10/19 Flashcards
ion channels definition
proteins that form pores in the plasma membrane
ion channels categorized by
gating (opening and closing) mechanism
ion selectivity
pharmacology
passive
allow ions to flow down their electrochemical gradient
ion flow is determined by
concentration gradient and electrical gradient
membrane potential overviw
excitable cells have a negative inward potential across the membrane due to the selective permeability of the resting membrane K+
K+ is high ___ and low ___
K+ is high inside (155 mM) and low outside the cell (4 mM)
Na+ is high ___ and low ___
Na+ is high outside the cell (145 mM) and low inside the cell (12 mM)
Ca is very low ___ and high ___
Ca is very low inside (100 nM) and high outside the cell (1.5 mM)
calcium can start to activate many pathways
need a ___ resting membrane potential
negative inward resting
type of channel expressed in cardiac smooth muscle
L-type, Cav1.2
this is the channel we want to block
CCBs block of channels in vascular smooth muscle:
vasodilation
-decrease BP
-relief of angina pectoris
block of channels in cardiac muscle and SA/AV node: antiarrhythmic
vascular smooth muscle contraction
Ca moves through (L type) channels, inc Ca conc., myosin LC kinase -> myosin LC -> phosphorylation + actin –> contraction
CCBs mechanism
if CCs are blocked, Ca can’t enter cell, Ca can’t be released from the SR, muscle can’t contract
CICR
- calcium influx (Cav1.2) induces release of Ca from intracellular stores vie RYR2 in the SR
- extracellular Ca is required for contraction of cardiac and smooth muscle (not skeletal)
cardiac smooth muscle contraction
Ca ions released from SR bind to troponin C, causes displacement of tropomyosin, allows myosin to bind actin -> CONTRACTION
