heart rate control

Question 1

How does the nervous system control heart rate? (2)

Answer 1

The SAN generates electrical impulses that cause the heart muscles to contract;

The medulla unconsciously controls the rate at which the SAN fires

Question 2

What types of receptors monitor blood pressure and chemical levels in the blood? (4)

Answer 2

Baroreceptors (pressure receptors):

Located in the aorta and vena cava, they detect high or low blood pressure;

Chemoreceptors:

Located in the aorta, carotid artery, and medulla, they monitor oxygen levels, carbon dioxide, and pH levels in the blood

Question 3

How do pressure and chemical receptors affect heart rate? (3)

Answer 3

1. Receptors send electrical impulses to the medulla via sensory neurones;
2. The medulla processes the information and sends impulses to the SAN via motor neurone;
3. To adjust heart rate

Question 4

What is the response when baroreceptors detect high blood pressure? (7)

Answer 4

Stimulus: High blood pressure;

Receptor: Baroreceptors detect high blood pressure;

Neurone: Impulses sent to the medulla;

Medulla sends impulses along the vagus nerve;

Which secretes acetylcholine that binds to receptors on the SAN;

Effector: Cardiac muscles;

Response: Heart rate slows to reduce blood pressure back to normal.

Question 5

What is the response when baroreceptors detect low blood pressure? (7)

Answer 5

Stimulus: Low blood pressure;

Receptor: Baroreceptors detect low blood pressure;

Neurone: Impulses sent to the medulla;

Medulla sends impulses along the accelerator nerve;

Which secretes noradrenaline that binds to receptors on the SAN;

Effector: Cardiac muscles;

Response: Heart rate increases to raise blood pressure back to normal.

Question 6

What is the response when chemoreceptors detect high blood O₂, low CO₂, or high pH? (7)

Answer 6

Stimulus: High O₂, low CO₂, or high pH in the blood;

Receptor: Chemoreceptors detect these chemical changes;

Neurone: Impulses sent to the medulla;

Medulla sends impulses along the vagus nerve;

Which secretes acetylcholine that binds to receptors on the SAN;

Effector: Cardiac muscles;

Response: Heart rate decreases to return O₂, CO₂, and pH levels to normal.

Question 7

What is the response when chemoreceptors detect low blood O₂, high CO₂, or low pH (e.g., during exercise)? (7)

Answer 7

Stimulus: Low O₂, high CO₂, or low pH in the blood;

Receptor: Chemoreceptors detect these chemical changes;

Neurone: Impulses sent to the medulla;

Medulla sends impulses along the accelerator nerve;

Which secretes noradrenaline that binds to receptors on the SAN;

Effector: Cardiac muscles;

Response: Heart rate increases to return O₂, CO₂, and pH levels to normal.

Question 8

How does the hormonal system help control heart rate? (4)

Answer 8

1. Adrenaline is released by the hormonal system;
2. Binds to specific receptors in the heart;
3. This causes the cardiac muscle to contract more frequently and with more force;
4. Leading to an increase in heart rate and more blood being pumped by the heart.