1- Cardiac Valves:
a- Prevent backflow of blood from the
ventricles to the atria during diastole.
b- The cusps of the semilunar valves attached
to the papillary muscles
c- The cusps of the AV valves pulled inward
toward the ventricles during systole.
d- Normally allow flow of some blood to the
atria during ventricular systole.
2- All are the functions of the atrium EXCEPT:
a- A blood reservoir.
b- Atrial systole is followed by ventricular
systole systo e
c- Pump the blood to the ventricle.
d- Contracts weakly to help move the blood into
3- Cardiac cells:
a- Represent 90 % of the total volume of the
b- Are rich in mitochondria (30% of cell volume)
as in skeletal muscle.
c- Contain sarcoplasmic reticulum which
takes up Ca2+ during contraction cycle cycle.
d- They function as a syncytium.
4- All are the functions of the intercalated disks
a- Connect two adjacent cardiac cells.
b- Provide strong union between fibers.
c- Connect actin filaments of adjacent cells at M
d Contain gap junctions that allow electrical
d- continuity between cardiac cells.
5- Cardiac gap junctions:
a- Composed of several voltage-gated channels
permeable to ions.
b Largely distributed in AV node b- node.
c- Are Low-resistance intercellular junctions.
d- Are little in Purkinje fibers.
a A rod like structure connects the actin
a- filaments of two adjacent cardiac cells.
b- Connects actin with extracelular matrix.
c- Helps platelets adhesion.
d- When dysfunctioned the connection between
cardiac cells becomes slow.
a- Very large elongated stiff protein.
b- Binds actin to the Z line.
c- Keeps myosin thick filaments centered in the
d- When dysfunctioned the heart is dialated
d abnormally in systole.
8- The resting cardiac cell membrane:
a- Is primarily permeable to K+ ions.
b- Has resting membrane potential - 65 mV.
c- Chloride equilibrium establishes its potential.
d. Influenced by extra-cellular Na+ ion
9- The cardiac resting membrane potential (RMP):
a- The delayed rectifying potassium channels are
responsible for establishing the RMP.
b- At both low and high K+ concentrations, the
membrane becomes less excitable.
c- Is about -85 mV in the ordinary cardiac cells.
d- When extracellular K+ ions is decreased to
very low levels, the Na-K pump is enhanced.
10- The inwardly rectifying K+ channels:
a- Responsible for establishing the resting
membrane potential at -100 mV.
b- Favor inward movements of K+ ions at
membrane potential -65 mV.
c- Inactivate with time.
d- Conduct outward current physiologically.
11- Regarding “cardiac action potential” all the
followings are correct EXCEPT:
a- Transient depolarization-repolarization.
b- At threshold voltage, the membrane becomes
primarily permeable K+ ions ions.
c- The membrane resists any change from the
d- Has long duration from 200 to 300 msec.
12- The cardiac fast voltage- gated Na+ channels:
a- Conduct inward current (INa) that responsible
for slow action potential upstroke.
b- INa depolarizes the membrane to levels of
activation of inward Ca2+ & outward K+ act at o o a d Ca out a d
c- Quickly depolarize the membrane to +47 mV.
d- Blocked by dihydropyridines “DHP”.
13- The followings cause the first rapid
l i ti f di t i l EXCEPT repolarization of cardiac ventricle EXCEPT:
a- Rapid inactivation of INa
b Transient efflux of K+
b- c- Transient influx of Cld-
Rapid influx of Ca+. d Ca .
14- Regarding “the plateau of ventricular action
potential” all are correct EXCEPT:
a- Unique to cardiac cell.
b- Provides sustained depolarization and
contraction needed to empty the heart.
c- Prevents premature activation.
d- Maintained by balance between inward Na+ y
current and outward K+ current.
15- Regarding “L- type Ca2+ current (Ica-L)” all
are correct EXCEPT :
a- Ligand operated current.
b- Blocked by dihydropyridines (DHP).
c- Induces Ca2+ release from sarcoplasmic
d- Inactivated very slowly.