Download chapter 9 - circulatory responses to exercise

Chapter 9:
Circulatory Adaptations
to Exercise
EXERCISE PHYSIOLOGY
Theory and Application to Fitness and Performance, 6th
edition
Scott K. Powers & Edward T. Howley
© 2007 McGraw-Hill Higher Education. All rights reserved.
Introduction
 One major challenge to homeostasis posed
by exercise is the increased muscular
demand for oxygen
 During heavy exercise, oxygen demands may
 by 15 to 25 times
 Two major adjustments of blood flow are;
 cardiac output
Redistribution of blood flow
 A thorough understanding of the
cardiovascular system is essential to exercise
physiology
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Objectives
 Give an overview of the design and function
of the circulatory system
 Describe cardiac cycle & associated electrical
activity recorded via electrocardiogram
 Discuss the pattern of redistribution of blood
flow during exercise
 Outline the circulatory responses to various
types of exercise
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Objectives
Identify the factors that regulate local
blood flow during exercise
List & discuss those factors responsible
for regulation of stroke volume during
exercise
Discuss the regulation of cardiac output
during exercise
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The Cardiovascular System
Purposes
1.
2.
3.
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The Circulatory System
Heart
Pumps blood
Arteries and arterioles
Carry blood ________ from the heart
Capillaries
Exchange of __________ with tissues
Veins and venules
Carry blood __________ the heart
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Structure of the Heart
Fig 9.1
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Pulmonary and Systemic Circuits
Systemic circuit
________ side of
the heart
Pumps _________
blood to the whole
body via arteries
Returns
____________
blood to the right
heart via veins
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Pulmonary circuit
________ side of
the heart
Pumps __________
blood to the ______
via pulmonary
arteries
 Returns ___________
blood to the ________
heart via pulmonary
veins
The Myocardium
Fig 9.3
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The Cardiac Cycle
Diastole
Systole
___________ phase _________ phase
Fig 9.5
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Arterial Blood Pressure
Expressed as systolic/diastolic
Normal is 120/80 mmHg
High is 140/90 mmHg
Systolic pressure (top number)
Pressure generated during ________________
(systole)
Diastolic pressure
Pressure in the arteries during _____________
(diastole)
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Blood Pressure
________________
Difference between systolic and diastolic
Pulse Pressure = Systolic - Diastolic
________________________ (MAP)
Average pressure in the arteries
MAP = _______________________
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Mean Arterial Pressure
Blood pressure of 120/80 mm Hg
MAP =
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Measurement of
Blood Pressure
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Fig 9.7
Factors That Influence Arterial
Blood Pressure
Fig 9.8
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How is Blood Pressure Regulated?
Acute regulation
Achieved by _____________________
Long term regulation
Function of the ___________________
They do so by control of ____________________
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Electrical Activity of the Heart
Contraction of the heart depends on
electrical stimulation of the
myocardium
Impulse is initiated in the __________
and spreads throughout entire heart
May be recorded on an
__________________ (ECG)
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Conduction System of the Heart
___________________
Fig 9.9
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________________
The amount of blood pumped by the
heart each minute
Product of _________________
Q = _________
______ = number of beats per minute
______ = amount of blood ejected in each beat
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Regulation of Heart Rate
2 prominent factors that influence HR
Decrease in HR
1. _____________________
Via ______________
Slows HR by inhibiting _________
Increase in HR
2. _____________________
Via cardiac ______________
Increases HR by stimulating ________
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Regulation of Stroke Volume
 SV at rest or during exercise is regulated by 3
variables
1. __________________ (EDV)
Volume of blood in the ventricles at the end of diastole
(“preload”)
2. __________________
Pressure the heart must pump against to eject blood
(“afterload”)
3. _________ of the ventricular contraction
“Contractility”
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End-Diastolic Volume
__________________
Greater preload results in stretch of ventricles
and in a more forceful contraction
Affected by venous return:
What factors regulate venous return?
1.
2.
3.
