This document provides an overview of the cardiovascular system, including its components, functions, anatomy, conduction system, blood flow patterns, cardiac cycle, arrhythmias, and other related topics. Key points covered include the heart functioning as a pump to circulate blood throughout the body via arteries and veins, delivering oxygen and nutrients while removing waste. The conduction system generates and conducts electrical signals to coordinate heart contractions. Various factors can influence heart rate and rhythm.

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Introduction to the
Cardiovascular System
Chapter 42

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The Cardiovascular System
• Components
– Pump (heart)
– Interconnected series of tubes that continually move
blood throughout the body
• Functions
– Delivering oxygen and nutrients to all of the cells of
the body
– Removing waste products for excretion

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Anatomy of the Heart

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Conducting System of the Heart

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Coronary Arteries and Veins

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Blood Flow Through the Systemic and
Pulmonary Vasculature Circuits

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Direction of the Blood Flow of the Heart
• Deoxygenated Blood
– Right atrium, through tricuspid valve to right
ventricle, through pulmonary valve to the lungs
• Oxygenated Blood
– Through the pulmonary veins to the left atrium,
through the mitral valve to the left ventricle, through
the aortic valve to the aorta

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Periods of the Cardiac Cycle
• Starling’s Law of the Heart
• Diastole
– Period of rest
– Blood is returned to the heart by veins
• Systole
– Period of contraction, or systole
– Blood is pumped out of the heart

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Components of the Conduction System of
the Heart
• SA Node
• Atrial Bundles
• AV Node
• Bundle of His
• Bundle Branches
• Purkinje Fibers

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Automaticity and Conductivity
• Automaticity
– The cells within the heart’s electrical system can
generate action potential or electrical impulses
without being excited by an external stimuli
• Conductivity
– The specialized cells of the heart can conduct an
impulse rapidly through the system so that the
muscle cells of the heart are stimulated at the
approximately the same time

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Question
What does Starlings law of the heart address?
a. Automatic properties of the heart
b. Conductive properties of the heart
c. Contractile properties of the heart
d. Pressure properties of the heart

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Answer
c. Contractile properties of the heart
Rationale: Starling’s law of the heart addresses the
contractile properties of the heart: the more the muscle
is stretched, the stronger it will react, until it is stretched
to a point at which it will not react at all

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Five Phases of the Action Potential of the
Cardiac Muscle Cell
• Phase 0
– Occurs when the cell reaches a point of stimulation
• Phase 1
– Short period when the sodium ion concentrations are
equal inside and outside the cell
• Phase 2
– Plateau stage: Occurs as the cell membrane becomes
less permeable to sodium

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Five Phases of the Action Potential of the
Cardiac Muscle Cell (cont.)
• Phase 3
– Period of rapid repolarization as the gates are closed
and potassium rapidly moves out of the cell
• Phase 4
– The cell comes to rest as the sodium–potassium
pump returns the membrane to its previous state

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Action Potentials

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A Sacromere, the Functioning Unit of
Cardiac Muscle

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Factors That May Affect the Cardiac Rate
and Rhythm
• Drugs
• Acidosis
• Decreased oxygen levels
• Changes in the electrolytes in the area
• Buildup of waste products

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Critical Points of the ECG
• P–R Interval
– Reflects the normal delay of conduction at the AV
node
• Q–T Interval
– Reflects the critical timing of repolarization of the
ventricles
• S–T Segment
– Reflects important information about the
repolarization of the ventricles

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Normal Electrocardiogram Pattern

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Types of Arrhythmias
• Sinus Arrhythmias
• Supraventricular Arrhythmias
• Atrioventricular Block
• Ventricular Arrhythmias

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Types of Supraventricular Arrhythmias
• Premature Atrial Contractions (PACs)
• Paroxysmal Atrial Tachycardia (PAT)
• Atrial Flutter
• Atrial Fibrillation

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Question
Tell whether the following statement is true or false.
When reading an EKG a nurse knows that the P-R interval
represents the normal delay of conduction
at the AV node.

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Answer
True
Rationale: P–R interval reflects the normal delay of
conduction at the AV node.

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Ventricular Arrhythmias
• Originate Below the AV Node
• PVCs
• Ventricular Fibrillation

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Courses of Circulation of the Blood
• Heart–Lung or Pulmonary Circulation
– The right side of the heart sends blood to the lungs.
– Carbon dioxide and some waste products are
removed from the blood.
– Oxygen is picked up by the red blood cells.
• Systemic Circulation
– The left side of the heart sends oxygenated blood out
to all cells in the body.

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Coronary Circulation
• Pulse Pressure
• End-Artery Circulation
• Supply of Blood to the Myocardium
• Myocardial Infarction
• Hypotension
• Hypertension
• Vasomotor Tone

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Forces Determining Oxygen Consumption
• Heart Rate
– The harder the heart has to work, the more oxygen it
requires
• Preload
– Amount of blood returned to the heart so that it can
be pumped throughout the body
• Afterload
– Resistance against which the heart has to beat
• Stretch on the Ventricles

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Renin-Angiotensin System

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Venous Pressure
• A pressure which may sometimes rise above normal
• Heart is not pumping effectively
• Results in a backup or congestion of blood

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Heart Failure
• Blood backs up and the system becomes congested
• Fluid lost in tissues results in pulmonary edema
• Peripheral, abdominal, and liver edema
• Drugs may affect the vascular system at any of these
areas

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Fluid Shift Within the Cells

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Question
A premature atrial contraction signifies a change in focus in
which of the following?
A. Automaticity
B. SA node
C. AV node
D. Contractility

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Answer
B. SA node
Rationale: Premature atrial contractions (PACs), which
reflect an ectopic focus (a shift in the pacemaker of the
heart from the SA node to some other site) in the atria
that is generating an impulse out of the normal rhythm.