Heart Flashcards
order of events in heart: impulse and contractions?
impulse arises at SA node, atrial contraction, AV node, bundle of his, purkinje fibers, ventricles contract
two types of cardiac action potentials and what parts of the heart
fast: purkinje fibers, atria, ventricles. slow: SA node, AV node
purkinje fiber action potential: type? how many parts?
fast: 5: phases 0 to 4
fast AP: phase 0? 1?
0: Na goes in = rapid depolarization. 1: Na goes in to a lesser extent; Na inactivation rapid replarization
fast AP: phase II shape? what’s happening? what is also happening at the same time?
looks like a plateau. Na/Ca go in through ion channels. electrogenic Na/Ca exchanges also happening so 3 Na in, 1 Ca out. Ca in = contraction
fast AP: fase II and IV?
III = final repolarization, K+ out. IV = pacemaker depolarization, Na/K dependent. ionic gradients being restored by na pump
SA node action potential: type? phases?
slow: three phases, phase 0, 3 and 4
slow AP: what happens in phase 0, 3, 4?
0: Ca/Na in, depolarization. III: K+ out, replarization. IV: Ca dependent pacemaker
autonomic impulses do what for cardiac contractions?
modulate, they don’t initiate
sympathetic outflow to heart: from where? which ganglia?
from T1 to T6. via superior cervical, inferior cervical, stellate ganglia
parasympathetic outflow to heart: from where? which ganglia?
from nucleus ambiguus. via vagus (CN 10) to cardiac parasympathetic ganglia
cardiac ganglia: is what? in where?
complex system of plexuses and interconnected ganglia, in atrial septum and in fat pads
sympathetic nerves: inhibitory and excitatory effects? via what?
presynpatic inhibitory a2 effect (to turn parasymp off), and a post synaptic excitatory a1 effect
how many neurons in heart ganglia? 4 other mediators?
10 ^ 6 neurons. galanin, adenosine, 5HT, CGRP
what NA receptors in all parts of heart? effects mediated by?
B1 receptors. effects mediated via cyclic AMP
