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NPB 101L > Lab 8 Prelab > Flashcards

Lab 8 Prelab Flashcards

1
Q

What is methacholine? What does it bind to?

A

An analog of ACh that will bind to mAChR

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2
Q

What does epinephrine bind to?

A

Beta 2 AR

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3
Q

What does ADP bind to?

A

P2Y purinergic receptors

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4
Q

List the main and accessory organs of the GI system.

A
  • Main: mouth, pharynx, esophagus, stomach, small and large intestine, rectum
  • Accessory: salivary glands, pancreas, liver, appendix
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5
Q

What are the basic functions of the GI system?

A
  • Taste, digestion of foods
  • Production of enzymes, hormones, etc.
  • Motility of foods through tract
  • Absorption of nutrients
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6
Q

List the 4 basic layers of the GI tract from outermost to innermost.

A
  • Serosa
  • Muscularis externa
  • Submucosa
  • Mucosa
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7
Q

What is the mucosa of the GI tract? Function? Components?

A
  • Epithelial layer where absorptive and secretory functions occur
  • Made up of the lamina propria and lamina muscularis mucosae
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8
Q

What is the submucosa of the GI tract? Function? Components?

A

Loose connective tissue, blood vessels and glands that nourish and support the GI tract

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9
Q

What is the muscularis externa of the GI tract? Function? Components?

A

2 layers of smooth muscle

  • inner layer of circular smooth muscle changes diameter
  • outer layer of longitudinal smooth muscle changes length
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10
Q

What is the serosa of the GI tract? Function? Components?

A

Connective and epithelial tissue that supports and surrounds the GI tract

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11
Q

What are the 2 primary patterns of gastrointestinal motility?

A
  • Segmentation

- Peristalsis

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12
Q

What happens during segmentation (GI motility)?

A

Mixes the bolus of food

  • pushes contents back and forth in small segments
  • increases time for enzymes to act and nutrient absorption
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13
Q

What happens during peristalsis (GI motility)?

A

Propels bolus forward through the contraction of circular muscle and relaxation of longitudinal muscle proximal to the bolus and the opposite distal to the bolus

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14
Q

What characteristics differentiate smooth muscle from skeletal muscle?

A
  • No striations
  • Contains tropomyosin but no troponin
  • Doesn’t contain sarcomeres or myofibrils
  • Doesn’t contain T-tubules or lateral sacs
  • Poorly developed SR
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15
Q

What are dense bodies?

A

Anchor points for actin on smooth muscle

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16
Q

What do gap junctions do?

A

Electrically join cells on smooth muscle for communication

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17
Q

Describe multi-unit smooth muscle. Where is this type of smooth muscle found?

A
  • Individual cells not electrically coupled –> one-to-one innervation
  • Cells can contract independently
  • Capable of fine muscle control
  • Found in eyes, skin, some blood vessels
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18
Q

Describe unitary smooth muscle. Where is this type of smooth muscle found?

A
  • Smooth muscle cells are electrically coupled in groups
  • Contract in a coordinated manner
  • Multiple cells innervated by single neuron
  • Pacemakers can initiate AP independently
  • Found in GI tract, uterus, large blood vessels
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19
Q

What facet of the nervous system innervates the GI tract?

A

Enteric Nervous System

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20
Q

What type of smooth muscle does the GI tract have?

A

Unitary

21
Q

What are pacemaking cells in the gut called?

A

Interstitial Cells of Cajal

22
Q

What do the Interstitial Cells of Cajal do?

A

Create a slow wave (Basal Electrical Rhythm) that varies throughout the tract

23
Q

What channels in the GI tract create the slow wave?

A
  • Voltage gated Ca2+ channels

- Ca2+ dependent K+ channels

24
Q

When do spike potentials superimpose on the basal electrical rhythm? Significance?

A
  • When threshold is reached

- More spike potentials = more contraction

25
Q

What are the 2 sources of Ca2+ for contraction?

A
  • Voltage gated Ca2+ channels –> influx of extracellular Ca2+
  • Ca2+ release from the SR –> CICR
26
Q

When there is an increase in cytosolic Ca2+, what does it bind to?

A

Calmodulin (CaM)

27
Q

What can the Ca-CaM complex bind to?

A
  • Caldesmon or calponin

- Myosin Light Chain Kinase (MLCK)

28
Q

What happens when Ca-CaM binds to caldesmon or calponin? Where does this occur?

A

On actin/tropomyosin complex

-To unmask myosin binding site

29
Q

What happens when Ca-CaM binds to Myosin Light Chain Kinase?

A

Activates MLCK –> MLCK phosphorylates myosin light chain regulatory protein to increase binding activity of myosin to actin

30
Q

What causes smooth muscle relaxation?

A
  • Decrease in intracellular Ca2+ by pumping out of cytosol via Na/Ca exchanger
  • Myosin Light Chain Phosphatase dephosphorylates myosin light chain
31
Q

What occurs to MLCK activity when intracellular Ca2+ is high? Low?

A
  • High: MLCK activity becomes higher than MLCP

- Low: MLCK activity is lower than MLCP

32
Q

Through what nerve do sympathetic neurons travel?

A

Splanchnic nerve

33
Q

Describe the effects of sympathetic innervation on the GI tract. What neurotransmitter is released? How does this affect tension?

A
  • Release norepinephrine
  • Results in a decrease in tension but doesn’t significantly decrease frequency
  • Fight or flight response suppresses GI
34
Q

Describe the effects of parasympathetic innervation on the GI tract. What neurotransmitter is released? How does this affect tension?

A
  • Release acetylcholine
  • Results in an increase in baseline tension
  • Rest and digest response stimulates GI
35
Q

What is the Enteric Nervous System?

A

Primary neural mechanism that controls GI functions

36
Q

Where are the 2 places ENS neurons are mostly found?

A
  • Submucosal plexus (b/t submucosa and muscularis layers)

- Myenteric plexus (b/t 2 layers of smooth muscle)

37
Q

List he 4 major processes of the GI system.

A
  • Secretion
  • Digestion
  • Motility
  • Absorption
38
Q

What are endocrine secretions? Function?

A

Hormones that regulate GI function

39
Q

What are exocrine secretions? Functions?

A

Enzymes, HCl, and HCO3- are important components of digestion

40
Q

Define motility.

A

Muscular contractions that mix the luminal contents w/ digestive secretions

41
Q

How did epinephrine affect gut activity?

A

DECREASE ACTIVITY

  • decreased baseline tension
  • decreased amplitude
42
Q

What part of the autonomic nervous system does epinephrine mimic?

A

Norepinephrine

43
Q

How did MCh affect gut activity?

A

INCREASE ACTIVITY

  • increased baseline tension
  • decreased amplitude
44
Q

How did ADP affect gut activity?

A

DECREASE ACTIVITY

  • decreased baseline tension
  • decreased amplitude
45
Q

How did Ca2+ free ringers affect gut activity?

A

DECREASE ACTIVITY

  • decreased baseline tension
  • decreased amplitude
  • decreased frequencies
46
Q

Why does frequency of gut activity decrease in Ca2+ free Ringers?

A

ICCs rely on Ca2+ to generate BER

47
Q

Where does absorption occur in the GI tract?

A

Microvilli of the small intestine

48
Q

Through what nerve do parasympathetic neurons travel?

A

Vagus nerve

NPB 101L (13 decks)

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