“BASIC SUMMARY”
of
CARDIOVASCULAR PHYSIOLOGY
 The purpose/goal
of

C.V.S. is :
adequate
PERFUSION
of the Tissues
PERFUSION = BLOOD FLOW,
 THUS,


DELIVERY of vital O2 nutrients, etc,
REMOVAL of wastes.
 “HEMODYNAMICS”
 (blood
refers to ALL the mechanisms
moving/changing) involved in keeping blood flow ‘normal’
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DETERMINANTS OF PERFUSION:
 1) CARDIAC OUTPUT
Proper Electrical and Mechanical Function
of the HEART as a PUMP
2) BLOOD VOLUME the vascular ‘tank’ must be
adequately filled with fluid to supply the need
3) BLOOD PRESSURE : “ FLOW” of a fluid is
dependent upon PRESSURE - and is always
from “high” pressure area to lower pressure area.
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At rest, typically,
Cardiac Output is
5 liters per minute
(recall that an average
man’s total Blood Volume
is ~ 5 liters)
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CARDIAC OUTPUT depends on 2
‘functions’ of the heart:
 A) ELECTRICAL function (Conduction system)
Generation and Propagation of a coordinated
Impulse to contract, from atrium to ventricle
Conduction system: SA node, AV node, AV Bundle,
R and L Bundle Branches, Purkinje system
(graphic measure of conduction: electrocardiogram)
ECG = “EKG”
p wave, QRS complex, t wave
B) MECHANICAL FUNCTION
1. CONTRACTILITY of the Myocardium
( strength / force of the contractions)
2. VALVULAR function
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Cardiac conduction system:
SA node AV node
Bundle of His
Right Bundle Branch
Left Bundle Branch
Purkinje Fibers
AV Bundle, (Bundle
of His)
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ELECTRICAL FUNCTION
 REGULATED RATE AND RHYTHM:
 Rate -




optimal rate depends on demand.
normal at rest 60-100 bpm
(Lance Armstrong’s is in the 30’s )
abnormal rates: bradycardia too slow
tachycardia too fast
RHYTHM -- SHOULD BE REGULAR
not skippy or chaotic
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Normal sinus rhythm, rate ~72 bpm
Nor
Normal sinus, rate ~64 bpm
Onset, supraventricular tachycardia,
rate ~120
Atrial fibrillation, V.rate
varies, ~130-150
Ventricular fibrillation,
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MECHANICAL FUNCTION
 CONTRACTILITY of the MYOCARDIUM:

the strength / force & completeness

of the Contractions
 (effects of ischemia / necrosis; CAD, HTN
drugs, etc)

The essence of “Congestive Heart Failure”
is usually that of INADEQUATE
squeeze capacity of the heart muscle
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Cardiac Cycle
 DIASTOLE - atria contract,

Vent. relax; blood flows thru
the AV valves, fills Ventricles.
(P wave on the EKG)
 SYSTOLE –Ventricles contract,
 Blood EJECTED into Aorta
and Pulm. Trunk, Art.
(QRS complex on the EKG)
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VALVULAR
FUNCTION
 NARROWED VALVE: STENOSIS diminished outflow
 INCOMPETENT VALVE: REGURGITATION or
INSUFFICIENCY: abnormal “Backflow “
the “ Heart Sounds “ are made by the valves closing –
‘ Lub Dupp lub dupp lub dupp
Murmur : swishing sound , made by TURBULENCE
of flow
can be either from Stenosis
or Regurgitation
*** abnormal valvular function affects Cardiac Output
directly, and indirectly by eventually
affecting Contractility of the muscle
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CARDIAC OUTPUT
 CARDIAC OUTPUT - HOW MUCH BLOOD CAN BE
PUMPED each minute?

normal, resting ~ 5 liters / min (roughly the
entire blood volume makes one cycle in one minute)
 CO
CARDIAC
OUTPUT
=
HR
x
SV
HEART RATE X STROKE VOLUME
pulse
beats per minute
amt blood ejected
each beat
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BLOOD
VOLUME
hypovolemia
Euvolemia
volume overload
 Multiple variants:

“Hydration” status (intake -- outgo) diuresis,
diarrhea, vomiting, sweating, hyperthermia/ fever,
 Proper blood production by bone marrow
 Lack of ‘hemorrhage’, or blood loss
 complex regulatory mechanisms
involving
kidney function, endocrine regulatory centers,
plasma protein conc., & others
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BLOOD PRESSURE
 1. It takes adequate BLOOD Volume for normal BP
 2. It takes adequate ‘FORCE’ on the FLUID

to make it
FLOW:
 A. Contractions of the Heart generate initial






PRESSURE SURGE, but, the chief
determinant of Blood pressure is:
B. VASCULAR RESISTANCE- affects the
BLOOD VOLUME IN THE ARTERIES:
Increased resistance VASOCONSTRICTION ^’s BP
(but less flow)
Decreased resistance decr’s BP: VASODILATION
(more flow)
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REGULATION of Arterial Resistance
 The regulation / changes made in Arterial resistance

in the various ‘REGIONs’ of the body
Account for the Alterations /adjustments in
 BLOOD FLOW to those areas
(increased flow to MUSCLES during exercise,
 Incr. Flow to Digestive tract after meals,
 ^ flowed to skin to dissipate heat,
Whereas Blood Flow to BRAIN and
KIDNEYS must remain rel. CONSTANT
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Measuring blood pressure:
 SPHYGMOMANOMETER AND
STETHOSCOPE


SYSTOLIC BLOOD PRESSURE /
DIASTOLIC BLOOD PRESSURE
(Korotkoff sounds)
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





other important effects
(on CO, and PERFUSION)
VENOUS RETURN:
THE FLOW OF BLOOD BACK TO THE HEART AFTER
DELIVERY TO THE CAPILLARIES
VEINS:
larger diameter, with elastic walls, increased
CAPACITANCE compared to corresp. Artery
 IMPORTANT - GRAVITY generally impedes
VENOUS return ----- so,
 VEINS have series of one way VALVES - which keep

the blood from flowing backwards
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Also:
 There are

2 FUNCTIONAL VENOUS
‘PUMPS’:
 1. SKELETAL MUSCLE CONTRACTIONS, and
 2. RESPIRATORY MOTIONS create negative
inspiratory pressure, which ‘’SUCKS’
VENOUS BLOOD INTO THE THORAX,
TOWARD THE HEART
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Modifications that promote venous return:
 Large lumens
 Valves

Muscular pump – skeletal
muscle activity “milks” blood
toward heart

Respiratory pump – pressure
changes during breathing move
blood toward heart
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
And FINALLY:
CAPILLARIES
must mention : CAPILLARIES –
 Where the ‘ACTION IS’ regarding EXCHANGE of

substances between the Vascular &

INTERSTITIAL spaces , at the
 Cells / Tissues level. (fluid, o2, co2 WBC’s,
molecules, etc ) can diffuse back and forth
( importance of hydrostatic and osmotic pressure )
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Structure of Capillaries:
ONLY
1 layer of endothelium
and A basement membrane,
with “SPACES” for DIFFUSION
no muscle or connective
tissue covering.
A large number of
capillaries in a specific
region is
called
a CAPILLARY BED
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5. Circulatory Shock
(or circulatory failure, a state
of hypoperfusion)
Inadequate blood flow to meet cellular needs.

Hypovolemic shock – due to decreased blood
volume.

Septic shock (or vascular shock) – due to
inappropriate vasodilation, brought about
by response to overwhelming infection.

Cardiogenic shock – due to poor heart function.