6.1.3 Control of heart rate

Question 1

Cardiac muscle is myogenic. What does this mean?

Answer 1

It can contract and relax without receiving electrical impulses from nerves

Question 2

Label the sinoatrial node (SAN), atrioventricular node (AVN), Bundle of His
and Purkyne tissue on a diagram of the heart

Answer 2

Question 3

Describe the myogenic stimulation of the heart and transmission of a
subsequent wave of electrical activity

Answer 3

1 - Sinoatrial node (SAN) acts as pacemaker → releases regular waves of electrical activity across atria
○ Causing atria to contract simultaneously

2 - Non-conducting tissue between atria / ventricles prevents impulse passing directly to ventricles
○ Preventing immediate contraction of ventricles

3 - Waves of electrical activity reach atrioventricular node (AVN) which delays impulse
○ Allowing atria to fully contract and empty before ventricles contract

4 - AVN sends wave of electrical activity down bundle of His, conducting wave between ventricles to apex where it branches into Purkyne tissue
○ Causing ventricles to contract simultaneously from the base up

Question 4

Where are chemoreceptors and pressure receptors located?

Answer 4

Chemoreceptors and pressure receptors are located in the aorta and carotid arteries

Question 5

Describe the roles of chemoreceptors, pressure receptors, the autonomic nervous system and effectors in controlling heart rate