1. Cardiovascular Physiology14

2. Structure of the Heart The heart valves ensure one-way flow
Figure 14-7g

3. Heart Valves
PLAY
Animation: Cardiovascular System: Anatomy Review: The Heart
Figure 14-9

4. Heart Valves

5. Histology of Myocardium
Involuntary muscle
Striated, has sarcomeres
Many mitochondria
Uni- or binucleated
Branched
Intercalated Disc
Rhythmic contractions
Does not fatigue as easily as skeletal
Does not have individual neuromuscular junctions
Independent contractions
Require high O2

6. Cardiac Muscle versus Skeletal Muscle
Smaller and have single nucleus per fiber
Have intercalated disks
Desmosomes allow force to be transferred
Gap Junctions provide electrical connection
T-tubules are larger and branch
Sarcoplasmic reticulum is smaller
Mitochondria occupy one-third of cell volume

7. Excitation-contraction coupling and relaxation in cardiac muscle
Sarcoplasmic
reticulum
(SR)
ECF
ICF
T-tubule
Ca2+
spark
Ca2+ signal SR
Ryanodine
receptor-channel
Ca2+ ions bind to troponin
to initiate contraction.
Voltage-gated Ca2+
channels open. Ca2+
enters cell.
Ca2+ induces Ca2+ release
through ryanodine
receptor-channels (RyR).
Local release causes
Ca2+ spark.
Action potential enters
from adjacent cell.
Summed Ca2+ Sparks
create a Ca2+ signal. 1 2 3 4 5 6
Figure 14-11, steps 1–6

8. Excitation-contraction coupling and relaxation in cardiac muscle
Myosin
Relaxation
Contraction
ATP
Sarcoplasmic
reticulum
(SR)
ECF
ICF
Actin
T-tubule
Ca2+
spark
Ca2+ signal SR
Ryanodine
receptor-channel
stores
Ca2+ ions bind to troponin
to initiate contraction.
Relaxation occurs when
Ca2+ unbinds from troponin.
Voltage-gated Ca2+
channels open. Ca2+
enters cell.
Ca2+ induces Ca2+ release
through ryanodine
receptor-channels (RyR).
Local release causes
Ca2+ spark.
Ca2+ is pumped back
into the sarcoplasmic
reticulum for storage.
Action potential enters
from adjacent cell.
Summed Ca2+ Sparks
create a Ca2+ signal. 1 2 3 4 5 6 8 7
Figure 14-11, steps 1–8

9. Excitation-contraction coupling and relaxation in cardiac muscle
Myosin
Relaxation
Contraction
ATP
3 Na+
2 K+
Sarcoplasmic
reticulum
(SR)
ECF
ICF
Actin
T-tubule
Ca2+
spark
Ca2+ signal SR
Ryanodine
receptor-channel
stores
Ca2+ ions bind to troponin
to initiate contraction.
Relaxation occurs when
Ca2+ unbinds from troponin.
Na+ gradient is maintained
by the Na+-K+-ATPase.
Voltage-gated Ca2+
channels open. Ca2+
enters cell.
Ca2+ induces Ca2+ release
through ryanodine
receptor-channels (RyR).
Local release causes
Ca2+ spark.
Ca2+ is pumped back
into the sarcoplasmic
reticulum for storage.
Ca2+ is exchanged
with Na+.
Action potential enters
from adjacent cell.
Summed Ca2+ Sparks
create a Ca2+ signal. 1 2 3 4 5 6 9 10 8 7
Figure 14-11, steps 1–10

10. Myocardial Contractile Cells
Action potential of a cardiac contractile cell
Phase
Membrane channels
PX = Permeability to ion X
+20
-20
-40
-60
-80
-100
Membrane potential (mV)
100
200
300
Time (msec)
PK and PCa
PNa
Na+ channels open
Na+ channels close
Ca2+ channels open; fast K+ channels close
Ca2+ channels close; slow K+ channels open
Resting potential 1 2 3 4
Resting membrane potential is -90mv.
Na+ passes through double gated voltage channels
Plateau results from decreased K+ and increased Ca++
Plateau end when flux is reversed
Figure 14-13

11. Myocardial Contractile Cells
Refractory periods and summation in skeletal and cardiac muscle- this prevents summation as it happens in skeletal muscle
Figure 14-14c

12. Modulation of Heart Rate by the Nervous System
Sympathetic stimulation targets If channels to open rapidly.
Parasympathetic stimuation targets K+ and Ca++ channels, it hyper-polarizes the cell and slows depolarization
Figure 14-16

