Cardiac Cycle And Sounds Flashcards
1
Q
Where does the fast action potential occur inc radial tissue?
A
In atrial and ventricular myocytes
2
Q
Where does the slow action potential of cardiac tissue occur?
A
In SA and AV nodes
3
Q
What results in the slow action potential of the SA and AV nodes?
A
Influx of Ca instead of Na
4
Q
What are the phases of the fast action potential in hte atrial and ventricular myocytes?
A
Phase 1 - initial repolarization
Phase 2 - plateau phase
Phase 3 - Repolarization
Phase 4 - heart at rest
Phase 0 - rapid upsweep
5
Q
What occurs in Phase 1 of the Fast Action potential seen in cardaic tissue?
A
Initial repolarization
- na channel closed (na doesn’t enter)
- voltage gated k channel open (k leaves)
—> causes cell to become more negative and repolarize
6
Q
What occurs in Phase 2 of the Fast Action potential seen in cardaic tissue?
A
Plateau phase
- ca channels open, Ca (+) leaves
- k channels still open
- negative and positive charges leaving stabilize RMP at more positive value
7
Q
Why is there no phase 2 in the Slow action potential of SA and AV node tissue?
A
Bc SA and AV node tisssue is NOT contractile
8
Q
What occurs in Phase 3 of the Fast Action potential seen in cardaic tissue?
A
Repolarization
- ca channels close
- voltage gated k channels still open
9
Q
What occurs in Phase 4 of the Fast Action potential seen in cardaic tissue?
A
Heart at rest
- Na, K and Ca voltage gated channels = clsoed
- cell at normal RMP = -70 - -90 mV
10
Q
What occurs in Phase 0 of the Fast Action potential seen in cardaic tissue?
A
Rapid upswept
- voltage gated Na Chanel opens
- cell is rapid DEPOLARIZED
11
Q
What are the phases seen in the SLow Action Potential of SA and AV nodal tissue?
A
Phase 4 - resting membrane potential (heart at rest)
Phase 0 - depolarization via Ca
Phase 3 - repolarization
12
Q
What occurs in Phase 4 of the Slow Action potential seen in cardaic tissue?
A
Resting membrane potential
- steady depolarization (never a plateua phase)
- Open Funny Na channels
13
Q
How do funny sodium channels contribute to heart rate?
A
How fast theses channels open
—> faster the depolarization
—> faster SA cells to threshold
—> faster HR
14
Q
Where are most Funny Na channels located?
A
Most are at SA node
^why the SA node serves as heart’s pacemaker
(brought to threshold fastest)
2nd most at AV node (backup pacemaker)
15
Q
What occurs in Phase 0 of the Slow Action potential seen in cardaic tissue?
A
Depolarization via Ca
- influx of Ca from extracellular fluid via ca channels
- ca is larger than Na causes a slower influx and overall slower rate of depolarization
16
Q
What occurs in Phase 3 of the SLow Action potential seen in cardaic tissue?
A
Repolarization
-K leaves via its voltage gated channels
17
Q
What does a P wave mean on a normal ECG?
A
Atrial depolarization
-initiated by SA node depolarization (influx of Na)
18
Q
What does a QRS complex mean on a Normal ECG?
A
Represent Ventricular Depolarization
Sum of all phase 0s - depolarization
19
Q
What wave is hidden in the QRS complex?
A
Wave for atrial REpolarization
20
Q
What does the T wave represent on a normal ECG?
What permeability would be high?
A
Ventricular Repolarization
K potassium permeability is high
21
Q
Where is the PR interval?
What does it represent?
A
P wave —> beginning of QRS
Represents time for depolarization to pass from ATRIA to VENTRICLES via AV node
22
Q
What is the most important determinant of the PR interval?
A
Slow conduction velocity of the AV node
23
Q
What would we see when there is damage to the AV Node?
A
Prolonged PR interval
24
Q
Where is the ST Segment?
What does it represent?
What has high permeability at this time?
A
End of QRS —> beginning of T wave
Represent Phase 2 of fast actin potential (plateau)
Ca has high permeability (will leave to help counter-act the K leaving)
25
Where is the QR interval?
What does it represent?
Beginning of QRS —> end of T-wave
Represent total time any ventricular myocytes are depolarized
26
What does the Cardaic cycle start with in the Wigger’s diagram?
Starts w/ P wave in ECG
27
What does the x-axis of the Wigger’s diagram represent?
Time (ms)
28
What are the units of the Y-axis of the Wigger Diagram?
Volume (mL) or pressure (mmHg)
29
What are the 4 pressures tracked on the Wigger’s Diagram?
Aortic pressure
Ventricular pressure
Atrial pressure
Jugular venous pressure
30
What do changes in pressure produce?
Volume changes
31
What is the route of blood thru the heart after entering via the Inferior and Superior Vena Cava?
