Cardiovascular Physiology

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Cardiovascular Physiology

• Blood
• Heart
• Peripheral Circulation

Solution of Nutrients/Wastes
Pump
Tubes
The primary function of the Cardiovascular system
is to 1) deliver nutrients/oxygen and 2)remove
wastes/CO2 from the cells in your body
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Cardiac Physiology
The primary function of the HEART is to generate
a Pressure gradient in the vascular system
Pressure gradient allows blood to move by BULK
FLOW through the body the lungs
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Bulk Flow Movement DOWN a Pressure Gradient
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Heart Anatomy
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4 chambers of human heart
Left Atrium
Right Atrium
Left Ventricle
Right Ventricle
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Valves Vessels
Vena Cavae
Pulmonary Arteries
Aorta
Pulmonary Veins
Aortic Valve
Left Atrioventricular Valve
Pulmonary Valve
Chordae Tendinae
Right Atrioventricular Valve
Papillary Muscle
Interventricular Septum
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The Heart is surround by cardiac muscle
Pericardium
Myocardium
Endocardium
Myocardial Fibers
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Myocardium Anatomy

• Myocardium is very similar to skeletal muscle
• Except
• Intercalated discs for Gap junctions between
  adjacent myocardial fibers
• Myocardial fibers branch
• SR and T-tubules are weakly linked.Ca2 is
  slowly released upon excitation

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Cardiac Cycle

• The cardiac cycle links
• 1) Electrical
• 2) Contractile
• 3) Pressure
• 4) Flow
• through the heart!

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Pacemaker Cells Heart is Autorhythmic!
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How do pacemaker cells spontaneously produce
action potentials?
Pacemaker cells have an UNSTABLE resting membrane
potential!

• Prepotential Few Na channels open,
• Na influx funny
  current
• 2) Depolorization VG Ca2 channels open
• INFLUX of Ca2
• 3) Repolarization K channels open
• EFFLUX of K

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Drugs to treat Arrhythmias sometimes work on Ca2
channels!
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Myogenic signal propagates down Myocardium
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Electrical Properties of the Myocardium
Plateau
Skeletal muscle AP look and behave like neural
cells
Due to the SLOW CLOSING OF Ca2,
Myocardium REPOLARIZES VERY SLOWLY
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Excitation-Contraction Coupling of Cardiac Muscle
1) Action Potential
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Ca2
ECF
Sacrolemna
2) VG Ca2 channels open, CA 2 Influx
ICF
RyR
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3) Ca2 influx triggers RyR channels on SR
to open Calcium Induced Calcium Release
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SR
Ca2
VG Ca2 Channel
4) Ca2 pours out of SR Ca2 Spark!
T-tubule
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Ca2 Spark
5) Sparks sum to create Ca2 signal
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Ca2 Signal
6) Ca2 binds Troponin, cross- bridge
formation, Contraction!
Sarcomere
Calcium Sparks Video
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Contraction
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Myocardium contraction is GRADED!
Amount of Ca2 entering myocardium is
proportional to contraction strength
Ca2
Force of Myocardium
Ca2
Amount of Calcium INFLUX
Ca2 Spark
Ca2 Signal
of Cross bridges Formed
Contraction
Amount of Calcium INFLUX
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Excitation-Contraction Coupling in Myocardium vs.
Skeletal Muscle
Skeletal Muscle
Refractory
Myocardium
Ca2 Plateau prolongs the refractory
period..summation cannot happen! Guarantees that
Cardiac Muscle Contract-Relaxes Rhythmically!!!!!
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Dont get CONFUSED!

• Pacemaker Potentials

• Cardiac Muscle Excitation

Pacemaker EXCITATION gtgtgtgtgtgtgtgtgtgtgtgtgtgtgtgtgtgtgtgt.Cardiac
Muscle Excitation- Contraction
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Hearts Electrical Conducting System
SA 100 min-1 AV node 40 min-1 AV
bundle Bundle branches Purkinje Fibers 10-30
min-1
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Why do the SA pacemaker cells beat a higher
frequency than AV, Bundle Branches Purkinje?
SA NODE
AV NODE
SA Node has More Funny Current (Na) channels
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What about Bundle Branches and Purkinje (10-30
min-1)?
SA Node Atrial Muscle AV Node AV
Bundle Bundle Branches Purkinje
Fibers Ventricular Muscle
No Plateau Phase Shorter Refractory Period
Excitation involves Calcium PLATEAU Huge
Refractory Period
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EKG Electrocardiogram
Pairs of Electrodes on limbs are called LEADS
Upward deflection e. current TOWARDS
lead Downward deflection e. current towards -
lead
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Einthovens Triangle
P
P
T
T
QRS
QRS
EKG ONLY ONLY ONLY records electrical events in
the heart!!!!!!!!!!!!
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Atrial Depolarization
P - wave
EKG
Atrial Repolarization Ventricular Depolarization
QRS - Complex
Ventricular Repolarization
T - wave
S
P
T
QRS
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Ventricular Systole Contraction
Ventricular Diastole Relaxation
Atria have Systole and Diastole TOO!
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Late diastole Atria Ventricles
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START
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Early Ventricular DIASTOLE.
Atrial systole
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S1
S2
Early Ventricular SYSTOLE
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Late Ventricular Systole
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Cardiac Cycle

• The cardiac cycle links
• 1) Electrical
• 2) Contractile
• 3) Pressure
• 4) Flow
• through the heart!

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High Ventricular Pressure Forces AV Valves Shut
Low Ventricular Pressure Forces Aortic/Pulmonary
Valves Shut
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Valves respond to pressure!Guarantees One-Way
Blood Flow
Chordae Tendinae
Papillary Muscle
Relaxed ventricular muscle (diastole) Low
pressure in ventricle AV valve flops open Aortic
Valve Shuts
Contracting ventricular muscle (systole) High
pressure in ventricle AV valve forced
shut Aortic Valve Opens
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Blood Flow through heart is driven by Pressure!
Isovolumetric CONTRACTION
Isovolumetric RELAXATION
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Blood Flow through Heart
R. AV Valve
L. AV Valve
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Cardiac Cycle

• The cardiac cycle links
• 1) Electrical
• 2) Contractile
• 3) Pressure
• 4) Flow
• through the heart!

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Wiggers Diagram
1) No electrical activity Atrial Ventricular
Diastole Pressure is low Volume is increasing

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3
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2) P-wave Atrial Depol. Atrial Systole
Atrial Pressure Rises Ventricular volume
increases
3) QRS Atrial Repol, Ventricular Depol.
Ventricular Systole, Atrial Diastole Ventricula
r Pressure rises dramatically Atrial Pressure
rises Ventricular Volume flat, then decreases
as AV closes and Aortic and Pulmonary
Valves Open
4) T-wave Ventricular Repol. Ventricular
Diastole Pressure drops dramatically in
ventricle rises in Atria Ventricular
Volume decreases then is flat as aortic and
pulmonary valves CLOSE
5) No electrical activity Atrial
Ventricular Diastole Pressure Volume slowly
rise as blood fills