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NASM Chapter 3THE CARDIORESPIRATORY SYSTEM
Learning Objectives
 The next two lectures covers how the cardiorespiratory
system responds to the demands of exercise and the
physiological adaptations that occur with specific training
programs.
 Upon completion of this chapter, you will be able to:
– Describe the anatomy and physiology of the cardiorespiratory
system
– Describe the acute and chronic responses to aerobic training
Components of the cardiorespiratory system
 Heart
 Vessels
 Lungs
 Airways
 Blood
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Heart
 The heart is about the size of
an adult fist and pumps
blood throughout the body.
 The heart is a muscular
pump that rhythmically
contracts to push blood
throughout the body.
 Heart muscle is termed
cardiac muscle and has
characteristics similar to
skeletal muscle.
 Control is involuntary.
 The heart is in the
mediastinum (the space
between the lungs)
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Structure of the Heart
 It is divided into four chambers: right
atrium, right ventricle, left atrium,
and left ventricle.
 Atria (top) are receiving chambers
 Ventricles (bottom) are the
propulsion chambers.
 Right side—receives venous blood
returning from the body
 Left side—receives arterial blood
returning from the lungs
 One-way Valves are necessary to
prevent backflow.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
The Heart: Blood flow
 The pathway of blood through the heart:
– Oxygen-poor blood coming from the body (via the
veins) enters the right atrium.
– From the right atrium, it is pumped to the right
ventricle, which sends it to the lungs (via the
pulmonary arteries) to give off carbon dioxide and
pick up fresh oxygen.
– Oxygenated blood returns to the heart (via the
pulmonary veins) entering the left atrium.
– It is then pumped to the left ventricle, which
pumps it through the aorta to the rest of the
body (except the lungs).
The Heart: Anatomy & Blood Flow Anatomy
Figure 12.2
Copyright © 2007 Lippincott Williams & Wilkins
The Heart: Cardiac Cycle
 The series of cardiovascular events occurring from the
beginning of one heartbeat to the beginning of the next is
called the cardiac cycle.
 The left and right sides of the heart work simultaneously.
– When the heart beats, both atria contract.
– Approximately 0.1 second after the atria contract,
both ventricles contract.
– The repeated contraction and relaxation is known as
systole and diastole.
• Systole: contraction phase (ventricles contract)
• Diastole: relaxation phase (ventricles fill)
Cardiac Muscle Contraction
A specialized conduction system
provides rhythm for the heart rate:
 Sinoatrial (SA) node:
– Located in the right atrium.
– Called the “pacemaker” because it
initiates the heartbeat
 Internodal pathways:
– Transfers the impulse from the SA to
the atrioventricular (AV) nodes
 Atrioventricular (AV) node:
– Delays the impulse before moving on
to the ventricles
 Atrioventricular (AV) bundle
(bundle of His):
– Passes the impulse to the ventricles
for contraction via the left and right
bundle branches of the Purkinje fibers.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
The Heart: Sympathetic Regulation
 Sympathetic fibers connect to the heart via the cardiac
accelerator nerves, which innervate the SA node and
ventricles.
 When stimulated, epinephrine and norepinephrine are
released, accelerating depolarization of the SA node and
increasing heart rate and contractility.
 At the onset of exercise, the initial increase in heart rate
(up to 100 bpm) is due to the withdrawal of
parasympathetic tone.
The Heart: Sympathetic Regulation (cont.)
 Increased cardiac output is influenced by:
– An increase in end diastolic volume, which causes a stretch in
cardiac fibers, thereby creating a stronger force of contraction
– Stronger contractility results in more blood pumped per beat
(i.e., a greater stroke volume)
 Increased blood flow to the working muscles is a result
of:
– Vasoconstriction of the vessels supplying non-working muscles
and viscera.
– Vasodilation of the vessels supplying the working muscles
– Autoregulation, which is the monitoring system of the
effectiveness of blood flow in response to the accumulation of
metabolites.
The Heart: Parasympathetic Regulation
 Parasympathetic fibers reach the heart via the vagus
nerves, which will make contact at both the SA node and
AV node.
 When stimulated, the vagus nerve endings release
acetylcholine, decreasing SA and AV node activity and
reducing heart rate.
Vessels: Introduction
 Blood vessels form a closed
circuit of hollow tubes that
allow blood to be
transported to and from the
heart:
– Arteries—carry oxygenated blood
away from the heart (with the
exception of the pulmonary artery)
– Veins—carry de-oxygenated blood
to the heart (with the exception of
the pulmonary vein)
– Capillaries—tiny vessels across
which the exchange of gases,
nutrients, and wastes occurs
between the blood and the cells of
the body
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Vessels: Arteries & Veins
Vessels: Arterial Blood Pressure
 Expressed as systolic/diastolic
– Normal is 120/80 mmHg
– High is 140/90 mmHg
 Systolic pressure (top number)
– Pressure generated during ventricular contraction (systole)
 Diastolic pressure
– Pressure in the arteries during cardiac relaxation (diastole)
Vessels: Measurement of Blood Pressure
Vessels: Blood Pressure throughout circulatory system
Vessels: 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
Oxygen Delivery
 Oxygen delivery is a function of cardiac output (the
quantity of blood pumped per minute).
– Cardiac output (Q) = Stroke volume (SV) x Heart rate (HR) (in
beats per minute)
• Stroke volume is the amount of blood pumped during each
heartbeat.
 Cardiac output increases due to increases in both SV
and HR.
– HR typically increases in a linear fashion up to maximal levels.
– SV increases to about 40–50% of maximal capacity, and then
plateaus.
Blood
 Blood acts as a medium to deliver and collect
essential products to and from the body’s tissues.
 The average human body holds about 5 L (roughly
1.5 gallons) of blood at any given time.
 Blood is a vital support mechanism; it:
•
•
•
•
Transports oxygen, hormones, and nutrients to specific
tissues and collects waste products.
Regulates body temperature and pH levels.
Protects from injury and blood loss through its clotting
mechanism to seal off damaged tissue.
Provides specialized immune cells to fight against foreign
toxins within the body, decreasing disease and sickness.
Monitoring Heart Rate
 Place index and middle fingers around the backside of
the wrist (about 1 inch from the top of wrist, on the
thumb side).
 Locate the artery by feeling for a pulse with the index
and middle fingers; apply light pressure to feel the
pulse.
 When measuring the pulse during rest, count the
number of beats in 60 seconds; when measuring the
pulse during exercise, count the number of beats in 6
seconds and add a 0 to that number
•
Example: Beats in 6 seconds = 17. Add a zero =
170. Pulse rate = 170 bpm
Blood Distribution During Exercise

Exercise affects the blood flow to various organ systems differently.
– For example, skeletal muscle receives about 15–20% of total cardiac output
during rest, but 80–85% during maximal exercise.

During resistance training, the working muscles experience a temporary
increase in fluid accumulation, which results in a feeling of fullness in the
muscle (transient hypertrophy), a.k.a. “muscle pump”