The heart is a very important muscle in our On Exam 1 you will be presented with an essay question. The essay topic is cardiac
body that keeps blood flowing to our impulse generation.
tissues to keep them nourished with
oxygen and help transport carbon dioxide You will be asked to compose an essay about the cardiac impulse generation and
waste to the lungs for gas exchange. The conduction.
heart uses electrical impulses from
specialized nodes to trigger the cardiac a. A discussion cardiac conduction should begin with description of the specialized
muscles to contract, which in turn leads to nodes (autorhythmic character) of the heart and their locations.
the continuous pumping function of the b. The sequence should be discussed as well as coordinating location in the heart.
heart. c. The actual innervation of the cardiac muscle and appropriate structures should be
considered.
The specialized nodes of the heart are the d. Correlation between the stages of impulse should be related to the flow of blood,
sinoatrial (SA) node and the atrioventricular contraction of the chambers and open and closing of the valves.
(AV) node. The SA node is located in the
right atrium and is inferior to the superior
vena cava entrance. The SA node is the
pacemaker of the heart and sets the rate of
depolarization that begins the
electrical signal that tells the heart to
contract. The AV node is located in the
lower atrial septum at the junction of the
atria and ventricles. The AV node's function
is to delay the contraction of the ventricles
until the atrial contraction is complete for
0.1s.
The sequence of impulse generation in the
heart start off at the SA node. The SA node
generates an electrical impulse which
begins atrial excitation. The signal is then
passed to the AV node where the signal is
delayed until the atria have finished their
contraction. Next, the impulse is passed to
Atrioventricular (AV) bundle located
superior interventricular septum and is then
passed through the left and right bundle
branches located in the interventricular
septum, which stimulates ventricular
excitation. When the impulse reaches the
Purkinje fibers in the left and right
ventricles, the ventricles contract.
The heart contains three layers of muscles
called the epicardium, myocardium, and
endocardium. The epicardium is the outer
muscle of the heart, the myocardium is the
middle layer of muscles, and the
endocardium is the inner layer of cardiac
muscle that actually comes into contact
with the blood in the heart. The heart is
composed of myocardial muscle cells that
make up the walls of the atria and the
ventricles that have contractile and elastic
properties that aid in cardiac contraction.
The contractile
Rios Saladoproperties
Bio202 of the
Exam 1
2/15
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