14.6 Controlling Heart Rate

Question 1

What nervous system is the heart rate controlled by?

Answer 1

autonomic nervous system

Question 2

What part of the brain is responsible for heart rate regulation?

Answer 2

medulla oblongata

Question 3

What is the medulla oblongata linked to, to increase heart rate?

Answer 3

it is linked to the sino-atrial node in the heart by motor neurones

Question 4

what are the two centres of the medulla oblongata and how do they control heart rate?

Answer 4

-One centre increases heart rate, by sending impulses through the sympathetic nervous system, these impulses are transmitted by the accelerator nerve
-One centre decreases heart rate, by sending impulses through the parasympathetic nervous system, these impulses are transmitted by the vagus nerve

Question 5

What nervous system works to decrease heart rate?

Answer 5

parasympathetic

Question 6

What nervous system works to increase heart rate?

Answer 6

sympathetic

Question 7

What nerve works to increase heart rate?

Answer 7

accelerator nerve

Question 8

What nerve works to decrease heart rate?

Answer 8

vagus nerve

Question 9

How does the medulla oblongata know to control heart rate?

Answer 9

depend on information received from receptors, baroreceptors and chemoreceptors

Question 10

What do chemoreceptors detect?

Answer 10

chemical changes in the blood stream, including changes in pH, carbon dioxide level etc.

Question 11

Where are chemoreceptors located?

Answer 11

aorta, carotid arteries, medulla

Question 12

What do baroreceptors detect?

Answer 12

changes in blood pressure

Question 13

Where are baroreceptors located?

Answer 13

aorta, vena cava, carotid arteries

Question 14

What happens when chemoreceptors detect a decrease in blood pH?

Answer 14

a response is triggered to increase heart rate

Question 15

Why do pH levels of the blood decrease?

Answer 15

If carbon dioxide levels in the blood increase, pH will decrease because carbonic acid is formed when carbon dioxide interacts with water

Question 16

Why do pH levels of the blood increase?

Answer 16

When the carbon dioxide levels in the blood decreases, the pH will rise

Question 17

When pH is high what happens?

Answer 17

There will be a reduction in the frequency of nerve impulses being sent from the medulla oblongata. In turn, this reduces the frequency of impulses being sent to the SAN via the sympathetic nervous system. Parasympathetic nervous system is stimulated to decrease heart rate through the vagus nerve

Question 18

What happens if blood pressure is too high?

Answer 18

Impulses are sent to the medulla oblongata to decrease heart rate. Medulla oblongata will send impulses along the parasympathetic nervous system via the vagus nerve to the SAN which decrease there firing rate therefore heart rate will decrease, reducing blood pressure back to normal

Question 19

What happens if blood pressure is too low?

Answer 19

Impulses are sent to the medulla oblongata to increase heart rate. Medulla oblongata will send impulses along the sympathetic nervous system via the accelerator nerve to the SAN which increases its firing rate therefore heart rate will increase, increasing blood pressure back to normal

Question 20

How is heart rate also controlled by hormones?

Answer 20

-In times of stress adrenaline and noradrenaline are released, which affect the SA node directly to speed up heart rate by increasing the frequency of impulses