HW #8 Heart 2
Which phase of the cardiac cycle is the shortest?
atrial systole
What structure carries the electrical signal from the septum of the heart through the ventricular myocardium?
Purkinje fibers
The portion of the tracing of an electrocardiogram, ECG, that represents ventricular depolarization is the __________.
QRS complex
If the connection between the vagus nerve and the heart is cut, which of these changes will occur?
The heart will beat faster.
If the cells of the SA node failed to function, how would the heart rate be affected? (Module 18.12B)
The heart would beat slower because the AV node would be the pacemaker.
Which valve(s) close(s) during ventricular contraction?
both AV valves
The heart is innervated by ________ nerves.
both parasympathetic and sympathetic
Which of these would cause stroke volume to increase?
both when venous return is increased and when diastolic blood pressure is decreased
The cusps (leaflets) of atrioventricular valves attach directly to
chordae tendineae.
The first heart sound ("lubb") is associated with
closing of the mitral valve
Which exterior heart structure returns "used" blood collected from the heart muscle itself (myocardium) back into the flow of blood to be delivered to the pulmonary circuit?
coronary sinus
The pulmonary veins carry blood to the
heart
Caffeine has effects on conducting cells and contractile cells that are similar to those of NE. What effect would drinking large amounts of caffeinated beverages have on the heart rate? (Module 18.14C)
heart rate would increase
Which of the following would decrease heart rate?
increased parasympathetic stimulation of nodal fibers
What are the two phases of ventricular systole? (Module 18.10B)
isovolumetric contraction and ventricular ejection
Heart rate is controlled by neurons of the cardiovascular center located in the
medulla oblangata
Compared to the right ventricle, the left ventricle has all the following characteristics except that it
pumps a greater volume
During the T wave of the electrocardiogram, the ventricles are electrically ________ and functionally ________.
repolarizing; relaxing
The volume of blood ejected from each ventricle during a contraction is called the
stroke volume
Which of the following would be greater?
the end-diastolic volume when the heart rate is 60 beats/minute
The amount of blood returning to the heart is the
venous return
Define autorhythmicity. (Module 18.12A)
Autorhythmicity is the ability of the heart to contract without neural or hormonal stimulation.
The following are structural components of the conducting system of the heart. 1. Purkinje fibers 2. AV bundle 3. AV node 4. SA node 5. bundle branches The sequence in which excitation would move through this system is which of the following?
4, 3, 2, 5, 1
Compute Joe's stroke volume if his end-systolic volume (ESV) is 40 mL and his end-diastolic volume (EDV) is 125 mL. (Module 18.16B)
85 mL
Cardiac output is increased by
All of the answers are correct.
What effect would an increase in venous return have on the stroke volume? (Module 18.15B)
An increase in venous return would fill the ventricles with more blood, increasing sarcomere length, which would increase the stroke volume.
IP: Intrinsic Conduction System of the Heart
Part A: SA Node Part B: electrical activity in the heart Part C: ventricular depolarization Part D: P wave Part E: AV node
The ________ is the volume of blood in a ventricle at the beginning of systole.
end-diastolic volume
The ________ is the amount of blood in a ventricle after it has contracted and before it begins to refill.
end-systolic volume
There are ________ pulmonary veins.
four
Pacemaker cells in the SA node
generate action potentials that spread to the myocardium.