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GI BLOCK > Physiology: Control of GI Tract > Flashcards

Physiology: Control of GI Tract Flashcards

1
Q

How long is the GI tube?

A

8 metres long

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2
Q

What are the functions of the GI tract?

A

Mechanically processes and moves food through the tract

Chemically processes and digests food

Absorbs nutrients and water

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3
Q

What are the accessory glands of the GI system?

A 
Teeth
Tongue
Salivary glands 
Liver 
Gallbladder 
Pancreas
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4
Q

What is the function of the accessory organs ?

A

Control secretions and breakdown of food

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5
Q

What part of the nervous system is responsible of sending signals to the GI tract?

A

Enteric nervous system & Autonomic nervous system

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6
Q

What does the Enteric nervous system control?

A

Peristalsis & motility

Secretion & absorption

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7
Q

What are the Gut peptides (GI peptides)?

A

Paracrines

Hormones

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8
Q

How does the ENS (Enteric nervous ) operate?

A

Intrisi che control: short reflexes - internal stimuli

Communicates with parasympathetic and sympathetic nervous systems but is autonomous

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9
Q

What are the two organised neural plexus in the ENS of the GI tract?

A

My enteric plexus

Submucosal plexus

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10
Q

Where is the myenteric plexus located? What is its function?

A

Between longitudinal and circular layers of muscle

Involved in control of digestive tract motility

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11
Q

Where is the submucosal plexus located?

A

Between the circular muscle and luminal mucosa

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12
Q

What is the function of the submucosal plexus?

A

Senses the environment of the lumen

Regulates GI blood flow and epithelial cell function

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13
Q

What secretes (22) hormones and paracrines in GI system?

A

Enteroendocrine cells (EEC)

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14
Q

What are Enteroendocrine cells (EEC)

A

Single cells scattered through the GI a tract

Density packed secretory vesicles

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15
Q

What are the functions of Enteroendocrine cells (EEC)?

A

Sense luminal contents: chemical, osmotic and ph

Release hormones and paracrines

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16
Q

What are the main hormones of GI?

A 
Gastric 
Secretin 
Cholecystokinin 
Goucagonlike
Somatostatin-like
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17
Q

Which event are part of GI motility?

A

Physical contractions

Tonic contractions

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18
Q

What are Phasic contractions?

A

Short lasting contractions : Peristalsis + segmented contractions

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19
Q

What is the function of Phasic contractions?

A

Movement of material in the small intestine

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20
Q

What are Tonic contractions?

A

Long lasting contractions

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21
Q

What are the functions of atomic contractions?

A

Closing of a sphincter

Control movement of material through the GI tract

Maintain ordered sequence of events

Compartmentalisation ensures processes are complete before passing to next area

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22
Q

What is the definition of Peristalsis?

A

Propulsion of material

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23
Q

Which neurones regulate Peristalsis?

A

Neurones in myenteric plexus : Interstitial Cells of Cajal (ICC)

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24
Q

What are Interstitial Cells of Cajal (ICC)?

A

Pacemakers of the gut

Differ in different regions of the GI tract

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25
Q

Where are the Interstitial Cells of Cajal (ICC) found?

A

In myenteric plexus

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26
Q

What do the Interstitial Cells of Cajal (ICC) do?

A

Electrical activity spreads via gap junctions from ICCs to muscle

ICCs produce slow waves

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27
Q

What are Slow waves?

A

Slow undulating changes in rating membrane potential NOT ACTION POTENTIAK

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28
Q

At what threshold do Slow waves cause contraction?

A

-40 mv

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29
Q

What activates Slow waves?

A

Distension: bolus of food (chyme) stimulates stretch receptors (local reflex)

Oral contraction
Aboral relaxation

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30
Q

What are the nerves of slow waves?

A

Parasympathetic nerves (ACh)

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31
Q

What is the neurotransmitter in slow waves ?

A

Acetylcholine (ACh)

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32
Q

Where do segmented contractions & mass movements take place?

A

Colon: 99% of the time

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33
Q

What is the function of the Colon?

A

Retain material - water reabsorption and fermentation

Mixing contents

Mass movement of material into aboral end via Gastro-colic response

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34
Q

How many times does Mass movement of material into aboral end of colon occurs?

A

2-3 Times per day

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35
Q

What is Hirschprungs disease aka TOXIC MEGA COLON?

A

Congenital disorder which presents shortly after birth

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36
Q

What are the characteristics of TOXIC MEGA COLON?

A

All or part of colon has no innervation
The colon is dilated

Treatment:
Surgical removal of the colon

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37
Q

What is mastication?

A

Breakdown of food

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38
Q

What is the role of Taste in the mouth ?

A

Inform brain about edibility/ duration

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39
Q

What is the role so Salivary production in the mouth?

A

Lubrication, protection and digestion

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40
Q

What is the role of Swallowing in the mouth?

A

Movement of digested macromolecules to stomach

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41
Q

What organs are responsible of Taste in the mouth ?

