Cardiac Histo
Does cardiac muscle have a short or long contraction duration?
What is the RMP of cardiac muscle?
What ions are involved in cardiac muscle APs?
-90mV
Na+, K+, Ca2+
What ion channels open or close in each phase of the myocyte AP? (Only need the ion type not the full name)
0: Na+ open, K+(ir) close
1: Na+ close, K+ open
2: Ca2+ open
3: Ca2+ close
4: K+(ir) open
What ion is proportional to the strength of myocyte contraction?
Ca2+
Decrease HR (negative chronotropic)
What is the normal HR range for a sinus rhythm
60-100 bpm
Does cardiac muscle contract more like skeletal or smooth muscle?
Na+
What phase of myocyte AP is the contraction?
Phase 2
What are the three mechanisms for removing intracellular Ca2+
Ca2+ ATPase pump (primary active, out of cell)
Na+/Ca2+ exchanger (secondary active, out of cell
SERCA pump (primary active, into SR)
What carries the AP from bundle branches to the myocardium?
Purkinje fibers
What is the function and location of desmosomes?
And gap junctions?
In the intercalated discs:
Desmosomes connect cells for efficient contraction
Gap junctions allow ions to move from one cell to the next for propagating APs
What ions are responsible for the plateau of phase 2 and what is their direction?
Ca2+ in, K+ out
What ion channels open or close in phase 3 of Nodal cell AP
K+ open
Ca2+ close
What receptor causes Ca2+ release from cardiac myocyte sarcoplasmic reticulum?
Ryanodine receptors
Atrial phase 2 is represented on the ECG by what?
PQ Segment
What type of cell spontaneously depolarizes and where is it found?
Nodal cell, in the SA node
What are the phases of Nodal cell APs
4, 0, 3
What ion channel opens when nodal cells reach threshold
Ca2+
What are the two mechanisms for increasing intracellular Ca2+
Ca2+ influx through voltage gated channels
Ca2+ induced Ca2+ release
ECG associations:
Atrial depolarization =
Atrial repolarization =
Ventricle depolarization =
Ventricle repolarization =
P wave
QRS
QRS
T wave
Where is the mitral? Where is the tricuspid valve?
Mitral separates L atria and L ventricle
Tricuspid separates R atria and R ventricle
What is the name of the ion channel responsible for spontaneous depolarization in Nodal cells? What is the direction of ion movement?
Na+ goes into the cell
What is the RMP and threshold of nodal cells?
-60 RMP
-40 threshold
Define chronotropic, dromotropic, and inotropic
Chrono = Alters the HR and rhythm
Dromo = Alters the conduction velocity thru AV node
Ino = Alters the force of muscular contraction
Where is cardiac conduction velocity the slowest?