Exam (elaborations)
NP235 Cardiovascular System Unit 4
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NP235 Cardiovascular System Unit 4
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NP235 Cardiovascular System Unit 4Cardiac Anatomy - ANS-The heart wall consists of three layers.
The epicardium is the outer layer of tissue;
the myocardium is the middle layer of muscle fibers that contract to pump blood, and the
endocardium is the lining of the inner surface of the heart chambers.
A membranous sac, the pericardium, surrounds the heart.
pericardium - ANS-a double-layered sac.
The double layer helps provide a barrier to infection, prevents displacement of the heart, and
contains pain and other receptors that elicit reflex changes in heart rate and blood pressure.
The pericardial space contains a thin layer of fluid (30 to 50 mL).
sinoatrial (SA) node - ANS-located in the right atrium and is called the "pacemaker" of the heart
because it normally initiates the electrical impulses.
atrioventricular (AV) node - ANS-or junction) is located in the lower part of the right atrium. It
relays the impulse from the SA node to the bundle of His and throughout the ventricles via the
Purkinje fibers.
The Cardiac Cycle - ANS-consists of contraction of the muscle (systole) and relaxation of the
muscle (diastole).
Ejection Fraction - ANS-the percentage of blood that is ejected from the left ventricle during
systole. A normal ejection fraction is 50% to 70%. As ejection fraction decreases with heart
failure, tissue perfusion diminishes.
Blood Pressure - ANS-the force that the blood exerts against the walls of the aorta and its
branches. The blood pressure is greatest during ventricular contraction, or systole when blood is
ejected into the aorta.
Diastolic pressure - ANS-the pressure when the ventricles are in the relaxation phase, or
diastole, just before the next contraction of the ventricles.
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