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Y2 S1 Physiology > Gut Motility & Gut Secretions > Flashcards

Gut Motility & Gut Secretions Flashcards

1
Q

What are the digestive processes in the small intestine?

A
  • Chyme mixed w digestive juices and moves along SI
  • chem digestion is completed
  • nearly all nutrient absorption occurs
  • moves undigested remains to LI
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2
Q

What are the 2 types of contractions in the intestines?

A
  • Mixing/Segmenting Contractions
  • Peristaltic Contractions
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3
Q

What do Segmenting Contractions do?

A
  • goes back and forth to break digestive contents down
  • the shape allows plenty of time for chyme to mix w digestive enzymes to be chemically broken down
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4
Q

What is the Migrating Myoelectric Complex and what does it do? and what is it initiated by?

A

= Peristaltic contraction in SI
- Replaces segmenting contractions when most of the meal is absorbed
- Moves undigested remains to LI
- MMC is initiated by increased chyme pH or Motilin

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5
Q

What are the Digestive Processes in the Large Intestine?

A
  • Absorption of H2O and electrolytes
  • Chem digestion by enteric bacteria
  • Propulsive actions
  • Excretion
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6
Q

Describe Mass Movements. What is it facilitated by?

A
  • simultaneous contraction of large segments from caecum to sigmoidal colon
  • facilitated by gastrocolic and duodeno-colic reflexes
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7
Q

LI Anatomy

A
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8
Q

What is Constipation?

A

= pass stools <2/week
Causes:
- IBS
- Pregnancy
- GI diseases

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9
Q

What is Diarrhoea?

A

= rapid movement of faecal matter through LI
Causes:
- Enteritis
- Ulcerative colitis
- Potentially Diabetes

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10
Q

Steps of Defecation Reflex

A
  1. Activation of stretch receptors -> Activation of Parasymp nerves -> Rectal contractions + relaxes Internal Anal Sphincter
  2. Activation of Enteric Neurons -> rectal contractions via Myenteric neurons + relaxation of Internal Anal Sphincter by Inhib. Myenteric Neurons
  3. Both Parasymp & Enteric Neurons -> mucous secretion
  4. Voluntary movement of external anal sphincter by inhibiting somatic motor neurons casuing external anal sphincter to relax.
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11
Q

What are the 7 functions of Saliva?

A
  1. Lubrication
  2. Digestion
  3. Protection
  4. Control of H2O intake
  5. Speech
  6. Absorption
  7. Taste Sensation
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12
Q

Is Salivary Secretion regulated by PNS or SNS?

A

PNS

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13
Q

Salivary Secretion steps

A
  1. Approach of food
  2. Higher centres (olfactory, visual, aud. cortex)
  3. Salivatory nucleus of Medulla
  4. Salivary glands
  5. Salivation
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14
Q

What happens in salivary glands to release saliva?

A

Activation of Muscarinic receptors by Ach -> increase in secretion of saliva

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15
Q

What drug could you give someone with excessive salivation and what type of drug is it?

A
  • Atropine
  • Muscarinic antagonist
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16
Q

What is Xerostomia and what type of drug could treat it?

A
  • Xerostomia = dry mouth
  • Muscarinic agonist can treat it
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17
Q

What are the 3 phases of Swallowing?

A
  1. Voluntary/Buccal Phase
  2. Pharyngeal Phase
  3. Oesophageal Phase
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18
Q

What does the Voluntary/Buccal Phase involve?

A
  • place food into mouth and chew
  • moves from back of mouth to top of pharynx
  • after food touches Mechanoreceptors, process becomes involuntary
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19
Q

What does the Pharyngeal Phase involve?

A

= all of food moves down Pharynx and through Upper Oesophageal Sphincter
- Urula rises and closes of nasal passage
- Epiglottis lowers and closes off trachea
- Involuntary

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20
Q

What does the Oesophageal Phase involve?

