Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology II > digestive 3 > Flashcards

digestive 3 Flashcards

1
Q

control of acid secretion:

cephalic phase of control: chewing, and the sight, smell, and taste of food are stimuli that are transmitted to the brain and cause increased activty in

A

parasympathetic neurons within the vagus N to the enteric nervous system of the stomach

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

cephalic phase of control results in enhanced release of

A

gastrin, carried by the blood to parietal cells

histamine, which diffuses to nearby parietal cells

the transmitter acetylcholine from plexus neurons onto parietal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

gastric phase of control:

the presence of ____/____ ____ in the stomach, a decreased ____ concentration in the stomach, and stomach ____ stimulate acid secretion

receptors that detect these stimuli send neural (via plexus neurons or to the brain and back via the ____ N) to enteric nervous system neurons, which in turn signal ____ , ____ , and ____ cells

A

peptides/amino acids H+ distension

Vagus gastrin-releasing, ECL (histamine), and parietal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

gastric phase of control:

these is negative feedback control here, because acid directly inhibits ____ release and stimulates ____ release (as the stomach becomes more acidic, items such as gastrin that trigger acid secretion decrease)

thus decreased acid removes the inhibtion of gastrin and decreases blood levels of the parietal-cell-inhibitor somatostatin

A

gastrin somatostatin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

gastric phase of control:

the increased stomach luminal peptide/amino acid concentration restults from the digestion of dietary ____ by ____

the decreased luminal H+ concentration restults from the buffering of acid by ingested ____ (that is, the H+ ions already present in the lumen bind to the ingested proteins and no longer contribute to acidity)

A

proteins pepsin

proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

intestinal phase of control:

the digestive activity of enzymes and bile salts in the SI is ____ by acid; thus it is essentail that the chyme entering the SI not be too acidic, and high acidity in the duodenum reflexively triggers the inhibition of acid secretion

high ____ levels in the SI, ____ of the SI, increased ____ of chyme in the SI, and the presence of ____ ____/____ ____ in the SI trigger reflexes that inhibit secretion by parietal cells

A

inhibited

acid distension osmolarity amino acids/fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

intestinal phase of control: the connection between SI receptor and stomach parietal cell in these reflexes is made:

1.

2.

A
  1. neurally (long and short reflexes)
  2. by secretin and other SI hormones (these hormones are collectively called enterogastrones and most work by affectin gacetylcholine, gastrin, histamine, and somatostatin secretion)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

pepsin is screted by ____ cells in an inactive form called ____

A

chief

pepsinogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

acid in the stomach lumen triggers the conversion of pepsinogen by an ____ process in which pepsinogen acts on itself to produce pepsin

A

autocatalytic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

“activated” pepsin is only active in the presence of a high ____ concentration (and pepsinogen is secreted at a high rate only when lots of ____ is present in the stomach lumen)

A

H+

acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

the main input to chief cells that increases pepsin secretion is from the ____ nervous system. most factors than stimulate or inhibit ____ secretion have the same influence on pepsin secretion

A

enteric

acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

filling: the volume of the empy stomach can increase ____ fold after a meal with little increase in pressure due to a reduction in smooth muscle tone; this effect is mediated by stomach receptors and then ____ neurons traveling from brainstem to stomach via the ____ N

A

25

parasympathetic

vagus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

mixing and emptying: weak peristalitic waves sweep from the upper-to-middle stomach toward the ____ about every ____ seconds, becoming much stronger as they travel inferiorly

A

antrum

20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

pyloric spincter

A

ring of muscle between stomach and SI, closes (mostly) as the peristaltic wave reaches it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

only a small amount of chyme passes into the duodenum with each peristaltic wave, with most of the antral contents being forced

A

back toward the body of the stomach; this mixes the stomach contents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

the wave rhythm of peristaltic waves in the stomach (every 20 seconds) is generated by

