Why do all ventricular muscle cells beat at the same time?
Their number is small
They are supplied by the vagus nerve
They are connected to each other by intercalated disc
They are supplied by sympathetic nerves
Why do all ventricular muscle cells beat at the same time?
Their number is small
They are supplied by the vagus nerve
They are connected to each other by intercalated disc
They are supplied by sympathetic nerves
Which of the following does NOT describe cardiac muscle?
It is a functional syncitium
It is striated
It is an anatomical syncytium
It exhibits myogenic rhythmicity
Which of the following does NOT describe cardiac muscle?
It is a functional syncitium
It is striated
It is an anatomical syncytium
It exhibits myogenic rhythmicity
Starling’s law of the heart states that the strength of contraction is proportional to what?
Myocardial oxygen supply
Arterial blood pressure
Stroke volume
The end diastolic volume
Starling’s law of the heart states that the strength of contraction is proportional to what?
Myocardial oxygen supply
Arterial blood pressure
Stroke volume
The end diastolic volume
About cardiac muscle, which statement is NOT true?
Form true syncytium
There is almost a special capillary for each fibre
Low electric resistance of the membrane at the intercalated discs
Obeys the all or none law
About cardiac muscle, which statement is NOT true?
Form true syncytium
There is almost a special capillary for each fibre
Low electric resistance of the membrane at the intercalated discs
Obeys the all or none law
Myocardial contractility is best correlated with the intracellular concentration of what?
K
Ca
Cl
Na
Myocardial contractility is best correlated with the intracellular concentration of what?
K
Ca
Cl
Na
Which of the following agents does NOT have a positive inotropic effect on the heart?
Digitalis
Norepinephrine
Acetylcholine
Glucagon
Which of the following agents does NOT have a positive inotropic effect on the heart?
Digitalis
Norepinephrine
Acetylcholine
Glucagon
What is the important function of the cardiac Purkinje system?
Amplify the cardiac impulses
Increase the force of ventricular contraction
Slow the conduction of impulses
Increase the conduction of impulses
What is the important function of the cardiac Purkinje system?
Amplify the cardiac impulses
Increase the force of ventricular contraction
Slow the conduction of impulses
Increase the conduction of impulses
Chronotropism refers to what?
Excitability
Contractility
Rhythmicity
Conductivity
Chronotropism refers to what?
Excitability
Contractility
Rhythmicity
Conductivity
Which statement about cardiac conductivity is NOT true?
It is decreased by vagal stimulation
It is slowest in the ventricular muscle
It is maximal in the Purkinje fibres
It is slowest in the A-V node
Which statement about cardiac conductivity is NOT true?
It is decreased by vagal stimulation
It is slowest in the ventricular muscle
It is maximal in the Purkinje fibres
It is slowest in the A-V node
What effect does sympathetic stimulation have on the heart?
It increases the heart rate
It decreases the permeability of S.A.N. to K
It decreases the conduction time in the A.V.N
It decreases the slope of the prepotential
What effect does sympathetic stimulation have on the heart?
It increases the heart rate
It decreases the permeability of S.A.N. to K
It decreases the conduction time in the A.V.N
It decreases the slope of the prepotential
The pacemaker potential is primarily due to what?
Slow increase in K+ permeability
Rapid increase in Ca++ permeability
Slow decrease in K+ permeability
Slow decrease in Na+ permeability
The pacemaker potential is primarily due to what?
Slow increase in K+ permeability
Rapid increase in Ca++ permeability
Slow decrease in K+ permeability
Slow decrease in Na+ permeability
Atrial fibrillation leads to what?
Irregular pulse with pulse deficit
Ventricular fibrillation
Ventricular bradycardia
Nodal rhythm
Atrial fibrillation leads to what?
Irregular pulse with pulse deficit
Ventricular fibrillation
Ventricular bradycardia
Nodal rhythm
The upstroke limb of the action potential in SAN cells is in response to what?
