How heart action is initiated and coordinated

Question 1

What term describes the nature of a heart to beat on its own?

Answer 1

myogenic-generates its own nerve impulses

Question 2

How are heart contractions coordinated?

Answer 2

by a network of specialised cardiac muscle cells called myocytes

Question 3

What are the 4 parts of the conduction system?

Answer 3

-the Sino Atrial node (pacemaker)
-the Atrioventricular node
-the bundle of His
-conduction/Perkinje fibres

Question 4

Where is the bundle of His and the Purkinje fibres located?

Answer 4

-bundle of His: between 2 atria
Purkinje: near apex, spreading up sides of heart

Question 5

Where is the SAN and AVN located?

Answer 5

-right wall of atrium
-SAN is above and to the left of AVN

Question 6

1st step of heartbeat

Answer 6

SAN sends a wave of depolarisation across the atria, causing atrial systole

Question 7

2nd step of heartbeat

Answer 7

A band of non conducting fibres block the nerve impulse from going further, causing the AV delay (0.1 secs) which allows the ventricle to fill with blood

Question 8

3rd step of heartbeat

Answer 8

-AVN is stimulated and sends wave of depolarisation down the bundle of His and through the Purkinje fibres

Question 9

4th step of heartbeat

Answer 9

-this causes ventricular systole and ventricles contract from apex, pushing blood up and into aorta

Question 10

5th step of heartbeat

Answer 10

nerves are no longer being stimulated and heart is in diastole