Download Cardiac Physiology 心臟生理學

心臟生理學
Cardiac Physiology
生理學科 鍾文彬 助理教授
TEL: # 3183
E.mail: [email protected]
1
Overview of the Heart:
1. Structure of the heart and its components
2. Excitation of the heart (cardiac muscles)
3. Conducting pathways of action potentials
4. Cardiac cycle and Rhythm of the heart
5. Works and regulations of the heart
6. ECG
2
Circulation System
Circulation
1.
2.
3.
system consists of:
Heart
Blood vessels
Blood
Two
separate circulation:
1. Systemic circulation
2.
Pulmonary circulation
3
The heart is a dual pump
4
From Sherwood 2007
Course overview of the Heart:
1. Structure of the heart and its components
cardiac muscles, valves, pacemakers, conductive pathways
2. Excitation of the heart (cardiac muscles)
excitation of pacemakers and contractile muscles
3. Conductive spread of the action potential
speed and properties of the conductive pathways
4. Cardiac cycle and heart rhythm
5. Works and regulations of the heart
6. ECG
5
From Sherwood 2007
6
Spread of Cardiac Excitation
From Sherwood 2010
7
Action potential conduction and excitatory
contraction of the Heart
SA Node
Conducting System of the Heart
Interatrial
pathway
Internodal pathway
Interatrial pathway
AV node
AV node
Bundle of His
SA node
LA
RA
Purkinje system
Ventricular Muscle
Left branch
of bundle of His
Internodal
pathway
Right branch
of bundle of His
LV
RV
Purkinje
fibers
From Sherwood 2010
8
Thickness of Ventricle Walls
Ventricular
Wall thickness: R/L= 2:10 mm
Work: R/L=1:7
Work of the heart?
Cardiac output (L/min)
From Sherwood 2010
9
Structure of Heart Valves
Atrioventricular
Fibrous tissue
Four valves
Left AV valve (bicuspid, mitral)
Right AV valve (tricuspid)
Aortic semilunar valve
Pulmonary semilunar valve
From Sherwood 2010
10
One-way Valves
Valve opened
When pressure is greater behind
the valve, it opens.
Valve closed
When pressure is greater in front
of the valve, it closes.
From Sherwood 2010
11
Actions of AV and Semilunar valves
12
From Sherwood 2010
Characteristics of Myocardium
1. Automaticity
2. Excitability
3. Contractility
4. Conductivity
13
Course overview of the Heart:
1. Structure of the heart and its components
cardiac muscles, valves, pacemakers, conductive pathways
2. Excitation of the heart (cardiac muscles)
excitation of pacemakers and contractile muscles
3. Conductive spread of the action potential
speed and properties of the conductive pathways
4. Cardiac cycle and heart rhythm
5. Works and regulations of the heart
6. ECG
14
Three Types of Myocardium
 Pacemaker cells
(autorhythmic cells)
 Electrical conducting cells
(1%)
 Contractile cells
(99%)
(pump cells)
15
How dose the rhythm of heart
beat make up by Pacemaker?
心跳的節率是如何產生的？
16
The action potential of an
autorhythmic pacemaker cell.
SA node cell
1. Sodium ions “
leaking”in through
the F-type [funny, sodium]
channels PLUS calcium ions moving
in through the T [transient,
calcium] channels cause a
threshold graded depolarization.
2. The rapid opening of voltagegated calcium channels is
responsible for the rapid
depolarization phase.
3. Reopening of potassium channels
PLUS closing of calcium channels
are responsible for the
repolarization phase.
17
Electrical properties of cardiac
auto-rhythmic pacemaker cells
(3)
1. Threshold potential
2. Peacemaker potential
3. Action potential
(1)
(2)
P: permeability
From Sherwood 2010
18
Contractile Myocardium
(Cardiac muscle)
(Pump cardiac muscle)
收縮型心肌細胞(幫浦細胞)的
興奮(去極化)是如何產生的？
19
The action potential of a
myocardial pumping cell.
Contractile cell
1. The rapid opening of
voltage-gated sodium
channels is responsible for
the rapid depolarization
phase.
2. The prolonged “
plateau”of
depolarization is due to the
slow but prolonged opening of
voltage-gated calcium
channels PLUS closure of
potassium channels.
3. Opening of potassium
channels results in the
repolarization phase.
20
Refractory period (RP): 心肌的不反應期
Prevention of cardiac muscle from tetanus contraction
Absolute refractory period : 95% RP
Relative refractory period : 5% RP
21
From Sherwood 2010
How does the rapid transduction
of action potential from excited
cell to its around (next) cells ?
心肌細胞的興奮是如何傳導/散佈到
周圍的細胞的？
The Gap Junction between cells
Presence of the Gap Junction:
Yes: Cardiac & smooth muscle cells
No: Skeletal muscle cells
22
Striated muscle
Thin / Thick filaments
Myofiber branches
From Sherwood 2010
Intercalated disks
Desmosomes: Resist stress
Gap junctions: Contract as unit
(Functional Syncytium)
Gap junction
23
一大團心肌細胞如何產生一致性
的心肌興奮與縮收作用？
24
Functional Syncytium (功能之一致性)
Upon fast action potential conductance through Gap Junctions,
a mass of cardiac muscle simultaneously contracting
25
心肌細胞興奮如何產生
機械性的縮收作用？
26
How dose the action potential
control the mechanical contraction
of pump cardiac muscle?
