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Physiology 1 : GI > Functions and control of the alimentary tract > Flashcards

Functions and control of the alimentary tract Flashcards

1
Q

What are the digestive functions of the stomach?

A

→ Accommodation and storage
→ Mechanical and enzymatic breakdown
→ Slow delivery of chyme to the duodenum

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2
Q

What does the vagal reflex inhibit?

A

→ Smooth muscle tone
→ Mechanoreceptors
→ Fundic relaxation

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3
Q

Where is the antral region?

A

→ Lower region of the stomach

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4
Q

What are physical properties of the antral region?

A

→ Thick and muscular

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5
Q

What does the antral region do?

A

→ Mixes/grinds food with gastric secretions

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6
Q

What does the stomach act as?

A

→ A reservoir for unmixed food

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7
Q

What allows a large volume of food to be stored in the stomach?

A

→ Fundus and the body of the stomach relax

→ 1.5 L storage

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8
Q

What two nerves are involved in receptive relaxation?

A

→ parasympathetic nerves

→ Vagus inhibitory nerves

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9
Q

How much gastric juice does the stomach store?

A

→ 2-3 L

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10
Q

What does gastric juice contain and what is the function of it?

A 
→ mucus
→ Pepsinogen 
→ intrinsic factor 
→Lipase 
→ helps in digestion + absorption of food
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11
Q

What does mucus do?

A

→ Acts as a lubricant by acting as a barrier that protects the stomach and colon especially from gastric acid

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12
Q

What does lipase do?

A

→ Converts triglycerides into fatty acids and glycerol

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13
Q

What does pepsin do?

A

→ Protein digestion

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14
Q

What is pepsin secreted by?

A

→ Secreted by chief cells or peptic cells

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15
Q

What is HCL secreted by?

A

→ Parietal cells

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16
Q

What is mucus secreted by?

A

→ Goblet cells or mucus cells

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17
Q

What are paracrine secretions?

A

→ Secreted from cells in the mucosa but the chemical acts locally on adjacent cells via interstitial fluid

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18
Q

What does somatostatin inhibit?

A

→ Gastric release in the stomach

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19
Q

What is somatostatin released by and what does it act on?

A

→ D cells and acts on G cells

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20
Q

Where are exocrine secretions secreted from?

A

→ Salivary glands
→ Gastric glands
→ Pancreas
→ Liver

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21
Q

What are endocrine secretions?

A

→ Hormones synthesized by ductless glands

→ Enter the bloodstream and travel to their target tissues where they bind to specific receptors to elicit their effects

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22
Q

What is gastrin secreted by?

A

→ G cells of the stomach

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23
Q

What are secretin and pancreozymin-cholecystokinin produced by?

A

→ Duodenal mucosa

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24
Q

Where is insulin secreted from?

A

→ Pancreas beta cells

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25
Q

Where does absorption of fluid occur?

A

→ Small intestine + colon

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26
Q

What does the colon absorb and what does it produce?

A

→ Colon absorbs 90% of water reducing volume to 200ml of semi solid fecal matter

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27
Q

What produces mechanical degradation?

A

→ The gastric antrum

28
Q

What mixes the lumen contents?

A

→ The small intestine

29
Q

How do drugs and normal products of metabolism leave the body?

A

→ saliva
→ bile
→ feces
→ vomit

30
Q

How does indigestible material leave the body?

A

→ Via feces

31
Q

What does the gut epithelium act as and what is it exposed to?

A

→ Interface with the outside world

→ Exposed to the external environment

32
Q

What helps protect the gut from external pathogens?

A

→ Sight, smell and taste
→ Vomit reflex
→ Acid in the stomach kills most harmful bacteria
→ Mucus secretions
→ Natural bacteria flora prevent colonization by harmful bacteria
→ Aggregation of lymphoid tissue can mount a response against food-borne antigens
→ Peyer’s patches

33
Q

What is the liver involved in?

A

→ Carbohydrate, nitrogen and lipoprotein metabolism

→ Production and excretion of bile + bilirubin

34
Q

How can the gut initiate its own responses?

A

→ It has an enteric nervous system which can initiate its own responses to gut stimuli without higher functions of the brain

35
Q

What are the contractions initiated by?

