CARDIOVASCULAR PHYSIOLOGY

1
CARDIOVASCULAR PHYSIOLOGY
INTRODUCTION AND OVERVIEW
2
CARDIOVASCULAR PHYSIOLOGYLECTURES

• STUDENT LECTURE NOTEBOOK
• Guido E. Santacana Ph.D.
• DEPT. of PHYSIOLOGY

3
MAIN FUNCTIONS OF THE CIRCULATORY SYSTEM

• Transport and distribute essential substances to
  the tissues.
• Remove metabolic byproducts.
• Adjustment of oxygen and nutrient supply in
  different physiologic states.
• Regulation of body temperature.
• Humoral communication.

4
THE MAIN CIRCUIT
COLLECTING
PUMP
TUBULES
DISTRIBUTING
THIN VESSELS
TUBULES
5
Pressure Drop in the Vascular System
ELASTIC TISSUE
MUSCLE
LARGE ARTERIES
SMALL ARTERIES
MEAN PRESSURE
ARTERIOLES
CAPILLARIES
VENULES VEINS
SMALL
LARGE
LARGE
INSIDE DIAMETER
6
Distribution of Blood in the Circulatory System

• 67 IN THE SYST. VEINS/VENULES
• 5 IN THE SYSTEMIC CAPILLARIES
• 11 IN THE SYSTEMIC ARTERIES
• 5 IN PULMONARY VEINS
• 3 IN PULMONARY ARTERIES
• 4 IN PULMONARY CAPILLARIES
• 5 IN HEART ATRIA/VENTRICLES

7
Organization in the Circulatory System
SERIES AND PARALLEL CIRCUITS
8
CARDIAC ELECTROPHYSIOLOGY

• LECTURE NOTEBOOK
• Guido E. Santacana Ph.D.

9
GENESIS OF THE MEMBRANE POTENTIAL AND EQUATIONS
TO REMEMBER!!
?
EK -60 LOG (Ki/Ko) -94mv
gt(
ENa -60 LOG (Nai/Nao) 70mv
PK (K)o PNa(Na)o PCl(Cl-)i
Em RT/F ln
PK (K)I PNa(Na)i PCl(Cl-)o
10
THE RESTING MEMBRANE POTENTIAL OF THE CARDIAC CELL
IN
OUT
K
K
145mEq
5mEq
Em -60LogKi/Ko
-90mv
11
EXTRACELL.
INTRA-CELL.
Em
145Mm
15Mm
Na
70mv
Ca
132mv
3Mm
10-7 M
K
-100mv
5Mm
145Mm
WHY NOT Na 0R Ca FOR THE CARDIAC CELL MEMBRANE
POTENTIAL ?
12
ACTION POTENTIALS FROM DIFFERENT AREAS OF THE
HEART
ATRIUM
VENTRICLE
SA NODE
time
13
ELECTROPHYSIOLOGY OF THE FAST RESPONSE FIBER
AMP
20
1
To oscilloscope
2
0
3
0
mv
Cardiac Cell
4
-80
0
300
t (msec)
14
PHASE 0 OF THE FAST FIBER ACTION POTENTIAL
Chemical Gradient
Electrical Gradient
15
K CURRENTS AND REPOLARIZATION

• PHASE 1-TRANSIENT OUTWARD CURRENT (TOC) Ito
• PHASE 1-3-DELAYED RECTIFIER CURRENT IK
• PHASE 1-4-INWARDLY RECTIFIED CURRENT IKl

16
THE PLATEAU PHASE AND CALCIUM IONS
OPEN
CLINICAL VALUE
L Ca CHANNELS
Ca BLOCKERS
10MV
T Ca CHANNELS
-20MV
NO (physiological)
17
Ca CHANNEL BLOCKERS AND THE CARDIAC CELL ACTION
POTENTIAL
DILTIAZEM
ACTION POTENTIAL
CONTROL
10 uMol/L 30 uMol/L
10
30
CONTROL
10
FORCE
30
TIME
18
OVERVIEW OF SPECIFIC EVENTS IN THE VENTRICULAR
ACTION POTENTIAL
19
ELECTROPHYSIOLOGY OF THE SLOW RESPONSE FIBER
0
2
0
mvs
-40
3
4
ERP
RRP
-80
time (msec)
RECALL INWARD Ca CURRENT CAUSES DEPOLARIZATION
20
CONDUCTION OF THE ACTION POTENTIAL IN CARDIAC
FIBERS
LOCAL CURRENTS
-
-
-
-
-
-
-
-







