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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 O 2 nutrients, etc, REMOVAL of wastes.

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basic summary of cardiovascular physiology
“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’

determinants of perfusion
DETERMINANTS OF PERFUSION:
  • 1) CARDIAC OUTPUT

Proper Electrical and Mechanical Function

of the HEART as a PUMP

  • 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.

slide3
At rest, typically, Cardiac Output is 5 liters per minute(recall that an average man’s total Blood Volume is ~ 5 liters)
cardiac output depends on 2 functions of the heart
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

slide7

Cardiac conduction system:

SA node AV node

Bundle of His

Right Bundle Branch

Left Bundle Branch

Purkinje Fibers

AV Bundle, (Bundle of His)

electrical function
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

slide12

Normal sinus rhythm, rate ~72 bpm

Nor

Onset, supraventricular tachycardia, rate ~120

Normal sinus, rate ~64 bpm

Rhythm strips

Atrial fibrillation, V.rate

varies, ~130-150

Ventricular fibrillation,

a terminal rhythm

mechanical function
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

cardiac cycle
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)

valvular function
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

cardiac output
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

blood volume euvolemia hypovolemia volume overload
BLOOD VOLUME Euvolemiahypovolemia 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

blood pressure
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)
regulation of arterial resistance
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

measuring blood pressure
Measuring blood pressure:

SPHYGMOMANOMETER AND STETHOSCOPE

SYSTOLIC BLOOD PRESSURE /

DIASTOLIC BLOOD PRESSURE

(Korotkoff sounds)

other important effects on co and perfusion
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
slide25
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

slide26
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
and finally capillaries
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 )

slide30

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

slide31
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.