Opening of voltage gated K+ channels
Opening of voltage gated Na+ channels
Opening of T-Ca++ channels
Opening of L-Ca++ channels
The upstroke limb of the action potential in SAN cells is in response to what?
Opening of voltage gated K+ channels
Opening of voltage gated Na+ channels
Opening of T-Ca++ channels
Opening of L-Ca++ channels
About the A.R.P. in the heart, which statement is NOT true?
It lasts approximately as long as the cardiac contraction
During it, the heart can not be stimulated
It corresponds in time with the whole duration of the action potential
It is longer than the A.R.P. of skeletal muscle
About the A.R.P. in the heart, which statement is NOT true?
It lasts approximately as long as the cardiac contraction
During it, the heart can not be stimulated
It corresponds in time with the whole duration of the action potential
It is longer than the A.R.P. of skeletal muscle
About cardiac contractility, which statement is NOT true?
It depends on interaction between actin & myosin
It increases when the serum K+ rises above normal
It is lost if the bathing medium is made Ca++ -free
It decreases by local application of acetyl choline
About cardiac contractility, which statement is NOT true?
It depends on interaction between actin & myosin
It increases when the serum K+ rises above normal
It is lost if the bathing medium is made Ca++ -free
It decreases by local application of acetyl choline
In the heart, parasympathetic stimulation causes all of the following effects EXCEPT?
Increased ventricular contractility
Coronary V.C
Decreased atrial contractility
Decreased rate of discharge from the S.A.N
In the heart, parasympathetic stimulation causes all of the following effects EXCEPT?
Increased ventricular contractility
Coronary V.C
Decreased atrial contractility
Decreased rate of discharge from the S.A.N
About the pacemaker potential, which statement is NOT true?
Its slope is decreased by increased permeability to K
Its amplitude is –80 to –90 mV
It is unstable
The firing level occurs at a potential difference of about –45 mV
About the pacemaker potential, which statement is NOT true?
Its slope is decreased by increased permeability to K
Its amplitude is –80 to –90 mV
It is unstable
The firing level occurs at a potential difference of about –45 mV
What phase of the cardiac cycle is the heart not responsive?
Is the absolute refractory period
Extends all through the action potential
Is the relative refractory period
Is shorter than that in the skeletal muscle
What phase of the cardiac cycle is the heart not responsive?
Is the absolute refractory period
Extends all through the action potential
Is the relative refractory period
Is shorter than that in the skeletal muscle
Why is the S.A.N. considered the normal pacemaker?
Muscular structure
Rate of impulse discharge
Neural control
Location in the atrium
Why is the S.A.N. considered the normal pacemaker?
Muscular structure
Rate of impulse discharge
Neural control
Location in the atrium
Which cardiac tissue has slowed rhythmicity?
Ventricular muscle
S.A.N. without vagal tone
S.A.N. with vagal tone
Purkinje fibres
Which cardiac tissue has slowed rhythmicity?
Ventricular muscle
S.A.N. without vagal tone
S.A.N. with vagal tone
Purkinje fibres
What is true about a ventricular extrasystole?
Is usually not followed by a compensatory pause
May fail to produce a pulse at the wrist
Is usually not followed by post extrasystolic potentiation
Always indicates a serious heart disease
What is true about a ventricular extrasystole?
Is usually not followed by a compensatory pause
May fail to produce a pulse at the wrist
Is usually not followed by post extrasystolic potentiation
Always indicates a serious heart disease
Which statement about initiation & propagation of cardiac impulse is NOT true?
The cells of the SA-node have a steady resting potential of - 90 mV
The action potentials in the heart are about 100 times longer than those of skeletal muscles
The conducting tissue of the heart is composed of specialized cardiac myocytes linked by gap junctions
The spread of cardiac excitation is delayed by about 0.1 sec. at AVN
Which statement about initiation & propagation of cardiac impulse is NOT true?
