Cardiac cycle, ECG, Physiology Flashcards
What is the normal sequence of heart contraction and relaxation?
- Atria contract
- Ventricles contract
- Ventricles and atria both relax
The tricuspid and mitral valves are called _
The tricuspid and mitral valves are called atrioventricular valves
* They are open during filling ventricles but close during contraction of ventricles
The pulmonary valve and aortic valve are called _
The pulmonary valve and aortic valve are called semilunar valves
The volume in the ventricles following atrial systole, just prior to their contraction is called the _
The volume in the ventricles following atrial systole, just prior to their contraction is called the end-diastolic volume (EDV)
At rest, atrial contraction only contribues about 10% of the blood that fills the ventricles; the other 90% comes from _
At rest, atrial contraction only contribues about 10% of the blood that fills the ventricles; the other 90% comes from passive venous return during diastole
When the heart beat is increased, both systole and diastole shorten; however, _ is shortened more
When the heart beat is increased, both systole and diastole shorten; however, diastole is shortened more than systole
* During tachycardia atrial contraction becomes more important
* Atrial contraction might account for 40% of blood in this case
Phase 1 of the cardiac cycle is _
Phase 1 of the cardiac cycle is atrial contraction
Phase 2 of the cardiac cycle is _
Phase 2 of the cardiac cycle is isovolumetric ventricular contraction
* This is the first phase of ventricular systole
What happens during isovolumetric ventricular contraction phase?
- Isovolumetric = no blood moves out
- The pressure in the pulmonary artery and aorta are still greater
- The purpose is to increase the pressure in the ventricles so that ventricular ejection can occur
Once the pressure in the ventricles becomes greater than the pressure in the atria, the _ valves close
Once the pressure in the ventricles becomes greater than the pressure in the atria, the atrioventricular valves close
* This marks the start of isovolumetric ventricular contraction
What marks the end of isovolumetric ventricular contraction?
Semilunar valves open; this happens once the pressure in the ventricles exceeds the pressure in the great vessels –> semilunar open to allow blood flow –> begin rapid ejection phase
Phase 3 of the cardiac cycle is _
Phase 3 of the cardiac cycle is rapid ventricular ejection
Phase 4 of the cardiac cycle is _
Phase 4 of the cardiac cycle is reduced ventricular ejection
Phase 4 of the cardiac cycle, the last phase of ventricular systole is called _
Phase 4 of the cardiac cycle, the last phase of ventricular systole is called reduced ventricular ejection
In which phase of the cardiac cycle do venticules get to the end-diastolic volume?
Atrial systole: marks the EDV
After reduced ventricular ejection, is phase 5, _
After reduced ventricular ejection, is phase 5, isovolumetric ventricular relaxation
* The pressure within the great vessels is now greater than ventricular pressure so aortic and pumonary valves close
* Atriventricular valves are also still closed
Phase 6 is _ , when _ occurs
Phase 6 is rapid ventricular filling , when atrioventricular valves open and blood rapidly refills the ventricles
Phase 7 of the cardiac cycle is _
Phase 7 of the cardiac cycle is reduced ventricular filling
* Ventricular slows as the pressure gradient decreases
* Brings us back to phase 1, atria contraction
The dicrotic notch occurs just after _
The dicrotic notch occurs just after closing of the aortic valve
* Due to rebound of the elastic aorta
Coronary blood flow peaks during _ phase of the cardiac cycle
Coronary blood flow peaks during isovolumetric relaxation phase of the cardiac cycle
The greatest oxygen demand of the heart occurs during _ phase of the cardiac cycle
The greatest oxygen demand of the heart occurs during isovolumetric contraction
The QRS lines up with _ phase of the cardiac cycle
The QRS lines up with isovolumetric contraction phase; this is when ventricular depolarization occurs
S1 heart sound occurs during _ phase of the cardiac cycle
S1 heart sound occurs during isovolumetric contraction
S2 heart sound occurs during _ phase
S2 heart sound occurs during isovolumetric relaxation
The pressure of the internal jugular vein is a good estimate of the _ pressure
The pressure of the internal jugular vein is a good estimate of the right atrium pressure
