Ppt chapter 42

Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Introduction to the
Cardiovascular System
Chapter 42

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

Anatomy of the Heart

Conducting System of the Heart

Coronary Arteries and Veins

Blood Flow Through the Systemic and
Pulmonary Vasculature Circuits

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

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

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

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

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

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

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

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

Action Potentials

A Sacromere, the Functioning Unit of
Cardiac Muscle

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

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

Normal Electrocardiogram Pattern

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

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

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.

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

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

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.

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

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

Renin-Angiotensin System

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

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

Fluid Shift Within the Cells

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

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.

Ppt chapter 42

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Ppt chapter 42