-
-
-
-
-
-
-
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FIBER A
FIBER B
DEPOLARIZED ZONE
POLARIZED ZONE
21
CONDUCTION OF THE ACTION POTENTIAL

• FAST RESPONSE Depends on Amplitude,Rate of
  Change,level of Em.
• SLOW RESPONSE Slower conduction.More apt to
  conduction blocks.
• WHAT ABOUT MYOCARDIAL INFARCTS AND CONDUCTION?

22
EFFECTS OF HIGH K ON CONDUCTION AND AP OF FAST
FIBERS
0MV
AP-AMP
Em
K3mM
K7mM
K14mM
0MV
K16mM
K3mM
WHAT HAS VARIED? LOOK AT Em,AP SLOPE-AMPLITUDE
23
HIGH K AND m/h Na GATES
LOWER Em
HIGH K
CLOSED h GATES (SOME)
LOWER AP AMPLITUDE
LOWER Na ENTRY
24
EXCITABILITY OF FAST AND SLOW FIBERS
FAST
m/h GATES COMPLETE RESET AFTER PHASE 3
CONSTANT AND COMPLETE RESPONSE IN PHASE 4
SLOW
LONG RELATIVE REFRACTORY PERIOD.
POST-REPOLARIZATION REFRACTORINESS
25
AFTER THE EFFECTIVE OR ABSOLUTE REFRACTORY PERIOD
(FAST FIBER)
0
MV
ARP
-80
RRP
TIME
26
POST-REPOLARIZATION REFRACTORINESS (SLOW FIBER)
200 MSEC
C
0
B
MV
A
-60
POSTREPO
TIME
27
RHYTMICITY
AUTOMATICITY
SA NODE
AV NODE
ectopic foci
IDIOVENTRICULAR- PACEMAKERS
28
THE SA NODE PACEMAKER POTENTIAL
29
CHARACTERISTICS OF THE PACEMAKER POTENTIAL
RECALL PHASE 4-PACEMAKER POTENTIAL(PP) OBSERVED
HERE. FREQUENCY DEPENDS ON
THRESHOLD,RESTING POTENTIALS

AND SLOPE OF THE PP
30
CAUSES OF THE PACEMAKER POTENTIAL
K
OUT
if
iCa
IN
iK
Na
Ca
31
THE PACEMAKER POTENTIAL CURRENTS AFTER
DEPOLARIZATION
iCa
if
iK
WHICH CURRENT WILL BE MORE AFFECTED BY ADRENERGIC
STIMULATION? WHICH BY CHOLINERGIC STIMULATION?
32
LOOKING AT THE PACEMAKER CURRENTS
voltage
iK
if
ionic currents
iCa
33
EFFECTS OF Ca CHANNEL BLOCKERS ON THE PACEMAKER
POTENTIAL
NIFEDIPINE
CONTROL
(5.6 X 10-7 M)
0
MV
-60
TIME
34
OVERDRIVE SUPRESSION AND AUTOMATICITY OF
PACEMAKER CELLS

• Na/K ATPase ENHANCEMENT BY HIGH FREQUENCY.
• CONSEQUENT HYPERPOLARIZATION.
• SUPRESSION OF AUTOMATICITY.
• RECOVERY TIME REQUIRED.
• ECTOPIC FOCI/SICK SINUS SYNDROME.

