What is the definition of the intrinsic cardiac conduction system?
It is the generation and conduction of action potentials by non-contractile myocardial cells (SA node, AV node, bundle of His, bundle branches, Purkinje fibers) that stimulate contractile myocardial cells to contract.
What are the types of nodal cells in the intrinsic cardiac conduction system?
What initiates the mechanism of depolarization in nodal cells?
The opening of funny Na+ channels (If) allows Na+ to enter, causing the resting membrane potential to move from -60mV to -55mV, stimulating T-type Ca++ channels.
What is the function of L-type Ca++ channels during depolarization?
They open at -40mV, allowing an explosive influx of calcium ions into the cell, moving the voltage from -40mV to +40mV, which depolarizes the nodal cell.
What is the threshold voltage for voltage-gated Na+ channels in contractile myocardial cells?
The threshold voltage is -70mV, which triggers Na+ channels to open and causes rapid depolarization of the cell.
What is the role of calcium ions in myocardial contraction?
Calcium ions stimulate the ryanodine receptor type 2, causing calcium to move from the sarcoplasmic reticulum into the cytoplasm, leading to muscle contraction.
The intrinsic cardiac conduction system includes the following components: - _______ - _______ - _______ - _______ - _______.
The intrinsic cardiac conduction system includes the following components: - Sinoatrial (SA) node - Atrioventricular (AV) node - Bundle of His - Bundle branches - Purkinje fibers.
The mechanism of depolarization begins with the opening of _______ which allows Na+ to enter the cell, moving the resting membrane potential to -55mV and stimulating _______.
The mechanism of depolarization begins with the opening of funny Na+ channels which allows Na+ to enter the cell, moving the resting membrane potential to -55mV and stimulating T-type Ca++ channels.
The threshold voltage for L-type Ca++ channels to open is _______ and allows an influx of calcium ions, moving the voltage to _______.
The threshold voltage for L-type Ca++ channels to open is -40mV and allows an influx of calcium ions, moving the voltage to +40mV.
In contractile myocardial cells, the threshold voltage for voltage-gated Na+ channels to open is _______, leading to rapid depolarization of the cell.
In contractile myocardial cells, the threshold voltage for voltage-gated Na+ channels to open is -70mV, leading to rapid depolarization of the cell.
What opens up actin heads to allow myosin to bind?
Presence of ATP
What is the voltage at the peak of nodal cell depolarization?
+40 mV
What channels open at +40 mV during nodal repolarization?
Voltage gated K+ channels
What happens to the inside of the cell when K+ leaves during repolarization?
It becomes increasingly negative
What is the resting membrane potential of the contractile myocardial cell?
-90 mV
What is the voltage at the peak of contractile cell depolarization?
+10 mV
What causes the voltage to plateau at 0 mV during repolarization?
K+ leaves at the same rate as Ca++ enters
What is the role of the ATP dependent Ca++/H+ exchanger?
To shunt calcium back into the sarcoplasmic reticulum
The intrinsic cardiac conduction system includes the _______, _______, and the _______.
The intrinsic cardiac conduction system includes the sinoatrial (SA) node, atrioventricular (AV) node, and the Bundle of His.
During the cardiac cycle, atrial depolarization begins and ends with the completion of _______.
During the cardiac cycle, atrial depolarization begins and ends with the completion of ventricular depolarization.
The action potential graph shows phases of _______ and _______.
The action potential graph shows phases of depolarizing and repolarizing.
What is the function of the SA node?
Pacemaker of the heart; sets the sinus rate and rhythm.
Where is the AV node located?
At the top of the interventricular septum.
What does the Bundle of His do?
Receives impulses from the AV node and conducts them to the bundle branches.
What is the function of Purkinje fibers?
Ensures the entire ventricular myocardium contracts as a unit (syncytium).
What is the intrinsic rate of the SA node?
60-80 beats/min.
What is the intrinsic rate of the AV node?
40-50 beats/min.
What is the intrinsic rate of the Bundle of His?
30-40 beats/min.
What is the location of Purkinje fibers?
In the sub endocardial layer of myocardium in the right and left ventricles.
