Control of Heart rate

Question 1

How is Heart Rate controlled?

Answer 1

The heart is myogenic, its heartbeat is initiated by the SAN

The Medulla Oblongata in the brain can increase or decrease heart rate

receives nerve impulses from chemoreceptors (respond to blood pH) in the carotid arteries and baroreceptors (respond to blood pressure) in the carotid arteries and aorta

sends impulse in sympathetic nerves to SAN to increase HR and sends impulse in parasympathetic nerves to SAN to decrease HR

Question 2

How does Exercise affect Heart Rate?

Answer 2

Exercise = muscle contraction, which requires respiration

Therefore, waste product CO2 is released into the blood

This lower pH of blood (acidic), which is detected by chemoreceptors in carotid arteries

Sends impulses to the medulla oblongata

Then medulla oblongata sends impulses to SAN via the sympathetic nerves causing the heart rate to increase

benefit = increase blood flow to lungs to remove CO2 and take in O2

Question 3

How does Low Blood Pressure affect Heart Rate?

Answer 3

If a person moves from lying/sitting to standing, blood pressure falls (reducing blood flow to the brain)

This is detected by pressure receptors in the carotid arteries and aorta

Sends impulses to medulla oblongata

then medulla oblongata sends impulses to SAN via the sympathetic nerves causing the heart rate to increase

benefit = increasing heart rate leads to an increase in blood pressure (so enough blood can reach the brain)