L12

Question 1

Ca.v (info)

Answer 1

open in response to depolaristion
Ca2+ is an important 2nd messenger used in muscle contraction, cell growth, synaptic transmission, gene expression, ion channels and protein kinases
only channels which directly convert electrical signals into biochemical work

Question 2

High voltage activated Ca.v pore-forming subtypes

Answer 2

L-type
- Cav1.1 skeletal muscle
- Cav1.2 cardiac/smooth muscle
- Cav1.3 secretion form glands
P/Q-type - Ca2.1 CNS transmitter release
N-type - Cav2.2 PNS and CNS transmitter release
R-type - Ca2.3 transmitter release

Question 3

Low voltage-activated Ca.v pore-forming subtypes

Answer 3

T-type
- Cav3.1, 3.2 and 3.3
all excitability of cells

Question 4

Diversity in Ca.v channels

Answer 4

There is further diversity in Ca.v channels by adding ß and alpha2delta accessory subunits.n
Alpha1:ß:Alpha2Delta stoichiometry
ß interacts with alpha subunits between a1-a2
structure-wise its the same as K+, with Beta and an a2ß

Question 5

Classical Calcium antagonists

Answer 5

L-type blockers:
- 1,4 dihydropyridines –> anti-hypersensitive
- phenylalkylamines –> anti-arrhythmic
- benzothiazepines –> Both

Question 6

K+ and RMP

Answer 6

RMP is dominated by ionic species, greatest permeability to K+ across membrane
Tetramer is important, enables channels to heteromultimerise, allowing diversity

Question 7

K.Ca

Answer 7

sensitive to voltage and [Ca2+]
Ca2+-binding domain to C-terminal domain

Question 8

SK.Ca and IK.Ca

Answer 8

voltage insensitive
activated by low [Ca2+], bind Ca2+ indirectly via calmodulin
function is AP repolarisation

Question 9

K.Ir

Answer 9

2 TM domains equivalent to S5-P-S6
several subfamilies
blocked by Mg2+
stabilise RMP near to Ek
strong rectifiers close upon strong depolarisation of Vm
Weak rectifiers pass more outward current at depolarised Vm