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Physiology 2001 > Gastrointestinal Physiology > Flashcards

Gastrointestinal Physiology Flashcards

1
Q

What are the functions of gut nerves and hormones?

A
  • Coordinate motility to deliver food to the appropriate area at a rate readily handled by the small intestine
  • Stimulate secretion when food is in the right place
  • Turn off secretion when food is absent
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2
Q

Digestion is controlled extrinsicly by the …………..

A

Autonomic nervous system via the Parasympathetics and Sympathetics

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3
Q

Digestion is controlled intrinsicly by the ……………

A

Enteric Nervous system via the Myenteric plexus and Submucous plexus

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4
Q

What are the phases of digestion?

A

Interdigestive
Cephalic
Gastric
Intestinal

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5
Q

What are the functions of Gastrointestinal system?

A

Secretion
Mixing and metering of food
Absorption
Excretion

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6
Q

Describe digestion in the mouth:

A
  • Teeth mechanically digest food
  • Salivary glands secrete mucous, lysozymes and salivary amylase
  • Amylase begins starch digestion
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7
Q

Salivary glands are activated by the __________ and chewing

A

Parasympathetics and Chewing

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8
Q

Sympathetic stimulation of the salivary glands _______________________________

A

Changes the composition of saliva

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9
Q

Ring-like __________ contractions move the bolus of food down the oesophagus

A

Peristaltic

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10
Q

The stomach is a _____________ of the alimentary canal and it is involved in ________, _______ and ________ of food

A

Muscular dilation

Digestion, Metering and Mixing

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11
Q

What does the stomach produce?

A

HCl
Pepsinogen
Mucous
Intrinsic Factor

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12
Q

Irrittations of the stomach can lead to ________, an increase in ________ pressure ejects food out of the stomach

A

Retropulsion aka vomiting

Abdominal

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13
Q

In the body region of the stomach there are glands that contain ________, _________, ______________ and ____________.

A

Chief Cells
Parietal Cells
Enterochromaffin-like cells ECL cells
Mucous Surface Cells

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14
Q

What do Chief Cells do?

A
  • Release pepsinogen, a proteolytic pro-enzyme
  • Pepsinogen is converted to pepsin when exposed to acid
  • pepsin begins protein digestion
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15
Q

What do Parietal Cells do?

A
  • Produce HCl
  • Acid is produced by a proton pump (K+ is pumped into the cell, H+ and Cl- are pumped out into the stomach)
  • Secrete intrinsic factor which is needed for vitamin B12 absorption
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16
Q

What do Mucous Surface cells do?

A
  • Produce mucous rich in HCO3 to protect the stomach wall from damage
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17
Q

What do Enterochromaffin-like Cells do?

A

Produce histamine to stimulate acid production

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18
Q

What do G cells do?

A

Producen gastrin to stimulare acid production

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19
Q

During the cephalic stage of digestion ____________ stimulate Gastric secretion.

A

Parasympathetic

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20
Q

Explain the factors that affect acid secretion during the cephalic phase:

A
  1. Sight/Smell/Taste stimulates the parasympathetics
  2. G cells are activated by Ach released from parasympathetic nerves
  3. ECL cells release histamine in response to Ach from parasympathetics and Gastrin
  4. Gastrin, Ach and Histamine (most important factor) bind to the parietal cell and cause acid secretion

This accounts for 30% of acid secretion

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21
Q

The stomach is usually collapsed during the __________, but when food enters the stomach it expands. This prevents ____________

A

Interdigestive phase

Pressure build up

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22
Q

Explain the factors that affect acid secretion during the gastric phase:

A
  1. Stretch receptors detect stomach distension and activate the parasympathetics
  2. G cells are activated by AAs/peptides detected by the villi on G-cells and Ach released from parasympathetic nerves
  3. ECL cells release histamine in response to Ach from parasympathetics and Gastrin
  4. Gastrin, Ach and Histamine (most important factor) bind to the parietal cell and cause acid secretion

