Gi #4: Pharmacology I

Front 1

Parasympathetic innervation of GI- pre or post-ganglionic? cholinergic or adrenergic? What is the effect on the GI tract?

Sympathetic innervation of GI- pre or post-ganglionic? cholinergic or adrenergic? What is the effect on the GI tract?

Back 1

Parasymp = preganglionic fibers (from vagus). Cholinergic. Activate smooth muscle contraction and secretion (secretory cells).

Symp= post-ganglionic, adrenergic fibers. Cell bodies in paravertebral/prevertebral ganglia. Inhibit motor and secretory activities.

Front 2

What is an example of a paracrine hormone that controls GI function?

What about an endocrine hormone?

Back 2

Histamine = paracrine. Secreted by ECL cell to act on nearby parietal cell.

*note: Gastrin = endocrine hormone (released into bloodstream).

Front 3

What is the lifetime prevalence of peptic ulcer disease (which includes gastric and duodenal ulcers)?

Imbalance between what two factors is thought to cause this disease?

Back 3

Lifetime prevalence = 10% (in fact, 50% of healthy people experience heartburn daily)

Imbalance between AGGRESSIVE factors (acid, pepsin, H. pylori) and PROTECTIVE factors (bicarb, mucous, prostaglandin)

Front 4

What are the three major pathways that regulate parietal cell secretion? Describe how.

Back 4

1. Gastrin (endocrine) --> stimulates Histamine release, and direct stimulation (via CCK2 receptor) via Ca2+ dependent activation

2. Vagus (neural) input via Ach --> stimulates directly via M3 receptor, activating Ca2+ which leads to pump activity

3. Histamine release --> bind H2 receptor and activate pump via cAMP.

Front 5

What is the role of Prostaglandins on gastric acid secretion?

Back 5

PG inhibit acid secretion by inhibiting cAMP-dependent pathway (thus H+ release)

Also stimulates mucus and bicarb release from Epithelial cells.

Front 6

How much water enters the small intestine each day? How much is excreted in the stool?

What is the function of mineralocorticoids such as aldosterone in the gut?

Back 6

9 L enters SI (2 from ingestion, 7 from intestinal secretions). While only 0.1 is excreted in stool, most of it (8L) get reabsorbed by SI and the rest is absorbed by the colon.

Alodsterone causes secretion of K+ and absorption of Na+ and water.

Front 7

Determine if the following are agents that enhance absorption/inhibit secretion or are secretagogues:

- VIP
- Dopaminergic agonists
- opioids
- cholinergic agonists
- somatostatin

Back 7

VIP, Cholinergic agnoists --> secretagogues (as well as PGs). Anything that stimulated parasymps is a secretagogue.

Dopaminergic agonists, opioids, and somatostatin --> inhibit secretion, enhance absorption. (others = ADH, adrenergic antagonists)

Front 8

What are some drugs that cause constipation? What about diarrhea?

Name some diseases that cause constipation and some that cause diarrhea?

Back 8

Drugs that cause constipation = NSAIDs, Anticholinergic, MAOis, Tricyclic antidepressants, Opiates

Diarrhea= prostaglandings, some antimicrobials, cholinergic agents

Diseases causing constipation = Parkinsons, DM, MS, HYPOthyroidism
Causing diarrhea= Infection, inflammation, tumor (esp. secretory tumors like VIPoma, carcinoid )

Front 9

Histologically, what type of cellular infiltrate do we see in Crohn's disease? What about in Ulcerative Colitis?

What type of T-cell is activated in either condition.

Back 9

Crohn's = lymphocytes, macrophages, granulomas, and submucosal fibrosis (remember, it's transmural). Th1

UC= lymphocyte and neutrophil (superficial lesions). Th2

Front 10

Describe the emetic response. What happens when someone takes a nausea producing chemo drug?

Back 10

Emetic response-

Drug passes blood-brain barrier and into the chemo receptor trigger zone. Efferent sent via vagus and phrenic to stomach and SI. This reduces gastric tone and increases reflux and dudoenal and jejunal tone.

Upper stomach relaxes + pylorus constricts, diaphragm and abs contract --> gastric contents empty