Brainscape's Knowledge GenomeTM

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


See full index

SGUL - Physiology 1 > Transport Along and Across GI Tract PART 1 > Flashcards

Transport Along and Across GI Tract PART 1 Flashcards

1
Q

What two mechanisms is transport from the gastric reservoir to the antral pump, mediated by?

A
  • Tonic contraction
  • Peristaltic waves in the gastric corpus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Name the area tonic contractions originate.

Name two areas tonic contractions can occur.

A
  • Originate at top of antrum
  • Stomach and sphincters in GI tract
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe storage.

A
  • Proximal stomach relaxes to store food at low pressure
  • Food acted upon by acid, enzymes and mechanical degradation.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe emptying.

A
  • Regulated to ensure adequate acidification/neutralisation
  • Ensure enzyme action and mechanical breakdown
  • Avoid duodenal swamping
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is gastroparesis?

A
  • Abnormal emptying of food by stomach
  • Low rate of passage of food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is gastric emptying dependent upon?

A
  • Propulsive force generated by tonic contractions of proximal stomach
  • Stomach’s ability to differentiate types of meals ingested and their components
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What factors decrease force and rate of gastric emptying?

A

Fatty, hypertonic, acidic chyme in the duodenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Summarise the emptying of liquids.

A
  • rapidly empty without lag time
  • rate of emptying is influenced by the nutrient content (nutrient-containing liquids retained longer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Summarise the emptying of solids. PART 1

A
  • 2 phases (lag time and linear phase); duration of Phase 1 related to particle size
  • Liquid part emptied and solid component retained in proximal stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Summarise the emptying of solids. PART 2

A
  • trituration of larger particles to smaller ones
  • pylorus regulates the passage of materal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define trituration.

A

Reducing particle size or creating homogenous solution through thorough mixing

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

Summarise emptying of fatty foods

A
  • liquefy at body temperature; float on top of liquid layer and empty at slow rate
  • fats are potent inhibitors of gastric motor events i.e gastric emptying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Summarise emptying of indigestible solids.

A
  • empties in immediate post-prandial period
  • MMC acitivity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the order of highest rate of gastric motility to lowest?

A

carbohydrates > proteins > fatty foods > indigestible solids

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

List 3 determinants of the rate of gastric motility.

A
  • type of food eaten
  • osmotic pressure of duodenal contents
  • hormones (somatostatin, secretin, CCK, GIP)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What factors can decrease or inhibit emptying?

A
  • Hormones
  • Hyperosmolar chyme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What decreases gastric motility?

A
  • vagal innervation upon over-distension
  • injury to intestinal wall and bacterial infections
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does ICC stand for?

A

Intestinal Cells of Cajal

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

What are the ICC and where are they located?

A
  • Specialised pacemaker cells involved in myogenic control of motility
  • Located in the wall of the stomach, small intestine, and large intestine.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is special about the cell membrane of the ICC?

A

Rhythmic depolarisation and repolarisation constantly occurring in membranes

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

What is the result of the rhythmic depolarisation and repolarisation in the ICC membranes?

A
  • Creates a slow wave- the BER
  • This wave transmitted to smooth muscle cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does BER stand for?

A

Basal electrical rhythm

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

What does BER determine?

A

Frequency of the contractions in the GI tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens when the BER reaches its plateau point?

A

Smooth muscle contraction

25
Q

What does the BER specificially allow the smooth muscle cells to do?

A

Depolarise and contract rhythmically when exposed to hormonal signals

26
Q

What causes depolarisation of the GI smooth muscle?

What causes repolarisation of the GI smooth muscle?

A

Depolarisation - calcium-sodium entry.
Repolarisation - K+ efflux.

27
Q

List some factors that will mediate a decrease in fundic motor activity.

A
  • CCK
  • secretin
  • VIP
  • somatostatin
  • gastrin-releasing peptide (GRP)
  • glucagon
28
Q

List a factor that mediates an increase in fundic contractions.

A

MOTILIN

29
Q

How is movement through the small intestine controlled?

A
  • Hormonal and nervous factors initiate and maintain peristalsis and mixing
  • Localised distention of the duodenum
30
Q

Name some factors that increase intestinal motility.

Name some factors that decrease intestinal motility.

