Physiology and Pharmacology of the Large Intestine Flashcards Preview

Human Epithelial Biology > Physiology and Pharmacology of the Large Intestine > Flashcards

Flashcards in Physiology and Pharmacology of the Large Intestine Deck (21)
1

What comprises the large intestine?

colon, caecum, appendix, rectum

2

How much ileocaecal matter does the large intestine receive every day?

1L

3

What are the features of the ileoceacal sphincter?

maintains a positive resting pressure
relaxes in response to distension of the duodenum
contracts in response to distension of the ascending colon

4

What controls the ileocaecal sphincter?

vagus nerve, sympathetic nerves and enteric neurons

5

What are the primary functions of the large intestine??

absorption of H20, Na, Ck and secretion of K, HCO3 and mucus
absorption of short chain fatty acids
Reservoir of storage
Periodic elimination of faeces

6

What are the patterns of motility in the large intestine?

haustration, peristalic propulsive movements, defaecation

7

how often does peristalisis occur in the large intestine?

1-3 times a day triggered by a meal via the gastrocolic response

8

What controls the gastrocolic reponse?

gastria
extrinsic nerve plexuses

9

What activates defacation?

activation of rectal stretch receptors

10

What does activation of the rectal stretch receptors trigger?

activation of the afferents in the spinal cord -> parasympathetic efferents -> contraction of sm. muscle -> relaxation of internal anal sphincter
activation of afferents in brain-> urge to poop -> altered firing in efferents to spinal cord

11

What is diarrhoea defined as?

the loss of 500ml of fluid from the GI tract in a day

12

What are the principle mechanisms of Na reabsorption in the Gut?

SGLT
Na-Amino acid cotransport
NHE
Parallel Na-H &Cl/HCO3 exchange
ENaC

13

What are the causes of diarrhoea?

infectious agents
chronic disease
toxins
drugs
psychological factors

14

What is the treatment of severe acute diarrhoea?

maintenance of fluid and electrolyte balance
use of anti-infective agents
use of non-antimicrobial antidiarrhoeal agents

15

What does diarrhoea cause?

Impaired absorption of NaCl
Non-absorbable solutes in the lumen
Hypermotility
Excessive secretion

16

How does Cholera affect secretion?

enzymatically inhibits GTPase activity of Ga subunit which increases the AC activity and thus cAMP
cAMP stimulates the CFTR causing hypersecretion of Cl, Na and water

17

What does rehydration therapy target?

SGLT 1

18

What can be contained within oral rehydration salts?

glucose
NaCl
NaHCO3
KCl

19

What are used as anti-motility agents in Diarrhoea?

opiate drugs

20

How do opiates act as anti-motility agents?

inhibition of enteric neurons
decreased peristalsis, increased segmentation
increased fluid absorption
constriction of pyloric, ileocolic and anal sphincters

21

What are the major opiates used in diarrhoea?

coedine
diphenoxylate
loperamide