Physio 9: LI, Defecation

Question 1

What are the functions of the colon?

Answer 1

Absorption of water, electrolytes (proximal half)

Storage of feces (distal half)

Question 2

What hormones act in both the principal cells of the nephron and the colon?

Answer 2

Aldosterone (Na reabs and K secretion), ADH (water reabsorption)

Question 3

Where is the majority of bilirubin eliminated?

Answer 3

Feces - 99%, Urine - 1%

Question 4

Trace bilirubin elimination

Answer 4

Begins in spleen, liver, feces and urine

Question 5

Describe what haustrations are.

Answer 5

Mixing - circular, segmental contractions that are simultaneous with longitudinal muscle contraction. The unstimulated portions bag out, forming haustra, and stimulated portions undergo haustral contractions.

Question 6

Describe mass movements.

Answer 6

Ring of constriction that is distended by digesta in the transverse/descending colon. Tenia coli contract colon like an accordion b/c it shortens and folds up. Chyme thus moves towards anus.

Question 7

What is the Valsalva maneuver?

Answer 7

Used to push baby out during child birth and during defecation. Thorax expands. Abdomen contracts.

Question 8

What is Hirschprung’s disease? Treatment?

Answer 8

Aganglionic megacolon - swelling of abdomen b/c neural system didn’t develop to colon, causing lack of mvt and constipation, sepsis, loss of appetite

Treatment: Colostomy

Question 9

What autonomic reflexes can affect bowels and inhibit intestine?

Answer 9

Intestino-intestinal, peritoneo-intestinal, reno-intestinal, vesico-intestinal, somato-intestinal

Question 10

What toxin causes secretory diarrhea?

Answer 10

Cholera toxin

Question 11

What heterozygote patients have better survival with cholera?

Answer 11

CFTR b/c lack functional CFTR channel, so lose less fluid

Question 12

How does cholera toxin work?

Answer 12

Raises cAMP, raises PKA, more choloride channels, more chloride secretion, Na/water loss

Question 13

What are the types of diarrhea? And how do you treat?

Answer 13

1. Osmotic diarrhea (i.e. lactose intolerance so avoid milk)
2. Secretory diarrhea (bac or viral cause - imodium)
3. Inflammatory diarrhea (dysentery or ulcerative colitis - dmg to intestinal mucosa - anti-inflammatory drugs)
4. Rapid transit diarrhea (decrease motility - block serotonin)
5. Bacterial diarrhea (oral rehydration therapy - lots of Na+ and glucose - uses SGLT1 channel - Na/glucose cotransport so more water is absorbed)

Question 14

Describe the steps of defecation .

Answer 14

1. Fill rectum, valves of Houston distend
2. Reflex contraction of rectum and relaxation of internal anal sphincter
3. Voluntary relaxation of external anal sphincter
4. Puborectalis relaxes
5. Flex hips, lower pelvic diaphragm

Question 15

What innervates external anal sphincter? Spinal cord levels?

Answer 15

Internal pudendal nerve - S2-4

Question 16

What innervates internal anal sphincter?

Answer 16

Pelvic splanchnics (post-ganglionic parasympathetics) that release NO, VIP, ATP on muscle to cause relaxation

Question 17

What does puborectalis muscle do?

Answer 17

Keeps inferior rectum bent so feces stays inside when feces are contracted

Question 18

What does leptin do? What produces it?

Answer 18

Decreases appetite

Adipose tissue

Question 19

What does Ghrelin (GHRP - GH releasing peptide) do? What makes it?

Answer 19

Hunger signal - ghrelin signals high before meals and low afterwards; fundus of stomach and epsilon cels of pancreas make it

Question 20

What does neuropeptide Y do? What makes it?

Answer 20

Increases appetite - made by many cells, esp beta cells of pancreas

Question 21

What drugs work for obesity?

Answer 21

Orlistat - inhibits intestinal lipase - best drug

Rimonabant - blocks cannabinoid receptors

Question 22

What is dyspepsia?

Answer 22

Stomach pain

Question 23

What is gastritis?

Answer 23

Inflammation in stomach (pre-ulcer)

Question 24

What is peptic ulcer disease?

Answer 24

Ulcer in stomach