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The Skeletal Muscle Pump
Rhythmic skeletal
muscle contractions
force blood in the
extremities toward the
heart
One-way valves in veins
prevent backflow of
blood
Fig 9.16
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Average Aortic Pressure
Aortic pressure is ___________ related to
stroke volume
High afterload results in a ___________
stroke volume
Requires greater force generation by the
myocardium to eject blood into the aorta
Reducing aortic pressure results in
_______ stroke volume
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Ventricular Contractility
Increased contractility results in ________
stroke volume
Circulating epinephrine and norepinephrine
Direct sympathetic stimulation of heart
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Factors that Regulate Cardiac Output
Parasympathetic
nerves
Mean arterial
pressure
Cardiac = Cardiac Rate x Stroke Volume
Output
Sympathetic
nerves
Fig 9.18
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Contraction
strength
EDV
Stretch
FrankStarling
Hemodynamics
The study of the
physical principles of
blood flow
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Physical Characteristics of Blood
___________
Liquid portion of blood
Contains ions, proteins, hormones
Cells
___________
Contain hemoglobin to carry oxygen
___________
___________
Important in blood clotting
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____________
Percent of blood composed of cells
Fig 9.19
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Hemodynamics
Based on interrelationships between:
___________
___________
___________
Since large increases in P are
hazardous to health – decreasing
resistance is the primary factor used to
achieve increases in BF during exercise
with a small rise in P
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Hemodynamics: Pressure
Blood flows from ___  ___ pressure
Proportional to the difference between
MAP and right atrial pressure (P)
BF depends on P at 2 ends of
vascular system
P at 2 ends of a vessel are equal =
__________
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Blood Flow Through the Systemic
Circuit
Fig 9.20
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Hemodynamics: Resistance
What factors contribute to the resistance
of blood flow?
1.
2.
3.
Resistance is directly
proportional to these 2 factors
Most important factor
determining vascular resistance
A _________ change in vessel diameter can have a
dramatic impact on resistance!
Resistance =
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Hemodynamics: Blood Flow
___________ proportional to the pressure
difference between the two ends of the
system
___________ proportional to resistance
Flow =
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Sources of Vascular Resistance
MAP __________ throughout the
systemic circulation
Largest drop occurs across the
_____________
Arterioles are called “resistance
vessels”
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Pressure Changes Across the
Systemic Circulation
Fig 9.21
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Oxygen Delivery During Exercise
Oxygen demand by muscles during
exercise is many times greater than at rest
Increased O2 delivery accomplished via 2
mechanisms:
1.
2.
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Changes in Cardiac Output
Cardiac output increases due to:
Increased ____
Linear increase to max
Max HR = 220 - Age (years)
Increased ____
Plateau at ~40% VO2max
Oxygen uptake by the muscle also ______
Higher arteriovenous difference
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Changes in
Cardiovascular
Variables During
Exercise
Fig 9.22
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Redistribution of Blood Flow
Muscle blood flow to working
skeletal muscle
Splanchnic blood flow  to less active
organs
Liver, kidneys, GI tract
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Changes in
Muscle and
Splanchnic
Blood Flow
During
Exercise
Fig 9.23
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Increased Blood Flow to Skeletal Muscle
During Exercise
 What regulates blood flow to various organs
during exercise?
1.
2.
 Blood flow increased to meet metabolic demands
of tissue
 This happens because of muscle vasodilation
 O2 tension, CO2 tension, pH, nitric oxide
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Redistribution of Blood Flow During
Exercise
Fig
9.24
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Circulatory Responses to Exercise
Heart rate and blood pressure
Depend on:
Type, intensity, and duration of exercise
Environmental condition
Emotional influence
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Transition From Rest  Exercise and
Exercise  Recovery
Rapid increase in HR, SV, cardiac
output
Plateau in submaximal (below
lactate threshold) exercise
Recovery depends on:
Duration and intensity of exercise
Training state of subject
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Incremental Exercise
Heart rate and cardiac output
Increases linearly with increasing work rate
Reaches plateau at 100% VO2max
Stroke volume
Systolic blood pressure
Increases with increasing work rate
Double product – also called___________
Increases linearly with exercise intensity
Indicates the work of the heart
Double product =
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Arm vs. Leg Exercise
At the same oxygen uptake arm work
results in higher:
_______
Due to higher ______________ stimulation
 _______
Due to _____________ of large inactive muscle
mass
.
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Heart Rate and
Blood Pressure
During Arm and
Leg Exercise
If these 2 factors
increase so will
_______________
__________
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Fig 9.26
Prolonged Exercise
 Cardiac output is maintained
 Gradual decrease in _________
 Gradual increase in _________
 Cardiovascular drift
 What is the drift due to?
1.
2.
.
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HR, SV, and Q During Prolonged
Exercise
Fig 9.27
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Cardiovascular Adjustments
to Exercise
Fig 9.23
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