This accounts for 60% of acid secretion

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23
Q

Coffee, Beer and Wine can ________ Gastrin secretion

A

Increase

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24
Q

H2 receptors in the parietal cells respond to _________

A

Histamine

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25
Muscarinic receptors in the parietal cells respond to _________
Ach from parasympathetics
26
Gastrin receptors in the parietal cells respond to _________
Gastrin | DUH
27
How are chief cells activated to secrete pepsinogen?
In the same was as parietal cells are activated to secrete HCl
28
What is the function of an Antral Somatostatin cell?
- Chemoreceptors on the villi on this cell detect changes in pH - When pH decreases it releases a localised dose of somatostatin to the G-cell and decrease Gastrin secretion - Decreased Gastrin = decreased acid production
29
The gel like structure of the __________ layer __________ the rate of H+ diffusion
Mucous layer | Decreases
30
To eject food, the _____ of the stomach pinches off and _________________ forces the chyme through the _______ sphincter
Antrum A wave of peristaltic contraction Pyloric Sphincter
31
When the first dose of chyme enters the duodenum we get the final _________________, However as more chyme leaves the stomach this quickly become _________
10% of acid secretion | Inhibitory
32
What are the sections of the small intestines?
Duodenum Jejunum Ileum
33
Explain how gastric emptying is controlled:
``` INTRINSICLY = Plexus in the duodenal wall and antrum detect distension of the duodenum and this slows emptying EXSTRINCLY = Vago-vagal nerve reflexes are also involved ```
34
________ stimulate secretion from the pancreas
Hormones
35
________ stimulate the contraction of the gall bladder
Hormones
36
The ____________ prevents secretions from the _______ and _______ entering the duodenum when food is absent
Sphincter of Oddi Pancreas Bile Salts
37
Acinar cells are _________ in structure that secrete into a _______
Grape-like | Lumen
38
What do Acinar cells produce?
Proteases Lipases Amylases Nucleic Acid enzymes
39
Intercalated duct cells are found in the ducts leading from the ________ and secrete _________
Acinar Cells | HCO3-
40
What factors control exocrine pancrease secretion?
- Vagus (Parasympathetic) nerve controls enzyme and HCO3- secretion - Hormone Cholecystokinin (CCK) controls enzyme secretion - Hormone Secretin controls HCO3- secretion
41
CCK RF and trypsin are ___________________ into the duodenal lumen. Trypsin _________ CCK RF and therefore CCK is _____________
Continuously released Breaks down Not release
42
Trypsin has a greater affinity for ___________ rather than _________. Therefore the concentration of _____ increases and causes release of enzymes
Dietary proteins CCK RF CCK
43
Explain how CCK stimulates Enzyme release:
1. CCK activates the vagal afferent which causes an increase in parasympathetic stimulation 2. Parasympathetics stimulate the acinar cells
44
If you cut the ________ or apply _______ you get inhibition of enzyme secretion
Vagal efferent | Atropine
45
Besides stimulating enzyme secretion, what are the other functions of CCK?
- Stimulates gall bladder contraction - Induces relaxation of the Sphincter of Oddi - Inhibits gastric secretion and emptying
46
Explain how Secretin causes secretion of the HCO3-:
1. Secretin is released from eneterocytes in response to acid 2. Secretin stimulates the vagal afferent like CCK which increases parasympathetic stimulation to the intercalated duct cells 3. Directly stimulates secretion via the blood as, unlike acinar cells, intercalated duct cells have receptors for Secretin
47
Bile is reabsroped in the ______ via the _______________. ___% of bile salts are reabsorped
Ileum Portal Circulation 95%
48
Hepatocytes absorb bile salts from the ________ and then transports them towards the _________
Capillaries | Bile Duct
49
Bile salts are ______________ with a hydrophillic and hydrophobic region
Planar Amphipaths
50
Bile salts _______ fats globules via _______. This increases the surface area for digestion by _______
Emulsify Agitation Lipases
51
Lipases breaks down triglycerides into ___________ and __________.
Monoglycerides | Free Fatty Acids
52
When micelles aproach the intestinal wall they ________. ____________ and __________ are then able to diffuse into the cells
Break apart Monoglycerides Free Fatty Acids
53
Most absorption occurs in the ________
Jejunum
54
________ and ______ are absorbed in the ______
Vitamin B12 and bile salts | Ileum
55
On the microvill of ________ there are _________ and lots of membrane bound _________
Enterocytes Glycocalyces Enzymes
56
Inside the enterocyte, _________ are reformed and coated with a _______ protein layer. They are then exocytosed into the interstitial fluid where they can be absorbed into ___________
Triacylglycerides Chylomicron Lymphatic vessels
57
________ cuts at the α-1,4 linkages in starch and we get __________, __________ and ________.
α amylase Maltose Maltotriose α-limit dextrans
58
Membrane bound enzymes break down complex sugars into ________, _________ and ________.
Glucose Fructose Galactose
59
_____ and _____ transport all simple sugars into the enterocyte. _____ transports fructose and _____ transports _______ and ______
GLUT5 and SGLT1 GLUT 5 transports fructose SGLT1 transports glucose and galactose
60
Isomaltase breaks down ________ into _______ and _______
α-limit dextrans Maltotriose Maltose
61
Glycoamylase breaks down ______ and _________ into __________________.
Maltose Maltotriose Single glucose molecules
62
Lactase breaks down _______ into ________ and _______
Lactose Glucose Galactose
63
Sucrase breaks down _______ into ________ and _______
Sucrose Glucose Fructose
64
______ transports Glucose and Fructose into the interstitial fluid where it can be ____________________
GLUT 2 | Absorbed into the blood
65
Enterocytes can absorbed peptides that are less than ___ AAs in length.
4
66
Peptides that are absorbed into the enterocytes are broken down further by _________ into _________
Peptidases | Single amino acids
67
Water in the intestines is absorbed in the same way as ____________. We absorbed about __% of water.
In the kidney | 95%
68
What are the main functions of the large intestines?
- Digestion of dietary fibre by bacteria - Dessication, removal of more water - Formation and storage of faeces
69
Faeces is made of:
- Dead Cells - Indigestible material - Bacteria - Water

Physiology 2001 (7 decks)

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