Inorganic ions and functions

Question 1

Na+ ions in movement of action potential

Answer 1

• sodium ions “jump” across nodes of ranvier in myelenated neurones

Question 2

Na+ ions in generating an action potential

Answer 2

• influx of sodium ions into axon
• voltage gated sodium channels open
• depolarisation of membrane

Question 3

Na+ ions in resting potential

Answer 3

• sodium ions pumped out, potassium ions pumped in
• maintains resting potential

Question 4

Na+ ions in muscle contraction

Answer 4

• acetylcholine released by presynaptic knob causes sodium ion channels to open in sarcolemma.
• Na+ channels open causing wave of depolarisation .
• Na+ ions spread through T tubules
• when action potential reaches endoplasmic reticulum, Ca2+ ion channels open

Question 5

Na+ ions in proximal convoluted tubule (PCT)

Answer 5

• Na+ actively pumped from tubule into bloodstream.
• creates concentration gradient of sodium ions moving into cells lining PCT.
• glucose is co-transported with the Na+ ions via carrier proteins

Question 6

Ca2+ ions in excretion if neurotransmitters

Answer 6

• Ca 2+ ions channels open
• Ca 2+ ions enter presynaptic knob
• Ca2+ causes vesicles containing acetylcholine to fuse with membrane and be released

Question 7

Ca2+ ions in excretion of insulin

Answer 7

• high glucose conc, glucose enters cell
• glucose -> ATP
• ATP causes K+ ion channels to close (ATP sensotive potassium ion channels)
• potassium trapped inside cell / can no longer diffuse out of cell
• cell gets a more positive charge. depolarisation
• voltage gated calium chsnnels open
• calcium ions cause vesicles of insulin to fuse to membrane