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ANSC 311 - Metabolic Physiology > Lecture 5 - Motility > Flashcards

Lecture 5 - Motility Flashcards

1
Q

How is feed procured?

A

lips, tongue, incisors

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2
Q

Molars

A

grind the feed
- vary in use depending on diet and species

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3
Q

Vertical vs lateral chewing

A
  • vertical = carnivores and omnivores
  • lateral = herbivores (better for grinding plant matter)
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4
Q

Floating

A
  • teeth wear unevenly due to grinding and continue to erupt
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5
Q

Indications for floating

A
  1. dropping feed
  2. dropping wt
  3. head tossing
  4. balls of chewed hay coughed out
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6
Q

2 swallowing phases

A
  1. oropharyngeal phase
  2. oesophageal phase
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7
Q

Oropharyngeal swallowing phase

A
  • bolus pushed back by tongue and triggers pressure receptors
  • uvula blocks nose
  • glottis and epiglottis blocks lung access
  • swallowing center in medulla coordinates and inhibits respiratory center
  • pharyngoesophageal sphincter opens
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8
Q

Oesophageal swallowing phase

A
  • peristaltic waves
  • skeletal muscle
  • cardiac sphincter opens
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9
Q

Peristalsis motility

A
  • waves of contraction
  • peristaltic reflex (duodenum) programmed by enteric nervous system
  • relaxation/contraction of longitudinal muscle and circular muscle
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10
Q

Gastric motility steps

A
  1. Fundus
    - receptive relaxation = making room
    - NO and VIP induced by ACh to induce relaxation
  2. Corpus
    - mixing vat for saliva, food, and gastric secretions
  3. Antrum
    - propulsion of food through pyloric sphincter to the duodenum
    - controlled by distension and parasympathetic
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11
Q

Gastric emptying

A
  • peristalsis
  • pyloric sphincter opens and chyme enters duodenum
  • regulated by force of contractions and signals from duodenum; rate dependent on physical and chemical state
  • vagal component: vagotomy decreases contractions, stimulation of vagal nerve increats contrations
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12
Q

Factors increasing gastric emptying

A
  1. neural control
    - distension of gastric wall
    - increased parasympathetic
  2. endocrine control
    - gastrin
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13
Q

Factors decreasing gastric emptying

A
  1. neural control
    - chemoreceptor, osmoreceptor, mechanoreceptor at duodenum
    - increased sympathetic
  2. endocrine control
    - CCK, GIP, secretin
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14
Q

Most common form of motility

A

Segmentation

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15
Q

Segmentation

A

contraction of circular muscle where digesta is not propagated in one direction; alternating contractions for mixing
- frequency decreases distally

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16
Q

Segmentation in the colon

A
  • haustration = clearing
17
Q

Motility regulation duodenum

A
  • stimulus = chyme distending duodenum
  • sensors = stretch receptors in duodenal wall
  • signal = nervous
  • effector smooth muscle
  • response = vigorous segmentation in duodenum
  • effect = removal of chyme
18
Q

Motility regulation in ileum/colon

A
  • stimulus = protein/digesta causing gastrin release
  • response =
    1. gastro-ileal reflex: stimulates segmentation in ileum, gastrin inhibits the ileo-caecal sphincter so it opens
    2. gastro-colic reflex: mass movements in colon
19
Q

Tonic contraction

A

sustained contraction of muscle

20
Q

Mechanism for contraction

A

Interstitial Cells of Cajal (ICC)
- pacemakers in circular and longitudinal muscle layers that set a constant pulse of depolarization/repolarization in ssmooth muscle cells

21
Q

Basic electrical rhythm

A

smooth muscle cells have an intrinsic rhythm of depolarization/ repolarization frequency

22
Q

When does contraction occur?

A

When depolarization goes above threshold to cause action potential
- Ach (parasympathetic) increases the basal membrane potential to stimulate APs and contraction
- Norepinephrine (sympathetic) decreases resting basal membrane potential and prevents generation of APs and contraction

23
Q

small intestine motility in fed state

A

Segmentation reflex
- major type of motility
- mix luminal content
- regulated by ENS

24
Q

small intestine motility in fasting state

A

Migrating Myoelectric Complex - to push things along

25
Q

3 phases of migrating myoelectric complex

A

Phase 1: quiescent period
Phase 2: intermittent contraction
Phase 3: powerful propulsions to sweep intestinal content out

26
Q

Motilin

A

stimulates stomach and duodenum
- intrinsic nerves stimulate distal duodenum and jejunum

27
Q

large intestine motility

A

Fxns:
- microbial digestion
- reabsorption of H2O and electrolytes
Haustral contractions for mixing
Peristaltic contractions to clear
Antiperistaltic movement to fill cecum
Aboral mass movement

28
Q

Antiperistaltic movement

A

motlilty in large intestine to fill cecum

29
Q

Stomach worms

A

increase gastric emptying

30
Q

vomiting center in the medulla

A
  • activated by visceral afferents anywhere in GI; blockage or mucosal irritation = stimulus
  • vestibular stimulation = motion sickness; signal from perception
  • efferent nerves activate upper GI, diaphragm, and abdominal muscles
  • closes glottis, LES relations, stops respiration, somatomotor signals, abdominal pressure
31
Q

2 concerns with vomiting

A
  1. significant fluid and electrolyte
  2. acid-base imbalance
32
Q

How are most signals sent in the gut?

A
  • interneurons; not being sent up the spinal cord to the brain
33
Q

Sympathetic effects

A
  • inhibits digestion
  • postganglionic neurons release norepinephrine to decrease:
    1. GI tract smooth m. motility
    2. exocrine secretion
    3. endocrine secretion
34
Q

Parasympathetic effects

A
  • promote digestion
  • postganglionic neurons release acetylcholine to increase:
    1. GI tract smooth m. motility
    2. Exocrine secretion
    3. Endocrine secretion
35
Q

Long reflex

A
  1. stimulus: distention, osmolarity, food, pH
  2. receptor cells: mechano and chemoreceptors
  3. CNS
  4. Ach (+) or Norep (-) released
  5. effector cells: smooth muscle and endocrine cells
  6. motility and secretion

OR

  1. Stimulus: smell, taste, sight
  2. activates CNS
  3. to enteric nervous system
  4. effector cells: smooth muscle and endocrine cells
  5. motility and secretion
36
Q

Short reflex

A
  1. stimulus: distention, osmolarity, food, pH
  2. receptor cells: mechano and chemoreceptors
  3. enteric nervous system: myenteric plexus (sym and para) and Submucosal plexus (para)
  4. effector cells: smooth muscle and endocrine cells
  5. motility and secretion
37
Q

Ileus

A
  • caused by inhibition of motor activity
  • increase activity upstream and decrease activity downstream
  • if blocked too long = distention then sympathetic reflex enters CNS = pain
  • common complication of inhibiting motor neuron activity

ANSC 311 - Metabolic Physiology (17 decks)

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