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Nutritional Physiology > Gastric Motility & Neural Control > Flashcards

Gastric Motility & Neural Control Flashcards

1
Q

What is the process of myosin phosphorylation?

A
  1. Calcium binds to calmoduin
  2. Activates myosin light chain kinase
  3. Phosphorylates myosin
  4. Phosphomyosin interacts with actin
  5. Contraction occurs
  6. Dephosphorylation occurs through myosin light chain phosphatase
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2
Q

What is the structure of the gut?

A
  • lumen
  • mucosa
  • submusoca
  • inner circular layer
  • outer longitudinal muscle layer
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3
Q

What does the SM cell look like at rest?

A
  • Kir channels let K+ out
  • Kc channels closed
  • Ca channels closed
  • low Ca2+ concentration
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4
Q

What happens in SM cells during depolarisation?

A
  • closes K channels

- opens voltage gated Ca2+ channel (L-type)

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5
Q

What are the pacemakers of gut SM?

A

Interstitial cells of Cajal

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6
Q

What are resting membrane potentials of SM cells?

A

-60mV

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7
Q

What does a slow wave look like?

A

Up stroke
Plateau
Down stroke

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8
Q

How fast do slow waves travel along the gut?

A

1cm/sec

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9
Q

Frequency of slow waves

A

3/min in stomach

11-12/min in duodenum

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10
Q

What is the slow wave mechanism in the interstitial cells of Cajal?

A
  1. Spontaneous release of Ca2+ from ER through RyR and IP3 channels
  2. Causes an influx of additional Ca2+ through T-type voltage gated channels
  3. Ca2+ influx opens chloride ANO1 channels (unusual amount of chloride inside)
  4. Efflux of Cl-
  5. Depolarisation occurs
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11
Q

The more ……, the more ………

A

Action potentials, contractions

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12
Q

What causes action potentials in gut SM?

A
  1. Stretch
  2. Acetylcholine
  3. Parasympathetics
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13
Q

What hyperpolarises SM?

A
  1. Noradrenaline

2. Sympathetics

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14
Q

Which nerves innervates the gut?

A 
Vague nerve
Sacral nerves (to large intestine)
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15
Q

Where does sympathetic gut inner action come from?

A

Thoracic and lumbar chord

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16
Q

The gut at rest is under ……. tone

A

Parasympathetic

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17
Q

Which receptors does ACh stimulate?

A

M3

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18
Q

What is eserine?

A

Anticholinesterase

19
Q

What is atropine?

A

M-cholinergic antagonist

20
Q

What is a slow excitatory post synapse potential (EPSP)?

A

Slow to onset, last a very long time - enteric nervous system

21
Q

Why to prolonged EPSP and IPSPs occur?

A

Long duration due to GPCR not ion channels as post-synaptic receptors

22
Q

What are the transmitters in the gut?

A

ACh: M-receptors, muscle contraction and secretion
Substance P: NK-receptors, contraction and secretion
VIP (vasoactive intestinal peptide) and NO inhibit contraction (VIP stimulates secretion)

23
Q

In the gut, sympathetic tone…..

A

Contracts sphincters (alpha receptors) and relax other tissues (beta receptors)

24
Q

What are the types of intestinal motility?

A
  1. Segmentation
  2. Peristalsis
  3. Migrating motor complex
  4. Retroperistalsis
25
Q

What is segmentation?

A

Mixes chyme, most common after eating

26
Q

What is peristalsis?

A

Moves chyme along the gut from oral to aboral

27
Q

What is migrating motor complex?

A

Moves material out of intestine in the inter digestive phase

28
Q

What is the velocity of peristaltic contractions?

A

0.5-2cm/sec

29
Q

What is total transit time usually?

A

3-5hrs

30
Q

What is motility increased by?

A

Cholecystokinin, gastrin, insulin

31
Q

What inhibits peristalsis?

A

Secretin, glucagon, opioids

32
Q

What is the neural activity of peristalsis?

A
  1. Stretch receptors detect food
  2. Activates intermediate neurons
  3. Many intermediate nerves use calcitonin gene related peptide (CRGP)
  4. Act on excitatory nerves which release ACh
  5. ACh acts on longitudinal muscle ahead of the food (distal) and the circular muscle behind the food (proximal)
  6. Inhibitory neurons use NO and VIP to inhibit circular smooth muscle ahead of the food (distal)
33
Q

What stops peristalsis from moving all the way through the intestine?

A

Tonic inhibition by enteric nerves

34
Q

What is chyme?

A

Partially digested food in the intestine

35
Q

What is the most common movement during the digestive phase?

A

Segmentation

36
Q

What happens without MMC between meals?

A

Bacterial overgrowth and accumulation of indigestible materials

37
Q

What is gastric accomodation?

A

Active relaxation of the stomach via the vagus nerve - stretch reflex

38
Q

Most of the vagus neurons are…….

A

Sensory

39
Q

What affects the emptying of the stomach?

A
  • inhibited by acid

- solids take longer to empty

40
Q

Effect of acid in duodenum on gastric emptying

A

Inhibits gastric emptying through secretin and intramural intrinsic plexus - increases sympathetic activity

41
Q

Effect of fat in duodenum on gastric emptying

A

Intramural intrinsic plexus

GIP, cholecystokinin inhibit

42
Q

Effect of hypertonicity in duodenum on gastric emptying

A

Intramural intrinsic plexus

Unknown hormone

43
Q

Effect of amino acids on gastric emptying

A

Gastrin - inhibits gastric emptying

44
Q

What inhibits gastric emptying?

A
  • acid
  • fat
  • hypertonicity
  • amino acids

Nutritional Physiology (13 decks)

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