48 Questions
What is the main function of Purkinje fibers in the heart?
Transmit electrical impulses from AV node to apex
Which phase in the cardiac contractile cells is characterized by a much larger release of Ca2+ known as Ca2+ sparks?
Plateau phase
What is the unique feature of the membrane potential in cardiac contractile cells during the plateau phase?
Maintained close to the peak positive level
Which component of an ECG represents the ventricular repolarization phase?
T wave
What event in the heart causes the 'dub' sound in the cardiac cycle?
Closure of semilunar valves
Which condition is characterized by disorganized and chaotic contraction of the ventricles?
Ventricular fibrillation
What type of cells in the heart muscle are responsible for generating the pulse that causes contractions?
Autorhythmic cells
Which type of nerve uses acetylcholine to bind to muscarinic receptors in the atria and slow the heart down?
Parasympathetic nerve
What is the main ion movement responsible for giving rise to the pacemaker potential in autorhythmic cells?
Increased inward Na+ current
What percentage of cardiac muscle cells do Contractile cells make up?
99%
Which type of nerve uses noradrenaline and adrenaline to increase heart rate by binding to beta receptors of atria and ventricles?
Sympathetic nerve
Where are most of the long-lasting Ca2+ channels located in contractile cells?
Transverse tubules
What stimulates the opening of ryanodine receptor Ca2+ channels located on the sarcoplasmic reticulum?
Ca2+ influx from T tubules
What distinguishes Autorhythmic cells from Contractile cells?
Autorhythmic cells don't contract
Which of the following is not part of the normal electrical conduction pathway in the heart?
Internodal pathway
What is the function of the AV node in the heart's electrical conduction system?
Delays the AP to allow atrial contraction to complete
Which structure in the heart is known as the normal pacemaker?
SA node
What is the primary role of Purkinje fibers in the heart?
Conduct electrical signals to the ventricles
What is the role of autorhythmic cells in the heart?
Generating action potentials responsible for contraction
Which ion movement is essential for the pacemaker potential in autorhythmic cells?
Increased inward Ca2+ current
During which phase do contractile cells of the heart display pacemaker activity?
Resting phase
What is the primary function of the autonomic nervous system in cardiac muscle excitation?
Controlling heart rate through neurotransmitter release
Which type of nerve is responsible for slowing down the heart rate by binding to muscarinic receptors?
Vagus nerve
During which phase in the cardiac contractile cells is the membrane potential maintained close to the peak positive level, leading to a much larger release of Ca2+ known as Ca2+ sparks?
Plateau phase
Which specialized conducting fibers in the heart are larger than cardiomyocytes, have fewer myofibrils, and a large number of mitochondria, allowing for synchronized contractions of the ventricles?
Purkinje fibers
Which electrical structure in the heart transmits electrical impulses from the AV node to the apex of the heart?
Purkinje fibers
In cardiac excitation-contraction coupling, which ion's release from the sarcoplasmic reticulum induces muscle contraction in cardiac cells?
Calcium (Ca2+)
Which phase in cardiac contractile cells is characterized by the maintenance of a membrane potential close to peak positivity due to a higher release of Ca2+ and is unique to these cells?
Plateau phase
What is the primary function of the AV node in the heart's electrical conduction system?
Synchronization of atrial and ventricular contractions
During which phase of the cardiac cycle does Ca2+ enter the cytosol from the T tubules stimulating the opening of Ca2+ channels on the sarcoplasmic reticulum?
Plateau phase
Which component of the heart's electrical conduction system serves as the normal pacemaker and is responsible for generating the heart's electrical impulses?
SA node
What is the purpose of the delay that occurs at the AV node in the heart's electrical conduction system?
To ensure complete atrial contraction before ventricular excitation begins
Which part of the heart's electrical conduction system extends from the SA node to the AV node, ensuring coordination between the atria and ventricles?
Internodal pathway
What is the role of the SA node in the heart's electrical conduction system?
SA node is the normal pacemaker of the heart.
Describe the pathway of the interatrial pathway in the heart's electrical conduction system.
The interatrial pathway extends from the SA node within the right to the left atrium.
What is the function of the AV node in cardiac excitation?
AV node serves as the only point of electrical contact between the atria and ventricles.
How does the delay at the AV node impact the heart's electrical conduction system?
The delay at the AV node allows atrial contraction to be completed before ventricular excitation begins.
Explain the significance of the Bundle of His in the heart's electrical conduction system.
The Bundle of His is responsible for relaying signals from the AV node to the Purkinje fibers.
What is the primary function of Purkinje fibers in the heart?
Purkinje fibers are specialized for electrical conduction in the heart.
How do Ca2+ sparks contribute to excitation-contraction coupling in cardiac muscle cells?
Ca2+ sparks lead to a much larger release of Ca2+ from the sarcoplasmic reticulum, inducing muscle contraction.
What is the primary function of long-lasting Ca2+ channels in contractile cells?
Long-lasting Ca2+ channels in T tubules allow Ca2+ to enter the cytosol, leading to a larger Ca2+ release.
Explain the concept of electrical excitation-contraction coupling between cardiac and skeletal muscle.
Electrical excitation in cardiac muscle must be complete before contraction begins to ensure coordinated function.
What is the significance of the coordinated excitation between the atria and ventricles in the heart?
Coordinated excitation ensures that atrial contraction is complete before ventricular contraction begins.
The SA node is responsible for delaying the signals to move to the Bundle of His.
False
The interatrial pathway extends from the SA node within the right atrium to the left atrium.
True
Excitation of the ventricles should be complete before atrial excitation occurs for proper cardiac function.
False
The primary function of Purkinje fibers is to act as the normal pacemaker of the heart.
False
During the refractory period, cardiac cells experience a period of increased excitability.
False
Learn about the specialized conducting fibers, larger than cardiomyocytes, with fewer myofibrils and a large number of mitochondria, that play a crucial role in transmitting electrical impulses and allowing synchronized contractions of the heart's ventricles.
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