The Cardiac Cycle Flashcards
Regarding the anatomy of the heart (true or false):
The heart is a specialised hollow muscular pump measuring 9 cm long by 9 cm wide and weighs
250-350 g
False. The heart is a specialised hollow muscular pump, however, it measures 12 cm long by 9 cm wide and weighs 250-350 g.
Regarding the anatomy of the heart (true or false):
The heart has four chambers built on a ring of fibrous tissue at the atrioventricular junction
True. The heart has four chambers built on the annulus fibrosus, which is a ring of fibrous tissue at the atrioventricular junction
Regarding the anatomy of the heart (true or false):
Valves within the heart ensure the unidirectional flow of blood
True. Valves within the heart ensure the unidirectional flow of blood.
Regarding the anatomy of the heart (true or false):
The heart is conical in shape
True. The heart is conical in shape and it lies obliquely across the middle of the mediastinum.
Regarding the anatomy of the heart (true or false):
The cardiac apex represents the left ventricle and lies behind the third left intercostal space
False. The tip of the cone, or the ‘cardiac apex’, represents the left ventricle and lies behind the fifth left intercostal space.
Regarding the anatomy of the heart (true or false):
The anterior surface of the heart is made up of the right atrium and right ventricle
True. Due to the rotation of the heart, its anterior surface is made up of the right atrium and right ventricle.
Regarding the anatomy of the heart (true or false):
The base of the heart is posterior facing and is formed mainly by the left atrium
True. The base is posterior facing and formed mainly by the left atrium.
Regarding ECGs (true or false):
Electrical activity in heart tissue is simultaneous with the corresponding mechanical event in the cardiac cycle
False. Electrical activity precedes the corresponding mechanical event in the cardiac cycle.
Regarding ECGs (true or false):
In a single muscle fibre, contraction starts just after the depolarisation and lasts for 50 ms after repolarisation is completed
True. In a single muscle fibre, contraction starts just after the depolarisation and lasts for 50 ms after repolarisation is completed.
Regarding ECGs (true or false):
The P wave is associated with atrial depolarisation and contraction (systole)
True. The P wave is associated with atrial depolarisation and contraction (systole).
Regarding ECGs (true or false):
The normal PR interval is 0.16 s
True. The normal PR interval is 0.16 s. The PR interval, between the P wave and the QRS complex, represents the time between the onset of atrial contraction and the beginning of ventricular contraction.
Regarding ECGs (true or false):
The QRS complex is <0.12 s in a normal ECG
True. Normally the duration of the QRS complex is <0.12 s: it represents ventricular depolarisation and precedes ventricular contraction.
Regarding ECGs (true or false):
The ST segment and T wave are associated with ventricular repolarisation
True. The ST segment and T wave are associated with ventricular repolarisation.
Regarding ECGs (true or false):
Ventricular contraction ends during the T wave
False. Ventricular contraction ends after the T wave.
Regarding ECGs (true or false):
The U wave is thought to represent the slow repolarisation of the papillary muscles
True. The U wave is thought to perhaps represent the slow repolarisation of the papillary muscles.
At a heart rate of 60 bpm, diastole lasts for 0.66 s and systole for 0.34 s. At double the heart rate (true or false):
Diastole lasts for 0.33 s and systole for 0.17 s
False. As heart rate increases, diastole shortens relatively more than systole.
At a heart rate of 60 bpm, diastole lasts for 0.66 s and systole for 0.34 s. At double the heart rate (true or false):
Duration of diastole increases
False. The duration of diastole reduces with an increase in heart rate.
At a heart rate of 60 bpm, diastole lasts for 0.66 s and systole for 0.34 s. At double the heart rate (true or false):
In a healthy young person, most of ventricular filling occurs during early diastole
True. For a healthy person, at a heart rate of 120 bpm, most ventricular filling occurs during early diastole.
At a heart rate of 60 bpm, diastole lasts for 0.66 s and systole for 0.34 s. At double the heart rate (true or false):
There is a linear relationship between heart rate and duration of the cardiac cycle
False. As heart rate increases with strenuous exercise, the phases of the cardiac cycle shorten. However, diastole and systole do not shorten to an equal degree, as shown in the following figure.
The four phases of systole occur in the following order:
A. Isovolumetric contraction, atrial systole, rapid ejection, reduced ejection
B. Atrial systole, isovolumetric contraction, reduced ejection, rapid ejection
C. Atrial systole, isovolumetric contraction, rapid ejection, reduced ejection
D. Atrial systole, rapid ejection, isovolumetric contraction, reduced ejection
C.
Regarding the 1st and 2nd heart sounds (true or false):
The mitral valve closes before the tricuspid valve
True
Regarding the 1st and 2nd heart sounds (true or false):
The pulmonary valve closes before the aortic valve
False
The area of the pressure-volume loop of the left ventricle represents which of the following?
A. Ventricular stroke volume
B. Ventricular stroke intensity
C. Ventricular stroke work
D. Compliance, measured as pressure/volume
C. Pressure x Volume can be reduced to Nm = J.
A. Incorrect. Volume is the width of the loop.
B. Incorrect
D. Incorrect. Compliance is the change in volume per change in pressure, i.e. volume/pressure.
Regarding right ventricular systole (true or false):
Ejection occurs early in systole due to high pulmonary vascular resistance
False. Ejection occurs early in systole due to low pulmonary vascular resistance.
Regarding right ventricular systole (true or false):
The pressure-volume loop of the right ventricle is triangular
True. The pressure-volume loop of the right ventricle is triangular, however, this makes it more difficult to define the individual phases of systole.
