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GI Physiology > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

1
Q

5 main functions of the GI system

A
  • digestion
  • absorption
  • excretion
  • fluid and electrolyte balance
  • immunological (respond to antigens and microbial pathogens)
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2
Q

In order to perform its functions, the GI system has two essential properties. Name them.

A

-motility and secretion

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3
Q

Motility (contractions of smooth muscle) allows for

A
  • increased surface area for digestion by enzymes which decreases size of nutrients
  • mixes nutrients with enzymes in the lumen
  • optimize time for digestion and absorption by propelling bolus from mouth to anus
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4
Q

Secretion of GI system is

A

The release of enzymes, lipids, detergents, ions, and water in the GI lumen by the GI epithelial and associated glands

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5
Q

Motility and secretion are regulated by (list 3 factors)

A

-various hormones, ENS, and CNS

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6
Q

Most important part of GI system

A

Duodenum

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7
Q

Liver synthesized _______ and stores it in the ______

A
  • bile

- gallbladder

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8
Q

3 parts of the small intestine are

A

Duodenum, jejunum and ileum

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9
Q

Enteroendocrine cells (EEC) are

A

Sensor cells in the GI system. Release peptides to control GI system

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10
Q

Associated glands of the GI system

A

Salivary, pancreas, liver & gallbladder, endocrine glands or cells

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11
Q

Define Sphincters

A

Specialized circular muscle structures (smooth or skeletal muscle) controlling the flow of GI content between distinct structure

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12
Q

Name the sphincters in the GI system

A
  • upper esophageal (bw pharynx and esophagus)
  • lower esophageal (bw esophagus and stomach)
  • pyloric
  • ileocecal
  • internal and external anal sphincters
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13
Q

Lymph transports

A

Hydrophobic substances (lipids, drugs, hydrophobic vitamins- A,D,E,K

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14
Q

Only organ to metabolize ammonia

A

Liver

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15
Q

Percentage of cardiac output received by GI

A

25%

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16
Q

Thoracic duct (lymphatic system) dumps into

A

Systemic blood

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17
Q

Epithelial cells of the mucosa are connected by

A

Tight junctions

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18
Q

Mucosa consists of three parts, the-

A
  • epithelium
  • lamina propria
  • muscularis mucosae
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19
Q

What are the functions of the epithelial cells of the mucosa and what is present in this layer

A
  • Glands and gland cells are present,
  • functions of the epithelial cells called enterocytes are secretion and absorption
  • enteroendocrine cells release peptides that control GI function
  • cells can vary among the GI tract
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20
Q

Lamina propria consists of

A
  • connective tissue
  • collagen
  • elastic fibers
  • also glands, lymph vessels and nodes, capillaries and nerve fibers are present
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21
Q

Muscularis mucosae is

A

The thin layer of smooth muscle cells in a folding configuration caused by contractions, (bottom of mucosa layer before submucosa)

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22
Q

Microvillar membrane of epithelial cells in the GI tract has a high % of

A

Cholesterol and sphingolipids

23
Q

Enterocytes

A

Epithelial cells in GI that secrete and absorb

24
Q

Main distinction between paracrine and endocrine

A

Paracrine does not release hormones into the blood circulation, endocrine does.

25
Q

ECL stands for ? And does what?

A

Enterochromaffin-like cells. They secrete histamine into interstitial space.

26
Q

Describe how ECL leads to increased acid secretion

A

ECL release histamine>histamine diffuses through interstitial fluid>histamine binds to parietal cells>parietal cells secrete HCl

27
Q

Describe Celiac diseases (gluten enteropathy):

A
  • affects 2 million people in North America;
  • Allergic response to a component in gluten of wheat flour, rye, and barley (gliadin- glycoprotein: antigenic -Pro-Ser-Gln-Gln- and -Gln-Gln-Gln-Pro-)
  • Density and length of microvilli are reduced;
  • Reduced absorption of nutrients;
  • Not restricted to GI only (example: neuropathies);
28
Q

IBD is

A

(Inflammatory bowel disease)~400,000 people in North America:
Large proliferation of lymphocytes and macrophages in the lamina propria;inflammation of intestine (severe pain and diarrhea);

29
Q

2 major types of IBD

A
  • Crohn’s disease (can affect any part of the GI tract and affects the whole bowel wall)
  • Ulcerative colitis (restricted to the colon and the rectum and only affects the mucosa)
30
Q

Sympathetic innervation does..

