electrical activity in the heart

Question 1

cardiac cycle

Answer 1

• SAN in the right atrium sets rhythm by sending out regular waves of electrical activity to atrial walls
• atria contracts at the same time
• non-conducting collagen tissue prevent transfer of activity to ventricles
• electrical activity transferred from SAN to AVN
• AVN responsible for passing the activity to bundle of His
• slight delay before this so ventricles can fill before contraction by activity
• bundle of His are muscle fibers that pass the activity to finer muscle fibers in left and right ventricle called Purkyne fibers
• Purkyne fibers carry activity to muscular walls of ventricles, causing contraction from bottom up

Question 2

why should electrical activity be passed form base of ventricles

Answer 2

• so ventricles can contract from the base
• blood can be pushed through the arteries

Question 3

electrocardiograph

Answer 3

• it is used to look at electrical activity of the heart
• heart muscle depolarizes when it contracts and repolarizes when it relaxes
• electrodes placed on chest
• in an electrocardiogram P wave is contraction of atria (depolarization)
• QRS complex is the contraction of ventricles
• T wave is relaxation of ventricles
• height of the wave shows how much charge is passing
• bigger wave means more electrical charge and stronger contraction

Question 4

tachycardia

Answer 4

heart beat too fast around 120bpm.normal in exercise but at rest is unable to pump blood efficiently

Question 5

bradycardia

Answer 5

heart beat too slow around 60bpm at rest

Question 6

ectopic heart beat

Answer 6

caused by early contraction of atria or ventricle but is an extra heartbeat and if it happens to a healthy person it is normal

Question 7

fibrillation

Answer 7

irregular heartbeat. atria or ventricles would lose rhythm and stop contracting properly and can lead to chest pain, death, faint