Control of Heart Rate.

Question 1

What is the autonomic nervous system?

Answer 1

This system controls the involuntary activities of internal muscles and glands.
It is split into two parts:
- Sympathetic
- Parasympathetic

Question 2

What is the sympathetic nervous system?

Answer 2

Stimulates effectors to speed up activity

Question 3

What is the parasympathetic nervous system?

Answer 3

Inhibits effectors to slow down any activity. Controls activities under normal restign conditions. Concerned with conserving energy and replenishing bodies reserves.

Question 4

How do the sympathetic and parasympathetic systems work together?

Answer 4

Antagonistically

Question 5

What region of the brain controls heart rate?

Answer 5

Medulla oblongata

Question 6

What two systems does the medulla oblongata contain?

Answer 6

1. A centre that increases heart rate, which is linked to the SAN by the sympathetic nervous system.
2. A centre that decreases heart rate, which is linked to the SAN by the parasympathetic nervous system.

Question 7

What stimulates the centres in the medulla oblongata?

Answer 7

Chemical changes in the blood.

Pressure changes in the blood.

Question 8

What are chemoreceptors?

Answer 8

Found in the walls of the carotid arteries. They are sensitive to changes in the pH of the blood that result in changes from CO2 concentration changes. In solution CO2 forms an acid which lowers pH.

Question 9

How do chemoreceptors affect the control of heart rate?

Answer 9

1. CO2 conc increases, pH lowers.
2. Chemoreceptors detect stimulus and increase freq of impulses to the centre in medulla oblongata that increases heart rate.
3. Impulses via sympathetic system increase, SAN increases heart rate.
4. Increased blood flow, more CO2 removed by lungs.
5. pH rises to normal and chemoreceptors reduces freq of impulses to medulla oblongata
6. Medulla oblongata reduces freq of impulses (parasympathetic) to SAN which reduces heart rate

Question 10

How do pressure receptors control heart rate when it is higher than normal?

Answer 10

1. Pressure receptors transmit a nervous impulse to the centre in the medulla oblongata that decreases heart rate.
2. Impulses sent via the parasympathetic system to the SAN to decrease heart rate

Question 11

How do pressure receptors control heart rate when it is lower than normal?

Answer 11

1. Pressure receptors transmit impulses to the centre in the medulla oblongata that increases heart rate.
2. Impulses sent via sympathetic system to the SAN which increases heart rate.