We often see _ sign in patients with disorders that involve elevated right atrial pressure
We often see jugular vein distention (JVD) in patients with disorders that involve elevated right atrial pressure
A measured JVD > 3 cm indicated elevated central venous pressure which is often seen in _
A measured JVD > 3 cm indicated elevated central venous pressure which is often seen in right sided heart failure (inability to empty the right ventricle)
The “a wave” represents _
The “a wave” represents atrial systole
The “c wave” represents _
The “c wave” represents ventricular contraction causing the tricuspid valve to protrude into the atrium
* C for cusp
The “x descent” represents _
The “x descent” represents atrial relaxation and less back pressure into the right atrium from the ventricle
The “v wave” represents _
The “v wave” represents atrial venous filling
The “y descent” represents _
The “y descent” represents ventricular filling where blood is leaving the right atrium
The S1 sound comes from the closing of the _ valves
The S1 sound comes from the closing of the tricuspid and mitral valves
* The pressure in the ventricles during systole causes these valve to close
_ is our “lub” sound
S1 is our “lub” sound
_ is our “dub” sound
S2 is our “dub” sound
S2 sound comes from the closing of _
S2 sound comes from the closing of aortic and pulmonary valves
* The ventricles begin to relax during diastole and the pressure drops below the pulmonary trunk and aorta which closes the valves
Describe physiologic splitting of S2
S2 is normally heard as two separate closures of the aortic and pulmonary valves in quick succession
* These are called A2 and P2
* Splitting of S2 can be heard in a normal individual during inspiration
The S2 sound is normally split during (expiration/ inspiration)
The S2 sound is normally split during inspiration
Name three types of pathologic S2 splitting
- Wide-split S2
- Fixed-split S2
- Paradoxical (reversed) splitting
Wide-Split S2
Wide-Split S2: means that a normal S2 split is exaggerated; during expiration a small split is heard and during inspiration, a widened split will be heard
Wide-Split S2 is caused by any condition that delays the closure of the _
Wide-Split S2 is caused by any condition that delays the closure of the pulmonary valve (P2)
* Pulmonary arterial hypertension right ventricle must pump against steeper pressure gradient
* Right bundle branch block depolarization of the right ventricle is slowed
* Pulmonary stenosis pulmonary valve is stiff and moves slowly
Fixed-Split S2
Fixed-Split S2: the S2 split can be heard equally wide in expiration and inspiration
A fixed-split S2 is mostly associated with _ defects
A fixed-split S2 is mostly associated with atrial septal defect (ASD)
* There is an abnormal hole in the septum that separates LA from RA (blood flows left atrium–> right atrium)
* Extra blood goes to right ventricule –> extra blood goes to pulmonary valve –> delays closure
Paradoxical Splitting
Paradoxical splitting occurs from a condition that delays aortic valve closure
* Aortic stenosis
* Involves splitting during expiration instead of inspiration
* P2 occurs before A2
Sometimes we can have an additional heart sound, S3 during _
Sometimes we can have an additional heart sound, S3 during rapid ventricular filling (right after S2)
* Ken .. tuck-ky (S1.. S2,S3)
* We should not be able to hear ventricular filling normally –> indicates overfilled ventricle
In a normal child or athlete, an S3 sound represents _
In a normal child or athlete, an S3 sound represents tensing of the chordae tendineae around the AV valve during ventricular filling
* S3 gallops are also normal pregnant women who have high cardiac output states
Pathologically, S3 presents in patients with volume overload such as _
Pathologically, S3 presents in patients with volume overload such as aortic valve regurg or dilated cardiomyopathy
S4 heart sound also occurs after S2 but later in diastole; it is generally pathologic and occurs from _
S4 heart sound also occurs after S2 but later in diastole; it is generally pathologic and occurs from ventricular walls that are stiff and noncompliant
* Longstanding hypertension
* Aortic stenosis
* We are hearing the stiff walls recoil against the atrial kick
Cardiac output equation
CO = SV * HR
The heart rate is controlled by the autonomic nervous system and can be altered by changing the firing rate of _
The heart rate is controlled by the autonomic nervous system and can be altered by changing the firing rate of SA node
