What causes the self-excitation (spontaneous generation of action potentials) of the cells of the sinoatrial (SA) node?
a) the condition of sinus block;
b) slow Na+ influx through non-inactivating sodium channels;
c) systemic neuronal inputs to the cells of the SA node.
What type of ion transport is responsible for the fast depolarization phase of the action potential in myocardial muscle cells?
a) Mg2+ influx;
b) Cl- efflux;
c) Na+ influx.
The plateau phase of the myocardial action potential is caused by the following ion transport:
a) passive Ca2+ transport;
b) passive Cl- and active Ca2+ transports;
c) active Na+ and passive Ca2+ transports.
In the electrical network of the heart, do structures other than the sinoatrial (SA) node have a pacemaker properties?
a) no;
b) yes;
c) depends on their functional state.
423. Under what circumstances the atrioventricular (AV) node takes over the role of leading pacemaker of the heart?
a) when there is a dysfunction of heart’s innervation;
b) when there is ectopic foci;
c) when there is a sinoatrial arrest.
Is there a difference in the rate (frequency) of sinoatrial and atrioventricular potentials?
a) yes, the sinoatrial node generates potentials with a faster rate;
b) no difference;
c) yes, the atrioventricular node generates potentials with a faster rate.
Is there a difference between the form and the amplitude of the action potentials generated in different locations of the electrical conductive system of the heart?
a) no difference;
b) yes, every point of the electrical network of the heart generates a potential with specific form and amplitude;
c) yes, the sinoatrial node has a specific potential which changes after passing through the atrioventricular node and remains constant until the target muscle cells.
Which of the following bioelectrical process take place during the diastolic phase of the heart?
a) recovery of the ionic concentrations of intra- and extracellular fluids myocardial cells;
flow of ionic currents between the Golgi apparatus and the endoplasmic reticulum;
generation of reverse action potentials, propagating from myocardial cells to the sinoatrial node.
The autonomous excitation of the heart is contributed to:
a) the regular variation of the threshold potential of ventricular myocytes;
b) the effect of mechanical pulse waves on the cardiac myocytes;
c) special type of ion channels found in the membranes of pacemaker cells.
Which of the following ions are responsible for the final repolarization phase of the myocardial cells?
a) K+ efflux;
b) Cl- influx;
c) Ca2+ influx.
What is the function of the artificial cardiac pacemaker?
a) to send electrical pulses to the heart;
b) to control the resting potential of pacemaker cells;
c) to take over the pumping function of the heart.
At the end of the “plateau” phase of the action potential in cardiac myocytes, the membrane permeability changes for this type of ions:
a) sodium ions;
b) potassium ions;
c) calcium ions.
The fast depolarisation phase of the action potential of cardiac pacemaker cells is due to:
a) sodium influx;
b) calcium influx;
c) potassium efflux.
The plateau phase of the action potential of cardiac myocytes is due to:
a) Ca2+ influx through slow voltage-gated channels;
b) K+ efflux;
c) N+ influx.
Which cardiac cells exhibit the spontaneous diastolic depolarization?
a) myocytes of the right atrium;
b) myocytes of the left ventricle;
c) pacemaker cells.
The approximate value of the resting potential of cardiac muscle cells is:
a) -90 mV
b) -90V
c) -40 mV
The so called “plateau” phase is found in the action potential of this type of cells:
.
a) pacemaker cells;
b) cardiac muscle cells;
c) sinoatrial node
The action of the anti-arrhythmic pharmaceutical “verapamil” is related to:
a) blockage of Na+ influx;
b) blockage of Ca2+ influx;
c) blockage of Mg2+ influx.
. Which of the following phases is characteristic for the action potential of pacemaker cells of the sinoatrial node?
a) spontaneous diastolic depolarization;
b) stable resting phase;
c) the “plateau” phase.
Which of the following phases is not fond in the action potential of cardiac mysocytes?
b) resting phase;
c) fast depolarization.
Which of the following phases is not found in the action potential of pacemaker cells of the sinoatrial node?
What type of cells are cardiac myocytes?
b) contractile cells;
c) they have both, contractile and pacemaker functions.
Self-excitation is a property of:
a) the electrical conduction system of the heart;
b) all cardiac cells;
c) the cardiac myocytes.
What type of cells make up the electrical conduction system of the heart?
a) pacemaker type;
b) phasic type;
c) tonic type.
Myocardial cells are specialised type of striated muscle cells that contract:
a) voluntarily;
b) involuntarily;
c) depends on the situation.
. Choose the correct order of excitation of components of the electrical conducting system of the heart.
......→......→......→......→......→......
a) bundle of His;
b) SA-node;
c) Purkinje fibers;
d) AV-node;
e) atrial myocytes;
f) ventricular myocytes.
Which of the following tissues has pacemaker cells?
a) myocytes of the ventricles;
b) myocytes of the atria;
c) the atrioventricular node.
Choose the correct order of occurrence of the ion currents that comprise action potentials of the cardiomyocytes:
idk answer
b) Ca2+ influx, K+ efflux;
c) K+ efflux, Cl- influx;
d) Na+ influx.
The slow depolarization phase of the action potential in first-order pacemaker cells is due to:
a) Ca2+ influx;
b) Na+ influx;
c) K+ efflux.
What is the original source of the bioelectrical pulses leading to the contraction of the heart?
a) central nervous system;
b) sinoatrial node;
c) cardiomyocytes.
The electrical conduction system of the heart is composed of:
a) muscle cells;
b) neurons;
c) lymphocytes
