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An Sc 311 Midterm 1 > Lecture 5 - Motility > Flashcards

Lecture 5 - Motility Flashcards

1
Q

Structures involved in prehension and chewing

A

Lips, tongue, incisors = procure the feed
Molars = grind the feed

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2
Q

How do molars vary in carnivores, omnivores and herbivores

A

Carnivores + omnivores = vertical movement
Herbivores = lateral movement (side to side)

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3
Q

Indications that a horse should be floated

A

Dropping feed
Losing weight
Head tossing
Balls of chewed hay coughed out

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4
Q

Two phases of swallowing

A

Oropharyngeal phase
Oesophageal phase

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5
Q

Describe the oropharyngeal phase of swallowing

A

Food pushed back by tongue, tongue prevents return to mouth
Uvula blocks nose
Glottis/epiglottis block access to lungs
Swallowing center in medulla coordinates and inhibits respiratory center
Pharyngoesophageal sphincter opens

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6
Q

Describe the oesophageal phase of swallowing

A

Peristaltic wave every 5-9s
Skeletal muscle
Oesophagogastric/cardiac sphincter opens

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7
Q

What is peristalsis

A

Waves of contraction
Rapid propulsion
Relaxation and contraction of longitudinal and circular muscles

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8
Q

What is the peristaltic reflex programmed by

A

The enteric nervous system

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9
Q

What are the three parts of the stomach

A

Fundus
Corpus
Antrum

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10
Q

What is the job of the fundus

A

Receptive relaxation (makes room when food enters)

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11
Q

What molecules are involved in relaxation of the fundus? What induces them?

A

Nitric oxide and vasoactive intestinal polypeptide
Induced by ACh

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12
Q

What is the role of the corpus

A

Mixing vat for saliva, food and gastric secretions

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13
Q

What is the role of the antrum

A

Propulsion of food through the pyloric sphincter to the duodenum
Size discrimination (small pieces only)

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14
Q

What is the antrum controlled by

A

Distention
Parasympathetic NS

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15
Q

Where/how does mixing occur in the stomach

A

In the corpus
Peristalsis acts against closed pyloric sphincter
HCl and pepsin stirred in
Protein digestion begins and lipid droplets form

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16
Q

How does gastric emptying occur

A

Peristalsis
Pyloric shincter opens
Chyme (digesta) enters duodenum

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17
Q

What regulates gastric emptying

A

Force of contraction
Signals from duodenum

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18
Q

What is gastric emptying

A

Empty the stomach into the SI

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19
Q

What factors increase gastric emptying

A

Neural control (distension of stomach wall, increased parasympathetic)
Endocrine control (gastrin)

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20
Q

What factors decrease gastric emptying

A

Neural control (chemoreceptors, osmoreceptors, mechanoreceptors at duodenum, sympathetic NS)
Endocrine control (CCK, secretin, gastric inhibitory peptide)

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21
Q

Why does increased sympathetic NS activity decrease gastric emptying

A

In fight or flight mode, do not want to waste energy on digestion

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22
Q

What is segmentation

A

Most common form of motility (contraction of circular muscle)
Alternating contractions = mixing (not directional)
Freq decreases distally duodenum -> colon

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23
Q

Motility in the colon

A

Haustration (segmentation) = mixing and movement
Clearing

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24
Q

Stimulus, sensor, signal, effector, response and effect of motility regulation in the duodenum

A

Stimulus = chyme distend walls
Sensor = stretch receptors in wall
Signal = nervous
Effector = smooth muscle
Response = vigorous segmentation
Effect = removal of stimulus

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25
Q

Stimulus of motility in the ileum/colon

A

Protein/digestion in stomach
Gastrin released from stomach

26
Q

Two responses to stimulus in ileum/colon

A
  1. Gastro-ileal reflex (stimulates segmentation in ileum, inhibits (opens) ilea-caecal sphincter)
  2. Gastro-colic reflex (mass movement in colon)
27
Q

What are tonic contractions? Examples?

