lecture of Cardiac physiology by Dr. Omid Nabavian; anesthesiologist; assistant professor in TUMS

1. Nabavian, O.; M.D.
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2. CARDIAC
PHYSIOLOGY
Miller’s Anesthesia
Chapter 16
Nabavian, O.; M.D.
Assistant Professor of Anesthesiology
TUMS
Vali-Asr Hospital
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3.  There
is difference between :
“ Intact heart” &
“ Isolated” heart muscle
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7. Ventricular structure
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8. Cardiac Vocabulary
 Preload:
Preload is the muscle length prior
to contractility, and it is dependent of
ventricular filling (or end diastolic volume…
EDV)
 The
most important determining factor for
preload is venous return.
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9. PReLOAD
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10. Cardiac Vocabulary
 Afterload:
is the tension (or the arterial
pressure) against which the ventricle must
contract.
 If arterial pressure increases, afterload also
increases.
 Afterload
for the left ventricle is determined by
aortic pressure.
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11. Afterload
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12. Law of Laplace


σ= P*R/2h
h = wall thickness
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13. Heart Rate and
Force-Frequency Relationship
 an
increase in the frequency of
stimulation induces an increase in the
force of contraction.
 This relationship is termed the “treppe”
phenomenon or
the force-frequency relationship
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15.  EF=(
LVEDV-LVESV)/LVEDV
 Stroke
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(External) work=SV * P
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16. Cardiac work
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17. External
work is expended to eject
blood under pressure, whereas
internal work is expended within
the ventricle to change the shape of
the heart and prepare it for
ejection.
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18. Diastolic Function
 (1)
Isovolumic relaxation
 (2) the rapid filling phase (80%)
 (3) slow filling, or diastasis;5%
 (4) final filling during atrial systole.
15%

 The
isovolumic relaxation phase is
energy dependent
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19. Assessing diastolic function
 (-dP/dt)
 Aortic
closing–mitral opening interval
 the isovolumic relaxation time
 peak rate of LV wall thinning as
determined by echocardiography
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20. CO=
SV * HR
Cardiac output in a living organism
can be measured with the
“Fick principle”
The Fick principle is based on the
concept of
conservation of mass
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21. Fick’s Principle
q1 =
× CpaO2
q3 =
× CpvO2
Because q1 + q2 = q3 ,
× (CpaO2 ) + q2 =
×(CpvO2
q2 =
× (CpvO2 ) −
× (CpaO2
q2 =
×(CpvO2 − CpaO2 )
= q2 /(CpvO2 − CpaO2 )
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23. Cellular Cardiac Physiology
Cellular
anatomy:
Cardiac
muscle tissue
 Conduction tissue
 Extracellular connective tissue
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26. Sarcoplasmic Reticulum (SR)
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Figure 9.526
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27. CARDIOMYOCYTE
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29. gap
junctions>>electrical
coupling
 “spot” desmosomes>>
mechanical linkage >>
cytoskeleton
 “sheet” desmosomes (or
fasciae adherens)>>
contractile apparatus
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30.  Cardiomyocytes
can be functionally
separated into:
 (1) the excitation system,
 (2) the ECC system,
 (3) the contractile system.
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31. Excitation System
Fast-response
action potentials>>
His-Purkinje system
atrial/ventricular
cardiomyocytes
 Slow-response action potentials,
pacemaker cells in the
SA and AV nodes
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34. phase
0:
much less steep,
phase 1: absent,
phase 2 :
indistinct from
phase 3 in the
slow-response
action potential
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35. ECC
Ca channel
phosphorylation
Faster contraction
Phospholamban
Faster relaxation

36. Pictorial E-C Coupling
Na+
Ca++
Sarcolemma
Na+ +
Na
Na+/Ca++ Exchanger
Ca++
Ca++
L-Type Ca++
Channel
Ca++
Ca++ Ca++
Ca++
Plb
SERCA
Ca++
Ca++
Ca++
Ca++
Ca++
++
Ca Ca++
Ca++
Ca++ Ca++ Ca++
++
Ca Ca++
++
Ca++
++
SR Ca++Ca
Ca Ca++ Ca++
RyR
Ca++
Ca++
Ca++
Ca++ Ca++
Ca
++
++
Ca +
+
Ca + C
++
+ a+
C+a ++
Ca ++
+
+
Ca Ca
Ca ++
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Ca ++
Ca ++ C
Ca ++
a+
+
Ca
Ca++
Ca++
Ca++
Ca +
Ca ++
Ca++
Ca++
+
a+ ++
+ C
Ca
++
Ca
++
Ca
++
Ca 36
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37. Contractile System
 The
basic working unit of contraction is
the sarcomere.
 A sarcomere is defined as the distance
between Z lines
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39. Sarcomere
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40. Nabavian, O.; M.D.
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41. Structure of Actin and Myosin
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42. Nabavian, O.; M.D.
Figure 9.4 (a)42
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(b)

43. Actin
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Figure 9.4 (c)43
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44. Troponin
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45. (+)
(−)
actin
myosin
(−)
actin
(+)
processive movement of
myosin V along F-actin
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47. actin

