released from what neurons?

Answer 65

Vagal neurons of the gastric mucosa

Question 66

What is the structure of visceral smooth muscle cells w/in the GI tract? How are the organized?

Answer 66

Long and slender. Organized in packed bundles (functional unit) separated by connective tissue

Question 67

How are visceral smooth muscle cells connected and what does this allow for?

Answer 67

Connected by low resistance gap junctions, allows for electrical propagation between adjacent fibers

Question 68

What do VSMC exhibit of the resting membrane potential due to variations in Ca2+ and K+ conductances?

Answer 68

Spontaneous oscillations (slow waves/ basic electrical rhythm)

Question 69

What happens if slow waves of VSMC reach depolarization threshold?

Answer 69

Action potential will superimpose on slow wave resulting in strong contraction of smooth muscle

Question 70

What cells initiate BER via long branched processes into the VSMC?

Answer 70

Interstitial cells of Cajal/ stellate pacemaker cells

Question 71

Do ACh or NE affect BER frequency?

Answer 71

No

Question 72

What effect does ACh have on the activity of VSMC? (3)

Answer 72

Increases: BER amplitude, number of spike potentials, VSMC tension

Question 73

What effect does NE have on the activity of VSMC? (3)

Answer 73

Decreases: BER amplitude, number of spike potentials, VSMC tension

Question 74

What are the 2 patterns of GI motility?

Answer 74

Segmentation and peristalsis

Question 75

Contraction and relaxation of adjacent segments (agitation/mixing type movement) is what GI motility pattern?

Answer 75

Segmentation

Question 76

Peristalsis requires contraction behind the bolus of food and relaxation ahead of the bolus of food. This results in what kind of movement?

Answer 76

Directed propulsive

Question 77

What are the 3 phases of digestion?

Answer 77

Cephalic, gastric, early and late intestinal

Question 78

During what phase are there low levels of motor, secretory and digestive activity?

Answer 78

Interdigestive

Question 79

Towards the end of what phase will you have a sense of hunger?

Answer 79

Interdigestive

Question 80

What is decribed by cycles of motor activity from the stomach to the ileum during the interdigestive phase?

Answer 80

Migrating motor complex (MMC)

Question 81

What regulated the migrating motor complex (MMC)

Answer 81

The "candidate" hormone motilin from the upper duodenum

Question 82

What is the "housekeeping" function of the MMC?

Answer 82

Removes undigested material from stomach (begins 2 hrs post prandial & stop when meal is taken)

Question 83

What type of contractions are produced by the MMC?

Answer 83

Intense and slow, 90 minute intervals

Question 84

What phase of digestion triggers autonomic and endocrine reflexes (prepares the GI tracts) via the anticipation of eating and 1st sensory contact w/ food?

Answer 84

Cephalic

Question 85

The cephalic phase of digestion is due to activation of what neural response?

Answer 85

PNS efferents (sight, smell, gustatory afferents enhance PNS)

Question 86

During the cephalic phase, PNS activity increases secretion of what things? (4)

Answer 86

Saliva, gastric acid, gastrin, pancreatic enzymes

Question 87

What is the daily salivary output?

Answer 87

0.5-1/5 L/day (flow rate varies w/ chewing)

Question 88

What is the site of formation of saliva?

Answer 88

Acinar cells in salivary glands

Question 89

What are the 5 components of saliva?

Answer 89

1. Mucus (lubricant) 2. a-amylase (starts starch digestion) 3. lingual lipase (starts fat digestion) 4. slightly alkaline solution (moistens food) 5. IgA & kallikrein

Question 90

What is the role of IgA and kallikrein in saliva?

Answer 90

Increase bradykinin = increased BF to salivary glands

Question 91

Saliva is hypo or hypertonic to plasma?

Answer 91

Hypo

Question 92

What ions are present at a lower concentrations in saliva, compared to plasma?

Answer 92

Na+ and Cl-

Question 93

What ions are present at a higher concentrations in saliva, compared to plasma?

Answer 93

K+ and HCO3-

Question 94

What 2 things change as saliva secretion rates increases?

Answer 94

Saliva becomes isotonic compared to plasma and pH increases (increased HCO3-)

Question 95

How does saliva change from isotonic to hypotonic after being release from acinar cells?

Answer 95

Salivary ducts are impermable to water, Na, Cl out > K, HCO3

Question 96

Nervous regulation of salivary secretion is mostly via what?

Answer 96

PNS (SNS contributes slight/ short-lived, mostly mucus secretion)

Question 97

What stimulates the salivary gland (in medulla)?

Answer 97

Taste and tactile stimulation in mouth (also smell)

Question 98

ACh and VIP from PNS nerve endings stimulate what with regards to the salivary response? (4)

Answer 98

1. saliva secretion 2. vasodilation 3. salivary duct dilation 4. secretion of amylase, lipase and mucus

Question 99

What is the PNS pathway for saliva regulation?

Answer 99

PNS → CN VII, X → release ACh on M receptors → IP3, Ca → Saliva

Question 100

What stimulates the PNS to increase saliva production? (3)

Answer 100

Operant conditioning, food/smell, nausea

Question 101

Will there be increased or decreased salivary secretion during dehydration, fear and sleep?

Answer 101

Decreased

Question 102

What area of the brain coordinates swallowing?

Answer 102

Medullary swallowing center (first voluntary then reflexive)

Question 103

What are the 3 phases of swallowing?

Answer 103

Oral (buccal), pharyngeal, esophageal

Question 104

During the oral phase of swallowing, what is stimulated after a bolus is formed during mastication and pushed voluntarily by the tongue toward the pharynx?

Answer 104

Stimulation of somatosensory receptors → involuntary swallowing reflex

Question 105

How is the pharyngeal phase of swalloing controlled?

Answer 105

Reflexively

Question 106

What process is inhibited during the entire pharyngeal phase of swallowing?

Answer 106

Breathing

Question 107

What prevents reflux into nasopharynx during pharyngeal phase of swallowing?

Answer 107

Upward movement of soft palate

Question 108

During the pharyngeal phase of swallowing, the epiglottis moves to cover the opening to the larynx and the larynx moves upwards against the epiglottis. What does this prevent?

Answer 108

Food from entering the trachea

Question 109

What is reflexivley inhibited and relaxes briefly during the pharynageal phase of swallowing?

Answer 109

UES (perstaltic waves propels food through the open sphincter)

Question 110

What causes the LES to relax during the esophageal phase of swallowing?

Answer 110

VIP

Question 111

At what point during the esophageal phase of swallowing does the LES contract?

Answer 111

As bolus passes into stomach

Question 112

An incomplete swallow or gastric regurgitation results in a second peristaltic wave/ secondary swallow. What is this controlled by?

Answer 112

ENS

Question 113

What is used to measure the esophageal pressure changes during swallowing?

Answer 113

Esophageal manometry (used if there is dysfunction)

Question 114

What disorder is caused by failure of the LES fails to relax during swallowing resulting in food accumulation/ dilation of esophagus?

Answer 114

Achalasia

Question 115

What are the 2 potential causes of achalasia?

Answer 115

Degeneration of myenteric plexus, defective release of NO and VIP

Question 116

During achalasia, when will food enter the stomach?

Answer 116

When esophageal pressure > LES pressure

Question 117

What is the cause of reflux esophagitis?

Answer 117

Loss of LES tone (or overindulgence)

Question 118

What does reflux esophagitis result in?

Answer 118

Acid reflux from stomach to esophagus = heartburn/ ulceration