cardiac conduction system

Question 1

what is automaticity

Answer 1

this is when the heart has its own ability to spontaneously depolarise itself and trigger action potentials

Question 2

what cells make up the myocardium

Answer 2

nodal cells and contractile cells

Question 3

where is the sinoatrial node found

Answer 3

superior aspect of the right atrium found below the superior vena cava

Question 4

what is the sinus rhythm

Answer 4

the beats the heart can generate without the help of the nervous system. 60-80 beats

Question 5

what does bachmans bundle do

Answer 5

carry action potentials from the right to the left atrium

Question 6

what carries the action potentials from the sinoatrial node to the av node

Answer 6

the internodal pathway

Question 7

describe the av node

Answer 7

runs from the right atrium to the interventricular septum and runs into the septum

Question 8

what does the av node do

Answer 8

provide action potentials to the ventricles. it ensures there is a 0.1 second delay to allow the atria to contract before the ventricles do

Question 9

why is there a delay between the contraction of the atria and ventricles

Answer 9

av node has less gap junctions - this means less ions can flow from cell to cell and this decreases the speed. the fibres are also of a smaller diameter, and the smaller diameter, the slower the conduction speed

Question 10

describe the order of the cardiac conduction system

Answer 10

• action potential generated at the sinoatrial node
• travels through the bachmans bundle to the left atrium so both contract
• internodal pathway takes the action potential to the av node
• av node gives action potentials to the bundle of his
• bundle of his becomes right and left bundle branch
• goes to purkinje fibres
• myocardium contraction is triggers
• ventricules contract