A

In general it inhibits GI function;

  • Exception: Sphincter muscles are activated by sympathetic innervation;
  • Sympathetic fibers ALSO carry sensory information toCNS.
31
Q

Parasympathetic Innervation

A
  • In general it enhances GI function
  • Synapses between pre- and post-ganglionic fibers are nicotinic
  • Parasympathetic fibers ALSO carry sensory information to CNS.
32
Q

Law of intestine

A

How the GI system propels food down the tract. The muscles behind a bolus contract while the muscles ahead of the bolus dialate so the food can be propelled along the system.
-independent of CNS

33
Q

CGRP

A

calcitonin gene related peptide

34
Q

VIP

A

vasoactive intestinal peptide

35
Q

Ach binding on muscarinic receptors causes

A
  • Contraction of smooth muscles,

- increased salivary, gastric, and pancreatic secretion

36
Q

Ach binding on nicotinic receptors causes

A

-contraction of the sphincters

37
Q

The sensation of pain in the GI is caused by what and what can relieve the pain?

A

The pain is caused by smooth muscle contracting too tightly. It can be relieved by blocking muscarinic receptors.

38
Q

NE causes what in GI

A

It causes

  • relaxation of smooth muscles
  • contraction of sphincters
  • increased salivary secretion
39
Q

Ach and NE both ________ salivary secretions

A

Increase

40
Q

VIP causes what in GI system

A
  • relaxation of smooth muscle

- increased intestinal, pancreatic, and gastric secretions

41
Q

NO stimulates

A

VIP release creating a positive feedback cycle bw the two

42
Q

Substance P is co-secreted with _____ and causes what?

A
  • it is co-secreted with Ach by cholinergic neurons

- it causes contraction of smooth muscle and salivary secretion

43
Q

GRP is ____ and causes what?

A
  • Gatrin Releasing Peptide

- causes increased gastric secretion and pancreatic secretion

44
Q

Enkephalins (opiates) cause

A
  • Increased contraction of smooth muscle

- and decreased intestinal

45
Q

Neuropeptide Y causes

A
  • increased relaxation of smooth muscle

- decreased intestinal secretion

46
Q

Name 2 pacemakers for the smooth muscle contraction

A
  • one in stomach

- one in pharynx

47
Q

Describe an important role of the interstitial cells between longitudinal and circular muscle layers

A

They are the pacemaker cells that transfer electrical activity to smooth muscle via GAP JUNCTIONS

48
Q

Action potentials and contractions

A

Longer durations (10-20 ms), poor overshoots;
• Caused by inflow of Na+ and Ca 2+;
• Ca2+ inflow helps and initiates contractions;
• Trains of APs that are modulated by various stimuli;
• Repolarization caused by various K+channels;
• Smooth muscle tone: baseline of muscle tension that is modulated by neurons,hormones, paracrine factors, drugs.

49
Q

CEPHALIC PHASE

A

• IDEA OF FOOD, OLFACTION, VISUAL STIMULI, AUDITIVE STIMULI TRIGGER RESPONSES IN THE GI SYSTEM IN THE ABSENCE OF FOOD INGESTION.

50
Q

The dorsal motor vagal nucleus

A

It’s the cell bodies of the vagal preganglionic neurons and is located in the lower pons/upper medulla

51
Q

The path of stimulation for parasympathetics during cephalic or oral phases

A

Sensory inputs–>cortex and hypothalamus–>dorsal motor vagal nucleus–> increase secretion of salivary, gastric, and pancreatic glands, contraction of gallbladder and relaxation of Oddi’s sphincter

52
Q

Sympathetic stimulation is inhibitory in the ______ but NOT for the ______

A
  • It inhibits the GI system

- it does NOT inhibit salivary system

53
Q

Oral phases response to meal

A
  • RESPONSES ARE THE SAME AS IN THE CEPHALIC PHASE BUT FOOD IS PRESENT IN THE MOUTH.
  • ADDITIONAL ACTIVATION OF GI FROM SENSORY INPUTS FROMTASTE BUDS (TONGUE) AND MECHANICAL RECEPTORS IN THE MOUTH AND UPPER PHARYNX.

GI Physiology (1 decks)

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