A

pacemaker cells in teh stomach smooth muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

pacemaker cells in the stomach produce slow wave (that is undergo a spontaneous depolarization-repolarization cycle) that do not normally cause significant contractions but that, in the presence of certain transmitters or hormones, result in

A

action potentials that cause significant contractions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

the slow waves and action potentials in the pacemaker cells of the stomach spread via ____ ____ throughout the stomach’s smooth muscle tissues

A

gap junctions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

the more action potentials per slow wave, the

A

stronger the resulting muscle contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

the transmitters and homrones alter not the frequency of contractions, but rather their ____ , and as force increases, the amount of gastric emptying per contraction ____

A

force

increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

the same stimuli that influence acid secretion can also influence

A

gastric motility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

stomach distention (detected by mechanoreceptors in the wall of the stomach) and ____ increase the force of contraction

A

gastrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

the force of peristaltic contraction/rate of gastric emptying is inhibited by duodenal stimuli:

1.

2.

3.

4.

A
  1. duodenal distenstion
  2. presence of high acid
  3. hypertonicity
  4. fats/amino acids in the duodenum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

the connection between duodenal receptor and stomach smooth muscle cells is made several ways (inhibits contraction/rate of gastric emptying):

1.

2.

3.

A
  1. short relfexes traveling through the plexuses/enteric nervous system
  2. long neural reflexes traveling to the CNS (or at least to sympathetic ganglia) and back leading to increased sympethetic signals and decreased parasympathetic signals to the stomach muscle tissue
  3. cholecystokinin (CCK) and other small intestinal enterogastrones that are released into teh blood; the blood carries these hormones to the stomach smooth muscle tissue (note that fats in the duodenum are an especially potent stimuli for CCK release)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

small intestine secretions:

mucosal epithelial cells secrete mucus and ions (particularly ____ , ____ , ____ ) into the SI lumen, and water follows due to osmotic considerations

Cl- is especially important in determining the amount of ____ , and several horones and paracrines can influenece Cl- secretion

A

HCO3- , Na+ , and Cl-

secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

local enteric nervous reflexes regulate SI secretions; tehse are initiated by

A

tactile or irritative stimui from chyme in the SI

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

small intestine: secretions:

mucus is largely secreted by

A

brunner’s glands and goblet cells and, in addition to being protective, mucus is alkaline and helps neutralize stomach acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

brunner’s glands are stimulated by ____ stimulation and inhibitied by ____ stimulation

A

vagal

sympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

hypertonicity of the chyme entering the SI from the stomach (due to a high concentration of solutes in a meal) can also cause

A

the osmotic movement of water into the SI lumen (in addition to Cl- secretion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

nearly all the secreted fluid (by the SI) is absorbed by the SI back into the blood; also abosrbed is much of the SI luminal fluid that came from

A

secretions of salivary glands, stomach glands, and the liver, gallbladder, and pancreas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

overall, there is a large net absorption of ____ in the SI

A

water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

absorption of water in the SI is largely achieved by ion transport (especially ____ ) from the SI lumen into the blood, with water following osmotically

A

Na+

33
Q

small intestine: motility

segmentation

A

rhythmic contractions of bands of muscle circling the SI resulting in back and forth movements (and continuous divisions and subidisons) of its contents

34
Q

segmentation mixes the chyme and brings it

A

into contact with the wall

35
Q

segmentation movements are elicited by

A

distention of the SI coujpled with pacemakers in teh SI smooth muscle that generate slow waves

36
Q

if threshold is reached during the depolarizing part of a slow wave,

A

action potentials are generated that increase the strength of contraction

37
Q

the frequency of segmentation in the duodenum is about ____ contractions/minute; this declines to about ____/min in the terminal portion of ____ , with the result that more chyme is forced down the tube than vice versa

A

12

9

ileum

38
Q

the force of segmentation contractions is controlled by

A

hormones, autonomic Nn, and the enteric NS

39
Q

SI motility sementation contractions:

parasympathetic stimulation ____ and sympathetic stimulation ____ contraction strength

