Calcium Channels

Question 1

L-type calcium channels

Answer 1

C: High activation threshold, slow inactivation
L/F: Plasma Membrane of many cells; main source of contraction in SMOOTH and CARDIAC
R: Blocked by DHP, phosphorylated by pKA in many cells (e.g. following B2 activation) which increases activation

Question 2

N-TYPE

Answer 2

C: Low activation TH, Slow inactivation
L/F: Main Ca source for transmitter release by nerve terminals
R: Blocked by w-conotoxin, used in pain management

Question 3

T-type

Answer 3

C: low activation T.H, Fast inactivation
L/F: Widely distributed in cardiac pacemaker cells, important in cardiac rhythm and neuronal firing pattens
R: blocked by mibefradil

Question 4

P/Q type

Answer 4

C: Low activation TH, slow inactivation
L/F: Found in Nerve Terminals and important in neurotransmitter release
R: blocked by w-agatoxin

Question 5

R-type

Answer 5

C: Low Threshold, Fast inactivation
L/F: Neurons and dendrites; control neuronal firing patterns
R: Blocked by tarantula toxin

Question 6

IP3

Answer 6

C: Activated by Ip3 binding and Ca binding

L/F: Located in endoplasmic/sarcoplasmic reticulum

Question 7

Ryanodine receptor

Answer 7

C: Directly activated in skeletal muscle via dihydropyridine receptor of T-tubules. Activated by Ca2+ in cardiac muscle
L/F: Endo/Sarco plasmic reticulum; pathway for contraction in striated muscle
Activated by caffeine and ATP

Question 8

Store operated calcium channels

Answer 8

C: Activated by sensor protein that monitors low levels of calcium
L/F: found in the sarcoplasmic reticulum