GIT tract 3

Question 1

net absorption

Answer 1

Take in a certain amount, excrete a certain volume alongside secretion and absorption

Question 2

aborption and secretion noral

Answer 2

volume moving from blood to gut lumen is less than lumen to blood

Question 3

malabsroption

Answer 3

absent or defective digestive enzymes
-	defects in transported protein
-	diseases/infections of the small intestine
examples of malabsroption
1)	lactase deficiency
-	lactose intolerance
2)	coeliac disease
-	abnormal immune response to gluten
-	loss of mucosal epithelium

Question 4

diarrhoea

Answer 4

Increase stool volume or increased frequency of defecation

Question 5

osmotic involvemtn in diarrhoea

Answer 5

increased solutes in lumen causes less water reasoprtion
- poorly absorbed substrate, high conc of substrate that cannot cross lumen so water moves into the lumen rather than increasing water levesl in gut

Question 6

secretory involvemetn in diarrohea

Answer 6

Increases secretion of water into the lumen (secretion exceeds absorption)
not due to osmotic effect
- cholera toxin (defect function of chloride channel opening up Cl- channel, too much chloride into gut, water follows increased secretion of water)
- laxatives, hormones, drugs (antidepressants), caffeine
- bile acid malabsorption

Question 7

cholera caused by

Answer 7

bacterial toxins from cholerae

Question 8

how does cholera work

Answer 8

toxin enters cells and is activated in the ER
binds a G protien
activates adenylate cyclase
production cyclic AMP
activates chloride channel
chrlodie moves out of channel into lumen of gut, followe by soidum and water

Question 9

inflammaiton involvemtn in diarrhoea

Answer 9

pathogens breach and damage the absorptive epithelium

• clostridium difficile
• invasive parasites

Question 10

degranged motility in diarrhoea

Answer 10

Altered transit time hence less time for water reabsorption

- irritable bowel syndrome

Question 11

colon motility and what it allows

Answer 11

segmented contractions in segmented region
allows
- mixing contents
- retain material in the proximal colon (fermentaion, water absroption)

Question 12

gasto colic repsonce

Answer 12

mass movement of material into aboral end of colon - ready for defection

Question 13

what allows defecation

Answer 13

regualting movemnt of material and opening of sphincters

Question 14

defecation

Answer 14

Faeces moved into rectum (via gasto colic response) – leads to dissension

• activates stretch receptors
• afferent signals to the spinal cord

Question 15

when convinemtn to defecate and what is involved

Answer 15

• voluntary motor nerves are inhibited allowing the external anal sphincter to relax
  Automimic informs need, voluntary decides whether it is convent

Symp and parasymp
- stimulate contraction of the rectum and relaxation of the internal anal sphincter

Question 16

voluntary and involuntary defacation

Answer 16

External is voluntary , internal is autonomic controlled

Question 17

incontinence and what it leads to

Answer 17

pelvic floor damage
pudendal nerev damaged
Alters ability to control and regulate
- can cause loss of control of emptying, defecation could occur involuntarily or problems being unable to defecate

Question 18

defecation failure causes

Answer 18

spinal injuries

outlet blockages

Question 19

storage vs empyting defacation muscles

Answer 19

storage
- contracted spincters and relazaiton of colon/rectum
emptying
- relaxation of spincters and contraction of colon/rectum

Question 20

emesis

Answer 20

protective mechanisms to prevent damafe to GI tract and ingestion of contaminated/toxic substances

Question 21

detectors of toxins
pre ingestion
pre absoption
post absroption

Answer 21

pre ingestion
- sight, smell ,tastes
pre absoption
- toxin dectection in lumen
- mechano/chemo receptors
- explusion
post absroption
- chemoreceptive trigger zone
induced nausea to prevent further ingestion
activates voimiting centters

Question 22

thngs that make us sick

Answer 22

1) food poisoning
2) bowel disease
3) motion/vestibular disease
4) pregnancy
5) head injury
6) radiation/chemotherapy
7) surgery/ anaesthesia
8) drugs
9) pain

Question 23

nausea symptoms

Answer 23

• pallor
• sweating
• salivation
• irregular breathing
• increased HR
• retching (several, increased force)

Question 24

GI motor control of nausea steps

Answer 24

1) contraction of small intestine
- retrograde giant
- contracts return intestinal contents to the stomach
2) stomach relaxes
- proximal stomach relates to accommodate returning intestinal contents
- antral motility inhibited to prevent gastric emptying
3) contraction of diapgragm and abdominal wall
- expulsion

Question 25

steps for vomiting

Answer 25

Deep inspiration allows closure of glottis, protects respiratory tract

• air and saliva drawn into oesophagus
• protection and decrease in oesophageal pressure
• soft pallet elevated to prevent entry into the nasopharynx and nose
• expiration against closed glottis and abdominal contraction
• increase intra abdominal pressure
• relaxation of lower oesophageal sphincter
• passage of contents into oesophagus
• relaxation of the UOS
• violent expulsion force stomach and abdominal contraction

Question 26

during retching

Answer 26

upper oesophageal spincter remains closed (open for vomiting)

Question 27

where is the vomiting centre

Answer 27

4th ventricel in medulla oblongata

Question 28

vomiting centre

Answer 28

contains cheoreceptors sampling blood

sigals from higher centres

Question 29

what detects motion sickness

Answer 29

vestibular system

Question 30

emetic repsonce to anticancer therapry

Answer 30

acute recognise toxins
delayed responce due to damae to epithelium as the entero chromaffin cells damaged
- anticipatory senssros to

Question 31

anti emetics work by

Answer 31

blocking activation of vomiting centre
Chemoreceptor trigger zone – Ondanstron (5-HT antagonist)

Block receptors for the histamines