13. Electrical Conduction in Myocardial Cells
1% of myocardial cells are designed to spontaneously generate an action potential.
They can contract without outside signal= autorhythmic.
Pacemaker cells do not have sarcomeres
Figure 14-17

14. Electrical Conduction in Heart
THE CONDUCTING SYSTEM
OF THE HEART
SA node
AV node
Purkinje
fibers
Bundle branches
A-V bundle
Internodal
pathways
SA node depolarizes.
Electrical activity goes
rapidly to AV node via
internodal pathways.
Depolarization spreads
more slowly across
atria. Conduction slows
through AV node.
Depolarization moves
rapidly through ventricular
conducting system to the
apex of the heart.
Depolarization wave
spreads upward from
the apex. 1 4 5 3 2
Purple shading in steps 2–5 represents depolarization.
Figure 14-18

15. Electrical Conduction & Einthoven’s Triangle
AV node
Direction of electrical signals
Delay the transmission of action potentials
SA node
Set the pace of the heartbeat at 70 bpm
AV node (50 bpm) and Purkinje fibers (25-40 bpm) can act as pacemakers under some conditions

16. Electrical Activity
Comparison of an ECG and a myocardial action potential
Figure 14-22

17. The Electrocardiogram
ECG give info on heart rate, heart rhythm, conduction velocity, and heart condition. Three major waves: P wave, QRS complex, and T wave
Waves correspond to events of the cardiac cycle.
Figure 14-20

18. Electrical Activity
Correlation between an ECG and electrical events in the heart
P wave: atrial
depolarization P
START
Atria contract.
PQ or PR segment:
conduction through
AV node and A-V
bundle Q
Q wave
R wave R
S wave QS
ELECTRICAL
EVENTS
OF THE
CARDIAC CYCLE
Repolarization
ST segment
Ventricles contract. S
The end
T wave:
ventricular T
Figure 14-21

19. Electrical Activity
The P wave reflects the activity of the atria. The atria contract from top to bottom so the P-wave ends after full atrial depolarization
P wave: atrial
depolarization
START
Atria contract.
PQ or PR segment:
conduction through
AV node and A-V
bundle P
ELECTRICAL
EVENTS
OF THE
CARDIAC CYCLE
Figure (2 of 9)

20. Electrical Activity
The P-Q segment reflects the flow of current along the interventricular septum via the AV node and AV bundle. This is the time when the ventricles are relaxed and filling with blood
P wave: atrial
depolarization
START
Atria contract.
PQ or PR segment:
conduction through
AV node and A-V
bundle P Q
Q wave
ELECTRICAL
EVENTS
OF THE
CARDIAC CYCLE
Figure (3 of 9)

21. Electrical Activity
The QRS complex occurs while the ventricles contraction (depolarize) from the apex & upwards. At the end of the contraction all blood volume to be expelled as been pushed out.
S-T segment happens during ventricular repolarization (relax)
P wave: atrial
depolarization
START
Atria contract.
PQ or PR segment:
conduction through
AV node and A-V
bundle P Q
Q wave
R wave R
S wave QS
ELECTRICAL
EVENTS
OF THE
CARDIAC CYCLE
ST segment
Ventricles contract. S
Figure (6 of 9)

22. Electrical Activity
The T-wave indicates ventricular repolarization- meaning that the muscle is coming back to a resting state. At this point the chambers are ready to receive blood
P wave: atrial
depolarization
START P
The end R
PQ or PR segment:
conduction through
AV node and A-V
bundle P T QS P
Atria contract.
T wave:
ventricular
Repolarization
Repolarization
ELECTRICAL
EVENTS
OF THE
CARDIAC CYCLE R P T QS P
Q wave Q
ST segment R
R wave P R Q S P
Ventricles contract. R Q P
S wave QS
Figure (9 of 9)

23. Electrical Activity Normal and abnormal electrocardiograms
Figure 14-23

24. Mechanical Events Mechanical events of the cardiac cycle PLAY
START
Late diastole: both sets of
chambers are relaxed and
ventricles fill passively.
Atrial systole: atrial contraction
forces a small amount of
additional blood into ventricles.
Isovolumic ventricular
contraction: first phase of
ventricular contraction pushes
AV valves closed but does not
create enough pressure to open
semilunar valves.
relaxation: as ventricles
relax, pressure in ventricles
falls, blood flows back into
cups of semilunar valves
and snaps them closed.
Ventricular ejection:
as ventricular pressure
rises and exceeds
pressure in the arteries,
the semilunar valves
open and blood is
ejected. 5 4 1 2 3
PLAY
Animation: Cardiovascular System: Cardiac Cycle
Figure 14-24