35
THE CONDUCTION SYSTEM OF THE HEART
36
ATRIAL AND ATRIOVENTRICULAR CONDUCTION
37
NODAL DELAY
REGION OF DELAY
38
UNI AND BIDIRECTIONAL BLOCKCLINICAL IMPLICATIONS
B
A
NORMAL
BI
D
C
UNI
REENTRY
39
AV NODE AND AV BLOCKS
FOCUS ON N REGION
ECG
NORMAL
1ST DEGREE
PROLONGUED AV CONDUCTION TIME
2ND DEGREE
1/2 ATRIAL IMPULSES CONDUCTED TO VENTRICLES
3RD DEGREE
VAGAL MEDIATION IN N REGION/COMPLETE BLOCK
40
CONDUCTION IN THE VENTRICLES

• PURKINJE FIBERS WITH LONG REFRACTORY PERIODS.
• PROTECTION AGAINST PREMATURE ATRIAL
  DEPOLARIZATIONS AT SLOW HEART RATES.
• AV NODE PROTECS AT HIGH HEART RATES.

41
CARDIAC MECHANICS

• MAIN THEMES
• THE HEART AS A PUMP
• THE CARDIAC CYCLE
• CARDIAC OUTPUT

CHAPTER 23 BL
42
LENGHT/ TENSION AND THE FRANK-STARLING RELATION
VENTRICULAR PRESSURE
INITIAL MYOCARDIAL FIBER LENGHT VENTRICULAR
END-DIASTOLIC VOLUME
43
PRELOAD AND AFTERLOAD IN THE HEART

• INCREASE IN FILLING PRESSUREINCREASED PRELOAD
• PRELOAD REFERS TO END DIASTOLIC VOLUME.
• AFTERLOAD IS THE AORTIC PRESSURE DURING THE
  EJECTION PERIOD/AORTIC VALVE OPENING.

44
LEFT VENTRICULAR PRESSURE AND AFTERLOAD
LEFT VENTRICULAR PRESSURE
AFTERLOAD (aortic pressure)
NOTE WHAT HAPPENS IN THE NORMAL HEART VS ONE IN
THE LAST PHASES OF CARDIAC FAILURE?
45
CONTRACTILITYTHE VENTRICULAR FUNCTION CURVE
EFFECT?
CHANGES IN CONTRACTILITY
46
dP/dt AS A VALUABLE INDEX OF CONTRACTILITY
MAX dP/dt
B
120
A
C
LEFT VENTRICULAR PRESSURE (mmHg)
40
.6
TIME (s)
.2
47
CARDIAC CYCLE
Rapid Ventricular Filling
Reduced Ejection
Atrial Systole
Rapid Ejection
Isovolumic Relax.
Reduced Ventricular Filling
Atrial Systole
Isovolumic contract.
Aortic opens
gtO
Aortic closes
Mitral opens
Mitral Closes
S1
gtD
S2
48
LEFT VENTRICULAR PRESSURE/VOLUME P/V LOOP
120
F
E
D
80
LEFT VENTRICULAR PRESSURE (mmHg)
40
B
A
C
0
100
150
50
LEFT VENTRICULAR VOLUME (ml)
49
PRESSURE/VOLUME RELATIONSHIPS UNDER DIFFERENT
CONDITIONS
PRELOAD
AFTERLOAD
CONTRACTILITY
50
CARDIAC OUTPUT AND THE FICK PRINCIPLE
BODY O2 CONSUMPTION
Lungs
250mlO2/min
PULMONARY ARTERY
PULMONARY VEIN
PaO2
PvO2
0.15mlO2/ml blood
0.20mlO2/ml blood
Pulmonary capillaries
O2 CONSUMPTION (ml/min)
CARDIAC OUTPUT
-
PvO2
PaO2
51
HEMODYNAMICS

• VELOCITY,FLOW,PRESSURE
• LAMINAR FLOW
• POISEUILLES LAW
• RESISTANCE(SERIES-PARALLEL)
• TURBULENT FLOW AND REYNOLDS NUMBER