A

increases

decreases

40
Q

peristaltic waves of contraction move toward the anus at a velocity of about ____/second, but each wave travels

thus net forward movement of teh chyme is much slower than 1cm/sec, and it typically takes ____ hours for chyme to travel the entire length of the SI

A

1 cm

only a short distance before dying out

3-5

41
Q

several hormones influence SI peristaliss, including ____ from the SI itself

A

motilin

42
Q

gastroileal relfex

A

the intensity of contractions in the ileum increases in response to stimuli in the stomach

43
Q

intestino-intestinal reflex

A

a complete stoppage of SI motility, initiated by significant distension of the intestine, injury to the intestinal wall, or bacterial infection in the intestine

44
Q

ileocecal valve:

functions as a valve:

functions as a sphincter:

A

valve: preventing backflow from the colon to the SI
sphincter: regulating the movement of ileal contents into the cecum

45
Q

normally the sphincter part of the ileocecal valve is

A

mildly constricted, which allows it to slow the emptying of ileal contents into teh cecum

46
Q

immediately after a meal, intensified peristalsis in the ilieum (as part of the gastroileal relfex) forces

A

the valve open, and the ileum empties

47
Q

distension of or irritation within the cecum cause

these reflexes are mediated by

A

increased contraction of the ileocecal sphincte muscle; this delays ileal emptying into the cecum

the GI nerve plexuses and by autonomic neurons bo the sphincter muscle

48
Q

hepatocytes make ____ and secrete it into tiny ducts called ____ ____

A

bile

bile canaliculi

49
Q

bile canaliculi converge to form the

A

(common) hepatic duct

50
Q

frrom the hepatic duct, bile

A

either empties into the duodenum or is diverted for minutes to hours through the cystic duct into the gallbladder

51
Q

contents of bile

A

bile salts

the phospholipid lecithin

HCO3- and other salts

cholesterol

bile pigments (bilirubin) and small amounts of other metabolic end products

trace metals

52
Q

trace metals (in bile) are extracted

A

from the blood by the liver and put into bile for purposes of excretion

53
Q

bile is secreted by 2 cell types:

what is secreted by hepatocytes:

what is secreted by epitheleial cell slining the bile ductules and ducts:

A

bile salts, lecithin, cholesterol, and bile pigments

watery solution rich in HCO3-

54
Q

most of the bile salts entering the duodenum via the bile are absorbed by

A

specific sodium-coupled transportes in the lower SI (not excreted in feces)

55
Q

bile salts entering the duodenum and absorbed by sodium-coupled transporters in the lower SI are returned via the hapatic portal vein to the ____ which again secretes them into the bile, this is called ____ ____

A

liver

enterohepatic circulation

56
Q

about 5% of bile salts escape enterohepatic circulation recyling and is lost in the ____ ; the liver synthesizes new bile salts from ____ to replace those that are lost

A

feces

cholesterol

57
Q

bile pigments are formed from the heme portion of hemoglobin when old or damaged red blood cells are broken down in the

A

liver or spleen

58
Q

bilirubin (main bile pigment) is yellow, and it and other bile pigments contribute to the color of

A

bile, urine, and feces

59
Q

regulation of bile secretion by the liver:

duodenum: increased acid → → → → duodenum: neutralization of acid

A

duodenum: increased acid → increased secretion of secretin → increased plasma secretin → Liver: secretion of HCO3- rich salt solution by cells lining the bile ducts → duodenum: neutralization of acid

60
Q

the liver always secretes some dilute bile, but between meals the sphincter of ____ is closed and the bile is shunted into the ____

A

oddi

gallbladder

61
Q

the gallbladder actively transports sodium across its wall into the blood; the sodium is followed by

this concentrates the remaining bile constituents, such as bile salts, and allows the gallbladder to

A

water, chloride, etc

store several hours’ worth of liver bile production

62
Q

shortly after the start of a meal, gallbladder contraction and sphincter of Oddi relaxtion

