Control of heartrate

Question 1

what does the cardiac muscle being myogenic mean?

Answer 1

it contracts on its own, but the rate of contraction is controlled by a wave of electrical activity

Question 2

where is the SAN located?

Answer 2

the right atrium

Question 3

what does SAN stand for?

Answer 3

sinoatrial node

Question 4

what is the SAN?

Answer 4

a tissue which can release a wave of electricity, to act as a pacemaker. when this hits the cardiac muscle, it causes contraction

Question 5

what does AVN stand for?

Answer 5

atrioventricular node

Question 6

where is the AVN located?

Answer 6

in between the right and left ventricle, whilst still in the atria

Question 7

what is the bundle of His?

Answer 7

conductive tissues

Question 8

where is the bundle of His located?

Answer 8

running through the septum

Question 9

where are the purkyne fibres located?

Answer 9

walls of the ventricles

Question 10

explain the process of controlling the heart (6)

Answer 10

-SAN releases a wave of depolarisation across the atria, causing contraction.
-AVN releases a wave of depolarisation, but this doesn’t travel to the ventricles due to a non-conductive layer.
-instead, the bundle of His conducts and passes the wave of depolarisation down the septum and purkyne fibres in the ventricle walls.
-as a result, the apex then the ventricle walls contract. there is a short delay before this whilst the AVN transmits the second wave.
-this allows time to pump all blood into the ventricles, so they are full. the cells then repolarise and the cardiac muscle relaxes.

Question 11

what part of the brain controls heart rate and via what part of the nervous system?

Answer 11

the medulla oblongata, via the autonomic nervous system

Question 12

what are the 2 parts of controlling heart rate?

Answer 12

-the centre linked to the SAN which increases heart rate via the sympathetic nervous system
-the centre that decreases heart rate vis the parasympathetic nervous system

Question 13

what are the receptors to pH called?

Answer 13

chemoreceptors

Question 14

what are the receptors to blood pressure called?

Answer 14

baroreceptors

Question 15

where are chemoreceptors and baroreceptors located?

Answer 15

the aorta and carotid artery

Question 16

what can happen if blood pressure is too high or too low?

Answer 16

artery walls may be damaged or there could be insufficient oxygen supplied to respiring cells

Question 17

what happens to pH and heart rate when there’s a high respiratory rate?

Answer 17

pH will decrease in the blood due to CO2 or lactic acid production. excess acid is removed so that enzymes won’t denature. this is achieved by an increased heart rate, so that CO2 diffuses out the alveoli quicker.

Question 18

describe the process when increased blood pressure is detected

Answer 18

the stimulus of increased pressure is detected by baroreceptors in the wall of the aorta and carotid artery, which are stretched due to high pressure.

more electrical impulses get sent to the medulla oblongata, which are then sent to the parasympathetic nervous system to the SAN to decrease the frequency.

the cardiac muscle and SAN tissues then reduce the heart rate.

Question 19

describe the process when decreased blood pressure is detected

Answer 19

the stimulus of decreased pressure is detected by baroreceptors in the wall of the aorta and carotid artery, which are not stretched due to low pressure.

more electrical impulses get sent to the medulla oblongata, which are then sent to the sympathetic nervous system to the SAN to increase the frequency.

the cardiac muscle and SAN tissues then increase the heart rate.

Question 20

describe the process when decreased pH is detected

Answer 20

the stimulus of decreased pH is detected by the chemoreceptors in the walls of the aorta and carotid artery.

more electrical impulses are sent to the medulla oblongata, which are then sent via the sympathetic nervous system to the SAN to increase the frequency.

the cardiac muscle and SAN tissues then increase the heart rate to deliver blood to the lungs rapidly to remove CO2.

Question 21

describe the process when increased pH is detected

Answer 21

the stimulus of increased pH is detected by the chemoreceptors in the walls of the aorta and carotid artery.

more electrical impulses are sent to the medulla oblongata, which are then sent via the parasympathetic nervous system to the SAN to decrease the frequency.

the cardiac muscle and SAN tissues then decrease the heart rate.