lecture 17

Question 1

what hormone signals the PI pathway

Answer 1

phenylephrine

Question 2

calcium spikes persist for as long as the hormone is present

Answer 2

if you double the concentration of the hormone the amplitude of the spikes remains constant but the frequency of the spikes increases

Question 3

calcium released from the ER feeds forward to stimulate further calcium release from the neighboring bit of ER

Answer 3

CICR - calcium induced calcium release

Question 4

temporal

Answer 4

is the spike

Question 5

spatial

Answer 5

in the wave

Question 6

peak of spike is when

Answer 6

the whole cell is full of calcium

Question 7

calcium movement is dependent solely upon diffusion which is slow
calcium will bind to the buffer proteins and all be mopped up so we need CICR otherwise there would be no wave or spike
CICR saturates all the buffers

Answer 7

The spikes allow the cell to get away with calcium being cytotoxic as its not in the cell for a long time at any point

Question 8

cardiac myocytes only contain

Answer 8

RyRs

Question 9

cADPR does cause RyRs to release calcium invitro

Answer 9

there’s an idea that when stimulates theres a pathway that causes cADPR to rise but researchers have no real proof

Question 10

biphasic curve

Answer 10

has an upward and downward phase

Question 11

as the cytosolic calcium increases we get more calcium release from the channels
at the peak the CICR stops and calcium release is inhibited
high cytosolic calcium inhibits calcium release

Answer 11

RyR has similar characteristics, curve is shifted to the right meaning you need higher cytosolic calcium concentration. also calcium release os only partially inhibited for RyR