Chloride Movement

Question 1

Secretion of chloride steps

Answer 1

Na sets up ion gradient
NaKCl symporter uses Na gradient to accumulate Cl- above it’s electrochemical gradient in cell
Cl leaves cell by passive diffusion thru ion channel
Na exits via basal Na pump and K+ via channel
Transport of Cl across epithelium induces para cellular Na and water fluxes

Question 2

Rate limiting step

Answer 2

Opening of Cl channel - it is strictly regulated / gated (Cystic Fibrosis Transmembrane conductance regulator) CFTR

Question 3

Secretory diarrhoea

Answer 3

Excessive stimulation of secretory cells - due to high concentrations of secretagogues produced

Question 4

What’s secretagogues

Answer 4

Hormone that causes epithelial cells to stimulate signalling pathways that open the chloride channel and cause it to start process of secretion

Question 5

Cholera toxin

Answer 5

Irreversibly activates adenylase cyclase causing activation of CFTR. Activates chloride secretion and pumps fluid out of body

Question 6

Oral hydration therapy

Answer 6

Treats secretory diarrhoea caused by cholera (water and sugar and salt) lifts hydration levels and with the glucose helps the cycle

Question 7

Cystic fibrosis

Answer 7

Affects children and young adults
Heterozygous have no symptoms but are carriers
Disease frequency varies among ethnic groups (Europeans 1/2500)

Question 8

Symptoms of cystic fibrosis

Answer 8

Clogs lungs (bronchial passages)
Blocks bile ducts
Makes pancreas unable to secrete enzymes
Colon becomes blocked
Male reproductive tracts blocked
Sweat becomes salty