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GI Final - MSI Spring > Intro to Physiology > Flashcards

Intro to Physiology Flashcards

1
Q

Name the extrinsic nervous system of the GI tract. Where are the cell bodies?

A

ANS
- Parasympathetic and sympathetic
Cell bodies are located outside the gut wall

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2
Q

Name the Intrinsic nervous system of the GI tract. Where are the cell bodies?

A

ENS
- Myenteric and submucosal plexuses
Cell bodies are located inside the gut wall

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3
Q

Describe parasympathetic innervation of the GI tract. Include the nerves, cell body location, neurotransmitters, and what it synapses with once in the gut wall

A

Via the vagus and pelvic nerves
Preganglionic nerve cell bodies in brainstem or sacral spinal cord
Postganglionic neurons lie in the wall of the organ
Nicotinic - ACh
Synapses with the myenteric plexus between the muscularis externa and submucosal plexus

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4
Q

Describe sympathetic innervation of the GI tract. Include the nerves, cell body location, neurotransmitters, and what it synapses with once in the gut wall

A

Via thoracolumbar region
Preganlionic efferent fibers arise within the spinal cord and end in prevertebral ganglia
Postganglionic fibers from prevertebral ganglia
Innervates myenteric and submucosal plexuses and direct innervation of the muscles
Pre-ACh Post - NE

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5
Q

With the vago-vagal reflux, how much of it is afferent vs efferent?

A

75% afferent

25% efferent

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6
Q

What is the sensory ganglion of the vagal nerve called?

A

nodose ganglion

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7
Q

Where are the centers that control food intake located?

A

within the hypothalamus

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8
Q

Describe paracrine signaling in the GI tract

A

Paracrines act locally
Signals reach target cells by diffusion over short distances
Released by enteroendocrine cells or other sensing cells
Ex. somatostatin and histamine

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9
Q

What is the main actions, site of release and stimuli for release of somatostatin?

A

Main actions: inhibits gastric H secretion directly through parietal cells or inhibit histamine or gastrin
Secreted by D cells inside the GI tract or hypothalamus and delta cells of exocrine pancreas
LOW luminal pH is the stimulus

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10
Q

What is the main actions, site of release and stimuli for release of histamine?

A

an amine that stimulates acid production through parietal cells (opposite of somatostatin)
Secreted by enterochromaffin-like cells in gastric glands
Stimuli - Gastrin (wikipedia)

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11
Q

Describe endocrine regulation in the GI tract

A

ECCs contain secretary granules filled with hormone peptides
Hormones are secreted into portal circulation and reach systemic circulation
Bind to specific receptors on target cells
Stimuli must not come from a nerve or AP, instead from a stimuli like mechanical stretch

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12
Q

What stimulates gastrin secretion? What is the site of secretion?

A

Small peptides and a.a, distention of the stomach, vagal stimulation via GRP

Site: G cells of the stomach

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13
Q

What are the main actions of gastrin?

A

Increase gastric acid secretion and stimulates growth of gastric mucosa

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14
Q

What is zollinger-ellison syndrome?

A

gastrin-secreting tumors causing an increase of circulating levels of gastrin, increase of acid secretion by parietal cells and the # of parietal cells.
Hypertrophy of gastric mucosa
duodenal ulcers
steatorrhea

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15
Q

what is steatorrhea?

A

pancreatic enzymes are impaired thus, there is an excretion of abnormal quantities of fat with the feces

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16
Q

What stimulates CCK secretion? What is the site of secretion?

A

Small peptides and a.a. and fatty acids (not including triglycerides)

Site: I cells of the duodenum and jejunum

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17
Q

What are the main actions of CCK?

A

increase pancreatic enzyme secretion, and bicarb secretion (indirectly through secretin)

Stimulates contraction of gallbladder and relaxation of sphincter of oddi

Stimulates growth of exocrine pancreas and gallbladder (trophic effect)

Inhibits gastric emptying to process fats longer
can act as paracrine signal

Increase gastric distention

Elicits satiety (acts on vagal->NTS->hypothalamus circuit to decrease release of ghrelin)

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18
Q

What are the receptors for CCK?

A

CCK1(A) - specific for CCK

CCKB - sensitivity for both gastrin and CCK

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19
Q

What stimulates secretin and what is the site of secretion?

A

H+ in the duodenum and fatty acids in the duodenum

S cells of the duodenum secrete secretin

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20
Q

What are the main actions of Secretin?

A 
increase pancreatic bicarb secretion
increase biliary bicarb secretion 
Decrease gastric H+ secretion 
Inhibits trophic effect of gastrin on gastric mucosa
Can act as paracrine signal
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21
Q

What stimulates the secretion of GIP and what is the site of secretion?

A

Fatty acids, a.a., and oral glucose

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22
Q

What are the main actions of GIP?

A

increases insulin secretion from pancreatic beta cells

decrease gastric H+ secretion

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23
Q

What would be more effective in increasing insulin secretion, oral glucose administration or intravenous glucose administration?

A

oral glucose stimulates GIP, which stimulates insulin secretion, and also has direct stimulatory effects on beta cells

24
Q

What is motilin?

