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NAS > Enteric Nervous System > Flashcards

Enteric Nervous System Flashcards

1
Q

Where does the ENS run from?

A

Runs from oesophagus to rectum

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2
Q

What does intrinsic innervation of the GIT mean?

A

All essential components are in the GIT, dont need connection elsewhere

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3
Q

What are Nuclei in the GIT

A

Neurones axons clumped together

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4
Q

Why is ENS known as a little brain?

A

Has network of neurones (80-100 million)

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5
Q

What are the 2 major plexuses?

A
  1. Submucosal (Meissners) plexus
  2. Myenteric (Auerbachs) plexus
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6
Q

Location of submucosal plexus

A

Stomach and intestine only

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7
Q

Location of myenteric plexus

A

Full length of GIT

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8
Q

Myenteric is sandwiched between two …… layers

A

Muscle

Longitudinal muscle
Circular muscle

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9
Q

Submucosal plexuses between

A

Circular muscle
Submucosa

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10
Q

Types of neurones found in the plexuses

A

Afferent (sensory) neurones
Interneurones
Efferent (secretomotor) neurones

Effectors

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11
Q

What receptors are associated with afferent neurones

A

Sensory
Mechano
Chemo

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12
Q

What are is the function of interneurones?

A

Coordinate input and output
Excitatory + inhibitory

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13
Q

What effectors do efferent neurones?

A

Smooth muscle
Secretory glands

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14
Q

What NTs does the efferent neurones use

A

ACh
Various peptides

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15
Q

What do enteric reflexes do?

A

Control:
Motility
Secretion
Blood flow

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16
Q

What plexus does the motor reflex involve?

A

Myenteric plexus

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17
Q

What do mechanoreceptors detect?

A

Detect physical presence of food in GIT

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18
Q

What do chemoreceptors detect?

A

Detect sensory chemicals released by food

19
Q

What is an example of a motor reflex

A

Peristalsis
Movement of food in a rhythmic Ashton along GIT

20
Q

How is bolus (food) pushed along the GIT via sensory info

A
  1. Sensory receptors (mechano/ chemo) detect contents of lumen
  2. Info from receptors transported into myenteric plexus
  3. Info distributed via interneurones to alter impact of efferent neurones that interact with muscle layers
21
Q

Mechanism used to push food down GIT

A
  1. Bolus stimulates mucosal sensory receptors
  2. Infro to Myenteric plexus
  3. Excitatory interneurones prod effect
  4. Effect = smooth musce contraction, decreases size of lumen, pushes bolus forward
  5. In front of bolus inhibitory interneurones = smooth muscles relax
  6. Occurs simultaneously so smooth movement
22
Q

What is secretory reflex?

A

Food stimulates sensory receptors
Bring info to submucosal plexus
Interneurones - efferent fibres - secretory cells
Secrete into lumen helping digestion and lubrication
(Enzymes, mucus, acid)

23
Q

Is blood flow to gut adjusted by the ENS

A

Yes involves both plexuses
Blood flow matches to activity of the gut

24
Q

How is the CNS integrated with the ENS

A

Symp/ parasymp is an intermediate
Brain can override the ENS

25
Q

How does CNS influence vary along GIT

A

Once food swallowed ENS cant stop food travelling
CNS controls sphincters so can control faeces

26
Q

What causes dysfunction in the GIT (associated with ENS)

A
  • Age
  • Congenital absence of ENS neurones (genetic) - peristalsis stopped
  • Abolition of rectoanalreflex
27
Q

What range of diseases can affect ENS

A

Specific diseases
General disease

28
Q

Specific Diseases associated with ENS:

A
  1. Changas disease
  2. Achalasia
  3. Hirschprungs disease
29
Q

What is Changas disease?

A

Endemic in South America
Parasite transferred into blood via insect bite
Toxins prod that kills ENS neurones
ENS shutdown so cant eliminate toxin

30
Q

What is Achalasia disease?

A

Affects oesophagus and oral cavity - hard to swallow
Nutritional status decreased
More common in elderly bc loss of inhibitory neurones in Myenteric plexus in
- sphincter at opening of stomach
- oesophagus

31
Q

General neurological conditions that affect ens

A
  • Parkinson’s disease
  • Peripheral neuropathies
  • Myasthenia Gravis
32
Q

How is irritable bowel syndrome caused?

A

Dysfunctional interaction between brain and ENS

33
Q

Are there opioid receptors in ENS?

A

Yes bcs ENS releases opoid NT
Target opoid receptors to change function of ENS and so GIT

34
Q

What is the active ingredient in anti- diarrhoeal agents and how they work

A

Loperamide that act at opioid receptors to reduce gut motility

35
Q

How do some pain meds (morphine/ codeine) cause constipation as a side effect

A

They are also opioids so thy can act on opioid receptors in the gut and reduce gut activity

36
Q

What are the 4 layers of small intestine superficial to deep

A

Serosa
Longitudinal muscle
Circular muscle
Submucosa
Mucosa

37
Q

Function of myenteric plexus

A

Increase tone of the gut
Control velocity and strength of gut contractions via inhibitory and excitatory interneurones
Controls GIT motility

38
Q

Function of submucosal plexus

A

Controls secretions
Controls local muscles
Controls absorption

39
Q

What are the two ways ENS works?

A
  • Autonomously (reflexes)
  • Via para/ symp NS
40
Q

What are the causes of the symp ns overriding the ENS

A
  • fight or flight
  • inhibits both plexuses
  • causes decrease in peristalsis, blood flow, absorption, secretion
41
Q

What are the causes of para NS overriding ENS

A
  • rest and digest
  • stimulates both plexuses
  • causes increase in peristalsis, blood flow, absorption, secretion
42
Q

Difference between short and long reflex of ENS

A

Short more common, can act fast and only involve neurones of GIT

Long uses integration of CNS

43
Q

Examples of long and short reflexes

A

Inhibition of stomach secretions and motility is an example of short reflexes, while the internal digestion of food and chemical secretions stimulation by senses are example of long reflexes.

44
Q

Other causes of dysfunction of ENS

A

Congenital absence of ENS neurones - genetic mutation
Peristaltic wave halts at section missing ENS neurones - faeces cant pass and builds up, (distending colon) breeding ground for infection
Abolition of rectoanalreflex - affects defection, manifests after birth

NAS (17 decks)

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