25. Mechanical Events Figure 14-24, steps 1–2 Late diastole: both sets of
START 1 2
Late diastole: both sets of
chambers are relaxed and
ventricles fill passively.
Atrial systole: atrial contraction
forces a small amount of
additional blood into ventricles.
Figure 14-24, steps 1–2

26. Mechanical Events Figure 14-24, steps 1–3 1
START 1 2 3
Late diastole: both sets of
chambers are relaxed and
ventricles fill passively.
Atrial systole: atrial contraction
forces a small amount of
additional blood into ventricles.
Isovolumic ventricular
contraction: first phase of
ventricular contraction pushes
AV valves closed but does not
create enough pressure to open
semilunar valves.
Figure 14-24, steps 1–3

27. Mechanical Events Figure 14-24, steps 1–4 1
START 4 1 2 3
Late diastole: both sets of
chambers are relaxed and
ventricles fill passively.
Atrial systole: atrial contraction
forces a small amount of
additional blood into ventricles.
Isovolumic ventricular
contraction: first phase of
ventricular contraction pushes
AV valves closed but does not
create enough pressure to open
semilunar valves.
Ventricular ejection:
as ventricular pressure
rises and exceeds
pressure in the arteries,
the semilunar valves
open and blood is
ejected.
Figure 14-24, steps 1–4

28. Mechanical Events Figure 14-24, steps 1–5 1
START 5 4 1 2 3
Late diastole: both sets of
chambers are relaxed and
ventricles fill passively.
Atrial systole: atrial contraction
forces a small amount of
additional blood into ventricles.
Isovolumic ventricular
contraction: first phase of
ventricular contraction pushes
AV valves closed but does not
create enough pressure to open
semilunar valves.
relaxation: as ventricles
relax, pressure in ventricles
falls, blood flows back into
cups of semilunar valves
and snaps them closed.
Ventricular ejection:
as ventricular pressure
rises and exceeds
pressure in the arteries,
the semilunar valves
open and blood is
ejected.
Figure 14-24, steps 1–5

29. Cardiac Cycle
Left ventricular pressure-volume changes during one cardiac cycle A B C 65
100
135
Left ventricular volume (mL)
120 80 40
EDV
ESV D
Stroke volume
KEY
EDV = End-diastolic volume
ESV = End-systolic volume
One
cardiac
cycle
Left ventricular pressure (mm Hg)
Figure 14-25

30. Cardiac Cycle
At the beginning of the diastolic phase the ventricles are relax and contain a very small amount of blood A 65
100
135
Left ventricular volume (mL)
120 80 40
KEY
EDV = End-diastolic volume
ESV = End-systolic volume
Left ventricular pressure (mm Hg)
Figure (1 of 4)

31. Cardiac Cycle
At then of the diastolic phase the volume as increased because the ventricle has filled after the ventricles contracted A B 65
100
135
Left ventricular volume (mL)
120 80 40
EDV
KEY
EDV = End-diastolic volume
ESV = End-systolic volume
Left ventricular pressure (mm Hg)
Figure (2 of 4)

32. Cardiac Cycle
At point C (systole phase) the pressure has increased but the volume has not changed A B C 65
100
135
Left ventricular volume (mL)
120 80 40
Left ventricular pressure (mm Hg)
EDV
KEY
EDV = End-diastolic volume
ESV = End-systolic volume
Figure (3 of 4)

33. Cardiac Cycle
At the end of systole the pressure is at is highest and the volume has dropped. Stroke volume= EDV - ESV A B C 65
100
135
Left ventricular volume (mL)
120 80 40
EDV
ESV D
Stroke volume
KEY
EDV = End-diastolic volume
ESV = End-systolic volume
One
cardiac
cycle
Left ventricular pressure (mm Hg)
Figure (4 of 4)

34. Wiggers Diagram
This diagram shows the relationship between the cardiac cycle, the ECG, the heart sounds, and pressure changes in the left ventricle and aorta
Electro-
cardiogram
(ECG)
Pressure
(mm Hg)
Heart
sounds
Left
ventricular
volume
(mL)
Dicrotic
notch P
Cardiac cycle
Atrial
systole
Ventricular
diastole T S2 S1
Atrial systole
Early
Late
Isovolumic
contraction
pressure
Left atrial 65
135 30 60 90
120
Time (msec)
100
200
300
400
500
600
700
800
Aorta
QRS
complex
Figure 14-26