CHAPTER 25 BL
52
HYDROSTATIC PRESSURE
100
136cm
0
200
100
0
200
P p x g x h
0
100mmHg
100
136cm
0
200
P Pressure mmHg p density g gravity h
height
100
0
200
0
53
REQUIRED CONCEPTS
VELOCITY DISTANCE / TIME V
D / T
FLOW VOLUME / TIME Q VL
/ T
VELOCITY -FLOW- AREA V Q / A
54
ENERGY OF A STATIC VS A DYNAMIC FLUID
TOTAL ENERGY POTENTIAL E. KINETIC E.
TE PE
KE
FLUID AT REST (HYDROSTATIC )
FLUID IN MOTION (HYDROSTATIC

HYDRODYNAMIC)
55
VELOCITY AND PRESSURE
100
0
200
0
56
CROSS SECTIONAL AREA AND VELOCITY
A 2cm2 10cm2 1cm2
Q10ml/s
a
b
c
V 5cm/s 1cm/s 10cm/s
V Q / A
57
POISEUILLES LAW GOVERNING FLUID FLOW(Q) THROUGH
CYLINDRIC TUBES
(Pi - Po) r
4
(FLOW)Q
8nL
DIFFERENCE IN PRESSURE
RADIUS
VISCOSITY
LENGHT
58
RESISTANCE TO FLOW IN THE CARDIOVASCULAR SYSTEM
BASIC CONCEPTS
Rt R1 R2 R3. SERIES RESISTANCE 1/Rt
1/R1 1/R2 1/R3 PARALLEL RES.
R1
PARALLEL
SERIES
R2
R1
R2
R3
R3
WHAT REALLY HAPPENS IN THE CVS?
LOWER R
LOWER R
HIGHER R
CAPILLARIES
ARTERY
ARTERIOLES
59
LAMINAR VS TURBULENT FLOWTHE REYNOLDS NUMBER
LAMINAR FLOW
TURBULENT FLOW
p density D diameter v velocity n
viscosity
Nr pDv / n
laminar 2000 or less
60
ARTERIAL SYSTEM