A

→ Excitatory reflexes and mediated by AcH or substance P

36
Q

What are relaxation effects mediated by?

A

→ VIP or NO

37
Q

What are splanchnic nerves?

A

→ Sympathetic

38
Q

When does receptive relaxation occur?

A

→ Which happens by mechanical stimuli
→ Food is expected in the stomach
→ Sphincter relax to allow food to enter

39
Q

When does adaptive relaxation occur and with what neurotransmitter?

A

→the food is within the stomach
→NANC
→Inhibitory AcH effect, preganglionic
The factors that induce relaxation is not AcH itself the post-ganglionic is mediated by NO and VIP

40
Q

What is feedback relaxation initiated by?

A

→CCK

41
Q

Why is CCK being released?

A

→ Due to lipids being in the food

42
Q

What does CCK do?

A

→ Decreases feeding because relaxation is occurring

43
Q

What does CCK promote?

A

→ Bile secretion

→ Gall bladder contracting

44
Q

How does food move through the duodenum?

A

→ Ripples of contraction move the food towards the antrum (thicker muscle layer)

→Pyloric sphincter is often relaxed but closes upon arrival of peristaltic wave

→Repulsion of chyme causes the opening of pyloric sphincter

→Small partially digested material is squirted through the pyloric sphincter into duodenum

→Repulsion of antral contents backwards towards the body allows mixing/grinding

45
Q

What is the sieving effect?

A

→ Viscous and solid matter are retained in the stomach
→pylorus can detect the size of food particles, 1-2mm are passed through
→anything larger goes back to the antrum for grinding.

46
Q

When is somatostatin released?

A

→ When there is hypersecretion of acid

47
Q

What does the vago-vagal reflex describe?

A

→ type of reflex in which both the afferent (“sensory”) and efferent (“motor”) axons are in the vagus nerve trunk

48
Q

What kind of circuit is the vago-vagal reflex?

A

→ Reflex circuit within the GIT

49
Q

What does the vago-vagal reflex control?

A

→control of responses to gut stimuli via the NTS and DMVN

50
Q

When is the vago-vagal reflex active?

A

→ during the receptive relaxation of the stomach in response to swallowing

51
Q

Where does the vago-vagal reflex go from and to?

A

→from stomach to brain and then back to stomach

52
Q

What does the vago-vagal reflex promote?

A

→motility and acid secretion

53
Q

What two nerve fibers are intrinsic to the gut and what are they for?

A

→Myenteric plexus - motor function

→ Submucosal plexus - Intestinal secretions

54
Q

What do the two plexuses do?

A

→ Reflexely regulate GI functions entirely within the wall of the gut
→Mediated by enteric nervous system

55
Q

How are the two plexuses connected to the CNS?

A

→ parasympathetic and sympathetic fibres

56
Q

What are the neurotransmitters used in the plexuses?

A

→ ACh, NO, NA, 5-HT, GABA and ATP

57
Q

Where are the two plexuses found?

A

→ The wall of the colon

58
Q

What does parasympathetic activity do to the colon?

A

→ Increases the contraction of the proximal colon

59
Q

What effects does the cholinergic innervation have on the auerbach plexus?

A

→ Increases gastric motility and secretion

60
Q

What effects does adrenergic stimulation have on the Auerbach plexus?

A

→ Decrease in gastric motility and secretion

61
Q

What does the rate of emptying depend on?

A

→ THe materials ability to be absorbed

62
Q

How do carbohydrates, proteins and fats get emptied?

A

→ Carbohydrates are emptied quicker
→ Proteins have slow emptying
→ Fatty foods have even slower emptying

63
Q

What is the result of having fatty foods in the duodenum?

A

→ Decrease in gastric emptying by increasing the contractility of the pyloric sphincter

64
Q

What is peristalsis like in the large intestine compared to the small intestine?

A

→ Slower in the large intestine

65
Q

What initiates contraction (peristalsis)?

A

→ Distension

66
Q

How does the bolus get moved along?

A

→ Contractions are initiated by excitatory activity mediated by substance P and AcH
→ The circular muscles have to relax infront and contract behind
→Longitudinal muscles are contracted

67
Q

Where are Peyer’s patches found?

A

→Lamina propria of the mucosa extend into the submucosa of the ileum

Physiology 1 : GI (15 decks)

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