Initiation and Coordination of the Action of the Hear

Question 1

What is the SAN and where is it found?

Answer 1

= right atroum wall- pacemaker
= depolorisase, triggers a wave of electrical exitation to spread across atria- causes atria to contract
= cannot pass down to the ventricles
=

Question 1

How is the heart myogenic?

Answer 1

= does not need an external signal to beat

Question 2

Why can the electrical impulse not go down to the ventricles?

Answer 2

= ventricles are seperated from the atria by a layer non-conducting tissue

Question 3

What does the AVN do and where is it found?

Answer 3

= connected to conducting fibres purkyne fibres
= these are bundled together to form the bundle of his , branched with fibrs running down to teh apex, base of the hearts and up the ewalls of the ventricles
=

Question 4

what does the avn do with the electrical impulses?

Answer 4

= detects electrical excitation, passing over the atria, short delay the AVN transmurts the electrical impulse down the purkyine fibres causes ventricles to contract, contract from the apex upwatds, so maximum volume of blood is pumped out

Question 5

why is there a slight delay?

Answer 5

= makes sures the atria contracts after the ventricles have contracted

Question 6

What happens last

Answer 6

cells repolroaise and the heart relaxes

Question 7

what controls the heart rate?

Answer 7

= medulla oblonganta

Question 8

What are the 2 parts?

Answer 8

= sinoatrial nerve: increases heart rate by sympathetic nerous system,
= decreases heart rate by parasympathetuc nerve