A

= bolus passes through Oesophagus (via Peristalsis) -> through Lower Oesophageal Sphincter -> into Stomach
- Constriction behind bolus (due to activation of circular smooth muscle)
- Shortening ahead of bolus (longitudinal smooth muscles contract)

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21
Q

Describe the Neuronal Control of Swallowing?

A
  • Buccal phase controlled by Cerebral Cortex
  • Involuntary phases controlled by swallowing centre in Medulla of brainstem
  • Efferent Impulses (Vagus Nerve):
    - Skeletal Muscle -> Pharynx, Upper Oeso sphincter, Early Oeso
    - Smooth muscle -> Lower Oeso, Gastroesophageal sphincter
  • Oesophageal Peristalsis controlled by:
    - Somatic nerves -> skeletal muscles
    - Autonomic nerves & Myenteric plexus -> controls smooth muscles
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22
Q

What is Dysphagia?

A

encompasses conditions associated w swallowing difficulty

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23
Q

What is Achalasia?

A
  • type of Dysphagia
  • Lower Oesophageal sphincter doesn’t fully relax
  • due to degeneration of nerves in Myenteric plexus
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24
Q

What are the digestive processes in the Stomach?

A
  • Storage area
  • Mechanical digestions & propulsion:
    • Peristaltic waves mix food w gastric secretions to from Chyme
    • Chyme empties into duodenum
  • Protein digestion
  • Intrinsic factor secretion
  • Absorption of some fat-soluble substances
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25
Q

What are the 4 types of Gastric glands?

A
  • Mucous cells
  • Parietal Cell
  • Chief Cell
  • Enteroendocrine cell
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26
Q

What do Mucous cells do?

A
  • secrete mucus
27
Q

What do Parietal cells do?

A
  • secretes HCl
28
Q

What do Chief cells do?

A
  • secrete pepsinogen
29
Q

What do Enteroendocrine cells do?

A
  • secretes gastrin
30
Q

Describe the process of Activation of Pepsinogen to Pepsin

A
  1. Chief cells secrete Pepsinogen
  2. Parietal cells secrete HCl
    - Optimal pH is 2 -> HCl secretion helps lower pH
31
Q

Why do we need gastric acid secretions?

A
  1. Activation of pepsinogen
  2. Kills ingested bacteria (sterilises the meal)
  3. Breakdown of cellulose
32
Q

How do Parietal Cells secrete HCl?

A
  • Cl- absorbed into parietal cell from the stomach veins
  • The process CO2 + H2O <-> H2CO3 occurs -> H+ gained from H2CO3
  • Cl- goes through channels into stomach lumen
  • H+ gets excreted into stomach lumen via H+/K+ ATPase pump
33
Q

How do we enhance HCl secretion in Parietal cells?

A

Activation of Gastrin, Histamine, or ACh -> prod of secondary messengers w/in cytoplasm of parietal cell -> insertion of H+/K+ ATPase pumps into luminal membrane -> increased acid secretion

34
Q

What is Gastrin?

A

Gastrin is a peptide hormone that stimulates secretion of gastric acid by the parietal cells of the stomach and aids in gastric motility

35
Q

How do we prevent the H+/K+ ATPase pump from inserting into the stomach lumen?

A
  • Proton pump inhibitors (PPIs) -> Less HCl secretion
36
Q

What are the 3 phases of HCl secretion after a meal?

A
  1. Cephalic phase
  2. Gastric phase
  3. Intestinal phase
37
Q

What happens in the Cephalic phase of HCl secretion?

A
  • Stim: approach of food
  • Pathway: from the brainstem (medulla oblongata) -> Activation of parasymp. nerves (via vagus nerve) -> innervates Parietal & G cells
  • Stim. to Parietal cell: ACh & Gastrin
38
Q

What happens in the Gastric phase of HCl secretion?

