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GI Midterm > DSA- Introduction to GI physiology > Flashcards

DSA- Introduction to GI physiology Flashcards

1
Q

Main functions of GI tract

A

digestion and absorption of nutrients

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2
Q

Main properties of GI tract

A
  • motility

- secretions

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3
Q

GI tract sphincter function

A

restrict passage of intestinal content to optimize digestion and absorption

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4
Q

List the GI tract sphincters (7)

A

1) upper esophageal sphincter (UES)
2) lower esophageal sphincter (LES)
3) Pylorus
4) sphincter of Oddi
5) Ileocecal valve
6) Internal anal sphincter
7) External anal sphincter

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5
Q

Intestinal Wall Structure

- layers and what they contain

A

4 layers

1) Mucosal Layer
- epithelium
- lamina propria
- muscularis mucosae
2) Submucosa
3) Muscle layers
- circular
- longitudinal
- myenteric plexus
4) Serosa

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6
Q

Enteric nervous system of GI

  • nicknames
  • what they consist of
  • innervation
A

“nervous system of GI tract”
“the second brain or little brain in gut”
- sensory neuron

1) submucosal plexus
2) myenteric plexus

Innervated by extrinsic autonomic nervous system

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7
Q

ENS functions

A

functions:

1) integrating center
2) can exert its functions without CNS input
3) control contraction, secretion, and endocrine function of GI tract
4) receive information from parasympathetic and sympathetic nervous system and CNS
5) receive sensory information from mechanoreceptor and chemoreceptors in mucosa

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8
Q

Role fo CNS in GI regulation

- pathway

A

vago-vagal reflex ( gastric receptive relaxation reflex)

modulate ENS responses

centers that control food intake are located in brain

**vagal afferents-> sensory ganglion of vagal nerve (Nodose ganglion)-> Nucleus of tractus solitarius (NTS)-> vagal efferents

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9
Q

Parasympathetic innervation of GI

  • nerves
  • location (2)
  • type of receptors
A
  • vagus & pelvic nerve
  • Preganglionic nerve cell bodies: at brainstem or sacral spinal cord
  • Postganglionic neurons: wall of organ (ENS in gut wall)
  • synapse between pre and post ganglionic cell is NICOTINIC (nAChRs)
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10
Q

Sympathetic innervation of GI

  • nerves
  • location (2)
  • type of hormones released
A
  • via nerves running between spinal cord and prevertebral ganglia
  • via nerves running between ganglia and GI organs
  • Preganglionic efferent fibers: at spinal cord and end of prevertebral ganglia (OUTSIDE GI tract)
  • Postganglionic fibers: innervate myenteric and submucosal plexus
  • Preganglionic efferent fibers release ACh
  • Post ganglionic nerve release NE
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11
Q

Cell Communication in GI tract: paracrine regulation

A 
Paracrine regulation (locally)
2 hormones: histamine and somatostatin
- peptide (somatostatin)
- messenger molecule (histamine)
- reach their target cells by diffusion over short distance
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12
Q

Somatostatin

  • location
  • stimuli
  • action
A

PARACRINE

secreted by

  • D cells of GI mucosa
  • hypothalamus
  • delta cells of exocrine pancreas

stimuli: low luminal pH

Action:

  • inhibit gastric H+ secretion
  • inhibit secretion of other GI hormones
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13
Q

Histamine

  • location
  • target
  • action
A

PARACRINE

stomach
- stored and secrceted by enterochromaffin-like cells (ECL) in gastric glands

target: parietal cells
action: stimulate acid production

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14
Q

Cell Communication in GI tract: Endocrine regulation

- hormones

A
  • action of hormones
  • enteroendocrine cells contain secretary granules filled with hormones that are released upon stimulation
  • hormones are secreted into circulation

4 hormones

1) Gastrin
2) Cholecystokinin (CCK)
3) Secretin
4) Glucose-dependent insulinotropic peptide (GIP)

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15
Q

Gastrin

- actions

A

ENDOCRINE

  • increase gastric H+ secretion
  • stimulate growth of gastric mucosa
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16
Q

CCK

- actions (6)

A

ENDOCRINE

1) increase pancreatic enzyme secretion
2) increase pancreatic HCO3- secretion (not direct effect- potentiates effects of secretin)
3) stimulates contraction of gallbladder and relaxation of sphincter of Oddi
4) stimulates growth of exocrine pancreas and gallbladder (trophic effect)
5) inhibit gastric emptying
6) act as paracrine signal

17
Q

Secretin

- actions (5)

A

ENDOCRINE

1) increase pancreatic HCO3- secretion
2) increase biliary HCO3- secretion
3) decrease gastric H+ secretion
4) inhibit trophic effect of gastrin on gastric mucosa
5) act as paracrine signal

18
Q

GIP

  • actions
  • best method of administration
A

ENDOCRINE

1) increase insulin secretion form pancreatic B cells (incretin effect)
2) decrease gastric H+ secretion

ORAL glucose administration more effective than IV glucose in increasing insulin secretion

19
Q

Cell Communication in GI tract: Neural regulation

- hormones

A
  • action of neurotransmitters
  • AP needed for NT release
  • NT molecules diffuse across synapse and bind to their specific receptors in postsynaptic cell

Hormones (8)

1) Ach
2) NE
3) Vasoactive intestinal peptide (VIP)
4) Nitric Oxide
5) Gastrin- releasing peptide (GRP)
6) Enkephalins
7) Neuropeptide Y
8) Substance P

20
Q

Acetylcholine

  • source
  • actions (5)
A

NEURAL

Source: cholinergic neurons

Actions

1) contraction of smooth muscle in wall
2) relaxation of sphincters
3) increase salivary secretion
4) increase gastric secretion
5) increase pancreatic secretion

21
Q

Norepinephrine (NE)

  • source
  • actions
A

NEURAL

Source: adrenergic neurons

Actions

1) relaxation of smooth muscle in wall
2) contraction of sphincters
3) increase salivary secretion

22
Q

Vasoactive Intestinal Peptide (VIP)

  • source
  • actions
A

NEURAL

Source: neurons of ENS

Actions

1) relaxation of smooth muscle
2) increase intestinal secretion
3) increase pancreatic secretion

23
Q

Nitric Oxide

  • source
  • actions
A

NEURAL

Source: neurons of ENS

Action
- relaxation of smooth muscle

24
Q

Gastrin- releasing peptide (GRP)

  • source
  • actions
A

NEURAL

Source: vagal neurons of gastric mucosa

Action
- increase gastrin secretion

25
Q

Enkephalins

  • source
  • actions
A

NEURAL

Source: Neurons of ENS

Action

1) contraction of smooth muscle
2) decrease intestinal secretion

26
Q

Neuropeptide Y

  • source
  • actions
A

Neural

Source: neurons of ENS

Action

1) relaxation of smooth muscle
2) decrease intestinal secretion

27
Q

Substance P

  • source
  • actions
A

NEURAL

Source: co-secreted with ACh by neurons of ENS

Action

1) contraction of smooth muscle
2) increase salivary secretion

GI Midterm (10 decks)

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