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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Heart and circulation
ƒMyocardial physiologic properties
ƒCardiac function
ƒPhysiology of blood vessel
ƒRegulation of cardiovascular activity
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Pulmonary
circulation
System
circulation
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
2009/4/11
April, 2009
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Myocardial physiologic Properties
ƒExcitability
Electorphysiologic
ƒConductivity
Properties
ƒAutorhythmicity
ƒContractility
Cardiac myocytes:
Working cell Atrial &Ventricular muscle
Autorhythmic cell Specific conduction system
Sino-atrial node (S-A node) Pacemaker cell
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Specific conduction system
Myocardial physiologic Properties
1.Membrane potential
Neuron
1）Working cell
Ca in
Resting Potential: -90mv K+
Na
in
K out
Ventricles
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Action Potential:
0: INa, Fast, 1ms Depolarization
1: Ito (Transient outward K+ currents)
2: ICa(Plateau) 0mv, 100~150ms
3: Ik, 100~150ms
4: Na+-Ca2+ exchanger,Na+pump
Repolarization
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Table 1. ION CONCENTRATIONS AND EQUILIBRIUM POTENTIALS IN CARDIAC
MUSCLE CELLS
Ion
Extracellular
Concentration(mM)
Na+
145
Intracellular
Concentration(mM)
Equilibrium
Potential(mV)
10
70
K+
4
140
-94
Ca++
2
10-4
132
Data from Ten Eick RE et al: Prog Cardiovasc Dis 24:157, 1981.
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Myocardial physiologic Properties
2）Autorhythmic cell
Pk Maximum depolarizing potential 0mv
Ca2+in
Pca,L
K+out
Maximum repolarizing potential
-70mv
Pk
SA node
Phase 0
7ms
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Slow
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Myocardial physiologic Properties
3）Refractory Period
-55mv
-60mv
-80mv
long
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Extrasystole &
Compensatory pause
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Skeleton
muscle
Cardiac muscle
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Myocardial physiologic Properties
4）The factors affecting myocardial excitability
Resting potential level
[K+]out, K+outward
Th
Threshold
h ld potential
t ti l level
l
l
+
Na channel(Resting state, Active state, Inactive
state)
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Myocardial physiologic Properties
2. Autorhythmicity
Normal pacemaker:
S-A
S
A node 100steps/min
1)Maximum repolarizing
potential & threshold
potential IK-ACh
(vegal nerves: ACh)
(sympathetic nerves: NE)
2)Spontaneous depolarizing
velocity
l it
NE/E: I Ca-L
（去甲肾上腺素/肾上腺素）
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Autonomic Nervous System
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Myocardial physiologic Properties
3. Conductivity
1)Intercalated discs: Gap Junction
2)Specific conduction system
S-A
node
Atria
A-V
node
A-V
bundle
0.3~0.6m/s 0.02m/s 0.05m/s
Delay 0.13 s
1m/s
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Purkinje
system
4m/s
Ventricles
1m/s
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Myocardial physiologic Properties
4. Contractility
1)Depending on extracellular Ca2+
calcium-induced calcium release
2)None tetanic contractions
3)” All or none” :
two functional syncytium
4)Two factors (a,b) determine
contraction force
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(a)The initial length
(b)The inotropic 17
effect
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
FrankFrank
Starling
Law
Ventricular function curve
(a)Initial length-preload (Heterometric autoregulation)
(b)Inotropic state
Excitation-contraction coupling
(Ca2+ influx, Active cross bridge, Activity of ATPase)
E/NE (Extrinsic regulation)
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Vagus (Parasympathetic)
Mainly to the SA and AV
nodes (Arrows)
Cardiac nerves (Sympathetic)
y
Mainlyy to the myocardium
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Human and Animal Physiology; Heart and Circulation
Lecture 1
Sympathetic
nerve(NE)
β1-receptors
Propranolol 普
萘洛尔(心得安)
Ca2+ influx
Rate of
depolarization
Heart Rate
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Contractility
y
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Paraympathetic
nerve(ACh)
Muscarinic
receptors
(Atropine阿托品)
K+ efflux
Ca2+ influx
Hyperpolarization
Rate of
depolarization
Contractility;
y Heart Rate
SA node, AV node, Atrial muscle
Ventricular
conduction
pathway,
Ventricular
muscle
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5. Electrocardiogram(ECG/EKG)
Limb leads
1mV
Lead I:
RA to LA
Lead II:
RA to LL
Lead III:
LA to LL
P wave:
PR segment:
QRS complex:
ST segment:
T wave:
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Atrial depolarization
AV nodal delay
Ventricular depolarization
Plateau phase
Ventricular repolarization
Einthoven’s
triangle
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
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Cardiac Function
1.Cardiac cycle 0.8s
ƒVentricular systole
0 3s
0.3s
ƒIsovolumetric contraction phase
ƒEjection phase Rapid ~ 0.10s
Slow ~
0.05s
0.15s
ƒVentricular diastole 0.5s
ƒIsovolumetric
I
l
t i relaxation
l
ti phase
h
0 06~0.08s
0.06
0 08
ƒFilling phase Rapid ~ 0.11s
Slow ~
0.22s
Atrium systole
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0.1s
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Atria
Ventricle
Cardiac cycle
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Cardiac
cycle
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Aortic pressure
Left ventricular
pressure
Left atrial pressure
Left ventricular
Volume
Heart sounds
Electrocardiogram
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©2009, Yingyu Sun
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Human and Animal Physiology; Heart and Circulation
Lecture 1
April, 2009
Cardiac Function
2.Cardiac output =stroke volume × heart rate
5L/min
25-30L/min
70ml/beat
150ml/beat
*Cardiac reserve of p
pumping
p g function
75beats/min
200beats/min
3.Regulation of cardiac output
1)Heart rate Autonomic nervous and catecholamines
2)Stroke volume
ƒHeterometric regulation (Frank-Starling mechanism)
preload-initial length: end-diastole pressure/volume
The heart
Th
h
t automatically
t
ti ll adjusts
dj t its
it output
t t tto match
t h it
its
venous return
ƒExtrinsic regulation by autonomic nervous system
ƒAfterload
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Arterial pressure
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©2009, Yingyu Sun
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