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Cardiac Output and Blood Pressure Lect

PHYL2001: Physiology of Human Body
Cardiac Output and
Blood Pressure
Dr Peter McFawn
Room: G.01 Anatomy Building
Ph: 6488 3341
email: peter.mcfawn@uwa.edu.au
Lecture Outline
Overall design of the circulatory system
Vascular compartments
Arterial Blood Pressure
Cardiac output
Cardiac Function Curve
Aims I
 List and define the compartments of the
cardiovascular system.
 Define Heart Rate, Stroke Volume, Cardiac
Output and Venous Return.
 Know typical values for Heart Rate, Stroke
Volume and Cardiac Output.
 List the variables which alter cardiac output and
make calculations from CO=HRxSV.
 Explain the interaction among venous return and
cardiac output for the left and right heart.
Aims II
Define TBW, ECF, ICF, IF, Plasma and Blood.
Calculate TBW, ECF, IF and blood volume.
Know typical values for blood volume and PCV.
Describe the systemic and pulmonary circulations and
explain the difference between them
Describe the Frank-Starling law of the heart and sketch the
cardiac function curve.
Define Systolic, Diastolic, Mean and Pulse Pressure for the
systemic arterial system.
Know typical values for systemic arterial systolic, diastolic,
mean and pulse pressure.
Calculate mean and pulse pressure from systolic and
diastolic pressure.
Functions of the Cardiovascular System
 Delivery of O2, Glucose and other nutrients to
active tissues.
 Removal of CO2, Lactate and other waste products
from active tissues.
 Transport of metabolites and other substances to
and from storage sites.
 Transport of hormones, antibodies and other
substances to site of action.
 Moves blood to transport stuff in the blood
Total Body Water (TBW) 60% of body weight
(males) is water (~50% females)
Fluid inside cells is intracellular fluid (ICF)
Fluid outside cells is extracellular fluid (ECF)
Two thirds of total body water (TBW) is in ICF
One third of TBW is in ECF
ECF found in solid organs is interstitial fluid
Plasma, lymph and IF are all part of ECF
Fluid in the blood vessels and chambers of
the heart
6 – 8% of body mass
A 70 kg person has about 5 L of blood
55% plasma (fluid)
Serum is fluid from clotted blood
45% cells (packed cell volume 0.45)
erythrocytes (red blood cells)
leukocytes (white blood cells)
Cells of the Blood
• Red blood cells
– gas transport
• White blood
– immune
• Platelets
– Blood clotting
• All are from haematopoietic stem cells in bone marrow
Outline of the Circulation
Arteries and Veins
 Arteries accept blood from the ventricles of the heart.
 Arterioles are small arteries; control flow.
 Microcirculation connects arterioles to venules, includes
direct connections (metarterioles etc), capillaries.
 Capillaries are where exchange occurs
 Venules are small veins; collect blood from
 Veins deliver blood to the atria of the heart; blood
storage vessels.
Systemic versus
Pulmonary circulation from
the right side of the heart.
Gains O2 from the lungs.
Systemic circulation is all the
Delivers O2 to the body.
Comes from the left side of
the heart.
The systemic and pulmonary
circulations are in Series with
each other.
Berne & Levy Principles of Physiology Ch 15
Systemic versus
Systemic arteries have
oxygenated blood.
Systemic veins have
deoxygenated blood.
Pulmonary arteries have
deoxygenated blood
Pulmonary Veins have
oxygenated blood.
Berne & Levy Ch 15
Some Numbers
Diastole: Relaxation of the heart.
Systole: Contraction of the heart
Diastolic pressure:
80 mmHg
lowest systemic arterial pressure, during diastole.
Systolic pressure:
120 mmHg
highest systemic arterial pressure, during systole.
Blood pressure  Systemic arterial pressure as:
systolic/diastolic e.g. 120/80 mmHg
Some (more) Numbers
Pulse Pressure:
the difference between systolic and diastolic
Mean arterial pressure:
90-95 mmHg
the arterial pressure averaged over the cardiac cycle.
Pa  Pd + ( Ps - Pd )
Pressure and Flow
Flow(Q) requires a pressure
Blood flows from high to low
Flow through the vascular
system is produced by the
arterial to venous blood
Rhoades & Pflanzer Human Physiology 2nd Ed Ch 18
Cardiac Output
How Much Blood Does the Heart Pump?
Cardiac output is the amount of
blood the heart pumps each minute.
About 5 l/min at rest
Cardiac Output
Volume pumped each minute depends on:
The number of strokes – heart rate
The volume per stroke – stroke volume
Even More Numbers
Heart Rate:
70 beats/min
number of contractions per unit time.
Stroke Volume:
70-80 ml
volume pumped by a ventricle in one contraction.
Cardiac Output:
5-5.5 l/min
flow rate out of one side of the heart, volume pumped per
unit time.
Cardiac Output = Heart Rate x Stroke Volume
Venous return:
flow rate into the heart.
5-5.5 l/min
Ventricular Volumes
 End diastolic volume ~130 ml
 End systolic volume ~50 ml
 Stroke volume
~80 ml
 Ejection fraction ~0.65 or 65%
Flow Through Regions Connected in Series
Rhoades & Pflanzer 2nd Ed Ch 18
Flow in =flow out
Q =5 l/min
Q =5 l/min
Flow in =flow out
Blood Volume is abbreviated as: Q
Blood Flow is abbreviated as:
Intrinsic Control of Cardiac Output
Venous return controls stroke
Cardiac Function Curve
Increasing venous return
increases the ventricular
end diastolic volume and
stretches the ventricles.
Stretching muscle cells
increases the pressure
they can generate.
Increasing pressure
increases stroke volume.
Frank-Starling Law
 “Within physiological limits the heart pumps all the blood
it receives.”
 Increased venous return stretches the ventricles and
increases force production until cardiac out put matches
venous return.
 Arteries, microcirculation and veins.
 Systemic versus Pulmonary Circulation.
 Systemic arterial pressure and an equation.
 Cardiac output, venous return, blood flow and another
 Cardiac function curves and the Frank-Starling Law.
 Lots of numbers and definitions.