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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
Where are the Interstitial Cells of Cajal (ICC) found?
In myenteric plexus
26
What do the Interstitial Cells of Cajal (ICC) do?
Electrical activity spreads via gap junctions from ICCs to muscle ICCs produce slow waves
27
What are Slow waves?
Slow undulating changes in rating membrane potential NOT ACTION POTENTIAK
28
At what threshold do Slow waves cause contraction?
-40 mv
29
What activates Slow waves?
Distension: bolus of food (chyme) stimulates stretch receptors (local reflex) Oral contraction Aboral relaxation
30
What are the nerves of slow waves?
Parasympathetic nerves (ACh)
31
What is the neurotransmitter in slow waves ?
Acetylcholine (ACh)
32
Where do segmented contractions & mass movements take place?
Colon: 99% of the time
33
What is the function of the Colon?
Retain material - water reabsorption and fermentation Mixing contents Mass movement of material into aboral end via Gastro-colic response
34
How many times does Mass movement of material into aboral end of colon occurs?
2-3 Times per day
35
What is Hirschprungs disease aka TOXIC MEGA COLON?
Congenital disorder which presents shortly after birth
36
What are the characteristics of TOXIC MEGA COLON?
All or part of colon has no innervation The colon is dilated Treatment: Surgical removal of the colon
37
What is mastication?
Breakdown of food
38
What is the role of Taste in the mouth ?
Inform brain about edibility/ duration
39
What is the role so Salivary production in the mouth?
Lubrication, protection and digestion
40
What is the role of Swallowing in the mouth?
Movement of digested macromolecules to stomach
41
What organs are responsible of Taste in the mouth ?
Papillae: taste organs
42
What are Papillae?
Raised protrusions on the tongue, soft & pallet, pharynx, epiglottis & larynx Visible to naked eye
43
Where are te Taste buds found?
In the Papillae
44
How many types of cell does each taste bud contain?
Epithelial cells Support cells Gustatory receptor cells (taste cells)
45
Which nerves innervate taste buds?
Gustatory afferent nerves
46
Is the moth a taste bud? Yes or no
Yes
47
What do Apical microvilli in the mouth do?
Increase surface area
48
How are receptor proteins in mouth exposed?
Through taste pore
49
Where are ion channels and receptors located in the mouth?
On villi
50
All flavours are encoded by how many taste modalities?
5
51
What are the taste modalities?
``` Sweet Salt Sour Bitter Umami ```
52
One taste cell responds to one modality True or false
True
53
What are the Ionotropic receptors in the mouth?
Salt : Na+ | Sour: H+ gated ion channels (K+/H+)
54
What are the metabotropic receptors in mouth ?
Sweet Bitter Umami
55
What is the Saliva?
Hypotonic solution containing more than 99% water and 1% dry matter such as proteins
56
What are the components of the Saliva?
``` Water Bicarbonate ions Enzymes Alpha-amylase Lipase Proteins (100s) ```
57
What is the role of Bicarbonate ions in saliva?
Buffering capacity | Protect from acid
58
What is the role of alpha - amylase in saliva?
Released from parotid gland to initiate carbohydrate digestion
59
What is the role of lipase in saliva?
Secretes within glands of the mucosa of the tongue (linguinal)
60
What is the role of Saliva in the mouth?
``` Anti-bacterial Anti-viral Anti-fungal Tissue coating Lubrification Viscoelasticity Mineralisation Buffering Digestion ```
61
Where does swallowing take place?
Mouth and oesophagus
62
What is the Oral phase?
First phase of swallowing
63
What are the phases of swallowing?
1- Oral phase 2- Pharyngeal phase 3- Oesophageal phase
64
What are the events of the oral phase?
Preparatory phase: chewing and biting Transfer phase: Respiration inhibited and tongue forces bolus into pharynx
65
What is the Pharyngeal phase?
Movement of bolus from pharynx into oesophagus
66
What is the oesophageal phase?
Delivers bolus to the stomach
67
What does the Esophageal manometry measures?
Oesophageal motility & problems swallowing
68
What is dysphagia?
Problems swallowing
69
What are the Gastric functions of the stomach?
Motility Digestion Protection Absorption
70
What are the phases of motility?
Gastric accommodation Trituration- gastric juices Gastric emptying
71
What are 2 Functional/motor regions?
1- Reservoir - tonic contractions | 2- Antral pump - Phasic contractions
72
What are the 4 anatomical regions of the stomach ?
``` Cardia Fundus Body (Corpus) Antrum Pyloric sphincter ```
73
Where is the gastric juice found?
The stomach
74
What are the components of the gastric juice?
``` Water and ions HCl Pepsinogens Intrinsic factor Mucus Gastrin ```
75
What is the role of HCl in the gastric juice?
