Physiology
SECTON IV
CIRCULATION
Chapter 9~11
Introduction
Definition
of circulation
Circulatory system is made up of the heart and
vessels in which blood is flowing in certain direction,
going round and begin again
Function
of circulation
Cardiovascular system transport the blood flow
circulating the whole body, maintain the homeostasis
►Heart---- as a blood pump
►Vessels---- distributing and collecting the blood
flow
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Introduction
Pulmonary
circulation
Gases exchange in the
lungs
Systemic
circulations
Metabolic substances
exchange in every well of
the body
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Introduction
Non-circulation
function
The heart and vessels as the endocrine
organs
►Atrial natriuretic peptide (ANP)…
►Endothelin (ET)…
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Content of the course
CHAP 9 ELECTRICAL PROPERTIES OF THE CARDIAC
MUSCLE
CHAP 10 THE ELECTROCARDIOGRAM
CHAP 11 THE HEART AS A PUMP
CHAP 12 DYNAMICS OF BLOOD AND LYMPH FLOW
CHAP 13 CARDIOVASCULAR REGULATORY
MECHANISMS
CHAP 14 CIRCULATION THROUGH SPECIAL REGIONS
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CHAP
9
ELECTRICAL
PROPERTIES
OF
CHAP 9 ELECTRICAL PROPERTIES OF
THE CARDIAC MUSCLE
THE CARDIAC MUSCLE
9.1 INTRODUCTION
9.2 RESTING MEMBRANE POTENTIAL AND
ACTION POTENTIAL
9.3 ORIGIN AND SPREAD OF CARDIAC
EXCITATION
9.4 EFFECT OF CARDIAC INNERVATION
STIMULATION
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9.1 INTRODUCTION
Physiologic
properties
►Electrophysiological properties
Excitability
Autorhythmicity
Conductivity
►Mechanical property
Contractility
Conducting
system
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9.1 INTRODUCTION
Cardiac
myocyte
►Contractile myocardium
Atrial muscles, ventricular muscles
►Autorhythmic myocardium
S-A node, A-V node, bundle of His and its
branches, Purkinje fibers
Electrical
activity of myocardium
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9.2 RESTING MEMBRANE POTENTIAL
AND ACTION POTENTIAL
9.2.1 Resting membrane potential
EK＝61.5·log [K+]o/ [K+]i
＝61.5·log [4]o/ [135]I
＝－90mv
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9.2 RESTING MEMBRANE POTENTIAL
AND ACTION POTENTIAL
9.2.2 The ion currents responsible for the
action potential
Ventricular action potential
►Depolarizing phase
Phase 0 : INa, IK , ICa(L)
►Repolarizing phase
Phase 1 : Ito
Phase 2 : ICa (L) , IK
Phase 3 : IK
Phase 4 :resting state, active ion exchange
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9.2 RESTING MEMBRANE POTENTIAL
AND ACTION POTENTIAL
Factors
affecting excitability of
myocardium
►Relationship of resting potential and
threshold level
►Characters of Na+ channel
Resting:
Active:
Inactive: effective refractory period
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9.2 RESTING MEMBRANE POTENTIAL
AND ACTION POTENTIAL
9.2.3 The pacemaker potentials
S-A node action potential
►Auto-depolarizing phase—4: IK, ICa(T),
INa(F), Ca2+ sparks
►Depolarizing phase—0: ICa(L)
►Repolarizing phase—3: IK
Purkinje
fibers
►4: INa(F), IK
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9.2 RESTING MEMBRANE POTENTIAL
AND ACTION POTENTIAL
Factors
affecting autorhythmicity of
myocardium
►Maximum diastolic potential
►Spontaneous depolarization
►Threshold potential
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9.3 ORIGIN AND SPREAD OF
CARDIAC EXCITATION
9.3.1 Anatomic consideration
►Spetial conductive system in heart
►SA node: normal pacemaker
►Autonomic innervations
Right vagus and sympathetic nerve→ SA
node
Left vagus and sympathetic nerve→ A-V
node
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9.3 ORIGIN AND SPREAD OF
CARDIAC EXCITATION
9.3.2 Spread of cardiac excitation
►Sequence of cardiac excitation
Normal pacemaker: S-A node function as
the pacemaker for the entire heart
Latent or sub ordinary pacemaker
Ectopic pacemaker
►Factors affecting conductivity
Speed and amplitude of depolarization
Excitability of neighbor cell
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9.4 EFFECT OF CARDIAC
INNERVATIONS STIMULATION
9.4.1 Effect of vagal cardiac nerves
stimulation
►The parasympathetic postganglionic fibers release
primarily acetylcholine (ACh), which binds to M2receptors →G(γ)
►Inhibiting the heart actions
9.4.2 Effect of sympathetic cardiac
nerves stimulation
►The sympathetic postganglionic fibers release
primarily norepinephrine (NE), which binds mainly to
2-receptors →Gs
►Exciting the heart actions
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CHAP 10 THE
CHAP
10 THE ELECTROCARDIOGRAM
ELECTROCARDIOGRAM
10.1 RECORDING LEADS OF ECG
10.2 NORMAL ECG (EKG)
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10.1 RECORDING LEADS OF ECG
Basic
principle
►Body is a volume conductor
►The heart is a current source in the center of a
volume conductor (Einthoven's triangle)
►The ECG may be recorded by using an exploring
electrod
►Depolarization moving toward an active electrode
in a volume conductor produces a positive
deflection, whereas depolarization moving in the
opposite direction produces a negative deflection
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10.1 RECORDING LEADS OF ECG
Recording
lead
►Bipolar recording
Standard limb leads
leads I, II, and III
Augmented limb leads
aVL, aVR, aVF
►Unipolar recording
 Precordial leads
Waves
of the ECG
►P, Q R S, T (,U)
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10.2 NORMAL ECG (EKG)
Duration
of the ECG
►PR interval: 0.18s
Atrial depolarization and conduction through AV node
►QRS duration: 0.08s
Ventricular depolarization and atrial repolarization
►QT interval: 0.40s
Ventricular depolarization plus ventricular
repolarization
►ST interval: 0.32s
Ventricular repolarization
ST segment
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CHAP
11
THE
HEART
AS
A
PUMP
CHAP 11 THE HEART AS A PUMP
11.1 MECHANICAL PROPERTIES OF THE
CARDIAC MUSCLE
11.2 MECHANICAL EVENTS OF THE
CARDIAC CYCLE
11.3 CARDIAC OUTPUT
11.4 CARDIAC RESERVE
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11.1 MECHANICAL PROPERTIES
OF THE CARDIAC MUSCLE
11.1.1 Contractile response
Dependent upon [Ca2+]o
[Ca2+]i↑ triggered by Ca2+o
No
tetanus
►Contractile response lasts about 1.5 times
as long as the action potential
►Long ERP: phase 0 →3(repolarization -50mv)
Contraction
in synchronism
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11.1 MECHANICAL PROPERTIES
OF THE CARDIAC MUSCLE
11.1.2 Relation between muscle fiber length and
tension
►Starling‘s law of the heart (Frank-Starling law )
 Energy of contraction is proportional to the
initial length of the cardiac muscle fiber.