48. actin
troponin

49. tropomyosin
actin
troponin

50. tropomyosin
actin
troponin

51. myosin binding site
tropomyosin
actin
troponin

53. Ca2+
Ca
2+
Ca2+
Ca2+

54. Ca2+
Ca
2+
Ca2+
Ca2+
Calcium ions are released from the sarcolemma after stimulation from the T
system
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55. Ca
2+
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Ca2+
Ca2+
Ca2+
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56. Ca
2+
Ca2+
Ca2+
Ca2+
the calcium ions bind to the troponin and changes its shape
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57. Ca
2+
Ca2+
Ca2+
Ca2+
the calcium ions bind to the troponin and changes its shape
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58. Ca
2+
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Ca2+
Ca2+
Ca2+
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59. Ca
2+
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Ca2+
Ca2+
Ca2+
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60. Ca
2+
Ca2+
Ca2+
Ca2+
the troponin displaces the tropomyosin and exposes the myosin binding sites
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61. Ca
2+
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Ca2+
Ca2+
Ca2+
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62. Ca
2+
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Ca2+
Ca2+
Ca2+
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63. Ca
2+
Ca2+
Ca2+
Ca2+
the bulbous heads of the myosin attach to the binding sites on the actin
filaments
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64. Ca
Ca2+
2+
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Ca2+
Ca2+
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65. Ca2+
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Ca2+
Ca2+
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66. Ca2+
Ca2+
Ca2+
the myosin heads change position to achieve a lower energy state and
slide the actin filaments past the stationary myosin
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67. Ca2+
P i Pi P i A
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Ca2+
Ca2+
P i Pi Pi A
P i Pi P i A
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68. Pi Pi Pi A
Pi Pi Pi Ca2+
A
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Ca2+
P i Pi P i A
Ca2+
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69. Pi Pi Pi A
Pi Pi Pi Ca2+
A
Ca2+
P i Pi P i A
Ca2+
ATP binds to the bulbous heads and causes it to become detached
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70. Pi Pi Pi A
P i Pi P i A
P i Pi P i A
Ca2+
Ca2+
Ca2+
ATP binds to the bulbous heads and causes it to become detached
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71. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
Ca2+
Ca2+
Ca2+
hydrolysis of ATP provides the energy to “re-cock” the heads
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72. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
Ca2+
Ca2+
Ca2+
hydrolysis of ATP provides the energy to “re-cock” the heads
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73. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
Ca2+
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Ca2+
Ca2+
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74. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
Ca2+
Ca2+
Ca2+
calcium ions are re-absorbed back into the T system
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75. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
calcium ions are re-absorbed back into the T system
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76. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
the troponin reverts to its normal shape and the tropomyosin move back to block
the myosin binding sites
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77. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
the troponin reverts to its normal shape and the tropomyosin move back to block
the myosin binding sites
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78. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
the troponin reverts to its normal shape and the tropomyosin move back to block
the myosin binding sites
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79. Pi
Pi Pi A
Pi
Pi
Pi Pi A
Pi Pi A
phosphocreatine regenerates ATP
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80. Pi
Pi
Pi Pi A
Pi Pi A
Pi Pi Pi A
phosphocreatine regenerates ATP
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81. Pi Pi Pi A
P i Pi Pi A
P i Pi Pi A
phosphocreatine regenerates ATP
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82. Mechanism of muscle
contraction
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84. All Things Science - Heart excitation contraction coupling.flv - YouTube.FLV
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85. NEURAL REGULATION OF
HEART
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86.  At
rest the heart has a tonic level of PNS
 Atria have more PNS innervation than
ventricles
 M1-M5, M2 most one
 M1,3,5, G proteine
 M2,4 pertussis toxin
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87.  SNS
more prominent in ventricles
 α receptors >> G protein>> phospholipase
C,D,A
 β receptors >> G protein>> cAMP
 β1,2,3
 β1, both atria ventricle, 80% β2 atria 20%
ventricles
 β2>> β1
 α1,2>>α1A,B,D
 α1 : cardiac hypertrophy
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88. Adrenoreceptors
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89. Hormones affecting cardiac
function
Hormone
source
Cardiac action
Increase with CHF
Adrenomedullin
Cardiomyocyte
+ inotropy/
+chronotropy
+
Aldosterone
Cardiomyocyte
?
+
Angiotensin II
Cardiomyocyte
+ inotropy/
+chronotropy
+
Endothelin
Cardiomyocyte
?
+
Natriuritic peptide
ANP
Atria
BNP
Ventricles
Neuropeptide Y
Vasopressin
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+
+
- Inotropy
Post pituitary
+ inotropy/
+chronotropy
+
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92. Chemoreceptor Reflex
 Mediated
by
– Chemosensitive cells in the carotid bodies and
the aortic body.
– Sinus nerve of Hering and vagus nerves
 At
PaO2 <50 mm Hg or in acidosis
– respiratory centers stimulated and increasing
ventilatory drive.
 Activation
of the parasympathetic system
– reduction in heart rate and myocardial
contractility.
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93. Bainbridge Reflex
 Bainbridge
(atrial) reflex –
a sympathetic reflex initiated by
increased blood in the atria
 Causes
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stimulation of the SA node
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94. Bezold-Jarisch reflex



Elicited by
– chemoreceptors and mechanoreceptors within the
LV wall
– ↑ parasympathetic tone
Noxious ventricular stimuli induces the triad of
hypotension, bradycardia, and coronary artery
dilatation.
Less pronounced in patients with
– Cardiac hypertrophy
– Atrial fibrillation
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95. Valsalva Maneuver
 Valsalva
maneuver → ↓CO and BP.
 Sensed by baroreceptors → sympathetic
stimulation
 ↑heart rate and myocardial contractility.
 When
the glottis opens, venous return ↑
→↑BP.
 Sensed by baroreceptors → stimulate
parasympathetic efferent pathways to the
heart.
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96. Cushing Reflex
Cerebral ischemia at the medullary
vasomotor center
↓
Activation of the sympathetic nervous
system
↓
↑ HR, BP, and myocardial contractility
↓
Improve cerebral perfusion
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97. Oculocardiac Reflex
Stretch receptors
↓
Short and long ciliary nerves
↓
Ophthalmic division of the trigeminal nerve
↓
Gasserian ganglion
↓
Increased parasympathetic tone
↓
Bradycardia.
 Incidence
during ophthalmic surgery30% to 90%.
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