A

INCREASE: CCK, gastrin, and motilin
DECREASE: Secretin

31
Q

Describe the feedback control of gastric emptying. PART 1

A
  • Contraction of the middle antrum elicits a descending inhibitor reflex, causing pyloric sphincter relaxation (via NO/VIP).
32
Q

Describe the feedback control of gastric emptying. PART 2

A
  • Duodenal stimuli induces the excitatory reflex, leading to pyloric contractions
  • Prevents duodenal-gastric reflux.
33
Q

What can cause duodenal stimuli?

A

Prsence of acidic chyme

34
Q

What can the pyloric sphincter contract in response to?

A

Antral/duodenal rhythm (e.g fatty acids in duodenum)

35
Q

How does pyloric contraction affect the antrum?

A

Cause liquids in the antrum to be squirted into the duodenum

36
Q

Describe the feedback control of gastric emptying. PART 3

A
  • Gastro-gastric reflexes provide balance between gastric reservoir and antral pump.
  • Distention of reservoir stimulates antral contractions.
  • Distension of the antrum prolongs reservoir relaxation.
37
Q

What are the different components of motility in the intestine? PART 1

A
  • segmentation (mixing contractions): stationary contractions and relaxation
  • peristalsis (propulsive): in the stomach
38
Q

What are the different components of motility in the intestine? PART 2

A
  • migrating motor complex
  • mass movements (evacuation)
39
Q

What are the phases of motor activity?

A
  • PHASE 1: quiscence/ quiet period
  • PHASE 2: irregular propulsive contractions
  • PHASE 3: peristaltic rush
40
Q

Where does segmentation originate?

A

ICC

41
Q

How does segmentation influence chyme?

A
  • Creates divisions of chyme, bringing chyme in contact with intestinal walls.
  • Chyme is divided, subdivided and mixed with luminal contents and pushed back and forth. Slowly migrates to ileum
42
Q

What is peristalsis and what is it used for?

A
  • Propulsive contractions of successive sections of circular smooth muscle preceded by relaxation
  • Spread the food out, allowing mixing with digestive enzymes
  • Push the food towards the anus
43
Q

What is segmentation and what is it used for?

A
  • Mixing contractions primarily churn the food, but also propel it towards the anus
44
Q

Describe the migrating motor complex (MMC) and when it occurs.

A
  • Cyclically recurring sequence of events
  • Occurs between meals, when the stomach/intestines are ‘empty’
  • Starts in lower portion of stomach
45
Q

Describe Phase 3 of motor activity.

A
  • High frequency, large amplitude contractions that migrate along the length of the intestine and die out
46
Q

What are the functions of the MMC? PART 1

A
  • Allows movement of indigestible contents from stomach by large contractions followed by opening of the pyloric sphincter during Phase 3
  • Removes dead epithelial cells by abrasion
47
Q

What are the functions of the MMC? PART 2

A
  • Prevents bacterial overgrowth
  • Prevents colonic bacteria from entering the small intestine
48
Q

Describe the control of the MMC through smooth muscle cells.

A
  • Smooth muscle contracts
  • Contractions are coordinated by ENS by ICC.
  • Initiated by the vagus nerve in the upper tract.
49
Q

Describe the control of the MMC through hormones

A
  • Cyclical secretion of motilin from the stomach and duodenum.
  • Inhibited by feeding
50
Q

How do the ICC link to the GI smooth muscle cells?

A

Form synaptic connections with GI smooth muscle fibres

51
Q

How long are the contractions in the ileum?
How long are the contractions in the jejunum/duodenum?

A

→ 8-9 contractions per min
→ 10-12 contractions per min

52
Q

In terms of passage along the GI tract:
How do liquids pass?
How do solids pass?
How do large indigestible materials pass?

A

→ in spurts
→ Broken down into 1-2mm sizes
→ Cleared by MMC or vomiting

53
Q

What do fatty acids in the duodenum cause?

A

Contraction of the pylorus

54
Q

What happens during duodenal over distension and chemical stimulation?

A

→ Vago-vagal reflex

55
Q

What does distension of the fundus cause?

A

→ Excitatory effects in the antrum
→ Antrum contracts

56
Q

What does antral over-distension cause?

A

→ Inhibitory signals
→ Vago- vagal reflex

57
Q

What control is the fundus under?

A

→ Vagal excitatory control

58
Q

What do the stomach cells produce from resting potential?

A

→ Electrical depolarisations
→ Move ripples towards the antrum

59
Q

How does gastric accommodation occur?

A

→ Decrease in cholinergic activity
→ VIP / NO promote accommodation

SGUL - Physiology 1 (68 decks)

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