• COMPLIANCE
• MEAN ARTERIAL PRESSURE
• PULSE PRESSURE
• PRESSURE MEASUREMENT

CHAPTER 26 BL
61
THE CONCEPT OF THE HYDRAULIC FILTER
SYSTOLE
DIASTOLE
COMPLIANT
RIGID
62
EFFECTS OF PUMPING THROUGH A RIGID VS A COMPLIANT
DUCT
0.1
PLASTIC TUBING
O2 CONSUMPTION (mlO2/100g/beat)
NATIVE AORTA
0
5
15
STROKE VOLUME (ml)
63
STATIC P-V RELATIONSHIP IN THE AORTA
INCREASE IN VOLUME
PRESSURE (mmHg)
64
ELASTIC MODULUS OR ELASTANCE
Ep ELASTIC MODULUS D MAX. CHANGE IN
AORTIC DIAMETER. D MEAN AORTIC DIAM.
Ep P / D/D
ELASTANCE COMPLIANCE
P
V
P
V
EP IS INVERSELY PROPORTIONAL TO C
65
MEAN ARTERIAL PRESSURE (MAP)
REMEMBER OHMS LAW?
CARDIAC OUTPUT
PERIPHERAL RESISTANCE
INSTANTANEOUS INCREASE
STEADY STATE INCREASE
66
EFFECT OF COMPLIANCE ON MAP
Qh- inflow (CO) Qr- outflow Ca- Compliance Pa- MAP
Pa Qh - Qr / Ca
SMALL Ca
ARTERIAL PRESSURE (mmHg)
LARGE Ca
INCREASE CARDIAC OUTPUT
TIME
67
PULSE PRESSURE
STROKE VOLUME
COMPLIANCE
V4
VB
V3
VOLUME
V2
VA
V1
P1
PA
P2
P3
PB
P4
PRESSURE
68
PULSE PRESSURE EFFECTS OF
TOTAL PERIPHERAL RESISTANCE
COMPLIANCE
TPR
69
CHAPTER 29 BL
COUPLING OF THE HEART AND BLOOD VESSELS
VASCULAR FUNCTION CURVE
HOW CARDIAC OUTPUT REGULATES CENTRAL VENOUS
PRESSURE
CARDIAC FUNCTION CURVE
HOW CENTRAL VENOUS PRESSURE (PRELOAD) REGULATES
CARDIAC OUTPUT
70
VASCULAR FUNCTION CURVE
HOW CHANGES IN CARDIAC OUTPUT INDUCE CHANGES IN
CENTRAL VENOUS PRESSURE?
8
Pmc
VASCULAR FUNCTION CURVE
B
CENTRAL VENOUR PRESSURE (mmHg)
A
-1
0
8
CARDIAC OUTPUT (L/min)
71
HOW BLOOD VOLUME AND VENOMOTOR TONE CHANGE THE
VASCULAR FUNCTION CURVE?
8
VASCULAR FUNCTION CURVE
TRANSFUSION
CENTRAL VENOUR PRESSURE (mmHg)
NORMAL
HEMORRHAGE
-1
0
8
CARDIAC OUTPUT (L/min)
72
TOTAL PERIPHERAL RESISTANCE AND THE VASCULAR
FUNCTION CURVE.
8
VASCULAR FUNCTION CURVE
CENTRAL VENOUR PRESSURE (mmHg)
VASODILATION
VASOCONSTRICTION
NORMAL
-1
0
8
CARDIAC OUTPUT (L/min)
73
THE CARDIAC FUNCTION CURVE
CARDIAC OUTPUT (L/min)
CENTRAL VENOUS PRESSURE (mmHg)
74
EFFECTS OF SYMPATHETIC STIMULATION ON THE CARDIAC
FUNCTION CURVE
CARDIAC OUTPUT (L/min)
CENTRAL VENOUS PRESSURE (mmHg)
75
HOW BLOOD VOLUME AND PERIPHERAL RESISTANCE CHANGE
THE CARDIAC FUNCTION CURVE?
VOLUME
RESISTANCE
CARDIAC OUTPUT (L/min)
CENTRAL VENOUS PRESSURE (mmHg)
76
THE CARDIAC FUNCTION CURVE IN HEART FAILURE
CARDIAC OUTPUT (L/min)
CENTRAL VENOUS PRESSURE (mmHg)
77
HEART - BLOOD VESSELSCOUPLING
MORMAL FUNCTION
PUMP
ARTERIES
VEINS
Qh
5L/min
Pa
COMPLIANCES Cv 19Ca CvgtgtgtgtCa
MPA102mmHg
CPV2mmHgPv
Qr
5L/min
PERIPHERAL R Pa - Pv / Qr
R 20mmHg/L/min
78
CARDIAC ARREST!INMEDIATE EFFECT
FLOW STOPS HERE
PUMP
ARTERIES
VEINS
Qh
0L/min
Pa
FLOW CONTINUES HRE TRANSFER ART--gtVEINS
CPV2mmHgPv
Qr
5L/min
Qr CONTINUES AS LONG AS A PRESSURE GRADIENT IS
SUSTAINED
R 20mmHg/L/min
Qr Pa - Pv/20
79
CARDIAC ARRESTSTEADY STATE
FLOW STOPPED
PUMP
ARTERIES
VEINS
Qh
0L/min
Pa 7mmHg
Pv 7mmHg MEAN CIRCULATORY PRESSURE OR Pmc
95mmHg
FLOW STOPPED
5mmHg
Qr
0L/min
Qr 0 ( NO Pa - Pv DIFFERENCE)
80
WE START PUMPING!INMEDIATE EFFECT
FLOW STARTS
SOME VENOUS BLOOD
PUMP
ARTERIES
VEINS
Qh
1L/min
Pa 7mmHg
Pv 7mmHg
NO FLOW HERE YET
Qr
0L/min
81
FLOW RETURNS AT Qr AT THE NEW Qh
PUMP
ARTERIES
VEINS
Qh
1L/min
Pa 26mmHg
Pv 6mmHg
FLOW STARTS
Qr
1L/min
R 20mmHg
Qr Pa - Pv / 20 1L/min
82
THE END