35. Wiggers Diagram
This shows the correlation between the carciac cycle and the ECG. Notice between the T wave of one and P wave of another the ventricles are relaxed while the atria are filling and beginning to empty prior to atrial depolarization
Electro-
cardiogram
(ECG) P
Cardiac cycle
Atrial
systole
Ventricular
diastole T
Atrial systole
Time (msec)
100
200
300
400
500
600
700
800
Early
ventricular
Late
Isovolumic
contraction
QRS
complex
Figure 14-26

36. Wiggers Diagram
Left
ventricular
volume
(mL)
Atrial
systole
Ventricular
diastole
Atrial systole 65
135
Time (msec)
100
200
300
400
500
600
700
800
Early
Late
Isovolumic
contraction
This phase shows the changes in blood volume as the ventricle contracts (depolarizes) or relaxes (repolarizes)
Figure 14-26

37. Wiggers Diagram
You can see the relationship between pressure chages in teh atrium and the cardiac cycle. Notice that the lowest atrial pressure is during ventricular diastole.
Pressure
(mm Hg)
Left
ventricular
volume
(mL)
Atrial
systole
Ventricular
diastole
Atrial systole
Left atrial
pressure 65
135 30 60 90
Time (msec)
100
200
300
400
500
600
700
800
Early
Late
Isovolumic
contraction
Figure 14-26

38. Wiggers Diagram
This shows changes in ventricular pressure and valve sounds as the AV valve (S1) and semilunar valves (S2) close.
Pressure
(mm Hg)
Heart
sounds
Atrial
systole
Ventricular
diastole S2 S1
Atrial systole
Left
ventricular
pressure
135 30 60 90
120
Time (msec)
100
200
300
400
500
600
700
800
Early
Late
Isovolumic
contraction
Figure 14-26

39. Wiggers Diagram
This shows changes in ventricular pressure and ventricular blood volume.
Pressure
(mm Hg)
Left
ventricular
volume
(mL)
Atrial
systole
Ventricular
diastole S2 S1
Atrial systole
pressure 65
135 30 60 90
Time (msec)
100
200
300
400
500
600
700
800
Early
Late
Isovolumic
contraction
Figure 14-26

40. Wiggers Diagram
The top line shows changes in pressure of the aorta as the left ventricle contracts or relaxes. The dicrotic notch occurs as a sharp drop in pressure results from a drop in blood flow once the ventricle begins to relax
Pressure
(mm Hg)
Heart
sounds
Dicrotic
notch
Atrial
systole
Ventricular
diastole S2 S1
Atrial systole
Left
ventricular
pressure 30 60 90
120
Aorta
Time (msec)
100
200
300
400
500
600
700
800
Early
Late
Isovolumic
contraction
Figure 14-26

41. Wiggers Diagram Figure 14-26 Pressure (mm Hg) Heart sounds Dicrotic
notch
Atrial
systole
Ventricular
diastole S2 S1
Atrial systole
Left
ventricular
pressure
Left atrial 30 60 90
120
Aorta
Time (msec)
100
200
300
400
500
600
700
800
Early
Late
Isovolumic
contraction
Figure 14-26

42. Wiggers Diagram
Electro-
cardiogram
(ECG)
Pressure
(mm Hg)
Heart
sounds
Left
ventricular
volume
(mL) P
Atrial
systole
Ventricular T S1
pressure
Left atrial 65
135 30 60 90
120
Time (msec)
100
200
300
Aorta
QRS
complex
This shows all the events that are happening during one complete ECG wave
Figure 14-26

43. This shows all the changes happening during ventricular diastole
Wiggers Diagram
Electro-
cardiogram
(ECG)
Pressure
(mm Hg)
Heart
sounds
Left
ventricular
volume
(mL)
Dicrotic
notch P
Cardiac cycle
Atrial
systole
Ventricular
diastole T S2 S1
pressure
Left atrial 65
135 30 60 90
120
Time (msec)
100
200
300
400
500
600
700
800
Aorta
Late
QRS
complex
This shows all the changes happening during ventricular diastole
Figure 14-26

44. These are all the events during one complete cardiac cycle
Wiggers Diagram
Electro-
cardiogram
(ECG)
Pressure
(mm Hg)
Heart
sounds
Left
ventricular
volume
(mL)
Dicrotic
notch P
Cardiac cycle
Atrial
systole
Ventricular
diastole T S2 S1
Atrial systole
pressure
Left atrial 65
135 30 60 90
120
Time (msec)
100
200
300
400
500
600
700
800
Aorta
Early
Late
Isovolumic
contraction
QRS
complex
These are all the events during one complete cardiac cycle
Figure 14-26