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Physiology (books) > Upper GIT (berne Ch. 26-28) > Flashcards

Upper GIT (berne Ch. 26-28) Flashcards

1
Q

Hormonal and Paracrine Mediators in the GI Tract

Gastrin
Source: 
Stimulus for Release:
Pathway of Action:
Targets: 
Effect:
A

Source: Gastric antrum (G cells)
Stimulus for Release: Oligopeptides
Pathway of Action: Endocrine
Targets: ECL cells and parietal cells of the gastric corpus
Effect: Stimulation of parietal cells to secrete H+ and ECL cells to secrete histamine

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2
Q

Hormonal and Paracrine Mediators in the GI Tract

Cholecystokinin
Source: 
Stimulus for Release:
Pathway of Action:
Targets: 
Effect:
A

Source: Duodenum (I cells)
Stimulus for Release: Fatty acids, hydrolyzed protein
Pathway of Action: Paracrine, endocrine
Targets: Vagal afferent terminals, pancreatic acinar cells
Effect: Inhibition of gastric emptying and H+ secretion; stimulation of pancreatic enzyme secretion, gallbladder contraction, inhibition of food intake

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3
Q

Hormonal and Paracrine Mediators in the GI Tract

Secretin
Source: 
Stimulus for Release:
Pathway of Action:
Targets: 
Effect:
A

Source: Duodenum (S cells)
Stimulus for Release: Protons
Pathway of Action: Paracrine, Endocrine
Targets: Vagal afferent terminals, pancreatic duct cell
Effect: Stimulation of pancreatic duct secretion (H2O and HCO3)

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4
Q

Hormonal and Paracrine Mediators in the GI Tract

Gluco-insulinotropic peptide (GIP)
Source: 
Stimulus for Release:
Pathway of Action:
Targets: 
Effect:
A 
Source: Intestine (K cells)
Stimulus for Release: Fatty acids, glucose
Pathway of Action: Endocrine
Targets: Beta cells of the pancreas
Effect: Stimulation of insulin secretion
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5
Q

Hormonal and Paracrine Mediators in the GI Tract

Peptide YY (PYY) 
Source: 
Stimulus for Release:
Pathway of Action:
Targets: 
Effect:
A

Source: Intestine (L cells)
Stimulus for Release: Fatty acids, glucose, hydrolyzed protein
Pathway of Action: Endocrine, paracrine
Targets: Neurons, smooth muscle
Effect: Inhibition of gastric emptying, pancreatic secretion, gastric acid secretion, intestinal motility, food intake

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6
Q

Hormonal and Paracrine Mediators in the GI Tract

Proglucagon-derived peptides 1/2 (GLP-1/2)
Source: 
Stimulus for Release:
Pathway of Action:
Targets: 
Effect:
A

Source: Intestine (L cells)
Stimulus for Release: Fatty acids, glucose, hydrolyzed protein
Pathway of Action: Endocrine, paracrine
Targets: Neurons, epithelial cells
Effect: Glucose homeostasis, epithelial cell proliferation

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7
Q

Blind-ending glandular structures that are invaginations of the lining of the duodenum; these glands empty their secretions (copious amounts of HCO3) into the gut lumen

A

Brunner’s glands

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8
Q

IN THE CLINIC

A regulatory peptide released from EECs cells in the gut wall in response to the presence of luminal carbohydrate and lipids.

A

Glucagon-like peptide 1 (GLP-1)

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9
Q

IN THE CLINIC

GLP-1 arises from differential processing of the glucagon gene, the same gene that is expressed in the pancreas and that gives rise to glucagon. GLP-1 is involved 1) ______ via stimulation of 2) ______and 3) ______

A

Regulation of blood glucose
Insulin secretion
Insulin biosynthesis

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10
Q

IN THE CLINIC

Agonists of the GLP-1 receptor improve insulin sensitivity. Administration of GLP-1 also reduces appetite and food intake and delays gastric emptying, responses that may contribute to improving glucose tolerance. 1) _____ is a long-acting agonist for the GLP-1 receptor that has been approved for the treatment of 2) _____.

A

Exanatide

Type 2 diabetes mellitus

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11
Q

The subdivision of the extrinsic neural innervation to the gut that arises via the vagus and pelvic nerves (craniosacral).

