Heart 2 Flashcards
beta adrenergic receptor: transduction mec
Gs: adenylyl cyclase, cAMP and PKA activation
beta adrenergics: effects on ion currents? (4)
ICa,L: Calcium influx. Ik: shortens AP. If: activates at more positive potentials. increased slope of pacemaker
beta-adrenergics also have other effects: 3?
phosphorylase kinase, glycogen synthetase. increased rate of Ca dissociation from myofilaments. accelerated pumping of Ca pumping back into SR.
phosphoyrlase kinase/glycogen synthetase?
phosphorylated especially in presence of high Ca = faster glycogen breakdown, slower glycogen synthesis = more energy for heart
beta-adrenergics: long term?
long term effects can alter gene expression so that heart responds better to sympathetic stimulation
ACh: receptors where? effects in 3 places?
only in supraventricular tissue. SA node, atria and AV node.
ACh effect on SA node?
slows sinus rate, decreases slope of pacemaker = bradycardia
ACh effect on atria?
shortens AP duration, reduces refractory period
ACh effect on AV node?
attenuates conduction
ACh cellular effects? (transduction pathway)
muscarinic receptor, coupled to Gi. inhibits AC = less cAMP = reduced Ca + L currents. direct activation of Gk, ACh channels
mammals: cardioacceleration initiated by? and then what?
initiated by vagal withdrawal. sympathetic activation has a slower onset
minute to minute regulation controlled by? so heart rate variability is an index of?
controlled by vagus. index of vagal function
cardiac pacemaking: what kind of process? involves balancing?
important, very delicate. balance between variety of ionic conductances. slight chang ein one conductance = profound effect on cardiac activity
how does ANS deal with slight changes in conductances having large effects?
negative feedback loops, baroreceptor reflex, receptor desensitization
too much sympathetic drive: turned off by?
muscarinic adrenergic interactions at level of adenylyl cyclase
