Control of the heart

Question 1

Why is the heart described as myogenic?

Answer 1

because it can produce its own contractions

Question 2

What are sinoatrial nodes?

Answer 2

specialised fibres in the right atrium that acts as the heart’s pacemaker

Question 3

How does the sinoartrial node work

Answer 3

it sends electricle stimulation waves to surrounding tissue allowing the atria to contract at the same time

Question 4

How come ventricular systole occurs at the same time as atrial dystole

Answer 4

tissue at the base of the atria is unable to conduct the wave of electical impulses therefore the ventricles can only contract after the wave has passed

this mainains a unidirectional flow

Question 5

How do ventricles contract?

Answer 5

• the exitatory wave reaches the atrioventricular nodes
• it’s then sent to the Bundel of His (a conductive tissue inside the septum of the heart) which passes down to the apex of the heart
• Then as the bundle moves up it branches into the Purkyne fibres, which are inside the walls of the ventricles and causes them to contract

Question 6

Where are chemoreceptors located?

Answer 6

in the aorta, carotid arteries and in the brain

Question 7

Where are the baroreceptors located?

Answer 7

in the sinus

Question 8

What is the purpose of chemoreceptors?

Answer 8

detects changes in pH by detecting changes in CO2 level

Question 9

What is the purpose of baroreceptors?

Answer 9

detects changes in pressure

Question 10

How do chemoreceptors respond to increases in CO2 levels?

Answer 10

• chemoreceptors sends electricle impulses to the medulla oblongata through the sympathetic pasthway (accelerator nerve)
• this increases frequency of electricle impuses sent to the SAN which causes the heart rate to increase
• this causes more blood to flow to the lungs and more CO2 to be expelled out thus decreasing CO2 concentration

Question 11

How do baroreceptors respond to increase in pressure?

Answer 11

• baroreceptors detect increase in pressure and sends electrical impulses to the medulla oblongata through the parasympathetic path (vagus nerve) to the SAN
• this causes the heart rate to decrease and therefore blood pressure to decrease