A

Parasympathetic innervations

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12
Q

The vagus nerve, the 10th cranial nerve, innervates the (7)

A

Esophagus, stomach, gallbladder, pancreas, first part of the intestine, cecum, and the proximal part of the colon

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13
Q

The pelvic nerves innervate the (3)

A

Distal part of the colon, anorectal region, and other pelvic organs that are not part of the GI tract

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14
Q

The preganglionic nerve cell bodies of the parasympathetic nervous system of the GIT lie in the 1) _____ or the _____ whereas; the postganglionic neurons lie in the 2) _____

A 
Brainstem (vagus), sacral spinal cord (pelvic) 
Gut wall (enteric neurons)
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15
Q

Sympathetic innervation is supplied by cell bodies in the spinal cord and fibers that terminate in the _____prevertebral ganglia (celiac, superior, and inferior mesenteric ganglia)

A

prevertebral ganglia (celiac, superior, and inferior mesenteric ganglia)

  • *these are preganglionic neurons that synapse with postganglionic neurons in the ganglia
  • *the fibers leave the ganglia and reach the end organ along the major blood vessels and their branches.
  • *Rarely, there is a synapse in the paravertebral (chain) ganglia.
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16
Q

The cell bodies for the vagal afferents, its central projection terminating in the nucleus of the tractus solitarius in the brainstem and the other terminal in the gut wall

A

Nodose ganglion

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17
Q

Segmentally organized cell bodies of the spinal afferent neurons that run with the sympathetic pathway

A

Dorsal root ganglia

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18
Q

Reflex-pathway mediated entirely via the vagus nerve, which has both afferent and efferent fibers.

A

Vagovagal reflex
**An example of an important vagovagal reflex is the gastric receptive relaxation reflex, in which distention of the stomach results in relaxation of the smooth muscle in the stomach; this allows filling of the stomach to occur without an increase in intraluminal pressure.

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19
Q

IN THE CLINIC

A congenital disorder of the enteric nervous system characterized by failure to pass meconium at birth or severe chronic constipation in infancy. The typical features are absence of myenteric and submucosal neurons in the distal part of the colon and rectum. It is a polygenic disorder with characteristic mutations in at least three different classes of genes involved in neuronal development and differentiation

A

Hirschsprung’s disease

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20
Q

These cells characterized by basally located nuclei, abundant rough endoplasmic reticulum, and apically located secretory granules that contain the enzyme amylase and other secreted proteins. These cells are located in what part of the secretory glands?

A

secretory end pieces or acini

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21
Q

What are the three kinds of ducts that transport secretions from the acinus to the opening in the gland?

A

Intercalated duct, striated duct, excretory duct

22
Q

What parts of the secretory duct are lined by cells responsible for modification of ionic composition and osmolarity of the secretion?

A

Striated and excretory ducts

23
Q

True or false
The important properties of saliva are small flow rate relative to the mass of gland, high osmolarity, high K+ concentration, and organic constituents, including enzymes (amylase, lipase), mucin, and growth factors

A

False – saliva have high flow and is a hypotonic solution (low osmolarity)

24
Q

The inorganic composition of saliva such as Na, K, HCO3 and Ca are entirely dependent on what 2 factors

A

Stimulus and rate of salivary flow

25
Q

This isotonic type of secretion is produced by acinar cells in the secretory end pieces (acini) and is modified by duct cells as saliva passes through the ducts. The concentration of the major ions is also similar to that in plasma

A

Primary secretion

26
Q

What mechanism is responsible for opening of apical Cl channels in the acinar cells thereby establishing an osmotic and electrical gradient which drives the secretion?

A

Ca+ +-dependent signaling

27
Q

Duct cells reabsorbs 1) _____ and _____; and secretes 2) ______ and ______

A

Na, Cl
K, HCO3

    • Na is exchanged for protons
    • some of the secreted protons are reabsorbed in exchange for K
    • HCO3 is exclusively secreted in exchange for Cl
28
Q

_____ in secretion flow rate, the resulting saliva more closely resembles the primary secretion and therefore plasma.

A

Increase

29
Q

This is responsible for high HCO3 level in the saliva even at high flow rates

A

Secretagogues

30
Q

In the SECRETORY ACINUS of salivary glands

The basolateral membrane of the acinar cells contains what type of transporters (2)

A

Na+,K+-ATPase and Na+-K+-2Cl- symporter

In the SECRETORY ACINUS of salivary glands

31
Q

Cl− and HCO3 leave the acinar cell and enter the lumen via what transporter?

A

Anion channel located in the apical membrane of the acinar cell

32
Q

IN THE CLINIC

The acinar cells and duct cells of the salivary glands respond to both cholinergic and adrenergic agonists.
Acetylcholine and substance P, acting on 1) _____ and ______ receptors, respectively, increase the cytosolic concentration of 2) ______in serous acinar cells.

