constipation and diarrhoea Flashcards
what are the 3 types of muscle in the lumen of the GI tract and what do they do?
- longitudinal: makes the lumen shorter and fatter
- circular: makes the lumen narrower and longer
- muscularis mucosae: changes the absorptive and secretory area
explain contraction in the GI tract which leads to slow waves?
smooth muscle contraction can be spontaneous, slow waves are formed because of gap junctions
what is the slow wave frequency of the:
- stomach
- duodenum
- ileum
stomach: 3 per min
duodenum: 1-12 per min
ileum: 8 per min
what is the name for muscle contractions that move food down the GI tract?
peristalsis
what is the name of contractions that cause circular layers of the GI tract to separate and mix GI content?
segmentation
what is normal faeces made up of?
100ml of water and 50ml of cellulose and bacteria
define diarrhoea?
the loss of over 500ml of fluid and solutes per day
absorption of water into cells from the GI tract causes what?
more solid faeces
describe the normal process of ions and water leaving the cell?
- Na+, K+ and Cl- enter the cell using co transport
- a very small amount Cl- leaves the cell via the CFTR channel
- Na+ is reabsorbed
- the negative Cl- outside of the cell attracts Na+ and water follows
describe what channel opening causes diarrhoea and what can trigger this?
bacteria, hormones and laxatives can cause the opening of the CFTR causing more water to leave the cell leading to diarrhoea
how do E.Coli and cholera cause diarrhoea?
inhibit GTPase activity, increasing adenylate cyclase, increasing cAMP which opens CFTR
what drugs are used to treat diarrhoea?
oral rehydration therapies
what drug class can cause constipation and how does it do this?
opioids : they decrease peristalsis and increase fluid adsorption
name a drug used to stop diarrhoea?
loperamide
