Transcript Cardiorespiratory Function and Performance

The Cardiovascular System
Cardiovascular Control
During Exercise
Chapter 11 and 12
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Heart Structure and Blood Flow

The atria receive
blood into the heart;
the ventricles eject
blood from the
heart.
Atria
Ventricles
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The Myocardium

Because the left
ventricle must
produce more power
than other
chambers, its
myocardium is
thicker due to
hypertrophy.
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Cardiac Conduction
Cardiac tissue is capable of
autoconduction.
 It initiates its own pulse without neural
control.

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Cardiac Conduction

The sinoatrial (SA) node is the heart’s
pacemaker, establishing the pulse and
coordinating activity throughout the
heart.
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Extrinsic Control
of Heart Activity

Heart rate and contraction strength can
be altered by the autonomic nervous
system or the endocrine system.
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Electrocardiography (ECG)
The ECG is a recording of the heart’s
electrical functioning.
 An exercise ECG may reveal underlying
cardiac disorders.

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Cardiac Function

The cardiac cycle:
• Relaxation = diastole.
• Contraction = systole.
• ECG waves: P, QRS, T.

Stroke volume.
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Cardiac Function
Ejection fraction from left ventricle
(60% at rest).
.
-1
 Cardiac output (4.8-6.4 L min )
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Vascular System:

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Arteries.
Arterioles.
Capillaries.
Venules.
Veins.
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Venous Return

Blood returns to the heart through the
veins, assisted by:
• Breathing.
• Muscle pump.
• Valves.

Valsalva Manuever
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Distribution of Blood

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Activity dictates distribution.
Vasoconstriction.
Vasodilation.
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Blood Pressure (NHLBI, 2003)
Pressure
Normal
Prehypertension
Stage I
Hypertension
Stage II
Hypertension
Systolic
< 120
120-139
140-159
> 160
Diastolic
< 80
80-89
90-99
> 100
Otherwise
healthy
None
None
Diuretics for
most,
possibly other
drugs
Two-drug
combo;
usually one is
a diuretic
With other
diseases
None
Medically treat Multiple
diseases
medications
Treatment
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Multiple
medications
Blood
Blood and lymph are the substances
that transport materials to and from
body tissues.
 Fluid from plasma enters tissues,
becoming interstitial fluid.

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Blood

Most interstitial fluid
returns to the
capillaries, but some
enters the lymphatic
system as lymph,
eventually returning
to the blood.
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Blood


Blood is about 55%
to 60% plasma and
40-45% formed
elements including
RBCs, WBCs, etc.
Hematocrit – ration
of blood cells to total
blood volume.
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Blood
Oxygen is primarily transported bound
to the hemoglobin in red blood cells.
 As blood viscosity increases, so does
resistance to flow.

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Total Peripheral Resistance

TPR = length x viscosity
______________
(Radius)4
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Response to Exercise

As exercise intensity increases, HR
increases.
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Exercise

The heart ejects blood more often, thus
speeding up circulation.
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Response to Exercise
Stroke volume also increases, so the
amount of blood ejected with each
contraction increases.
 Increases in HR and SV increase
cardiac output.

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Response to Exercise

More blood is forced out of the heart
during exercise then when at rest, and
circulation speeds up.
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Response to Exercise

This insures that adequate supplies of
the needed materials - oxygen and
nutrients - reach the tissues and that
waste products, which build up much
more rapidly during exercise, are
quickly cleared away.
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Major Changes in Blood
During Exercise
The a-vO2 difference increases.
 Increased extraction of oxygen from the
blood for use by the active muscles.

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Major Changes in Blood
During Exercise
Plasma volume decreases during
exercise.
 Water is forced into tissues by
increased blood pressure.
 Water also evaporates.

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Major Changes in Blood
During Exercise
Hemoconcentration occurs as plasma
fluid (water) is lost.
 Although the actual number of red blood
cells might not increase, the relative
number of red blood cells per unit of
blood increases, which increases O2
carrying capacity.

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Major Changes in Blood
During Exercise
pH levels drops from resting values of
7.4 to 7.0 or lower.
 Muscle pH decreases even further.
 The decrease in pH results primarily
from increased blood lactate
accumulation with increasing exercise
intensity.

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