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PHYSIOLOGY SEMESTER 2 > lecture 15- Intro to GI tract physiology > Flashcards

lecture 15- Intro to GI tract physiology Flashcards

1
Q

list the layers of the gut tract will from outer to inner

A

serosa –> longitudinal smooth muscle layer –> myenteric plexus –> circular smooth muscle layer –> meissner’s plexus –> submocusa –> mucosa

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2
Q

what is the serosa continuous with

A

mesentery (pathway for blood vessels to gut tube)

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3
Q

what is the serosa replaced with when it is absent

A

replaced with adventitia connecting to abdominal wall

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4
Q

what does the submucosa incorporate

A

blood vessels and submucosal plexus

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5
Q

what does the mucosa support

A

supports simple columnar epithelium with goblet cells which lines entire gut tract

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6
Q

what collectively forms the enteric nervous system of the gut tract

A

myenteric and meissner’s plexuses

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7
Q

how does the enteric nervous system operate autonomously

A

via intrinsic regulation and sensory reflexes

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8
Q

what do parasympathetics typically do to GI tract activity

A

increases it

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9
Q

what do sympathetics typically do to GI tract activity

A

decreases it

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10
Q

what are the neurons of the enteric nervous system supported by

A

intrinsic glial cells

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11
Q

where is the myenteric plexus located

A

between longitudinal and smooth muscle layers

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12
Q

what is the myenteric plexus primarily controlling

A

intestinal smooth muscle and participates in tonic and rhythmic contractions

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13
Q

what does the meissner’s plexus mainly control

A

GI secretion, absorption and local blood flow

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14
Q

what is meissners plexus concerned with

A

controlling function within inner wall of each minute segment of the intestine

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15
Q

what is the usual stimulus for propulsive movements

A

distension

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16
Q

what plexus is required for propulsive movements

A

myenteric

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17
Q

what reflex is involved in receptive relaxation

A

vagovagal reflex

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18
Q

what is the receptive relaxation initiated by

A

stomach distension

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19
Q

what increases the distensibility of proximal end of stomach during receptive relaxation

A

CCK

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20
Q

what is mixing and digestion in stomach stimulated by

A

vagus nerve increases gastric contractions; sympathetic decreases gastric contractions

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21
Q

what is the gastroileal reflex mediated by

A

extrinsic ANS and gastrin

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22
Q

what senses food and releases serotonin during peristaltic contractions

A

enterochromaffin cells in intestine

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23
Q

where does most colonic water absorption occur

A

in proximal colon

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24
Q

what does the valsalva maneuver result in

A

increased abdominal pressure

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25
Q

where do slow waves originate

A

in interstitial cells of canal (pacemakers)

26
Q

what do spike potentials excite

A

muscle contraction

27
Q

what are spike potentials responsible for

A

opening calcium channels and smaller number of sodium channels in GI smooth muscle cells

28
Q

what factors cause depolarization

A

stretching of muscle;
stimulation by acetylcholine (parasympathetic);
stimulation by specific GI hormones

29
Q

what factors cause hyperpolarization

A

norepinephrine and epinephrine; stimulation of sympathetic nerves

30
Q

what are some causes of tonic contractions

A

continuous repetitive spike potentials, hormones and continuous entry of calcium ions

31
Q

what reflexes are integrated entirely within the gut wall enteric nervous system control

A

much of GI secretion, peristalsis, mixing contractions and local inhibitory effects

32
Q

what reflexes are from the gut to the pre vertebral sympathetic ganglia and then back to GI tract

A

transmit signals long distance to other areas of gut tract, cause evacuation of the colon (gastrocolic reflex), inhibit stomach motility and secretion (enterogastric reflex), and empty ileal contents into the colon (colonileal reflex)

33
Q

what reflexes are from the gut to the spinal cord or brain stem and then back to GI tract

A

reflexes from stomach and duodenum to brainstem and back to stomach control gastric motor and secretory activity, pain reflexes cause general inhibition of the entire GI tract, defecation reflex extend from the colon to the rectum to the spinal cord and back

34
Q

what are the 4 official GI hormones

A

gastrin, CCK, secretin, GIP

35
Q

where does all biologic activity of gastrin occur

A

in the 4 C-terminal aa

36
Q

what is stimulus for secretion of gastrin

A

small peptides and aa in stomach lumen, dissension of stomach, vagal stimulation mediated by GRP

37
Q

what inhibits secretion of gastrin

A

acid from stomach and somatostatin

38
Q

what are the actions of gastrin

A

stimulates gastric acid secretion by parietal cells and stimulates mucosal growth by stimulating synthesis of RNA and new protein

39
Q

when does Zollinger-Ellison syndrome occur

A

from gastrin secreting non-beta cell tumors of pancreas

40
Q

what is CCK homologous to

A

gastrin

41
Q

where is the biologic activity of CCK

A

C-terminal heptapeptide

42
Q

what is the stimulus for secretion of CCK

A

small peptides and aa, fatty acids and monoglycerides

43
Q

what is the site of secretion of CCK

A

I cells of duodenum, jejunum and ileum

44
Q

what is secretin homologous to

A

glucagon

45
Q

what is the stimulus for secretion of secretin

A

acid and fat in lumen of duodenum

46
Q

what is the site of secretion of secretin

A

S cells of duodenum, jejunum and ileum

47
Q

what stimulates pepsin secretion

A

secretin

48
Q

what is GIP homologous to

A

secretin and glucagon

49
Q

what is the stimulus for secretion of GIP

A

only GI hormone released in response to protein,fat and carb. released in response to orally administered glucose

50
Q

what is the site of secretion of GIP

A

K cells of duodenum and jejunum

51
Q

what are the actions of GIP

A

stimulates insulin release and inhibits gastric acid secretion by parietal cells

52
Q

what is the stimulus for secretion of motilin

A

fat, acid and nerve action

53
Q

what is the site of secretion of M cells

A

duodenum and jejunum

54
Q

what are the actions of motilin

A

stimulates gastric and intestinal motility. secreted during fasting

55
Q

what contributes to the slow emptying of cyme into the small intestine

A

stretching of stomach wall due to increased food volume promotes increased emptying of stomach due to local myenteric reflexes in the wall

56
Q

what factors are continually monitored in the duodenum and can initiate enterogastric inhibitory reflexes

A

degree of distension, presence of any degree of irritation of the duodenal mucosa, degree of acidity of duodenal chyme, presence of certain breakdown products in the chyme

57
Q

what is the most potent hormone in controlling the duodenum

A

CCK

58
Q

what are the 2 types of movement in the intestine

A

mixing and propulsive contractions

59
Q

irritation of _____ can cause powerful and rapid peristalsis

A

intestinal mucosa

60
Q

what intensifies peristalsis and emptying of ileal contents into cecum immediately after a meal

A

gastroileal reflex

61
Q

what are the principal functions of the colon

A

absorption of water and electrolytes from chyme. storage of fecal matter until it can be expelled

62
Q

what are haustrations produced by

A

produced by large circular constrictions plus contractions of the teniae coli

PHYSIOLOGY SEMESTER 2 (20 decks)

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