_ is the volume of blood expelled from the heart during one heartbeat (mL)
Stroke volume is the volume of blood expelled from the heart during one heartbeat (mL)
Stroke volume is proportional to contractility, which in most patients is determined by _
Stroke volume is proportional to contractility, which in most patients is determined by amount of calcium available in the cytoplasm
Digoxin (increases/ decreases) contractility by _ calcium levels; it is called an _
Digoxin increases contractility by increasing calcium levels; it is called an inotrope
An inotropic effect is one that _
An inotropic effect is one that increases intracellular calcium and contractility
The sympathetic nervous system increases contracility of the heart (atria and ventricles) by activating _ receptors
The sympathetic nervous system increases contracility of the heart (atria and ventricles) by activating beta1 receptors
The degree of ventricular stretching at the end of diastole is called _
The degree of ventricular stretching at the end of diastole is called preload
* Stroke volume is proportional to preload
The two parameters that can estimate preload are _ and _
The two parameters that can estimate preload are end-diastolic volume and end-diastolic pressure
Frank Starling Law
Frank starling law: stroke volume increases as preload increases
As sarcomere length increases, the number of actin and myosin cross bridges _ and contractility _
As sarcomere length increases, the number of actin and myosin cross bridges increases and contractility increases
A decreases in intrathoracic pressure will cause preload to (increase/ decrease)
A decreases in intrathoracic pressure will cause preload to increase
* Inverse relationship between intrathoracic pressure and preload
* When you take a deep breath, more venous blood returns to the heart
Afterload is the _
Afterload is the pressure against which the ventricle must work to eject blood from the heart
In normal physiology, the afterload is mostly determined by _
In normal physiology, the afterload is mostly determined by systemic vascular resistance
* This can be estimated by arterial blood pressure
* Afterload is inversely related to cardiac output
People with high blood pressure (hypertension) often have (high/low) systemic vascular resistance and (high/ low afterload)
People with high blood pressure (hypertension) often have high systemic vascular resistance and high afterload
* Aortic stenosis also increases afterload
The cardiac function curve plots _ on the x-axis and _ on the y-axis
The cardiac function curve plots EDV on the x-axis and cardiac ouput on the y-axis
Dobutamine and digoxin are both _ drugs which (increase/decrease) contractility
Dobutamine and digoxin are both inotropic drugs which increase contractility
(True/ False) The greater the pressure difference between the venous system and the right atrium, the greater the flow back to the heart
True; The greater the pressure difference between the venous system and the right atrium, the greater the flow back to the heart
* So a higher right atrial pressure, the smaller the venous return
The vascular function curve measures _ on the x-axis and _ on the y-axis
The vascular function curve measures right atrial pressure on the x-axis and venous return on the y-axis
The right artrial pressure at which the venous return becomes zero is called the _ ; it is the point when venous pressure is equal to the right atrial pressure
The right artrial pressure at which the venous return becomes zero is called the mean circulatory filling pressure ; it is the point when venous pressure is equal to the right atrial pressure
As venous tone increases, venous return (increases/ decreases)
As venous tone increases, venous return increases
As afterload increaes, venous return (increases/ decreases)
As afterload increaes, venous return decreases but MCFP does not change!
If we graph the cardiac and vascular function curves on the same graph, we get an intersection where the cardiac output matches the venous return and the system operates at a steady state; this is called the _
If we graph the cardiac and vascular function curves on the same graph, we get an intersection where the cardiac output matches the venous return and the system operates at a steady state; this is called the steady-state operating point
Which represents a vasoconstricting drug like NE and which represents a vasodilator like a calcium channel blocker?
