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“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” refers to ALL the mechanisms

(blood 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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AV Bundle, (Bundle of His)

Cardiac conduction system: SA node AV node Bundle of His Right Bundle Branch Left Bundle Branch Purkinje Fibers

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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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Nor

Normal sinus, rate ~64 bpm

Onset, supraventricular tachycardia, rate ~120

Normal sinus rhythm, rate ~72 bpm

Atrial fibrillation, V.rate varies, ~130-150

Ventricular fibrillation, a terminal rhythm

Rhy

thm

str

ips

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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 duppMurmur : 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

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 = HR x SV

CARDIAC HEART RATE X STROKE VOLUME

OUTPUT pulse amt blood ejected

beats per minute each beat

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BLOOD VOLUME Euvolemia hypovolemia 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

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

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.