Cardiac Muscle Flashcards
What connects cardiac myocytes?
intercalated discs
what two things to intercalated discs have?
desmosomes and gap junctions
pathway of electrical signal in the heart
SA node Internodal tract AV node common bundle of his bundle branches purkinje fibers contraction
does the SA node have an RMP?
nah never has a flat line
why is there a delay at the AV node?
this delay allows for adequate ventricle filling prior to contraction of the ventricle
which two locations in the heart do not have a consistent RMP?
SA and AV nodes
are cardiac APs longer or shorter than neuronal APs?
much much longer…allows for more contractility and blood output
name the 5 phases of cardiac AP
0-depolarization 1-partial repolarization 2-plateau 3- rapid repolarization 4- RMP
what channel is opening during phase 0 of heart AP?
voltage gated Na channels
3 channel changes during phase 1 of cardiac AP?
Na voltage gated are inactivated
outward K+ channels open
Calcium (L-type) channels open
channel opening/closing during phase 2 of the cardiac AP?
outward K+ channels closing
voltage Na+ inactivated still
voltage gated Calcium channels open
delayed rectifier K+ channels opening
channel opening/closing during phase 3 of cardiac AP?
Ca voltage channels inactivated
outward K channels inactivated
delayed rectifier K+ channels open
phase 4 channel that is open?
internal rectifier K+ channel
how does calcium cause cardiac muscle contraction?
it enters through the calcium voltage gated channels and then induces the opening of the SR calcium channels (ryanodine)…calcium induced calcium release
3 ways cardiac cells decrease Calcium concentration following contraction?
SERCA pump
secondary active transport with the Na influx and Ca efflux
primary transport of calcium out with ATPase
what is the name of the special channel in SA node cells?
Hyperpolarization activated cyclic nucleotide gated channels
HCN channels
what is the role of HCN channels in the SA node?
open at negative potentials and allow Na and K to pass through…they are sensitive to NE and Epi so are a point of contact for ANS control of cardiac
Allows a little more Na to pass so it leads to rise in MP
when are the HCN channels open in the SA node?
during the weird RMP time where the MP is rising a bit toward the AP
T-type Ca channels definition and when are they open?
transient channels that open briefly just before the AP occurs at negative voltages like -50mV