A

discharge bile into the duodenum

63
Q

regulation of bile secretion by the gallbladder:

duodenum: increased fatty acids → → → → → → increased bile flow into dueodenum

A

duodenum: increased fatty acids → increases secretion of CCK → increased plasma CCK → 1 and 2

1 → gallbladder contraction → increased bile flow into (common) bile duct → increased bile flow into duodenum

  1. → sphincter of Oddi: relaxation → increased bile flow into duodenum
64
Q

the gallbladder is stimulated less strongly by ____ - secreting neurons from both the ____ Nn and the intestinal ____ nervous system

A

acetylcholine

vagus

enteric

65
Q

large intestine: secretions and absorption:

secretions are scanty and consist mostly of mucus and fluid containing ____ and ____ ; theres is normally a net movement of both these ions from the blood ____ the lumen

A

HCO3- and K+

into

66
Q

large intestine mucus secretion is regulated:

although the distal half of the LI can increase mucus secretion in response to:

A

by direct tactile stimulation of LI epithelial cells and some local nervous reflexes

parasympathetic stimulation

67
Q

much of the entering LI material consists of

A

undigested cellulose (fiber) and of secretions from the lower SI (since most of the ingested food has been absorbed by this time)

68
Q

large intestine: secretions and absorption:

the main absorption is of ____ by active transport with ____ following osmotically

the amount of water absorbed is largely determined by the amount of time the:

A

Na+ water

fecal material remains in the LI

69
Q

poor LI motility causes

A

greater absorption, and hard feces in trasnverse colon cause constipation

70
Q

the LI absorbs some of the products formed there by bacterial action, including some products of

A

bacterial polysaccharide digestion and some vitamins, especially vitamin K

71
Q

some LI bacterial products include flatus (gas), resulting from

A

bacterial fermentation of undigested polysaccharides

72
Q

large intestine motility:

sementation-like mixing movemnets occur, but

they involve:

A

much more slowly than in the SI

large circular muscle constrictions coupled with contractions of longitudinal strips of muscle called teniae coli

73
Q

large intestine motility__:

segmentation-like mixing movements (involving large ircular muscle constrictions coupled with conraction of longitudinal strips of muscle called teniae coli caused the unstimulated parts of the LI to bulge outward into baglike sacs called ____

A

haustrations

74
Q

large intestine motility:

1-3 times/day, so-called mass movements take over the

A

propulsive role

75
Q

large intestine motility:

mass movements are a modified type of peristalsis in which a constricted ring appears in response to a distended point, usually in the transverse colon. then rapidly, 20 or more cm of colon distal to the ring loses it:

this propels the fecal material en masse:

another mass movement then occurs, perhaps further down the colon. if this forces a mass of feces into the rectum, the desire for:

A

haustrations and instead contracts as a unit

further down the colon

defecation is felt

76
Q

large intestine motility:

the appearance of mass movements after meals is facilitated by the gastrocolic reflex (initiated by ____ ___ ) and the duodenocolic reflex (initiated by ____ ____ )

A

stomach distension

duodenal distension

77
Q

large intestine motility:

both the gastrocolic reflex and duodenocolic reflexes appear to be mediated by signals in

A

autonomic neurons to the enteric neurons and smooth muscle cells of the colon

78
Q

distention of the rectum stimulates ____ that initiate sensory signals which, via neural pathways, produce:

A

mechanoreceptors

the defacation reflex

79
Q

defection reflex:

1.

2.

3.

4.

A
  1. sigmoid colon and rectal smooth muscle contraction
  2. relaxation of the internal anal sphincter, which is made of smooth muscle and controlled by signals in the nerve plexuses
  3. relaxation of the external anal sphincter which is made of skeletal muscle and controlled by somatic motor neurons
  4. usually the defecation reflex is intensified by signals in parasympathetic neurons to teh sigmoid colon, rectum, and sphincters

Physiology II (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions