My revision notes: A2 Biology: Control of Heart Rate

All cells, e. muscle cells have different requirements, depending on the activity e.g. exercising - muscle cells require an increase in oxygen, glucose and removal of carbon dioxide.

The average heart rate is 70 beats / min
SAN controls this with no need of neurone impulses

If you exercise you need to increase:

• Heart rate
• strength of contraction
• stroke of volume  volume of blood pumped / beat

When you exercise you produce more CO2 - which dissolves to form carbonic acid - lowers pH

> This is detected by chemoreceptors in carotid arteries (going to head and aorta)

> They send an impulse to the cardiovascular centre which in turn sends an impulse down an accelerator nerve to SAN 

> So heart beats faster and stronger

Why are the chemoreceptors in the head and aorta?

Carotid artery is going to the brain ensures that the blood is not acidic

Going for aorta as its the biggest artery as it has the most amount of blood passing through

If you eercise you got receptors in muscles > gets stretched > impulse sends to cardiovascular neurone > SAN  > Increase in heart rate

Stop eercising > decrease in CO2/muscle receptors not stretched > impulse vagus nerves > SAN > slows heart rate back to normal