A

Sustained (long-term) contraction of muscle
Divide GIT into functional segments
e.g. esophageal sphincter, pyloric sphincter, ileocecal sphincter

28
Q

What do the interstitial cells of cajal do

A

set a constant pulse in smooth muscle cells and are considered the pacemakers of the GIT

29
Q

What smooth muscle layers make up the GIT

A

Circular and longitudinal muscle layers

30
Q

Smooth muscle cells have an intrinsic rhythm of ________________________________________

A

depolarization and repolarization

31
Q

When do contractions occur in smooth muscle

A

When depolarization is high enough (reaches the threshold) to cause action potential

32
Q

Which hormones regulate depolarization for contraction

A

Acetylcholine (parasym) increase resting basal membrane potential = stimulates AP and contraction
Norepinephrine (sym) decrease resting basal membrane potential = prevent AP and contraction

33
Q

Small intestine motility in the fed state

A

Segmentation reflex (mixes contents, regulated by ENS)

34
Q

Small intestine motility in fasted state (post meal)

A

Migrating myoelectric complex
- peristaltic activity
- uninterrupted in herbivores

35
Q

Three phases of migrating myoelectric complex

A
  1. Quiescent period (nothing)
  2. Intermittent contraction (cross threshold periodically)
  3. Powerful propulsion sweeps intestinal contents out (contract every time)
36
Q

Functions of large intestine motility

A

Microbial digestion
Reabsorption of water/electrolytes

37
Q

What kind of motility is there in the large intestine

A

Stationary haustral contractions (mixing)
Peristaltic contractions
Antiperistaltic movement (fill the cecum)
Aboral mass movement (evacuate entire length of colon = defecation)

38
Q

Aboral vs oral

A

Aboral = away from mouth
Oral = towards mouth

39
Q

What can alter GIT motility

A

Stomach worms = increase gastric emptying
-> MMC reduced and replaced with migrating action potential complex (faster)

40
Q

Where is the vomiting centre

A

Medulla

41
Q

What is the vomiting centre activated by

A

Visceral afferents anywhere in GIT (nerves to brain) due to blockage, mucosal irritation
Vestibular stimulation (motion sickness)
Efferent nerves activate upper GIT and diaphragm and abdominal muscles

42
Q

Slide 27**

A

vomiting

43
Q

What does the vomiting centre do pre-vomit

A

Close soft palate, close glottis
Respiration stops
Abdominal pressure (diaphragm contracts)

44
Q

Major concerns surrounding vomiting

A

Significant fluid and electrolyte loss (dehydration)
Acid-base imbalance

45
Q

Plexuses of the enteric nervous system

A

Myenteric (Auerbach) plexus
Submucosal (Meissner) plexus

46
Q

Characteristics of the myenteric plexus

A

Between circular and long smooth muscle
Extensive, long interneurons
Sympathetic and parasympathetic

47
Q

Characteristics of the submucosal plexus

A

In submucosa
Interneurons minor
Only parasympathetic

48
Q

Afferent neurons aka? Efferent neurons aka?

A

Sensory, motor

49
Q

Slide 32, 33

A

Afferent and efferent neurons

50
Q

What nervous system do efferent and afferent neurons fall under

A

Peripheral NS

51
Q

What nervous system do the sympathetic and parasympathetic pathways fall under

A

Peripheral NS
Autonomic neurons

52
Q

Two types of efferent neurons

A

Autonomic
Somatic

53
Q

What kind of activity do the autonomic effector tissues have

A

Intrinsic (spontaneous or tonic) activity

54
Q

What is the sympathetic NS

A

Inhibit digestion
Fear, fight or flight responses
Postganglionic neurons release norepineephrine (stop enteric NS)

55
Q

What is the sympathetic NS

A

Inhibit digestion
Fear, fight or flight responses
Postganglionic neurons release norepinephrine

56
Q

What does the sympathetic NS decrease

A

GI tract smooth muscle motility
Exocrine secretion (into gut)
Exocrine secretion

57
Q

What is the parasympathetic NS

A

Promotes digestion
Postganglionic neurons release acetylcholine

58
Q

What does the parasympathetic NS increase

A

GI tract smooth muscle motility
Exocrine secretion
Endocrine secretion

59
Q

Slide 36

A

Symp and parasymp

60
Q

What is an ileus

A

Caused by inhibition of motor activity
Increased activity upstream, decreased downstream
Blocked long time = distention, sympathetic reflex enters CNS = pain
Common after surgery

61
Q

Slide 38**

A

Summary of ENS

An Sc 311 Midterm 1 (8 decks)

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