Download The Cardiovascular System

Chapter 5
The Cardiovascular
System
Learning Objectives
• Know the components of the
cardiovascular system.
• Know the basic, general anatomy and
physiology of the cardiovascular system.
• Understand the responses of the
cardiovascular system during exercise.
• Understand the responses of the
cardiovascular system to exercise training.
Cardiovascular System
Composition & Primary Function
• Heart
• Blood vessels
• Blood
1
The Heart—
Its Function as 2 Pumps
Types of Blood Vessels
•
•
•
•
•
•
Arteries
Veins
Pulmonary veins
Arterioles
Capillaries
Venules
Anatomy of the Heart
• Four chambers
• A muscular organ w/ striated muscle
– Muscle fibers are stimulated by the nervous
system, which triggers contractions
2
Basic Anatomy of the Heart
Origin of Electrical Activity
in the Heart
•
Normal conditions in an intact heart:
•
Abnormal conditions in which SA slows
its impulse frequency
Conducting System
of the Heart
3
The Cardiac Cycle
• The heart’s cyclical pattern of contraction
& relaxation
– Diastole
– Systole
• Unidirectional blood flow
– Regulated by valves, which are critical for
preventing backflow of blood & for blood
pressure
• Atrial contraction
• Ventricular contraction
(continued)
The Cardiac Cycle
(continued)
• End diastolic volume (EDV)
– Amount of blood in each ventricle at the end
of diastole
• End systolic volume (ESV)
– Amount of blood in each ventricle at the end
of systole
• Stroke volume (SV)
– The difference between EDV and ESV (the
amount of blood ejected out of each ventricle
with each cardiac contraction)
Events of the Cardiac Cycle
4
Cardiac Output
• The amount of blood ejected by the heart each
minute:
Formula for Determining
Cardiac Output
Control of Heart Rate
& Stroke Volume
• Heart rate is influenced by the effect of the
autonomic nervous system on the SA
node.
• Stroke volume is determined largely by
end diastolic volume, which is related to
ventricular contraction force.
– The Frank-Starling law of the heart
5
Factors Affecting Heart Rate
Factors Affecting Stroke Volume
One-Way Valves of the Veins
6
Clinical Application:
Heart Murmurs
• May be caused by irregularities in vessel
walls or malformed cardiac valves, and
may result in regurgitation of blood or
restricted blood flow—and cause the heart
to work harder.
• The heart compensates for increase in
retained blood by increasing its contraction
force and consuming more oxygen.
• In some cases, heart murmurs may
severely limit exercise tolerance.
Your Viewpoint
• Exercise programs can be beneficial for
so many different health problems, but
patients with heart murmurs may have
damaged heart valves. What would you
counsel such a patient about engaging in
strenuous exercise?
Heart Rate Is More Important than
Stroke Volume in Aerobic Exercise
•
•
•
Stroke volume ↑s very little w/ ↑ in
metabolism, until it levels out at
approximately 8x the resting level.
Heart rate is proportional to the work load
imposed.
Heart rate is proportional to oxygen
consumption during exercise.
7
Typical Heart Rate
Response to Exercise
Heart Rate ∆s in a Moderately
Conditioned, Middle-Aged Subject
∆s in Cardiovascular Function
Following Endurance Training
8
Effects of Training on the Heart
• Both resting heart rate and heart rate for a given
submaximal exercise load ↓
• Stroke volume ↑s
• Three mechanisms work to meet demands on
tissues during intense exercise:
– Reserve of heart rate
– Stroke volume reserve
– Greater extraction of oxygen from blood
Graphic Representation of Changes
during Continuous, Moderate Intensity
Exercise
Anatomy of Blood Vessels
• Aorta and large arteries
– Allow vessels to distend and recoil
• Arterioles
– Act as resistance vessels, which protect
capillaries
• Venules and veins
– Serve as collecting vessels, draining
various tissues
9
Hemodynamics:
Principles Governing Blood Flow
Distribution of Blood to
Systemic Tissues
At Rest and During Heavy Exercise
Microcirculation
• Well-organized network in which arterioles
give rise to metarterioles
• True capillaries arise from metarterioles
• AV shunts provide another route for blood
flow
10
Diagram of Microcirculation
Blood Distribution
• Blood flow to the tissues is controlled by
changes in the diameter of small arteries
& arterioles
• Two mechanisms:
Blood Pressure
• Is the driving force for moving blood through the
circulatory system
• Plays a role in health problems such as heart
attacks, stroke & kidney disease
• Affected by several factors: Age, gender,
emotional state, time of day & body position
• Defined as systolic pressure over diastolic
pressure
• Measured by a sphygmomanometer
11
Blood Pressure ∆s
During Exercise
• Rhythmic exercise—
• Isometric or static exercise—
Typical Time Course of the Arterial Blood
Pressure Response in a Healthy Young Male
Where to Learn More
• Cardiovascular system:
– www.innerbody.com/image/cardov.html
• American Heart Association:
– www.americanheart.org
• Heart.org:
– www.theheart.org/index.cfm
• American Association of Cardiovascular
and Pulmonary Rehabilitation
(AACVPR):
– www.aacvpr.org
12
Can you?
• Describe normal cardiorespiratory
responses to static and dynamic exercise
in terms of heart rate, blood pressure, and
oxygen consumption?
– What sort of cardiorespiratory response would
you expect to see when someone is pushing
a heavy sofa that does not move?
– What response would you expect to see in
someone who is cleaning his house?
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