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Type 1 second-degree heart block is considered more benign than type 2 second-degree heart block. [4] The type 1 does not have structural changes found on histology. Both types are named after Woldemar Mobitz. [5] [6] Type I is also named after Karel Frederik Wenckebach, [7] and type II is also named after John Hay. [8] [9]
[1] [2] The aqueduct of Sylvius is the channel which connects the third ventricle to the fourth ventricle and is the narrowest part of the CSF pathway with a mean cross-sectional area of 0.5 mm 2 in children and 0.8 mm 2 in adults. [3] Because of its small size, the aqueduct is the most likely place for a blockage of CSF in the ventricular system.
First degree AV block does not generally cause any symptoms, but may progress to more severe forms of heart block such as second- and third-degree atrioventricular block. It is diagnosed using an electrocardiogram , and is defined as a PR interval greater than 200 milliseconds. [ 1 ]
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Examples of single line tokens: Tablet on left, key token on right. The operation of a bidirectional single track line has the hazard of two trains colliding. The simplest way to prevent such collisions is to have only one train in the section at any given time. Such a system is known as "one-engine-in-steam” (OES) or “one-train working ...
Third-degree atrioventricular block (AV block) is a medical condition in which the electrical impulse generated in the sinoatrial node (SA node) in the atrium of the heart can not propagate to the ventricles. [1] Because the impulse is blocked, an accessory pacemaker in the lower chambers will typically activate the ventricles.
Signalling block systems enable the safe and efficient operation of railways by preventing collisions between trains. The basic principle is that a track is broken up into a series of sections or "blocks". Only one train may occupy a block at a time, [citation needed] and the blocks are sized to allow a train to stop within them. [1]
Automatic block signaling (ABS), spelled automatic block signalling or called track circuit block (TCB [1]) in the UK, is a railroad communications system that consists of a series of signals that divide a railway line into a series of sections, called blocks. The system controls the movement of trains between the blocks using automatic signals.