What is the delay in conduction at the AV node?
Conducts impulses very slowly (0.1 second delay).
How does the AV node affect high-frequency impulses?
Reduces high frequency impulses from traveling into ventricles from atria in conditions like atrial fibrillation.
What area of the heart's electrical conduction is responsible for initiating the heartbeat?
Sinoatrial (SA) node
What is the function of the atrioventricular (AV) node?
It acts as a gatekeeper, slowing the electrical signal before it moves to the ventricles.
What does the bundle of His do in the heart's conduction system?
It transmits impulses from the AV node to the ventricles.
What are Purkinje fibers responsible for?
They distribute the electrical impulse throughout the ventricles.
What is the pathway of electrical conduction in the heart?
SA node → AV node → Bundle of His → Purkinje fibers
What is the definition of the intrinsic cardiac conduction system?
It is the generation and conduction of action potentials by non-contractile myocardial cells (SA node, AV node, bundle of His, bundle branches, Purkinje fibers) that stimulate contractile myocardial cells to contract.
What are the types of nodal cells in the intrinsic cardiac conduction system?
What initiates the mechanism of depolarization in nodal cells?
The opening of funny Na+ channels (If) allows Na+ to enter, causing the resting membrane potential to move from -60mV to -55mV, stimulating T-type Ca++ channels.
What is the function of L-type Ca++ channels during depolarization?
They open at -40mV, allowing an explosive influx of calcium ions into the cell, moving the voltage from -40mV to +40mV, which depolarizes the nodal cell.
What is the threshold voltage for voltage-gated Na+ channels in contractile myocardial cells?
The threshold voltage is -70mV, which triggers Na+ channels to open and causes rapid depolarization of the cell.
What is the role of calcium ions in myocardial contraction?
Calcium ions stimulate the ryanodine receptor type 2, causing calcium to move from the sarcoplasmic reticulum into the cytoplasm, leading to muscle contraction.
The intrinsic cardiac conduction system includes the following components: - Sinoatrial (SA) node - Atrioventricular (AV) node - Bundle of His - Bundle branches - Purkinje fibers.
The mechanism of depolarization begins with the opening of funny Na+ channels which allows Na+ to enter the cell, moving the resting membrane potential to -55mV and stimulating T-type Ca++ channels.
The threshold voltage for L-type Ca++ channels to open is -40mV and allows an influx of calcium ions, moving the voltage to +40mV.
In contractile myocardial cells, the threshold voltage for voltage-gated Na+ channels to open is -70mV, leading to rapid depolarization of the cell.
What happens to the inside of the cell when K+ leaves during repolarization?
It becomes increasingly negative
What causes the voltage to plateau at 0 mV during repolarization?
K+ leaves at the same rate as Ca++ enters
What is the role of the ATP dependent Ca++/H+ exchanger?
To shunt calcium back into the sarcoplasmic reticulum
The intrinsic cardiac conduction system includes the sinoatrial (SA) node, atrioventricular (AV) node, and the Bundle of His.
During the cardiac cycle, atrial depolarization begins and ends with the completion of ventricular depolarization.
What does the Bundle of His do?
Receives impulses from the AV node and conducts them to the bundle branches.
What is the function of Purkinje fibers?
Ensures the entire ventricular myocardium contracts as a unit (syncytium).
What is the location of Purkinje fibers?
In the sub endocardial layer of myocardium in the right and left ventricles.
How does the AV node affect high-frequency impulses?
Reduces high frequency impulses from traveling into ventricles from atria in conditions like atrial fibrillation.
What area of the heart's electrical conduction is responsible for initiating the heartbeat?
Sinoatrial (SA) node
What is the function of the atrioventricular (AV) node?
It acts as a gatekeeper, slowing the electrical signal before it moves to the ventricles.
What does the bundle of His do in the heart's conduction system?
It transmits impulses from the AV node to the ventricles.
What are Purkinje fibers responsible for?
They distribute the electrical impulse throughout the ventricles.
What is the pathway of electrical conduction in the heart?
SA node → AV node → Bundle of His → Purkinje fibers
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