The cells of the SA-node have a steady resting potential of - 90 mV
The action potentials in the heart are about 100 times longer than those of skeletal muscles
The conducting tissue of the heart is composed of specialized cardiac myocytes linked by gap junctions
The spread of cardiac excitation is delayed by about 0.1 sec. at AVN
What describes the contractile response of cardiac muscle?
Starts at the same time of electric excitation
Obeys the all or none law
Last for the same time as its action potential
Is triggered by the release of Ca++ from SR as in skeletal muscle
What describes the contractile response of cardiac muscle?
Starts at the same time of electric excitation
Obeys the all or none law
Last for the same time as its action potential
Is triggered by the release of Ca++ from SR as in skeletal muscle
In an ECG recording, what represents the time between atrial depolarization & ventricular depolarization?
QRS complex
P-wave
S-T interval
P-R segment
In an ECG recording, what represents the time between atrial depolarization & ventricular depolarization?
QRS complex
P-wave
S-T interval
P-R segment
Which statement about the ECG of an adult human is NOT true?
The R-wave coincides with depolarization of the apex of the heart
The P-wave coincides with depolarization of the atria
P-R interval of 0.3 seconds indicates impaired conduction
The Q-wave coincides with depolarization of the atria
Which statement about the ECG of an adult human is NOT true?
The R-wave coincides with depolarization of the apex of the heart
The P-wave coincides with depolarization of the atria
P-R interval of 0.3 seconds indicates impaired conduction
The Q-wave coincides with depolarization of the atria
What happens when activity in the SA-node is suppressed in a normal heart?
Shortening of the Q-T interval
Normal P-wave
A-V node becomes the pace maker of the heart
Prolongation of P-R interval
What happens when activity in the SA-node is suppressed in a normal heart?
Shortening of the Q-T interval
Normal P-wave
A-V node becomes the pace maker of the heart
Prolongation of P-R interval
At a heart rate of 72 beats per minute, which ECG interval is the longest?
Q-T interval
P-R interval
Duration of the QRS complex
Duration of the P-wave
At a heart rate of 72 beats per minute, which ECG interval is the longest?
Q-T interval
P-R interval
Duration of the QRS complex
Duration of the P-wave
In the ECG, what does the T-wave represent?
Ventricular depolarization
Atrial depolarization
Ventricular repolarization
Atrial repolarization
In the ECG, what does the T-wave represent?
Ventricular depolarization
Atrial depolarization
Ventricular repolarization
Atrial repolarization
If a person's ECG has no P-wave but normal QRS & T-wave, where is the pacemaker located?
AV-node
SA-node
Purkinje system
Bundle of His
If a person's ECG has no P-wave but normal QRS & T-wave, where is the pacemaker located?
AV-node
SA-node
Purkinje system
Bundle of His
Why do all ventricular muscle cells beat at the same time?
They are supplied by sympathetic nerves
Their number is small
They are supplied by the vagus nerve
They are connected to each other by intercalated disc
Which of the following does NOT describe cardiac muscle?
It exhibits myogenic rhythmicity
It is a functional syncitium
It is striated
It is an anatomical syncytium
Starling’s law of the heart states that the strength of contraction is proportional to what?
Myocardial oxygen supply
Stroke volume
The end diastolic volume
Arterial blood pressure
About cardiac muscle, which statement is NOT true?
Obeys the all or none law
Form true syncytium
There is almost a special capillary for each fibre
Low electric resistance of the membrane at the intercalated discs
Myocardial contractility is best correlated with the intracellular concentration of what?
Na
K
Cl
Ca
Which of the following agents does NOT have a positive inotropic effect on the heart?
Norepinephrine
Digitalis
Glucagon
Acetylcholine
What is the important function of the cardiac Purkinje system?
Increase the conduction of impulses
Amplify the cardiac impulses
Increase the force of ventricular contraction
Slow the conduction of impulses
Which statement about cardiac conductivity is NOT true?
It is decreased by vagal stimulation
It is slowest in the A-V node
It is slowest in the ventricular muscle
It is maximal in the Purkinje fibres
What effect does sympathetic stimulation have on the heart?
