Control of heart rate (14)

Question 1

What is the equation for cardiac output?

Answer 1

cardiac output = stroke volume x heart rate

Question 2

What is meant by myogenic?

Answer 2

contraction of the heart is initiated within the muscle itself rather than by nerve impulses

Question 3

What are the 2 nodes?

Answer 3

sinoatrial node (SAN)
atrioventricular node (AVN)

Question 4

Where is SAN found?

Answer 4

within the wall of the right atrium

Question 5

Where is AVN found?

Answer 5

near the lower end of the right atrium in the wall that separates the 2 atria

Question 6

How is a heartbeat initiated and coordinated?

Answer 6

1) SAN initiates wave of depolarisation
2) WoD spreads across both atria causing atria to contract (known as atrial systole)
3) layer of fibrous, non-conducting tissue delays impulse while ventricles fill and valves close
4) AVN conveys WoD down septum via Bundle of His, which branches into the Purkinje fibres along ventricles
5) causes ventricles to contract from apex upwards

Question 7

What is the autonomic nervous system?

Answer 7

system that controls involuntary actions of the glands and muscles

Question 8

What is the autonomic nervous system made from?

Answer 8

2 subdivisions

Question 9

What are the 2 subdivisions of the autonomic nervous system?

Answer 9

sympathetic
parasympathetic

Question 10

What is the sympathetic nervous system involved in?

Answer 10

fight or flight response

Question 11

What is the role of the sympathetic nervous system?

Answer 11

stimulates effectors to increase activity

Question 12

What is the parasympathetic nervous system involved in?

Answer 12

normal resting conditions

Question 13

What is the role of the parasympathetic nervous system?

Answer 13

inhibits effectors to decrease activity

Question 14

What are the 2 types of receptor involved in heart rate?

Answer 14

baroreceptors
chemoreceptors

Question 15

What is the role of baroreceptors?

Answer 15

detect changes in blood pressure

Question 16

Where are baroreceptors located?

Answer 16

carotid artery

Question 17

What is the role of chemoreceptors?

Answer 17

detect changes in pH

Question 18

What could cause a decrease in pH?

Answer 18

increase in CO2 concentration

Question 19

Where are chemoreceptors located?

Answer 19

carotid artery and aortic artery

Question 20

If blood pressure increases, heart rate should…

Answer 20

decrease

Question 21

If blood pressure decreases, heart rate should…

Answer 21

increase

Question 22

If CO2 concentration increases/pH decreases, heart rate should…

Answer 22

increase

Question 23

How does the body respond to an increase in blood pressure?

Answer 23

1) baroreceptors send more impulses to cardioinhibitory centre in the medulla oblongata
2) more impulses to SAN via the parasympathetic nervous system
3) stimulates release of acetylcholine, which decreases heart rate

Question 24

How does the body respond to a decrease in blood pressure?

Answer 24

1) baroreceptors send more impulses to cardio-acceleratory centre in medulla oblongata
2) more impulses to SAN via sympathetic nervous system
3) stimulates release of noradrenaline, which increases the heart rate and strength of contraction

Question 25

How does the body respond to an increase in CO2 concentration/pH decrease?

Answer 25

1) chemoreceptors detect pH decrease and send more impulses to the cardi-acceleratory centre in the medulla oblongata
2) more impulses to SAN via sympathetic nervous system
3) heart rate increases so rate of blood flow to lungs increases, which increases the rate of gas exchange and ventilation