14.5 control of heart rate

Question 1

what is the involuntary (subconscious) nervous system divided into?

Answer 1

• sympathetic nervous system

- parasympathetic nervous system

Question 2

what is the sympathetic nervous system?

Answer 2

• stimulates effectors

- speeds up any activity

Question 3

what is the parasympathic nervous system?

Answer 3

• inhibits effectors

- slows down any activity

Question 4

what does antagonistic mean?

Answer 4

oppose one another

Question 5

what does SAN stand for?

Answer 5

sinoatrial node

Question 6

where can you find the SAN?

Answer 6

right atrium of the heart

Question 7

what is heart muscle of the heart called?

Answer 7

cardiac muscle

Question 8

The heart controls and coordinates the regular contraction of the atria and ventricles. Describe how.
[5 marks]

Answer 8

• SAN → AVN → bundle of His /Purkyne fibres;
• Impulses / electrical activity (over atria);
• Atria contract;
• Non-conducting tissue (between atria and ventricles);
• Delay (at AVN) ensures atria empty/ ventricles fill before ventricles contract;
• along the bundle of His
• Ventricles contract from apex upwards;

Question 9

what are changes to the heart rate controlled by?

Answer 9

medulla oblongata

Question 10

what are the 2 centres of the medulla oblongata?

Answer 10

• a centre that increases heart rate

- a centre that decreases heart rate

Question 11

what is the centre that increases heart rate linked to?

Answer 11

sinoatrial node by the sympathetic nervous system

Question 12

what is the centre that decreases heart rate linked to?

Answer 12

sinoatrial node by the parasympathetic nervous system

Question 13

effect of exercise on cardia output

Answer 13

• increased muscular/ metabolic activity
• more CO2 produced by tissue from increased respiration
• blood pH is lowered
• chemical receptors in the carotid arteries increase frequency of impulses to the medulla oblongata
• centre in medulla oblongata that speeds heart rate, increases frequency of impulses to SAN via the sympathetic nervous system
• SAN increases heart rate
• increased blood flow removes carbon faster
• carbon dioxide concentration returns to normal

Question 14

where do pressure receptors occur?

Answer 14

• carotid arteries

- aorta

Question 15

how do pressure receptors operate when blood pressure is higher than normal?

Answer 15

• pressure receptors transmit more nerve impulses to the centre in the medulla oblongata that decreases heart rate
• centre sends impulses via the parasympathetic nervous system
• to SAN, which leads to a decrease in the heart beat rate

Question 16

how do pressure receptors operate when blood pressure is lower than normal?

Answer 16

• pressure receptors transmit more nerve impulses to the centre in the medulla oblongata that increases heart rate
• centre sends impulses via the sympathetic nervous system
• to SAN, which leads to an increases in the heart beat rate