The length of the muscle fibers (ie, the
extent of the preload) is proportionate to the
end-diastolic volume
►Heterometric regulation: dependent on
initial length of myocardium fibers
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11.1 MECHANICAL PROPERTIES
OF THE CARDIAC MUSCLE
►Contractility— inotropic effect
Homometric regulation:
independent of initial length
Active regulation by the organism
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
11.2.1 Cardiac cycle
Pumping function is periodicity action
Heart
rate: 60~100 beats/min
Cardiac cycle: 0.8s (~72 beats/min)
Systole and diastole
►Atria systole and diastole
►Ventricular systole and diastole
►Whole cardiac diastole
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
Mechanism
events: filling and ejection:
driving the blood flow from vein to
artery in certain direction
►Difference pressure between atria,
ventricles and arteries
►Valves status: opened or closed
►Change of volume in ventricular chambers
►Direction of blood flow
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
11.2.2 Atria systole
Events in late diastole
►The mitralis and tricuspid are opened and
the aortic and pulmonary valves are closed
►Blood flows: into the heart from caval vein,
filling the atria and ventricles
►Pressure in the ventricles remains low
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
Atria
systole
►Atrial systole starts after the P wave of
the ECG
►Propels some additional blood into the
ventricles
►Vena cava and pulmonary veins narrowed
►Vome regurgitation of blood into the veins
during atrial systole
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
11.2.3 Ventricular systole
Ventricular systole starts near the end of
the R wave and ends just after the T wave
of the ECG
Isovolumetric
ventricular contraction
►lasts about 0.05 s
►Mitral and tricuspid (AV) valves all closed
►Intraventricular pressure rises sharply as
the myocardium presses on the blood
►No blood into or out the ventricles
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
Ventricular
ejection
►the ventricular pressures exceed aorta (80
mm Hg; 10.6 kPa) and pulmonary artery (10
mm Hg)
►The aortic and pulmonary valves open
►Propels blood into the large arteries more
rapidly
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
11.2.4 Ventricular diastole
Isovolumetric
ventricular relaxation
►Ventricular pressure continues to drop
rapidly
► The aortic and pulmonary valves are closed
Ventricular
filling
►Pressure falls below the atrial pressure
►the AV valves open, permitting the
ventricles to fill
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11.2 MECHANICAL EVENTS OF
THE CARDIAC CYCLE
11.2.5 Heat sounds
►1st sounds: 0.15 s, 25-45 Hz
Myocardium contraction
Flow impacting the cardiac wall
Vibration set up by closure of A-V valves
►2nd sounds: 0.12 s, 50 Hz.
Vibrations associated with closure of arterial
valves
Arterial roots vibration
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11.3 CARDIAC OUTPUT
11.3.1 Cardiac output in various conditions
►Stroke volume & ejection fraction
►Cardiac output (CO, minute cardiac
output)
CO=Stroke volume × Heart rate
CO=70mL/beat×72/min=5.0L/min
►Cardiac index=CO/m2
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11.3 CARDIAC OUTPUT
11.3.2 Factors controlling cardiac
output
Control
of stroke volume：the major
factors influencing force of contraction
►Intrinsic regulation: the Frank-Starling
mechanism
Venous flow returned →changes in end-diastolic
volume →heterometric autoregulation
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11.3 CARDIAC OUTPUT
►Extrinsic regulation: sympathetic
stimulation, epinephrine
To increase myocardial contractility
(inotropic status)→ the force of
contraction at any given end-diastolic
volume → hotmometric regulation
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11.3 CARDIAC OUTPUT
►Afterload: the arterial pressures
Against which the ventricles pump
Increasing pressures decrease the
strength of contraction
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11.3 CARDIAC OUTPUT
Control
of heart rate
►Cardiac nerves
Parasympathetic nerves (Cardiac Vagus) :
 heart rate
Sympathetic nerves:  heart rate
►Epinephrine
 heart rate
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