1. Blood enters via inferior and superior vena cava
2. O2 poor blood —> RA
3. RA —tricuspid valve —> RV (atrial contraction)
4. RV contracts (ventricular contraction)
5. RV —pulmonic valve —> Pulmonary A. —> lungs
6. Lungs —> Pulmonary Vs.
7. Pulmonary Vs. w/ Oxygen rich blood —> LA
8. LA —bicuspid valve (mitral) —> LV (atrial contraction)
9. LV —aortic valve —> aorta —> body
32
What is the Dicrotic Notch produced by?
Produced by closing of the aortic valves as ventricles relax
33
What is the A-wave?
Result of atrial contraction
| Increase in atrial pressure
34
What is the C -wave?
Coincides with ventricle contraction
| Increase in atrial pressure bc of AV bulgin backward
35
What causes a V -wave?
Due to venous return accumulating in atria (causing increase in atrial pressure)
36
The jugualr pressure curve is same as what other pressure curve?
Atrial
Due to non-functional valve b/w jugular v. And RA
37
What is the End Systolic volume?
When is it measured?
Lowest volume of blood in the ventricle @ ~50 mL
Measured right after aortic valve closes (end of systole)
38
What is the End-diastolic volume?
When the volume is at maximum capacity
39
When is hte rapid filling phase?
Tuburlen blood flow into the ventricles rapidly increased ventricular volume
40
When is the first heart sound heard?
W/ closing of AV valves at beginning of Period of Isovolumetric Contraction
41
When is the 2nd heart sound heard?
W/ closing of Aortic/Pulmonic Valves
| Aka same time as Dicrotic notch in aortic pressure wave
42
When is the 3rd heart sound heard?
Period of rapid filling of ventricle after AV valve opens
43
When is the 4th heart sound heart?
When blood is being forced into ventricle during atrial contraction
44
What can cause abnormal heart sounds (2)?
Blood going in Wrong Direction (regurgitation)
Blood has trouble going in the RIght direction (stenosis)
45
What do almost all murmurs reflect?
Changes to the valves
46
What is stenosis of a valve?
Narrowing
Valve doesn’t fully open when it is supposed to making it hard for proper blood flow
47
What is regurgitation?
Valve can’t close or stay close
Blood will flow in wrong direction
48
What is a systolic Murmur?
Murmur is superimposed b/w lub and dub (during ventricular systole)
49
What are the 2 things that can cause a systolic murmur?
1. Stenosis of Aortic/pulmonic valves (would normally be open)
2. Regurgitation of AV valves
(Should be closed)
50
What are the two things that can cause a Diastolic Murmur?
1. Regurgitation of Aortic/pulmonic valves (should be closed)
2. AV valve stenosis (should be open)
51
At the P-wave, how are the atria and ventricles?
Both in diastol
52
How is the electrical activity at time of the P wave?
P-wave = atrial depolarization
- Both atrial and ventricular myocytes are in Phase 4 (RMP)
- SA and AV node in Phase 4 (RMP w/ funny Na channels)
53
What are the physical conditions of the heart during the P-wave?
P-wave = atrial depolarization
- AV valve open, Aortic/pulm. Valves closed
- both atria & ventricle at rest
- blood is entering ventricles
54
What is the atrial pressure @ diastole?
4 mmHg
55
What is the ventricular pressure during Diastole?
Close to 0 (allows blodo from atria to get into ventricles)
56
At the P wave, how are the pressures of the Pulmonary a., aorta and jugular v.?
PA and Aorta approaching diastolic values bc blood is moving to periphery
Jugualr v. Has higher pressure than both atria and ventricle (so blodo can leave it)
57
The rate at which blood leaves the aorta/pulmonary a. Is determined by what?
By the resistance to blood flow
Vascoconstriction = high resistance = higher diastolic pressure
Vasodilation = low resistance = lower diastolic pressure
58
Atrial contraction causes what changes in pressure?
Increases atrial pressure slightly
Increases ventricular pressure too
59
What causes the delay in ventricular contraction?
Delayed ventricular depolarization due to slow conduction velocity thru AV Node
** this is crucial to normal functioning of the heart
60
Ventricular contraction causes what changes in pressure?
Increases ventricular pressure to get up to systolic pressure (120 mmHg)
Slightly increases atrial pressure bc of reverse building of AV valve
61
Ventricular relaxation causes what changes in pressure?
Decreases ventricular pressure until it is in diastole
62
What are heart sounds a result of?
Result of vibrations produced by blood moving (to not being able to move)
63
What does atrial systole do?
Atrial systole = atrial contraction
Will top off ventricular volume and produce the 4th heart sound
64
What does Ventricular systole start rom?
Start from level added by Atria
65
How is aortic pressure affected by atrial systole?
It is not affected
-it will continually decrease during as blood leaves aorta for periphery
66
At the end of atrial systole, how are the conditions of the heart?
- atria is relaxing, pressure decreasing
- AV valves are open
- aortic/pulmonary valves are closed
- QRS complex has/is occurring
67
What happens to ventricular pressure at the beginning of ventricular systole?