E-C coupling
27
E-C Coupling:
Action
potential
Excitation-Contraction Coupling
Contractile
response
28
Calcium ions regulate the
contraction of cardiac muscle
Opening L-type
Calcium channel
about 95% of
Ca2+ is from
intracellular
poor: SR
CICR
(Calcium-Induced Calcium Release)
29
Course overview of the Heart:
1. Structure of the heart and its components
cardiac muscles, valves, pacemakers, conductive pathways
2. Excitation of the heart (cardiac muscles)
excitation of pacemakers and contractile muscles
3. Conductive spread of the action potential
speed and properties of the conductive pathways
4. Cardiac cycle and heart rhythm
5. Works and regulations of the heart
6. ECG
30
How dose the action potential
conduct throughout the heart
rapidly?
Highway system
心肌細胞興奮如何快速
傳遍整個心房或心室？
31
Spread of Cardiac Excitation
32
Conducting System of the Heart
Interatrial
pathway
SA Node
AV node
SA node
LA
RA
Left branch
of bundle of His
Internodal
pathway
Internodal pathway
Interatrial pathway
AV node
Bundle of His
Purkinje system
Ventricular Muscle
Right branch
of bundle of His
LV
RV
From Sherwood 2010
Purkinje
fibers
33
Dose the rhythmic action potential
flow throughout a full heart at the
same conducting velocity ?
心肌的電興奮傳導途徑的
傳導速率一樣嗎？
34
Transmission of the cardiac impulse
Conductive
Tissue
Conduction
Rate (m/s)
SA node
0.05
Atrial pathway
1
AV node ( delay )
0.05
His bundle
1
Purkinje fibers
4
Ventricular muscle
1
35
AV nodal delay
Insulation:
cause A & V contractions
independently
deceleration:
Narrow down the wide of
conducting route
36
Is SA node the “only one”
pacemaker of the heart ?
NO !!
The frequency determination of the
autorhythm of the heart
Conductive
tissues
Action
potential
/min
SA node
70-80
AV node
40-60
His Bundle &
20-40
Purkinje Fibers
20-40
37
How to determine the
peacemaker of the heart?
該由誰帶領心肌的興奮頻
率呢？如何決定？
38
From Sherwood 2010
39
From Sherwood 2010
40
Cardiac Cycle
1. 腔室與大動脈之壓力變化？
2. 瓣膜開閉狀況？
41
Systole (ventricles)
= 1 x isovolumetic contraction
+ 1 x ejection
等容積性縮收期
心室射血期
42
Diastole (ventricles)
= 1 x isovolumetic relaxation
+ 1 x filling
等容積性舒張期
心室充血期
<
>
43
Aortic pressure
(mmHg)
Left ventricular
pressure (mmHg)
Left atrial
pressure (mmHg)
Left ventricular
volume (mL)
Heart sound
44
From Sherwood 2010
Course overview of the Heart:
1. Structure of the heart and its components
cardiac muscles, valves, pacemakers, conductive pathways
2. Excitation of the heart (cardiac muscles)
excitation of pacemakers and contractile muscles
3. Conductive spread of the action potential
speed and properties of the conductive pathways
4. Cardiac cycle and heart rhythm
5. Works and regulations of the heart
Stroke volume, heart rate; Modulations by ANS, hormones, EDV
6. ECG
45
How can we evaluate
the WORK a heart
done or doing?
Cardiac Output (CO)
46
Cardiac Output (CO)
CO = SV x HR
SV, stroke volume; HR, heart rate
Average CO = 5 L/min at rest
Average HR = 72 beat/min, at rest
Average SV = 70 mL
Average blood volume = 5.5 L
47
Controls of Cardiac Output
CO
HR
Parasympathetic
activity
Sympathetic
Activity &
(epinephrine)
SV
EDV
Venous return
From Sherwood 2010
48
SV:
1. Intrinsic control:
EDV, effecter of Frank-Starling Rule
2. Extrinsic control:
Sympathetic stimuli: enhance myocardium contraction
Epinephrine & norepinephrine: increase contraction force
HR: extrinsic ANS control only
• Sympathetic stimuli: increase HR
• Parasympathetic stimuli: decrease HR
49
ANS Inputs to the Heart
50
The regulation of “SV”
SV的調控因子
51
Sympathetic Effect on Cardiac Contraction
Sympathetic nor-/epinephrine:
•stronger contraction
•more rapid of contraction
•more rapid relaxation
52
Ventricular Volume and Stroke Volume
1. EDV, volume of blood in ventricle at end of diastole
2. ESV, volume of blood in ventricle at end of systole
3. SV = EDV - ESV
53
Sympathetic effects on SV
EDV
175 ml
EDV
135 ml
SV ?
