CARDIOVASCULAR SYSTEM P. 347-352
Heart Actions
CARDIAC CYCLE

One complete heartbeat

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Pressure within heart


Atrial contraction, ventricular relaxation
Atrial relaxation, ventricular contraction
Rises and falls as chambers fill and empty
Atrial or Ventricular Contraction

(Systole) Pressure


Atrial or Ventricular Relaxation

Diastole Pressure


Pressure increases sharply
Pressure goes back down
AV Valves are opening and closing during
pressure changes
HEART SOUNDS
Vibrations in heart tissue produce opening and
closing of valves
 Heard as LubDup through stethoscope


Lub


Dup


Heard during ventricular contraction (AV valves are closing)
Heard during ventricular relaxation (pulmonary and aortic
valves are shutting)
MurMur

Abnormal sound

Usually occurs when heart valves don’t properly close causing
blood to leak through
CARDIAC MUSCLE FIBERS
Act like skeletal muscles but connect to a
network of sending impulses to contract all as a
unit.
 Functional Syncytium


Mass of merging cells that act as a unit
CARDIAC CONDUCTION SYSTEM
Coordinates events of cardiac cycle
 Sinoatrial Node (SA Node)







Small mass of elongated specialized cardiac muscle
tissue
Cells reach threshold on own and membranes
contract one another
Initiate impulses that spread into the surrounding
myocardium and stimulate cardiac muscle fiber to
contract
Rhythmic activity
70-80 impulses/min. (Pulse)
Pacemaker (Rhythmic contracting)
ATRIOVENTRICULAR NODE (AV NODE)
Located in septum
 Receives slow impulse
 After received impulse AV node sends it on to AV
Bundle
 Purkinje Fibers


Allow transmission of impulse for contraction of the
ventricles and pushes blood on out to aorta
ECG/EKG…ELECTROCADIOGRAM
Recording of the electrical changes in the
myocardium during cardiac cycle
 Deflections = waves on paper
 Polarization and repolarization causes pen to
move

P QRS T WAVES

P wave


QRS Complex


Time for complete excitation of ventricles
Q-T Interval


Wave travels through AV node, AV bundles, bundle branches and
purkinje fibers
S-T Segment


Ventricles relax, pattern ends
P-R Interval


Waves correspond to depolarization of ventriular fibers that contract
ventricles, atriums relax, ventricles contract
T wave


Depolarization, contraction of atriums
Time required for complete excitation and recovery of ventricles
T-P Interlude

Time from completion of ventricular repolarization to next atrial
excitation
REGULATION OF CARDIAC CYCLE

Read p. 356

Arrhythmia
Abnormal heart rhythm
 http://www.youtube.com/watch?v=xw4nDMgTOrw

REVIEW
Describe the pressure changes in the atria and
ventricles during a cardiac cycle.
 What causes heart sounds?
 What is a functional syncytium?
 How is a cardiac impulse imitated?
 How is a cardiac impulse transmitted from the
right atrium to the other heart chambers?
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