A

Hormone that is secreted by upper duodenum

Increases motility and is released every 90 min

25
Q

What is pancreatic polypeptide?

A

In response to carbs, proteins or lipids, it is released from pancreas and inhibits bicarb secretions

26
Q

What is enteroglucagon?

A

in response to low blood glucose, it is released from intestines to increase glycogenolysis and gluconeogenesis

27
Q

What is GLP 1?

A

glucagon-like peptide that is from L cells of small intestine
Increases insulin secretion from beta cells
inhibits glucagon, appetite, and gastric emptying

28
Q

Describe neural regulation in the GI tract

A

Neurotransmitters
AP are needed for neurotransmitter release from nerve terminals in GI tract
Diffuse across synapse

29
Q

What are the actions of ACh in GI tract?

A

contraction of Sm m.
relaxation of sphincters
Increase of salivary, gastric, and pancreatic secretion

(cholinergic)

30
Q

What are the actions of NE?

A

Relaxation of Sm m.
Contraction of sphincters
Increase of salivary secretion

(adrenergic)

31
Q

What are the actions of VIP?

A

Relaxation of the Sm m.
Increase intestinal secretion
Increase pancreatic secretion

(source - neurons of the mucosa and sm m)

32
Q

What are the actions of GRP?

A

gastrin-releasing peptide causes increase of gastrin secretion

(source-neurons from gastric mucosa)

33
Q

What are the actions of enkephalins?

A

contraction of sm m.
Decrease of intestinal secretion

(source - neurons of the mucosa and sm m. )

34
Q

What are the actions of neuropeptide Y

A

Relaxation of sm m.
decrease intestinal secretion

(source - neurons of the mucosa and sm m)

35
Q

What are the actions of substance P

A

Contraction of sm m.
increase salivary secretion

(source - co release with ACh)

36
Q

Name the neuronal centers of the hypothalamus that participate in the regulation of food intake

A 
lateral nuclei (LH) - feeding center
Ventromedial nuclei (VM) - satiety center
Paraventricular nuclei (PV)
Dorsomedial nuclei (DM)
Arcuate nuclei (Arc) - axons project onto satiety feeding centers
37
Q

What are the types of signals that the hypothalamus receives?

A

Neural - GI tract
Chemical - nutrients in blood, GI hormones, leptin from adipose tissue
Physical - sight, smell, taste (cerebral cortex)

38
Q

Where does most of the integration signaling regulating food intake and energy expenditure happen?

A

in the arcuate nucleus

39
Q

Describe the pathway that insulin, leptin and CCK promotes in the arcuate nucleus

A

Promotes the alpha-melanocortin (a-MSH) pathway
a-MSH released by pro-opiomelanocortin (POMC) neurons
a-MSH binds to MCR-4 present in 2nd order neurons
Inhibits food intake and increases metabolism (Anorexigenic)

40
Q

Describe the pathway that ghrelin promotes and that insulin, leptin, and CCK inhibits

A

The Neuropeptide Y (MPY) pathway
Hunger signals stimulate the release of NPY
NPY binds to Y1R
Neurons that release NPY also release agouti-related peptide (AGRP)
Increase feeding behavior and storage of calories (orexigenic)

41
Q

What is an antagonist of MCR-4?

A

AGRP

42
Q

What peptides that stimulate the a-MSH pathway also inhibit the NPY system?

A

Insulin, leptin, CCK

43
Q

Some cases of obesity have been related to mutations in the ____ and _____ genes

A

POMC and MCR-4

44
Q

What is Ghrelin mainly secreted by?

A

endocrine cells in the stomach

45
Q

Ghrelin binds to growth hormone _________ receptors

A

Secretagogue

46
Q

What does ghrelin stimulate in the hpothalamus?

A

neurons that release NPY

Appears to initiate the feeding response

47
Q

What are the main actions of ghrelin?

A

increase appetite, gastric motility, gastric acid secretion, adipogenesis, insulin secretion(?)

48
Q

What hormone is transported across blood brain barrier and binds to receptors in satiety and hunger centers within the hypothalamus?

A

insulin

49
Q

What are the main actions of insulin?

A

decrease appetite and increase metabolism

50
Q

In patients with type I diabetes mellitus there is an ____ in food intake associated with _____ insulin

A

increase

decrease

51
Q

What are the actions of peptide YY (PYY)?

A

Binds to Y2 receptors of the hypothalamus after release from EECs (L cells) of the ileum and colon

Inhibits NPY neurons
Releases inhibition of POMC neurons

52
Q

What is leptin secreted by?

A

cells in adipose tissue and endocrine cells in the stomach

53
Q

What does leptin bind to?

A

receptors in satiety and hunger centers w/i the hypothalamus (POMC and NPY systems)

Inhibits NPY, stimulates POMC

54
Q

What are the main actions of leptin?

A

appetite-suppressing hormone

decreases appetite, increases metabolism and decreases ghrelin release

55
Q

Which muscle layer of the muscularis externa is more densely innervated and thicker?

A

Circular muscle layer

GI Final - MSI Spring (11 decks)

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