SV,70 ml
ESV
65 ml
EDV
135 ml
Sympathetic
stimulation (B)
SV, 100 ml
SV, 140 ml
Sympathetic
stimulation (A)
Sympathetic
stimulation (A)
ESV
35 ml
ESV
35 ml
54
Frank-Starling Mechanism (Rule)
EDV
175 ml
EDV
135 ml
SV= ?
70 ml
ESV
65 ml
100 ml
ESV
65 ml
To increase the heart’
s SV:
Fill it more fully with blood. The increased stretch of
the ventricle will align its actin and myosin in a more
optimal pattern of overlap.
55
Frank-Starling Mechanism (Rule)
To further increase the SV:
Fill it more fully with blood.
Deliver sympathetic signals (norepinephrine and epinephrine);
It will also relax more rapidly, allowing more time to refill.
56
Intrinsic and extrinsic controls of SV
Stroke volume
Extrinsic
control
Strength of
cardiac contraction
Intrinsic
control
Sympathetic activity
(and epinephrine)
EDV
Intrinsic
control
Extrinsic
control
From Sherwood 2010
Venous return
57
The regulation of “HR”
HR 的調控因子
58
Polarized potential: hyper-/ hypo-polarization
HR regulations:
ANS
Pacemaker potential: in-/ de-creased slope
parasympathetic
stimulation
sympathetic
stimulation
59
From Sherwood 2010
Control of Cardiac Output
CO
HR
Parasympathetic
activity
Sympathetic
Activity &
(epinephrine)
SV
EDV
Venous return
From Sherwood 2010
60
Course overview of the Heart:
1. Structure of the heart and its components
cardiac muscles, valves, pacemakers, conductive pathways
2. Excitation of the heart (cardiac muscles)
excitation of pacemakers and contractile muscles
3. Conductive spread of the action potential
speed and properties of the conductive pathways
4. Cardiac cycle and heart rhythm
5. Works and regulations of the heart
6. ECG
waves, intervals, segments
61
ElectroCardioGraph
ECG, EKG
62
ECG
ST interval
63
The SA node is the heart’
s
pacemaker because it initiates
each wave of excitation with
atrial contraction.
The Bundle of His and other parts
of the conducting system deliver
the excitation to the apex of the
heart so that ventricular contraction
occurs in an upward sweep.
64
ECG: bipolar leads
Bipolar Leads:
Lead I
Lead II
Lead III
I
III
II
I
+ III
= II
65
ECG: unipolar leads
aVR
aVL
Uni-polar Leads:
Chest leads:
V1, V2, V3, V4, V5, V6
Augmented Limb leads:
aVR, aVL, aVF
aVF
66
67
Significant criteria of ECG
Three waves : P, QRS, T
Two segments: PR, ST
Four intervals: PR, QRS, ST, QT
ST interval
0.04 s
0.1 mV
68
ECG: Two segments
PR (AV node delay)
End of atrial depolarization till beginning of ventricular depolarization
ST
End of ventricular depolarization till beginning of ventricular
repolarization
PR ST
69
ECG: Three obvious waves
P
Atrial depolarization
QRS
Ventricular depolarization
T
Ventricular repolarization
QRS
P
T
70
ECG: Four intervals
Interval
Electrical Events
PR
Atrial depolarization and conduction
of AP to AV node
QRS
Ventricular depolarization and atrial
repolarization
ST
Ventricular depolization and
Ventricular repolarization
QT
Ventricular depolarization plus
ventricular repolarization
71
Electrical Activity
Abnormalities in heart rate:
1. Tachycardia: HR>100 bpm
2. Bradycardia: HR<60 bpm
NORMAL RATE AND RHYTHM
ABNORMALITIES IN RATE
From Sherwood 2007
Tachycardia
72
Electrical Activity
Abnormalities in rhythm:
1.Rhythm: regularity of the ECG waves
2.Arrhythmia: any variation from the normal rhythm
73
Electrical Activity
Atrial fibrillation:
1. Rapid, irregular, uncoordinated atrial depolarizations
with no definite P waves
2. Irregular ventricular response
3. Pulse deficit
74
Electrical Activity
Complete heart block
1. Complete atrial and ventricular dissociation
2. Atrial rate > ventricular rate (escape rhythm)
Heart block
75
Electrical Activity
Ventricular fibrillation:
1. Irregular with no detectable pattern or rhythm,
serious and lethal arrhythmia
2. Irreversible brain damage: >4 mins
Ventricular fibrillation
From Sherwood 2007
76
Summary:
1. Structure of the heart and its components
cardiac muscles, valves, pacemakers, conductive pathways
2. Excitation of the heart (cardiac muscles)
excitation of pacemakers and contractile muscles
3. Conductive spread of the action potential
speed and properties of the conductive pathways
4. Cardiac cycle and heart rhythm
5. Works and regulations of the heart
6. ECG and electrical Activity of the heart
77
References:
1. Sherwood: Human Physiology –from cells to systems, ed.7
2. Widmaier, Raff &.Strang: Vander’
s Human Physiology- the
mechanisms of body function, ed.11
3. Fox: Human Physiology, ed.11
78