Chapter 25 Quiz Flashcards
Heart muscle differs from skeletal muscle tissue by being able to generate:
action potentials.
Heart muscle, or myocardium, has the unique capability of
generating and conducting electrical impulses
Heart muscle similarities to skeletal muscle include
contractility, calcium influx, and actin-myosin (sarcomeres) binding.
During ventricular systole, closure of the atrioventricular (AV) valves coincides with
isovolumetric contraction.
Ventricular systole is divided into two parts
isovolumetric and ejection period
isovolumetric contraction when
the AV valves close and ventricles fill
ejection period
when the semilunar valves open and blood is ejected through the aortic valve into circulation.
Preload represents the volume work of the heart and is largely determined by:
venous blood return.
Preload represents
the amount of blood the heart must pump with each beat
Pressure (resistance), contraction, and ventricular emptying are all related to
afterload
A patient has entered hypovolemic shock after massive blood loss in a car accident. Many of the patient’s peripheral blood vessels have consequently collapsed. How does the Laplace law account for this pathophysiologic phenomenon?
Blood pressure is no longer able to overcome vessel wall tension.
In circulatory shock there is a decrease in blood volume and
vessel radii
A male patient with a history of angina has presented to the emergency department with uncharacteristic chest pain and his subsequent ECG reveals T-wave elevation. This finding suggests an abnormality with which of the following aspects of the cardiac cycle?
Ventricular repolarization
The T wave on electrocardiography (ECG) corresponds to
ventricular repolarization
Atrial depolarization is represented by the
P wave
ventricular depolarization is represented by the
QRS complex
The isoelectric or zero line between the P wave and the Q wave represents
depolarization of the AV node, bundle branches, and Purkinje system.
A patient who lives with a diagnosis of angina pectoris has taken a sublingual dose of nitroglycerin to treat the chest pain he experienced while mowing his lawn. This drug has resulted in a release of nitric oxide, which will have what effect?
Smooth muscle relaxation of vessels
Nitroglycerin produces its effects by releasing
nitric oxide in vascular smooth muscle
nitroglycerin results in
relaxation of the muscle and increased blood flow
Release of which of the following humoral factors will result in vasodilation?
Histamine
Histamine has a powerful _______ effect
vasodilator
histamine has the ability to
increase capillary permeability, allowing leakage of both fluid and plasma proteins into the tissues.
Norepinephrine, angiotensin II, and serotonin are all potent
vasoconstictors
The difference between the end-diastolic and end-systolic volumes is the
stroke volume
Cardiac output is determined by
stroke volume and heart rate
Ejection fraction is the volume ejected from the
left ventricle
Cardiac reserve is determined by
cardiac output
A large increase in heart rate can cause:
decreased stroke volume
The tissue factor that contributes to humoral control of blood flow by causing vasoconstriction is:
serotonin
Histamine, bradykinin, and nitric oxide cause _______ of blood vessels.
vasodilation
In the days following a tooth cleaning and root canal, a patient has developed an infection of the thin, three-layered membrane that lines the heart and covers the valves. What is this patient’s most likely diagnosis?
Endocarditis
The endocardium is a
thin, three-layered membrane that lines the heart and covers the valves
Following several weeks of increasing fatigue and a subsequent diagnostic work-up, a patient has been diagnosed with mitral valve regurgitation. Failure of this heart valve would have which of the following consequences?
Backflow from the left ventricle to left atrium
Harmful effects on cardiac action potential are most likely to result from a deficit of which of the following electrolytes?
Potassium
the ions directly involved in the cardiac action potential are
sodium, calcium and potassium
Turbulent blood flow can be caused by a number of factors, including:
increased velocity.
Vessel length affects the _____ of flow rather than the type of flow.
rate
Long-term autoregulation of local blood flow in the microcirculation is mediated by:
collateral circulation
Short-term (increase/decrease) autoregulation is mediated by mechanisms that include
arteriovenous shunting of blood, the metabolic needs of the tissues, and autonomic nervous system controls.
A patient with a diagnosis of secondary hypertension has begun to experience signs and symptoms that are ultimately suggestive of decreased cardiac output. Which of the following factors that determine cardiac output is hypertension likely to affect most directly?
Afterload
In the arterial-venous circulatory system, pressure is inversely related to:
volume
Arterial circulation contains a lower percentage of total blood volume and has higher pressure than the venous circulation, which contains the majority of
circulating blood
Flow is related to
viscosity
radius is related to
wall tension
Velocity is inversely proportional to the
cross-sectional area of the vessel.
The parasympathetic nervous system causes a slowing of the heart rate by increasing:
vagus nerve activity
Norepinephrine is the main neurotransmitter for
sympathetic neurons
Which of the following factors is the primary governor of the local control of blood flow?
The nutritional needs of the tissue involved
Action potentials, cardiac contractility, and preload are all aspects of
overall circulation
Similarly, feedback from arterial baroreceptors and chemoreceptors inform the _____ ____ of systemic blood pressure, but not the local control of blood flow.
neural control
