It is important that the contraction of all the muscle cells of the heart wall is coordinated and synchronised so that the pumping action of the heart is both effective and efficient.
The 'conducting (conduction) system' is made up of...
cardiac veins and coronary arteries
small groups of specialised neuromuscular cells
What normally initiates the heartbeat?
SA (Sino-Atrial) Node
AV (Atrioventricular) Node
Bundle of His
Within which wall is the SA Node situated?
There is a brief pause in the conduction of the impulse at the AV Node so that atrial contraction (and thus ventricular filling) is completed before ventricular contraction begins.
The Bundle of His divides into how many branches?
The order in which the heartbeat impulse moves is...
Bundle of His, AV Node, SA Node, Bundle Branches, Purkinje Fibres
SA Node, Bundle of His, Purkinje Fibres, AV Node, Bundle Branches
SA Node, AV Node, Bundle of His, Bundle Branches, Purkinje Fibres
Which areas of the heart contract first?
Even though the SA Node normally initiates the heartbeat, the cells of the conducting system and of the heart muscle itself are also able to spontaneously depolarise and initiate a heartbeat.
Which part of the conducting system is known as the 'pacemaker'?
The rhythm of the pacemaker is known as...
The conducting system requires no external stimulus to initiate or coordinate the heartbeat - this means that the heart shows 'autorhythmicity'. It can only be modified or regulated by other inputs such as hormones and nervous inputs.
What does the P wave stand for on an ECG?
What does the 'QRS' complex stand for on an ECG?
What does the T wave stand for on an ECG?
When the heart is in complete diastole (passive ventricular filling)...
the atrioventricular valves are open, the semilunar valves are shut
the atrioventricular valves are shut, the semilunar valves are open
During passive ventricular filling how much blood enters the ventricles?
During atrial systole, how much more blood enters the ventricles?
During atrial systole...
During ventricular systole...
the atrioventricular valves are open, the semilunar valves are shu
During atrial systole, does the pressure within the atria and ventricles...
During ventricular diastole, the ventricular pressure is...
higher than that in the systemic and pulmonary arteries
lower than that in the systemic and pulmonary arteries
During ventricular diastole...
the semilunar valves are shut, the atrioventricular valves are open
the semilunar valves are open, the atrioventricular valves are shut
What is a typical heartbeat?
How long does each cardiac cycle take to complete, according to the heartbeat in the previous question?