Unit 1 Section 5: Electrical activity of the heart

Question 1

Cardiac muscle is MYOGENIC…meaning?

Answer 1

it can contract and relax without signals form nerves

Question 2

Sino-Atrial Node (SAN)

Answer 2

• a pacemaker in the wall of the right atrium
• Sets the rhythm by sending waves of electrical activity over the artial wall.
• causes Atria to contract at same time
• Non-Conductive collagen tissue Prevents signal being transferred directly to the ventricles
• These waves go from the SAN to the AVN

Question 3

Atrioventricular Node (AVN)

Answer 3

• responsible for transferring the electrical activity to the bundle of his
• there is a slight delay to ensure the atria have emptied before the ventricles contract

Question 4

Bundle of His

Answer 4

• Runs through the septum
• group of muscle fibres
• conduct the waves of electrical activity to the purkyne tissue

Question 5

Purkyne tissue

Answer 5

• fine muscle fibres in the right and left ventricle walls

* Carries the waves to the ventricle muscles causing them to contract from the Apex (bottom) up

Question 6

Why is it important that the ventricles contract from the Apex

Answer 6

To ensure maximum blood flow out of the ventricles

Question 7

ECG?

Answer 7

ElectoCardioGram

*the peak of the heartbeat together with the dips on either side is caused by the contraction of the Ventricles

Question 8

Heart muscle depolarises (loses electrical charge) when

Answer 8

It contracts

Question 9

Heart muscle repolarises (Regains Charge)

Answer 9

When it relaxes

Question 10

Formula to work out heart rate

Answer 10

Heart rate(bpm) = 60/time taken for one heartbeat (S)