can go thourh this slides once. dr anjani kumar jha ,nomc,nepal

1. CARDIAC CYCLE
DR ANJANI KUMAR JHA
RESIDENT,INTERNAL MEDICINE
NOBEL MEDICAL COLLEGE

2. The Cardiac Cycle
Cardiac cycle = the period between the start of
one heartbeat and the beginning of the next
 Consists of systole + diastole
 Systole=contraction
 Diastole=relaxation

3. The Cardiac Cycle
 Correlate the EKG with systole + diastole
of the heart
 Electrical events occur before mechanical
contraction
 EKG animation

5. The Cardiac Cycle
Atrial Cardiac Cycle
1. Atria passively fill (end of diastole)
2. Atria isovolumetrically contract (start of systole)
3. Atria eject blood into ventricles (end of systole)
4. Atria relax (start of diastole)
Ventricular Cardiac Cycle
1. Ventricles passively fill as atria fill and contract (end of
diastole)
2.-4. Same steps as above

6. The Cardiac Cycle

7. Blood Flow and Pressure
 During systole blood pressure increases
 During diastole blood pressure decreases
 Blood flows from high low pressure
 Contractions and valves dictate blood flow
through the heart

8. The Cardiac Cycle
 Start at ventricular diastole and left side of
heart (highest pressure values)
 Blood flows from high low pressure
 Contractions and valves dictate blood flow
 Blood pressure in each chamber rises during
systole and falls during diastoles

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Ventricular fillingVentricular filling
Mid-to-late
diastole
Atrial contraction
Isovolumetric
contraction
Ventricular
ejection
Isovolumetric relaxation
OpenAtrioventricular valves
Aortic and pulmonary
(semilunar) valves
Phase
Open
Ventricular
pressureAtrial
pressure
Ventricular
volume
Aortic pressure
OpenClosed
ClosedClosed
1 2 3 4 1
Left atrium
Right atrium
Right ventricle
Left ventricle
Electrocardiogram
Heart sounds
Systole
Early diastole
110
70
40
0
130
100
60
Pressure(mmHg)volume(mL)

10. Copyright © 2011 Pearson Education, Inc.

13. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. The Cardiac Cycle
1. Ventricular Filling (Phase 1 on diagram)
 Blood relaxed atria atrioventricular valves ventricles
 Driven by pressure in veins (venous return)
 Atria contract more blood in ventricles atria diastole
 and ventricular systole begins
2. Isovolumetric Contraction (Phase 2)
 Ventricles start to contract (systole)
 Ventricular pressure > atrial pressure  AV valves close
 Semilunar valves are closed because ventricular pressure <
pulmonary + aortic arterial pressures
 So, no blood flowing=isovolumetric-same volume

16. The Cardiac Cycle
3. Ventricular Ejection (Phase 3)
 Ventricles continue contracting
 Ventricular pressure > aortic pressure
 Blood aorta + pulmonary arteries (ventricular ejection)
4. Isovolumetric Relaxation (Phase 4)
 Eventually ventricular pressure < aortic pressure semilunar
valves close—start of diastole
 All valves are closed so some blood is still in ventricles as they
relax
 Ventricular pressure < atrial pressure so AV valves open and
ventricle passively fill with blood until they contract again

17. Copyright © 2011 Pearson Education, Inc.
Ventricular Pressure

18. Copyright © 2011 Pearson Education, Inc.
Aortic Pressure

19. Aortic Pressure
 During ventricular contraction the aorta stored
energy by stretching (pressure reservoir)
 During ventricular diastole aorta releases pressure
to maintain blood flow to body
 This is why aortic pressure is higher than
ventricular pressure during diastole
 MAP=profusion pressure to organs
 Dicrotic notch shows semilunar valves closing

20. Copyright © 2011 Pearson Education, Inc.
Heart Sounds
**Heart Murmur=sounds produced by regurgitation through valves

21. Copyright © 2011 Pearson Education, Inc.
Changes in Ventricular Volume
** Left ventricle

22. Cardiodynamics
Figure 20–19 A Simple Model of Stroke Volume

23. Cardiodynamics
 The movement and force generated by cardiac
contractions
 End-diastolic volume (EDV)
 End-systolic volume (ESV)
 Stroke volume (SV)= volume of blood ejected per beat
 SV = EDV – ESV
 Ejection fraction
 The percentage of EDV represented by SV
 Cardiac output (CO)
 The volume pumped by left ventricle in 1 minute
 CO=SV X HR

24. Na+ and Ca2+ influx
Sympathetic neurons
(NE or Epi)
Rate of depolarization
Heart rate
Muscarinic receptors
of autorhythmic cells
K+ efflux; Ca2+ influx
Parasympathetic
neurons (Ach)
Hyperpolarizes cell and
rate of depolarization
Heart rate
1-receptors of
autorhythmic cells
Integrating center
Efferent path
Effector
Tissue response
Cardiovascular
control
center in medulla
oblongata
KEY
Catecholamines Modulate HR

25. Catecholamines Modulate SV

26. Stroke Volume & Starling’s Law
Increase EDV by increasing venous return
via:
• Skeletal muscle pump
• Respiratory pump
• Sympathetic nervous system
• Arterial vasoconstriction
Increase strength of contraction
Increase stroke volume
Increase stretch of cardiac fibers

27. Starling’s Law

28. Green= w/ adrenergic stimulation
Blue= normal
Yellow and red= heart failure; increased volume does not equal increase contraction
and stroke volume

29. Stroke Volume and Heart Rate Determine Cardiac Output
determined by
is influenced by
which varies with
is a function of
increases
increases
determined by
CARDIAC OUTPUT
aided by
Heart rate
Due to
parasympathetic
innervation
Sympathetic
innervation and
epinephrine
Venous returnVenous constriction
End-diastolic
volume
Rate of depolarization
in autorhythmic cells
Stroke volume
Contractility
Respiratory
pump
Skeletal muscle
pump
Decreases Increases
Force of contraction in
ventricular myocardium

30. Arterial Blood Pressure (mm Hg)
Pressure in the aorta varies with the cardiac
cycle.
Two pressure readings:
 Systolic blood pressure = maximum pressure
 Due to ejection of blood into aorta
 Diastolic blood pressure = minimum pressure
 Not zero due to elastic recoil of aorta
 Normal BP 120/80 mm Hg
 Higher than normal= hypertension
 Lower than normal= hypotension
30

31. Figure 14.8
Arterial blood pressure
31

32. Blood pressure values: what do they mean?
Pulse pressure (PP)= SP-DP
 Force your heart generates when it contracts
 Use SP, DP, and PP as indicators of cardiovascular health
 Patient 1: 120/80; PP=?
 Patient 2: 140/100; PP=?
 Who is at greater risk?
MAP = DP + 1/3 (SP-DP)
 Pressure required to profuse brain, coronary arteries, and
kidney with blood
> 60 mm Hg
CO = MAP
TPR
CO = SV x HR 32

46. REFERENCES:
 GUYTON AND HALL TEXTBOOK OF MEDICAL
PHYSIOLOGY,13TH EDITION
 GANONG’S REVIEW OF MEDICAL
PHYSIOLOGY,26TH EDITION
 USMLE FIRST AID,2018

47. THANK YOU