A
  • Stim: swallowed food enters stomach | Semi-digested protein | rising pH
  • Pathway: Local (enteric) and long autonomic (parasympathetic reflexes: Parietal & G cells
  • Stim to Parietal cell: ACh & Gastrin
39
Q

What happens in the Intestinal phase of HCl secretion? (stim? pathway? stim to parietal cell?)

A
  • Stim: Chyme empties into duodenum | Acidity | Protein digestion products
  • Pathway: Intestinal endocrine secretions (secretin, gastric, inhib peptide) | Inhib. of Vagal Nuclei in medulla + local neuronal reflexes
  • Stim to Parietal cell: Decreased Ach & Gastrin secretion
40
Q

What is Chyme and what does it do?

A

= Chyme is Pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food
- It increases the surface area of food by breaking it down into smaller components

41
Q

What is Secretin?

A

= Secretin is a hormone that regulates water homeostasis throughout the body and influences the environment of the duodenum by regulating secretions in the stomach, pancreas, and liver.

42
Q

What is Bile and what does it do?

A

= Bile, or gall, is a yellow-green fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine

43
Q

What is the Optimal pH of different sections of the GIT?

A
44
Q

What is the pathway of bile secretion into the gut lumen?

A
45
Q

What do bile salts do?

A

Help to emulsify fats in the small intestine

46
Q

What is the precursor of bile salts?

A

Cholesterol

47
Q

What does Lecithin (a phospholipid) do?

A

Combines w bile salts to emulsify fats

48
Q

What are bile pigments produced from?

A

Produced by the breakdown of haem

49
Q

What does Pancreatic Lipase do?

A

Break down triglycerides into fatty acids and monoglycerides

50
Q

Describe the 6 steps in the Regulation of Bile Secretion

A
51
Q

What does acidity in the GIT lead to the secretion of?

A

Leads to more Secretin to be produced which leads to more bile secretion

52
Q

What does the presence of fats in the GIT lead to the secretion of?

A

Leads to more Cholecystokinin (CCK) to be secreted which causes sphincter to relax which allows bile to be secreted into the duodenum lumen

53
Q

What are the 5 main roles of Cholecystokinin in Fat Emulsification?

A
  1. Gallbladder contraction
  2. Hepatopancreatic sphincter relaxes
  3. Pancreas secretes Lipase
  4. Stomach inhibits churning
  5. Pyloric sphincter constricts -> slows emptying of fatty chyme into duodenum
54
Q

What does Colipase do and what is it secreted by?

A

Colipase pushes aside bile salts on emulsion droplet allowing pancreatic lipase to get in contact with the emulsion droplet

55
Q

What are 2 Endocrine secretions of the Pancreas?

A
  • Insulin
  • Glucagon
56
Q

What do Ductal cells do?

A

secrete Alkaline pancreatic fluid (HCO3-)

57
Q

Why do Ductal cells secrete Alkaline Pancreatic Fluid?

A
  • Activation of Pancreatic enzymes
  • Protects intestinal mucosa from excess acid
  • Micelle formation (fat emulsification/digestion)
58
Q

What do Acinar cells do?

A

secrete Pancreatic enzymes

58
Q

What are the enzymes released by the pancreas?

A
59
Q

Describe the activation of Pancreatic Proteases

A
60
Q

What is Pancreatitis?

A

Inflammation of Pancreas

61
Q

What are 4 causes of Pancreatitis?

A
  • defective ductal secretion of HCO3- and H2O
  • significantly decreased release of pancreatic enzymes
  • inappropriate activation of pancreatic enzymes
  • excessive alcohol intake
62
Q

What are symptoms of Pancreatitis?

A
  • continuous abdominal pain
  • weight loss
  • fat malabsorption
63
Q

What is some treatment for Pancreatitis?

A
  • improve nutrition w pancreatic supplements
  • remove alcohol
  • pain relief -> aspirin, opiates

Y2 S1 Physiology (13 decks)

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