intracellular signalling pathways

Question 1

what are the concentrations like of calcium inside and outside the cell

Answer 1

more outside

Question 2

how are calcium concentration gradients set-up and maintained ?

Answer 2

relative impermeability of the plasma membrane to Ca2+

pumps- PMCA and SERCA- use ATP and transporters that move Ca out of the cytoplasm - NCX

Ca buffer proteins

Question 3

how is calcium ion concentration increased

Answer 3

ca2+ movement across the plasma membrane- influx
ligand gated ion channels
voltage gated calcium channels

Ca2+ movement out of the ER/SR

• IP3R
• ca2+ induced Ca2+ release
• both move calcium from lumen into cytoplasm

Question 4

intropy in the heart

Answer 4

both blood-borne adrenaline and sympathetically released noradrenaline can interact with ventricualar beta1-adrenoreceptors to increase the force of contraction

this is done by activating the Gs protein which activated adenylyl cylase which converts ATP to cAMP which activates cAMP dependant protein kinase A which phosphorylates the VOCC allowing influx of calcium ions

Question 5

noradrenaline and smooth muscle contraction

Answer 5

it can interact with vascular smooth muscle alpha-adrenoreceptors to cause vasoconstriction

Question 6

acetylcholine and smooth muscle contraction

Answer 6

it can interact with bronchiolar smooth muscle M3-muscarinic receptors to cause bronchoconstriction

Question 7

G - protein-coupled receptors

Answer 7

can contract gastrointestinal and gento-urinary smooth muscle

Question 8

amplication

Answer 8

allows control on all signalling pathways, allowing relatively small changes in extracellular signal to elicit physiologically significant changes in cellular behaviour

example- one ligand binding allows the GCPR to activate multiple G proteins- activation of one adenylyl cyclase allows for many ATP molecules to covert to cAMP

Question 9

ligand gated ion channel

Answer 9

Ligand gated
-initiating the depolarisation in response to a ligand, allow small amound of sodium ions to enter and result in a small decrease of the membrane potential

Question 10

voltage gated ion channel

Answer 10

Involved in the conduction of action potentials from the axon hillock down the length of the axon.

They are triggered to open by the local positive voltage change and allow even more Na+ to enter inside
the axon.

They will only begin conducting once a threshold is
reached, as only then can an action potential begin.