A

Papillae: taste organs

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42
Q

What are Papillae?

A

Raised protrusions on the tongue, soft & pallet, pharynx, epiglottis & larynx

Visible to naked eye

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43
Q

Where are te Taste buds found?

A

In the Papillae

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44
Q

How many types of cell does each taste bud contain?

A

Epithelial cells

Support cells

Gustatory receptor cells (taste cells)

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45
Q

Which nerves innervate taste buds?

A

Gustatory afferent nerves

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46
Q

Is the moth a taste bud?

Yes or no

A

Yes

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47
Q

What do Apical microvilli in the mouth do?

A

Increase surface area

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48
Q

How are receptor proteins in mouth exposed?

A

Through taste pore

49
Q

Where are ion channels and receptors located in the mouth?

A

On villi

50
Q

All flavours are encoded by how many taste modalities?

A

5

51
Q

What are the taste modalities?

A 
Sweet
Salt
Sour
Bitter
Umami
52
Q

One taste cell responds to one modality

True or false

A

True

53
Q

What are the Ionotropic receptors in the mouth?

A

Salt : Na+

Sour: H+ gated ion channels (K+/H+)

54
Q

What are the metabotropic receptors in mouth ?

A

Sweet
Bitter
Umami

55
Q

What is the Saliva?

A

Hypotonic solution containing more than 99% water and 1% dry matter such as proteins

56
Q

What are the components of the Saliva?

A 
Water 
Bicarbonate ions 
Enzymes 
Alpha-amylase 
Lipase 
Proteins (100s)
57
Q

What is the role of Bicarbonate ions in saliva?

A

Buffering capacity

Protect from acid

58
Q

What is the role of alpha - amylase in saliva?

A

Released from parotid gland to initiate carbohydrate digestion

59
Q

What is the role of lipase in saliva?

A

Secretes within glands of the mucosa of the tongue (linguinal)

60
Q

What is the role of Saliva in the mouth?

A 
Anti-bacterial
Anti-viral
Anti-fungal
Tissue coating 
Lubrification
Viscoelasticity
Mineralisation 
Buffering 
Digestion
61
Q

Where does swallowing take place?

A

Mouth and oesophagus

62
Q

What is the Oral phase?

A

First phase of swallowing

63
Q

What are the phases of swallowing?

A

1- Oral phase
2- Pharyngeal phase
3- Oesophageal phase

64
Q

What are the events of the oral phase?

A

Preparatory phase: chewing and biting

Transfer phase: Respiration inhibited and tongue forces bolus into pharynx

65
Q

What is the Pharyngeal phase?

A

Movement of bolus from pharynx into oesophagus

66
Q

What is the oesophageal phase?

A

Delivers bolus to the stomach

67
Q

What does the Esophageal manometry measures?

A

Oesophageal motility & problems swallowing

68
Q

What is dysphagia?

A

Problems swallowing

69
Q

What are the Gastric functions of the stomach?

A

Motility
Digestion
Protection
Absorption

70
Q

What are the phases of motility?

A

Gastric accommodation
Trituration- gastric juices
Gastric emptying

71
Q

What are 2 Functional/motor regions?

A

1- Reservoir - tonic contractions

2- Antral pump - Phasic contractions

72
Q

What are the 4 anatomical regions of the stomach ?

A 
Cardia
Fundus
Body (Corpus)
Antrum 
Pyloric sphincter
73
Q

Where is the gastric juice found?

A

The stomach

74
Q

What are the components of the gastric juice?

A 
Water and ions 
HCl
Pepsinogens 
Intrinsic factor 
Mucus 
Gastrin
75
Q

What is the role of HCl in the gastric juice?

A

Provide low ph (1 or 2)
Prevent bacterial growth
Catalyse cleavage of pepsinogens to pepsin

76
Q

What is the role is Pepsinogens in the gastric juice?

A

Proenzyme of pepsin

Pepsin breaks down proteins into peptides

77
Q

What is the role of Intrinsic factor in the gastric juice?

A

Glycoproteins

Binds to vitamin B12 to allow digestion in the ileum

78
Q

What is the role of the Mucus in the gastric juice?

A

Protects gastric mucosa

79
Q

What is the role is Gastrin in gastric juice?

A

(From G cells)

Regulates acid secretion

80
Q

Which cells are involved in gastric secretion?

A

Mucus neck cells
Parietal cells
Chief cells
Endocrine cells

81
Q

What do Mucus neck cells secrete?

A

Mucus

82
Q

What do Parietal cells secrete?

A

HCl

Intrinsic factor

83
Q

What do Chief cells secrete?

A

Pepsinogen

84
Q

What do Endocrine cells secrete?

A

G cells-gastrin to stimulate acid secretion

D cells-somatostatin to inhibit acid secretion

85
Q

How is Bicarbonate formed?

A

CO2 in parietal cells reacts with H2O

86
Q

How is HCL secreted?

