Control of Heart Rate(better version)

Question 1

what is a characteristic of cardiac muscle?

Answer 1

it is myogenic
- so contacts on its own, the rate of contraction is controlled by a wave of electrical activity

Question 2

what are the 4 main components of controlling heart rate?

Answer 2

• sinoatrial node
• atrioventricular node
• Bundle of His
• purkyne tissues

Question 3

where are the atrioventricular nodes located?

Answer 3

between left and right ventricle (within atria)

Question 4

where are the sinoatrial nodes located?

Answer 4

• in the right atrium (known as pacemakers)

Question 5

where are the Bundle of His located?

Answer 5

• runs through septum of heart

Question 6

where are the Purkyne tissues located?

Answer 6

• located in the walls of venticles

Question 7

what is an equation linking CO, V and R?

Answer 7

CO=RxV
cardiac output = heart rate x stroke volume

Question 8

what is the role of the autonomic nervous system?

Answer 8

controls the involuntary activities of internal muscles and glands

Question 9

what is the autonomic nervous system split into?

Answer 9

• sympathetic nervous system
• parasympathetic nervous system

Question 10

what is the role of the sympathetic nervous system?

Answer 10

• ‘fight or flight’ system

Question 11

what is the role of the parasympathetic nervous system?

Answer 11

• rest and digest response, calms the body

Question 12

explain the process of controlling heart rate?

Answer 12

• SAN acts as a pacemaker, sending out regular waves of electrical impulses to atrial walls = atrial systole
• band of non-conducting tissue prevents waves of electrical impulses from being passed from atria to ventricles, waves of electrical impulses transferred from SAN to AVN
• slight delay before AVN reacts, allowing the atria to be emptied before the ventricles contract
• AVN responsible for passing waves of electrical impulses to Bundle of His
• Purkyne tissues carry waves of electrical activity to muscles of left and right ventricles = ventricular systole

Question 13

where are chemoreceptors located?

Answer 13

• aorta
• carotid arteties
• medulla

Question 14

where are pressure receptors located?

Answer 14

• aorta
• carotid arteties

Question 15

what is the medulla?

Answer 15

unconsciously controls the rate at which SAN fires

Question 16

what happens to heart rate when there is high blood pressure?

Answer 16

• pressure receptors detect high blood pressure and sends impulses along the sensory neuron to the medulla, which send impulses along the parasympathic neurones
• these secrete acetlycholine, which bind to receptors on the SAN
• causes heart rate to slow down and reduce BP to normal

Question 17

what happens to heart rate when there is low blood pressure?

Answer 17

• pressure receptors detect the low blood pressure and sends impulses along the sensory neuron to the medulla which sends impulses along sympathetic neurons
• these secrete noradrenaline, which binds to receptors on the SAN
• causes heart rate to speed up to bring BP to normal

Question 18

what happens to heart rate when there is high blood O2, high blood pH and low CO2?

Answer 18

• chemoreceptors detect chemical changes in blood and sends impulses along the sensory neurones to the medulla, which send impulses along the parasympathetic neurones
• these secrete acetylcholine which binds to receptors of the SAN
• this causes heart rate to decrease, returning oxygen, carbon dioxide and pH levels back to normal

Question 19

what happens to heart rate when there is low blood O2, low blood pH and high CO2?

Answer 19

• chemoreceptors in the carotid arteies, aorta or medulla detects the chemical changes in blood and increases the frequency of electrical impulses along the sensory neurone to the medulla oblongata, which increases rate of impulses along the sympathetic neurones
• these secrete noradrenaline, which binds to receptors of the SAN
• this causes heart rate to increases to return oxygen, carbon dioxide and pH levels to normal