7.3.2 - Electrical Activity In The Heart

Question 1

Describe What Is Meant By ‘Myogenic’
(2 Points)

Answer 1

~ Contract and relax without receiving signals from neurones.

~ Cardiac muscle is myogenic.

Question 2

Describe The SAN
(3 Points)

Answer 2

~ Sinoatrial node.

~ Located in the wall of the right atrium.

~ Sets the rhythm of the heartbeat, by sending out regular waves of electrical activity to the atrial walls.

Question 3

Describe The Bundle Of His

Answer 3

Collection of conducting tissue in the septum.

Question 4

Describe How The Normal Electrical Activity Of The Heart Coordinates The Heart Beat
(8 Points)

Answer 4

~ SAN, initiates a wave of depolarisation causing the atria to contract.

~ A band of non-conducting tissue, which prevents the depolarisation spreading straight to the ventricles.

~ Instead the depolarisation is carried to the atrioventricular node (AVN).

~ After a slight delay, the AVN is stimulated and passes the stimulation along the bundle of His.

~ The delay means the ventricles contract after the atria.

~The bundle of His divides into two conducting fibres, called purkyne tissue and carries the electrical activity along them.

~ Purkyne fibres spread around the ventricles, and initiate the depolarisation of the ventricles from the apex of the heart.

~ Makes the ventricles contract from the bottom up, and blood is forced out the ventricles into the pulmonary artery and aorta.