The Heart Flashcards
What is the SA node
it’s the pacemaker of the heart, it provides a constant supply of action potentials, and it causes contraction of the atriums. made up of p cells
What is the AV node
it’s the Atrioventricular node which then passes the signal to …
What is the bundle of his
it’s the conduction cords between the ventricles
What is the perkinge fibers
they are the fibers that cause contraction of the ventricles.
what is the pathway of action potentials in t heart
1 Sa node
2 av node
3 bundle of his
4 perkinge fibers
What are the steps for the action potentials of the Sa node
- -70mV the funny channels open, allows Na+in
- -60mV the T type voltage gated Ca+ channels open
- -50mV = threshold - L type voltage gated Ca+ channels open
- at complete depolarization the Ca+ channels close and a K+ channel opens
- once back to -70mv the cycle starts again.
how many AP’s/min from sa node
70-80
how many AP’s/min from av node
40-60
how many AP’s/min from perkinge system
20-40
what i are the conductive velocities of
- AV node
- perkenje system
- ventricular muscle fibers
- slow
- fast (allows for whole ventricle to contract simultaneously
- slow
what is the whole process of cardiac action potential conduction
- p cells depolarize causing an action potential
- AP passes through cells via gap junctions, and through the interatrial pathway. (both atria contract simultaneously)
- impulse is delayed at the AV node
- impulse rapidly passes through bundle of his and purkinje fibers (so they can contract simultaneously)
- ventricular muscle contracts from top to bottom.
why does AP pause at AV node
to allow blood to enter ventricles before they contract
What do gap junctions do
they allow the AP to pass from one cell to another
what are the differences between AP/contraction in cardiac muscle as compaired to skeletal muscle
- in cardiac the action potential lasts almost as long as the contraction
what is autorythmicity
the fact that the heart doesn’t require innervation from any neurons
