Page 1667 - Saunders Comprehensive Review For NCLEX-RN

this is an abnormal finding, and the causes include
cardiac hypertrophy, disease, or injury to the
ventricular wall.

K. Heart rate

1. The faster the heart rate, the less time the heart has for
filling. At very fast rates the cardiac output decreases.
2. The normal sinus heart rate is 60 to 100 beats per
minute.
3. Sinus tachycardia is a rate more than 100 beats per
minute.
4. Sinus bradycardia is a rate less than 60 beats per
minute.
L. Autonomic nervous system
1. Stimulation of sympathetic nerve fibers releases the
neurotransmitter norepinephrine, producing an
increased heart rate, increased conduction speed
through the AV node, increased atrial and ventricular
contractility, and peripheral vasoconstriction.
Stimulation occurs when a decrease in pressure is
detected.
2. Stimulation of the parasympathetic nerve fibers
releases the neurotransmitter acetylcholine, which
decreases the heart rate and lessens atrial and
ventricular contractility and conductivity. Stimulation
occurs when an increase in pressure is detected.
M. Blood pressure (BP) control
1. Baroreceptors (specialized nerve endings affected by
changes in the arterial BP), also called pressoreceptors,
are located in the walls of the aortic arch and carotid
sinuses.
2. Increases in arterial pressure stimulate baroreceptors,
and the heart rate and arterial pressure decrease.
3. Decreases in arterial pressure reduce stimulation of
the baroreceptors and vasoconstriction occurs, as does
an increase in heart rate.
4. Stretch receptors, located in the vena cava and the
right atrium, respond to pressure changes that affect
circulatory blood volume.
5. When the BP decreases as a result of hypovolemia, a
sympathetic response occurs, causing an increased
heart rate and blood vessel constriction; when the BP
increases as a result of hypervolemia, an opposite
effect occurs.
6. Antidiuretic hormone (vasopressin) influences BP
indirectly by regulating vascular volume.
7. Increases in blood volume result in decreased
antidiuretic hormone release, increasing diuresis,

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