Keep coming back to

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Review your functional anatomy at
http//www.blaufuss.org/
Keep coming back to The Cardiac Cycle
http//www-medlib.med.utah.edu/kw/pharm/hyper_hear
t1.html
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Please recite the mantra in unison
Preload Afterload Heart rate Contractility
Types of regulation Intrinsic Treppe Neural
control sympathetic Hormonal control
epinephrine
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It all works together
Chronotropic heart rate Iontropic contractile
strength
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Regulation of the heart, contd
http//www-medlib.med.utah.edu/kw/pharm/hyper_hear
t1.html
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Functions of the large vesselsArteries and veins

• l

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FUNCTIONS OF THE ARTERIAL SYSTEM
ACTS AS A BLOOD CONDUIT Small pressure loss
Smooth, non-thrombogenic DAMPS CARDIAC
PRESSURE PULSES Impedence matching The
ventricuar pump is a discontinuous pump and the
cells need a continuous supply of O2 etc.
Ventricular ejection (ml/min)
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Blood ejected from the ventricle during systole
is stored in the large arteries
Large arteries
Systole
To cells during diastole
Diastole
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Capacitance
So, how much blood can be stored with each
systole?
Capacitance is a measure of a vessel's ability to
distend and store blood when the intravascular
pressure is raised.
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FUNCTIONS OF THE VENOUS SYSTEM

• CONDUITS
• Blood exiting tissues collects in venules and
  veins and returns to the heart. The veins are
  active in the process
• BLOOD RESERVOIR
• Blood can be shifted from one part of the
  cardiovascular system to another

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Determinants of venous volume distribution - 1
Passive Postural changes 300 - 800 ml of blood
can be displaced out of the thorax
and into the legs on standing.
This decreases venous return and thus, cardiac
filling. Leads to arterial hypotension because of
decreased end diastolic pressure Reflexes cause
Increase heart rate, peripheral resistance,
cardiac contractility Decrease venous
capacitance (venoconstriction)
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Determinants of venous volume distribution - 2
External Compression Intermittent contraction of
skeletal muscles as in exercise compresses
underlying veins. Venular valves ensure
movement of blood in the direction of the heart
- the muscle pump. Patients are given pneumatic
leggings which compress the veins and drive
blood into the central circulation. Increases
in intrathoracic pressure during
exhalation. Reduced external pressure Intrathora
cic pressure decreases with inhalation
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Determinants of venous volume distribution - 3
Active contraction of smooth muscle in venular
walls moves blood toward the heart. Can be a
direct effect of stretch (i.e. a myogenic
response - vessels to constrict as the
intraluminal pressure rises. Can be part of a
neural reflex Vascular beds vary in the amount
of venoconstriction that occurs. Skin, liver,
lungs, and spleen are important blood reservoirs
because they undergo substantial
venoconstriction.
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DETERMINANTS OF THE SYSTEMIC ARTERIAL PRESSURE

• TWO COMPONENTS TO THE ARTERIAL PRESSURE

Pulse pressure determines arterial distension
with each beat, mean pressure determines the flow
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DETERMINANTS OF THE MEAN SYSTEMIC ARTERIAL
PRESSURE
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DETERMINANTS OF THE SYSTEMIC ARTERIAL PULSE
PRESSURE

• The stroke volume is a key factor in determining
  the pulse pressure
• During an individual cardiac cycle
• Systolic Entry Volume Diastolic Exit Volume
• With each heart beat the movement of a stroke
  volume is associated with a corresponding aortic
  pressure rise.
• Capacitance relates the pressure change to the
• volume change.

For each pulse Systolic Entry Volume Diastolic
Exit Volume
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DETERMINANTS OF THE SYSTEMIC ARTERIAL PULSE
PRESSURE

• Arterial capacitance is variable and depends on
  arterial pressure, age, contraction of smooth
  muscle, and pathology.

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DETERMINANTS OF THE SYSTEMIC ARTERIAL PULSE
PRESSURE
What happens when Iyou elevate your stroke volume?
Stroke volume B
Stroke volume A
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DETERMINANTS OF THE SYSTEMIC ARTERIAL PULSE
PRESSURE
What happens if you maintain a constant stroke
volume and increase capacitance?
Pulse pressure decreases.
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DETERMINANTS OF THE SYSTEMIC ARTERIAL PULSE
PRESSURE
What happens if you maintain a constant stroke
volume and capacitance and increase the total
peripheral resistance? Mean pressure (P COxR)
increases but the pulse pressure doesnt change,
unless the capacitance changes.
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DETERMINANTS OF THE SYSTEMIC ARTERIAL PULSE
PRESSURE

• What happens to pulse pressure when you age and
  arterial capacitance becomes non-linear?
• What is the outcome if I incease my blood
  pressure (e.g. because of increased peripheral
  resistance)? This is reality for many!

Hypertension from vasoconstriction with a
constant stroke volume would elevate mean
pressure. Arterial capacitance decreases if mean
pressure is raised. Look at the slope of the
line. At the higher mean pressure the pulse
pressure is raised, especially the systolic.
This is how your aged patients will look
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The shape of the arterial pressure pulse
Mean Pressure 120 118 116 113 111
How is it possible for the pressures to rise
along the vessel length?
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The pulse as an indicator of health

• in the peak of Sanskrit medicine there were
  more than 100 descriptions of the arterial pulse.
  The Chinese art of pulse feeling, which is still
  practiced, recalls 33 different patterns. The
  features that are used in classification are
  depth, rate, force, rhythm etc 1.

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How about shifting to pulse diagnosis
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CARDIAC OUTPUT Cardiac output volume squirted
with each beat x beats/min VASCULAR
RESISTANCE Vascular resistance size of vessels
x number of vessels x viscosity BLOOD PRESSURE
Blood pressure cardiac output x vascular
resistance Blood pressure stroke volume x
heart rate x vascular resistance
But pressure changes during the cardiac cycle
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Systolic pressure
Mean pressure
diastolic pressure
Decrease compliance here
Mean pressure
Mean pressure
Increase stroke volume
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Cardiac cycle from the University of Utah(again)
Blaufuss
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urani pulse diagnosis.htm