A

H+ is catalysed by the enzyme carbonic anhydrase

H+ transported actively by proton pumps into gastric lumen in exchange for K+ ions

Both K+ and Cl- diffuse passively down a concentration gradient out of the cell

The bicarbonate produces is transported into the capillaries in exchange for Cl- ions by anti porters

87
Q

What controls ACID secretion?

A

Neulroendocrine - ACh
Endocrine - gastrin
Paracrine - histamine

88
Q

What are the phases of motility ?

A

Cephalic phase: 30%
Gastric Phase : 60%
Intestine phase:10%

89
Q

Where is the duodenum?

A

First loop of small Intestine?

90
Q

What is the role of the duodenum?

A

Digestion of bolus

Reflex inhibition motility- enterogastric gastric reflex

91
Q

What are Brunner’s glands in the duodenum?

A

Secrete alkaline fluid of mucin- anti-acid function coating the duodenal epithelium protecting it from the acidic chyme of the stomach

92
Q

The duodenum receives secretions from where?

A 
Gall bladder (liver)
Pancreas
93
Q

Which metal ions are absorbed in the duodenum?

A

Fe2+
Mn2+
Ni2+
Cu2+

94
Q

What is the name of the exocrine part (85%)of the pancreas secrete?

A

Acinus

95
Q

What does the Acinus secrete?

A

Water and ions- neutralise duodenal contents to prevent damage and ph for enzyme

Bicarbonate

Enzymes- essential for normal digestion

96
Q

What is the name of the endocrine part do the pancreas?

A

Islets of Langherans

97
Q

What do the Islets of Langherans secrete?

A

Alpha-cells : glucagon

Beta-cells: insulin

98
Q

What does Pancreas secrete?

A

Pancreatic juice via hormonal control

99
Q

Where is the Pancreatic juice secreted?

A

CCK acts in acidario cells to produce pancreatic juice which in enzymes

100
Q

What does Secretin do?

A

Acts on pancreatic ducts to cause large secretion of very alkaline pancreatic juice rich in HCO3 and poor in enzyme

101
Q

What do CCK and Secretin do together?

A

Add enzymes to pancreatic juice and ensure that they are washed into the intestine

102
Q

What are the Pancreatic enzymes? What do they digest?

A

Trypsinogen - trypsin
Chymotrypsinogen - chymotrypsin
Proelastase - elastase
Procarboxypeptidase - carboxypeptidase

Lipase and phospholipase- Fats
Nucleases- Nucleic acids
α-amylase- Carbohydrates

103
Q

What is blood supply to the liver?

A

Hepatic artery - oxygenated blood
Portal vein - nutrient rich blood from gut
Hepatic vein - deoxygenated blood from the liver

104
Q

What is Bile?

A

produced by the liver and concentrated in gall bladder (x15) - biliary system

105
Q

What is the structure of the Liver?

A

●Divided into lobules
●Portal triad- bile duct, portal vein and hepatic artery
●Central canal- hepatic vein

106
Q

Bile is alkaline, what is its ph?

A

7.8-8.6

107
Q

What are the components of Bile?

A

Water
Bile pigments- bilirubin
Salts, cholesterol and lecithin - micelles

108
Q

What do Bile salts do?

A

Bile salts emulsify fats (micelles) - large surface area (facilitates action of lipase enzymes)

109
Q

What happens to 95% of bile salts?

A

95% bile salts reabsorbed in terminal ileum by active transport and returned via hepatic portal vein to liver to be recycled

110
Q

What is the secretion of abile controlled by?

A

Secretin stimulates bile secretion
CCK stimulates release of bile by
Relaxing Sphincter of Oddi
Contracting gall bladder

111
Q

What are the roles of the jejenum & ileum?

A 
Absorption – pancreatic enzymes
   water
Digestion -
Carbohydrate – monosaccharides
protein – peptides & amino acids
lipid - free fatty acids
Secretion of Fluid –
Crypt cells- NaCl
Goblet cells- mucus
EECs-hormones
Panneth cells- defensins
112
Q

What is Malabsorption?

A

Absent or defective digestive enzymes
Defects in transporter proteins
Diseases or infections of small intestine

113
Q

What are examples of malabsorption?

A

Lactase deficiency - lactose intolerance

Coeliac disease – abnormal immune response to gluten – loss of mucosal epithelium

114
Q

How is the motility of the large intestine?

A

Slow movement of contents

115
Q

What are the stages of motion in the large intestine?

A

Segmented contractions

Mass movements

116
Q

What are Segmented contractions?

A

Retain material in the proximal colon (water reabsorption and fermentation)

Mixing contents

117
Q

What are Mass movements?

A

2-3 times a day

movement of material into aboral end of colon- ready for defecation

118
Q

What are the functions of the large intestine?

A

High mucus secretion- goblet cells

No carrier mediated transport of nutrients (absorption by diffusion)

Efficient water reabsorption - follows Cl- and Na+ movement

HCO3- buffers acid produced by bacterial fermentation

GI BLOCK (13 decks)

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