Rapidly increases and exceeds atrial pressure w/in milliseconds
Causes AV vlaves to close = first heart sound
68
What is the first heart sound caused by?
Closing of AV valves that causes the blood entering the atria to hit the now closed valve/cardiac structure
69
How are the aortic/pulmonic valves during ventricular systole?
What does this cause?
Aortic/pulmonic valves are closed
Causes Period of unchanged ventricular volume
—> Isovolumetric contraction period
70
What happens during the Peirod of Isovolumetric contractioN?
Ventricle contract, increase the pressure
Causes AV valves to bulge back and increases atrial pressure
(thus increases venous pressure)
Aortic pressure decreases
71
How are AV valves prevented from everting during the Period of Isovolumetric contraction?
Prevented from everting by contraction of the papillary muscles attached to the valve leaflets
72
What will end isovolumetric contraction?
The opening of the Aortic/pulmonic valves
73
What are the normal blood pressure of the Aorta?
120 = when aortic valve is opened
70 = when aortic valve is closed and just about to open
74
What is the Normal blood presssure of the Pulmonary a.?
25 = when pulmonary valve open
15 = when pulmonary a. Is in diastole
75
In order to open the pulmonary valve or aortic valve, ventricular pressure must be greater than what?
Must be greater than the diastolic pressure in each artery
| Greater than 70 and greater than 15
76
What happens to the ventricular volume and pressure as ejection of blood occurs?
Ventricular volume decreases
Ventricular pressure initially increase to peak systolic pressure and as ejection occurs, it drops
77
What causes the drop in ventricular pressure during the ejection of blood?
Due to,
1. Less blood in ventricle
2. Less able to generate pressure (squeezing on something empty)
78
What is occurring, electrically, during the ejection of blood?
T-wave occurs (depolarization of ventricular myocytes)
-need this to occur so we can enter ventricular relaxation)
79
What happens to the aortic pressure during ejection of blood
Initially increases and then slowly declines as blood leaves to go to periphery
80
What happens t atrial prssure during the ejection of blodo?
Atrial pressure increases due to blood accumulating in atria
81
What happens to ventricular and aortic pressure during ventricular relaxation?
Pressure drop
-ventricle pressure drops faster than aortic pressure
82
What is the rate of blood moving into he periphery dictated by?
Total peripheral resistance (TPR)
83
What is Total Peripheral resistance determined by?
By how much vasoconstriction/vasodilation there is
84
When do the aortic/pulmonary valves close?
When Pventricle < Paorta/pulmonary
85
What does the closing of the Aortic/pulmonic valves cause?
Causes S2 and dicrotic notch
86
What causes the Dicrotic notch?
The dip and rapid rise in aortic blood pressure is cause by back flow of blood when aortic/pulmonic valves close
(Is quickly corrected as blood that moved backward resumes normal direction of flow)
87
What is occurring during the Period of Isovolumetric relaxation ?
AV and aortic/pulmonic valves = closed
Ventricle is relaxing, pressure dropping
Pressure in aorta also dropping (though slow)
88
When does the Peirod of Isovolumetric relaxation end?
When Patria > Pventricle
89
What will the venous return of blood to the atrium cause?
Causes gradual increase in atrial pressure
Opens AV valves
90
How is Ventricle filling initially?
Initially is a rapid process bc blood has acccumulated in atria
blood hitting left over blood = 3rd heart sound
91
What causes the slow filling of the ventricle?
Filling slows down due to Elastic Recoil of Ventricle
92
What is the Period of slowed filling called?
Diastasis
93
What does the heart spend the majority of its time in?
Diastole
94
What will a change in heart rate affect more, diastole or systole?
Diastole
95
What will a fast HR sacrifice?
Causes a decrease in what?
Will sacrifice ventricular filling time, decreases BP
96
What will a low HR do?
Causes prolonged diastole
97
What is the A-wave in the jugular pressure graph:
Atrial contraction
| Pressure generated by contraction is reflected back into the great veins bc of non functioning valves
98
What is the C wave in the jugualr pressure curve?
C-wave = isovolumetric contraction Peirod
Bulging of AV valves, increases atrial pressure, therefore increasing jugular pressure
99
What is the V-wave in the Jugular pressure curve?
V wave = ventricular contraction
- blood begins to accumulate in atria, increasing pressure, therefore venous pressure is also higher
100
How is pressure on the right side of the heart compared to the left?
Lower pressure due to low resistance in pulmonary vascular bed
101
What is th pressure of the
Right ventricle compared to Left V.?
P-RV = 20/0
P-LV = 120/0
102
What is the prssure of the
Pulmonary a. Vs the aortic a. ?
P-PA = 25/15
P-aorta = 120/80
103
How does the amount of blood pumped differ form the RV to LV?
No difference
RV = LV
104
How do the pressure curves change from R side of heart to L?
Pressure curves have the same shape but different amplitudes
105
What side are normal heart sounds heard from?
They are heard from BOTH sides, not just left