A

1) Muscarinic, tachykinin

2) Calcium

33
Q

IN THE CLINIC

Agonists that mobilize Ca+ + elicit a secretion that is ________

A

more voluminous but has a lower concentration of amylase

34
Q

IN THE CLINIC

Norepinephrine, acting on β receptors, and VIP, acting at its receptor, elevate the_____ in acinar cells

A

cAMP concentration

35
Q

IN THE CLINIC

Agonists that elevate the cAMP concentration in serous acinar cells elicit a secretion ______

A

Rich in amylase

36
Q

Anatomically, the stomach is divided into three regions (1); functionally, the stomach is divided into two regions (2); the stomach is also divided according to structures of gland lining its surface (3).

A

1) Cardia, Corpus/fundus and Antrum
2) Proximal and distal
3) Small cardiac glandular region (mucus), parietal gland region (acid), pyloric gland region (mucus HCO3)

37
Q

Gastric gland from the oxyntic glandular region

Parietal cells: 
Mucous neck cells: 
Chief or peptic cells: 
enterochromaffin-like (ECL):
D cells:
A 
Parietal cells: HCl and intrinsic factor (involved in absorption of vitamin
B12)
Mucous neck cells: Mucous and HCO3
Chief or peptic cells: pepsinogens
Enterochromaffin-like (ECL): histamine
D cells: somatostatin
38
Q

The ionic composition of gastric juice depends on the rate of secretion. The higher the secretory rate, the 1)_____ the concentration of H+ ions. At lower secretory rates, [H+] 2) _____ and [Na+] ______.

A

1) Higher

2) Lower, higher

39
Q

Prolonged vomiting may lead to ______

A

Hypokalemia

40
Q

At all rates of secretion, what is the major anion of gastric juice.

A

Cl

41
Q

At high rates of secretion, gastric juice resembles an (A) isotonic, (B) hypotonic or (C) hpertonic solution of HCl.

A

A

42
Q

Parietal cells have a distinctive ultrastructure. What structure course through the cytoplasm and are connected by a common outlet to the cell’s luminal surface

A

Secretory canaliculi

43
Q

What structure in the cytoplasm of unstimulated parietal cells contains the transport proteins responsible for secretion of H+ and Cl− into the lumen of the gland?

A

tubulovesicular system.

44
Q

The fusion of these two structures is the result of parietal cells stimulation to secrete HCL

A

tubulovesicular membranes and plasma membrane of the secretory canaliculi.

45
Q

The cellular mechanism of H+ secretion by the parietal cell

This anion enters the cell across the basolateral membrane in exchange for HCO3 generated in the cell by the action of carbonic anhydrase, which produces HCO3 and H+

A

Cl

    • HCO3 exits the parietal cells and goes to the bloodstream
  • *from the bloodstream, Cl enters the parietal cell in exchange for the HCO3
46
Q

H+ is secreted across the luminal membrane by what transporter and in exchange for what cation

A

H,K-ATPase pump, K

47
Q

Parasympathetic activation, via gastrin-releasing peptide from intrinsic neurons, releases gastrin from G cells located in the gastric glands in the gastric antrum. Gastrin enters the bloodstream and, via an endocrine mechanism, further stimulates the parietal cell to secrete H.
Parietal cells express what type of receptors for gastrin?

A

Cholecystokinin 2 (CCK 2)

48
Q

True or false

ECL cells which secrete histamine express muscarinic and gastrin receptors

A

True – gastrin and vagal efferent activity induce the release of histamine

49
Q

Strongest agonist of Hsecretion

A

Histamine

50
Q

Specialized group of cells in the intestinal wall that are involved in the transmission of information from enteric neurons to smooth muscle cells. It is the “pacemaker” cells that have the capacity to generate the basic electrical rhythm, or “slow wave” activity that is a consistent feature of GI smooth muscle

A

Interstitial cells of Cajal (ICC)

51
Q

IN THE CLINIC

There are times when the gastric mucosal barrier fails. Superficial breakdowns of the GI lining not involving the submucosa and generally heal without intervention are called ______. Breakdown of the GI lining involving the muscularis and deeper layers are called _____

A

Erosions, ulcers

52
Q

IN THE CLINIC

A spiral bacterium that has now become widely recognized as one factor that can lead to gastritis, ulcer formation, and in humans, gastric carcinoma

A 
H. pylori
** Other factors that magnify the harmful effect of H+ on the stomach/duodenum or act separately from H+ include pepsin, bile,and the class of drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs).

Physiology (books) (9 decks)

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