Electrical System of Heart #3 Flashcards
SA Node purpose
generates the rhythm of heart through rapid depolarization
SA Node depolarization rate
90-100 times per minute
3 pathways of SA Node
posterior, middle, and anterior
names of internodal tracts
posterior, middle, and one branch of anterior pathways
what are internodal tracts
the electrically conductive fibers that connect SA Node to AV Node. They also branch out into myocardial cells
Depolarization rate of AV Node
40-60 times per minute
Why does SA Node govern AV Node
SA Node depolarizes faster, so it forces myocardial cells to contract more. It also controls the AV Node via internodal tracts
location of AV node
in the septum, in between the pulmonary artery and aorta
location of SA Node
in the right atrium, below the superior vena cava
Purpose of delay in electrical transmission between SA and AV Nodes
allows time for the heart to mechanically contract and pump blood to the bottom chambers
How long is the internodal delay?
about 40 milliseconds
purpose of atrioventricular ring
insulates the top half of heart from bottom half, creates a wall
only way to pass electricity from top to bottom half of heart
via the AV Node
6 step pathway of electricity from top to bottom of heart
1.) SA Node
2.) 3 Internodal tracts
3.) AV Node
4.) AV Bundle left/right
5.) Purkinjie fibers
6.) myocardium
purpose of Purkjie fibers
smallest electrical pathways that connect to the myocytes of the heart
3 ways the lower chambers of the heart contract
1.) chambers contract inwards
2.) septum contracts upwards
3.) heart twists
vagus nerve location
10th cranial nerve (from the brainstem), which attaches to SA and AV Nodes
purpose of the vagus nerve
slows down heart beat despite fast beating of SA Node, part of parasympathetic nervous system