Point 1: vasoconstricting drug like NE
Point 2: vasodilator like a calcium channel blocker
When does the mitral valve close?
When does the aortic valve open?
When does the mitral valve open?
When does the aortic valve close?
Determine systolic and diastolic BP from the graph
The area within the pressure-volume curve represents _
The area within the pressure-volume curve represents stroke work
* This is force exerted by LV times the volume ejected
What does this PV loop represent?
Increased preload
What does this PV loop represent?
Increased afterlod
What does this PV loop represent?
Increased contractility
Drugs that cause vasodilation like ACE inhibitors are useful in treating heart failure because they are able to _
Drugs that cause vasodilation like ACE inhibitors are useful in treating heart failure because they are able to decrease afterload
With an increase in contractility, the end-systolic pressure-volume relationship (ESPVR) line gets (steeper/ flatter)
With an increase in contractility, the end-systolic pressure-volume relationship (ESPVR) line gets steeper
Explain how the SA node, which can be spontaneously depolarized, gets activated by the sympathetic nervous system
- NE activates B1 receptors in the heart
- B1 receptor activation increases cAMP
- cAMP triggers the opening of more HCN channels (mixed Na+/ K+ channels that conduct funny current)
- Spontaneous depolarization
Positive chronotropy means _
Positive chronotropy means elevation of heart rate (via SA node activation)
Sympathetic innervation can also cause faster contraction through the AV node, which is called _
Sympathetic innervation can also cause faster contraction through the AV node, which is called positive dromotropy
* Instead of funny current, increasing inward Ca2+ steepens the AV node curve
SNS also directly increases _ which is termed positive inotropy
SNS also directly increases cardiomyocyte contractility which is termed positive inotropy
1. Increases Ca2+ current
2. Increases SERCA activity, increasing amount of Ca2+ stored inside the sarcoplasmic reticulum
Parasympathetic innervation of the heart via the vagus nerve is asymmetric; the right vagus mostly controls _ and left vagus mostly controls _
Parasympathetic innervation of the heart via the vagus nerve is asymmetric; the right vagus mostly controls SA node and left vagus mostly controls AV node
PNS will decrease the rate of the SA node in what is called _
PNS will decrease the rate of the SA node in what is called negative chronotropy
PNS will also decrease depolarization of the AV node in what is called _
PNS will also decrease depolarization of the AV node in what is called negative dromotropy
(True/ False) PNS causes negative inotropy
False; the PNS does not innervate ventricular cardiomyocytes so it has little to no direct effect of myocardial contractility
Blood pressure equation
BP = CO * SVR
The SNS has implications in blood pressure regulation because of its influence on _ specifically
The SNS has implications in blood pressure regulation because of its influence on vascular tone (impacts SVR)
Increasing SNS, (increases/ decrease) vascular tone
Increasing SNS, increases vascular tone (vasocontriction)
The net effect of NE on the vasculature is _
The net effect of NE on the vasculature is vasoconstriction
a1: vasoconstriction
b2: vasodilation
SNS is involved in BP control via three mechanisms:
- SNS stimulates renin from juxtaglomerular cells via b1 activation –> kidneys absorb sodium and water –> increase blood volume
- SNS constricts renal afferent arteriole (a1 receptors) –> decreases GFR
- Stimulates sodium reabsorption from renal tubules
Pacemaker cells have action potentials that lack step _ and _
Pacemaker cells have action potentials that lack step 1 and 2
What happens at each step of the cardiac myocyte AP?
Explain the difference between a voltage-gated Na+ channel that is resting vs. inactivated
Resting channel: closed; there is no ion movement but it is able to open in response to depolarization
Inactivated channel: no ion movement and it is unable to open due to absolute refractory period; inactivation gate is blocking it
Describe the steps of the nodal cell action potential
