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Human physiology (2) > Gastrointestinal: regulation > Flashcards

Gastrointestinal: regulation Flashcards

1
Q

What is the role of the lateral hypothalamus?

A

Feeding centre (promotes eating)

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2
Q

What is the role of the ventromedial hypothalamus?

A

Satiety centre (inhibits eating)

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3
Q

What are the 4 satiety signals?

A

Nervous - reflexes initiated by distension
Hormonal - feedback by cholecystokinin
Chemical - glucostatic and lipostatic
Thermal

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4
Q

What is the cycle of leptin? (4)

A
  • Increased food intake, decreased energy expenditure
  • Adipose tissue, increased fat deposits, increased leptin synthesis
  • Increased plasma leptin conc.
  • Hypothalamus, increased activation of leptin receptors
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5
Q

What are the 5 peptides in the hypothalamus that increase food intake?

A 
Neuropeptide Y
Orexins
Galanin
Melanin
Ghrelin (stomach)
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6
Q

What are the 6 peptides in the hypothalamus and intestines that decrease food intake?

A

CCK - small intestine
Corticotropin-releasing hormone - hypothalamus
a-melanocyte-stimulating hormone - hypothalamus
CART - hypothalamus
Glucagon-like peptide-1 - intestines
PYY 3-36 - intestines

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7
Q

What are the 2 paths for GI regulation?

A

Neural and endocrine

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8
Q

How is food intake regulated? (3)

A

Not based on homeostasis concept
Maximise absorption - regardless of need
Lumen of GI tract conditions regulated to max. absorption

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9
Q

What neural pathways are the enteric nervous system comprised of? (2)

A

Submucosal plexus

Myenteric plexus

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10
Q

What is the short reflex pathway? (4)

A

Stimulus in lumen
GI receptors
Intrinsic nerve plexus
Effector organ in GI tract

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11
Q

What is the long reflex pathway? (5)

A 
Stimulus in lumen 
GI receptors
Central nervous system
Intrinsic nerve plexus
Effector organ in GI tract
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12
Q

What are the 4 GI hormones?

A

Gastrin - stomach
Cholecystokinin - duodenum, jejunum
Secretin - duodenum and jejunum
Glucose-dependent insulinotropic peptide - duodenum and jejunum

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13
Q

What is the role of gastrin? (3)

A

Stimulates gastric secretion and motility
Stimulates ill motility and relaxes ileocecal sphincter
Stimulates mass movement of colon

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14
Q

What is the role of cholecystokinin? (2)

A

Inhibits gastric secretion and motility

Stimulates gallbladder

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15
Q

What is the role of secretin? (2)

A

Inhibits gastric secretion and motility

Potentiates actions of CCK on pancreatic enzyme secretion

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16
Q

What is the role of glucose-dependent insulinotropic peptide? (2)

A

Inhibits gastric secretion and motility

Stimulates insulin secretion by pancreas

17
Q

What are the 3 phases of gastrointestinal control?

A

Cephalic phase - thoughts, taste and smell
Gastric phase - stimuli originate in stomach
Intestinal phase - stimuli originate in small intestine

18
Q

What is involved in short-term regulation: hunger verses satiety? (3)

A

Insulin
CCK
Neural input from mechano/chemo receptors

19
Q

What is involved in long-term regulation? (6)

A
  • Leptin = hormone released from adipose cells when calories exceeds demands
  • Leptin suppresses hunger and increases metabolism
  • Saliva secretion
  • Acid and pepsinogen secretion in the stomach
  • Secretion of pancreatic juice and bile
  • Rates of fluid movement in the digestive tract
20
Q

What are the steps in saliva secretion? (5)

A 
Taste and texture of food
Mechanoreceptors and taste receptors in mouth
Salivary centre of medulla
Autonomic nervous system
Stimulate salivation
21
Q

What are the 2 types of autonomic input to salivary glands and what do they produce? (3)

A

Parasympathetic: watery saliva
Sympathetic: more mucus, thick saliva

22
Q

How is gastric acid secreted and what does it do? (7)

A
  • Parietal cells produce HCl
  • Carbonic anhydrase catalyses bicarbonate and H+
  • H+ actively secreted into the lumen of the stomach
  • Bicarbonate is transported into interstitial fluid for Cl-
  • Cl- diffuses into lumen of stomach
  • H+ & Cl- secreted into stomach lumen
  • bicarbonate enters the interstitial fluid then blood
23
Q

How are these secretions regulated? (3)

A

Parasympathetic nervous system
Gastrin
Histamine

24
Q

What causes an increase in acid and pepsinogen secretion? (5)

A 
Sight of food
Taste
Smell
Chewing
Swallowing
25
Q

What is the action when there is a stimuli to increase secretions? (5)

A
  • Stimuli
  • Increase in parasympathetic activity
  • G cells increase gastrin secretion
  • Increase in plasma gastrin
  • Parietal cells and chief cells increase acid and pepsinogen secretion
26
Q

What is the gastric phase regulation of secretion? (4)

A

Stimuli of gastric secretion
- proteins, peptides and A.A.
- distension of stomach
Short and long reflex pathways trigger gastrin, acid and pepsinogen release

27
Q

Describe the steps in the gastric phase: (6)

A
  1. Distension of the stomach
  2. chemo/mechano detect and respond
  3. short and long reflexes
  4. G cells increase gastrin secretion
  5. increase in plasma gastrin
  6. parietal cells and chief cells increase acid and pepsinogen secretion
28
Q

How is secretion inhibited in the gastric phase? (2)

A

Exit of food removes stimuli for secretion

Increased acidity inhibits gastrin release

29
Q

How is secretion inhibited in the intestinal phase? (5)

A 
Entry of food into duodenum causes:
- increased osmolality
- Increased fat and acid
- Increased distension
Long and short reflex pathways inhibit acid and pepsinogen secretion
30
Q

How is pancreatic juice secreted? (2, 4)

A 
Acinar cells
- small volume of primary section
- water, electrolytes, digestive enzymes
Duct cells
- large volume
- bicarbonate rich secretion
31
Q

What does CCK stimulate?

A

Acinar cells to secrete enzymes

  • small stimulant for bicarbonate release
  • CCK potentiates effects of secretin on bicarb. release
32
Q

What does secretin stimulate? (3)

A

Duct cells to secrete bicarbonate

  • small stimulant for enzyme release
  • secretin potentiates effects of CCK on enzyme release
33
Q

What is the stimuli for CCK release?

A

Fat and amino acids in duodenum

34
Q

What is the stimuli for secretin release?

A

Acidity in duodenum

35
Q

What does secretin stimulate into the duodenum?

A

Bile secretion from liver

36
Q

What does CCK stimulate?

A

Gallbladder contraction

Relaxation of sphincter of Oddi

Human physiology (2) (22 decks)

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