It decreases the permeability of S.A.N. to K
It decreases the slope of the prepotential
It increases the heart rate
It decreases the conduction time in the A.V.N
The pacemaker potential is primarily due to what?
Slow decrease in K+ permeability
Slow increase in K+ permeability
Slow decrease in Na+ permeability
Rapid increase in Ca++ permeability
Atrial fibrillation leads to what?
Ventricular fibrillation
Ventricular bradycardia
Nodal rhythm
Irregular pulse with pulse deficit
The upstroke limb of the action potential in SAN cells is in response to what?
Opening of T-Ca++ channels
Opening of L-Ca++ channels
Opening of voltage gated Na+ channels
Opening of voltage gated K+ channels
About the A.R.P. in the heart, which statement is NOT true?
It lasts approximately as long as the cardiac contraction
It corresponds in time with the whole duration of the action potential
It is longer than the A.R.P. of skeletal muscle
During it, the heart can not be stimulated
About cardiac contractility, which statement is NOT true?
It is lost if the bathing medium is made Ca++ -free
It depends on interaction between actin & myosin
It decreases by local application of acetyl choline
It increases when the serum K+ rises above normal
In the heart, parasympathetic stimulation causes all of the following effects EXCEPT?
Decreased atrial contractility
Decreased rate of discharge from the S.A.N
Coronary V.C
Increased ventricular contractility
About the pacemaker potential, which statement is NOT true?
It is unstable
Its amplitude is –80 to –90 mV
The firing level occurs at a potential difference of about –45 mV
Its slope is decreased by increased permeability to K
What phase of the cardiac cycle is the heart not responsive?
Is the relative refractory period
Is shorter than that in the skeletal muscle
Is the absolute refractory period
Extends all through the action potential
Why is the S.A.N. considered the normal pacemaker?
Neural control
Location in the atrium
Muscular structure
Rate of impulse discharge
Which cardiac tissue has slowed rhythmicity?
S.A.N. with vagal tone
Ventricular muscle
Purkinje fibres
S.A.N. without vagal tone
What is true about a ventricular extrasystole?
Is usually not followed by post extrasystolic potentiation
Always indicates a serious heart disease
Is usually not followed by a compensatory pause
May fail to produce a pulse at the wrist
Which statement about initiation & propagation of cardiac impulse is NOT true?
The spread of cardiac excitation is delayed by about 0.1 sec. at AVN
The action potentials in the heart are about 100 times longer than those of skeletal muscles
The conducting tissue of the heart is composed of specialized cardiac myocytes linked by gap junctions
The cells of the SA-node have a steady resting potential of - 90 mV
What describes the contractile response of cardiac muscle?
Last for the same time as its action potential
Starts at the same time of electric excitation
Obeys the all or none law
Is triggered by the release of Ca++ from SR as in skeletal muscle
In an ECG recording, what represents the time between atrial depolarization & ventricular depolarization?
QRS complex
S-T interval
P-wave
P-R segment
Which statement about the ECG of an adult human is NOT true?
P-R interval of 0.3 seconds indicates impaired conduction
The P-wave coincides with depolarization of the atria
The R-wave coincides with depolarization of the apex of the heart
The Q-wave coincides with depolarization of the atria
What happens when activity in the SA-node is suppressed in a normal heart?
Normal P-wave
Prolongation of P-R interval
A-V node becomes the pace maker of the heart
Shortening of the Q-T interval
At a heart rate of 72 beats per minute, which ECG interval is the longest?
P-R interval
Duration of the P-wave
Duration of the QRS complex
Q-T interval
In the ECG, what does the T-wave represent?
Atrial depolarization
Ventricular depolarization
Atrial repolarization
Ventricular repolarization
If a person's ECG has no P-wave but normal QRS & T-wave, where is the pacemaker located?
Bundle of His
AV-node
Purkinje system
SA-node
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