Provide low ph (1 or 2) Prevent bacterial growth Catalyse cleavage of pepsinogens to pepsin
76
What is the role is Pepsinogens in the gastric juice?
Proenzyme of pepsin | Pepsin breaks down proteins into peptides
77
What is the role of Intrinsic factor in the gastric juice?
Glycoproteins | Binds to vitamin B12 to allow digestion in the ileum
78
What is the role of the Mucus in the gastric juice?
Protects gastric mucosa
79
What is the role is Gastrin in gastric juice?
(From G cells) | Regulates acid secretion
80
Which cells are involved in gastric secretion?
Mucus neck cells Parietal cells Chief cells Endocrine cells
81
What do Mucus neck cells secrete?
Mucus
82
What do Parietal cells secrete?
HCl Intrinsic factor
83
What do Chief cells secrete?
Pepsinogen
84
What do Endocrine cells secrete?
G cells-gastrin to stimulate acid secretion D cells-somatostatin to inhibit acid secretion
85
How is Bicarbonate formed?
CO2 in parietal cells reacts with H2O
86
How is HCL secreted?
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
What controls ACID secretion?
Neulroendocrine - ACh Endocrine - gastrin Paracrine - histamine
88
What are the phases of motility ?
Cephalic phase: 30% Gastric Phase : 60% Intestine phase:10%
89
Where is the duodenum?
First loop of small Intestine?
90
What is the role of the duodenum?
Digestion of bolus Reflex inhibition motility- enterogastric gastric reflex
91
What are Brunner’s glands in the duodenum?
Secrete alkaline fluid of mucin- anti-acid function coating the duodenal epithelium protecting it from the acidic chyme of the stomach
92
The duodenum receives secretions from where?
``` Gall bladder (liver) Pancreas ```
93
Which metal ions are absorbed in the duodenum?
Fe2+ Mn2+ Ni2+ Cu2+
94
What is the name of the exocrine part (85%)of the pancreas secrete?
Acinus
95
What does the Acinus secrete?
Water and ions- neutralise duodenal contents to prevent damage and ph for enzyme Bicarbonate Enzymes- essential for normal digestion
96
What is the name of the endocrine part do the pancreas?
Islets of Langherans
97
What do the Islets of Langherans secrete?
Alpha-cells : glucagon | Beta-cells: insulin
98
What does Pancreas secrete?
Pancreatic juice via hormonal control
99
Where is the Pancreatic juice secreted?
CCK acts in acidario cells to produce pancreatic juice which in enzymes
100
What does Secretin do?
Acts on pancreatic ducts to cause large secretion of very alkaline pancreatic juice rich in HCO3 and poor in enzyme
101
What do CCK and Secretin do together?
Add enzymes to pancreatic juice and ensure that they are washed into the intestine
102
What are the Pancreatic enzymes? What do they digest?
Trypsinogen - trypsin Chymotrypsinogen - chymotrypsin Proelastase - elastase Procarboxypeptidase - carboxypeptidase Lipase and phospholipase- Fats Nucleases- Nucleic acids α-amylase- Carbohydrates
103
What is blood supply to the liver?
Hepatic artery - oxygenated blood Portal vein - nutrient rich blood from gut Hepatic vein - deoxygenated blood from the liver
104
What is Bile?
produced by the liver and concentrated in gall bladder (x15) - biliary system
105
What is the structure of the Liver?
●Divided into lobules ●Portal triad- bile duct, portal vein and hepatic artery ●Central canal- hepatic vein
106
Bile is alkaline, what is its ph?
7.8-8.6
107
What are the components of Bile?
Water Bile pigments- bilirubin Salts, cholesterol and lecithin - micelles
108
What do Bile salts do?
Bile salts emulsify fats (micelles) - large surface area (facilitates action of lipase enzymes)
109
What happens to 95% of bile salts?
95% bile salts reabsorbed in terminal ileum by active transport and returned via hepatic portal vein to liver to be recycled
110
What is the secretion of abile controlled by?
Secretin stimulates bile secretion CCK stimulates release of bile by Relaxing Sphincter of Oddi Contracting gall bladder
111
What are the roles of the jejenum & ileum?
``` 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
What is Malabsorption?
Absent or defective digestive enzymes Defects in transporter proteins Diseases or infections of small intestine
113
What are examples of malabsorption?
Lactase deficiency - lactose intolerance | Coeliac disease – abnormal immune response to gluten – loss of mucosal epithelium
114
How is the motility of the large intestine?
Slow movement of contents
115
What are the stages of motion in the large intestine?
Segmented contractions Mass movements
116
What are Segmented contractions?
Retain material in the proximal colon (water reabsorption and fermentation) Mixing contents
117
What are Mass movements?
2-3 times a day movement of material into aboral end of colon- ready for defecation
118
What are the functions of the large intestine?
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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