A chemoreceptor is a sensor, also known as [Interoreceptor]

Found in blood vessels they provide information about the internal environment.

A pressoreceptor [Baroreceptor] is a sensor capable of responding to changes in blood, air, or fluid pressure.

For a sensor to function properly, four events must take place.

1] Stimulus,-    A change takes place which activates certain sensory neurons.

2] Transduction,-    The receptor must respond and convert the stimulus to an electrical response,

[receptor potential] or [generator potential]

3] Conduction,-     The generator potential reaches its threshold and an impulse is conducted to the central nervous

system by a first order neuron.

4] Translation,-     The impulse reaches the central nervous system and is interpereted.

The chemoreceptors that we are concerned with are located close to the baroreceptors in the Carotid sinus and the

Arch of the aorta, called the Carotid and Aortic Bodies.

These chemoreceptors are sensative to changes of oxygen and even more so to changes in carbon dioxide and

hydrogen ion levels in the blood.

Hypoxia, [severe deficiency of oxygen] an increase in hydrogen ions, [acidosis]

or excess carbon dioxide, [hypercapnia] stimulates the chemoreceptors.

Which in turn sends impulses to the cardiovascular centre causing increased sympathetic stimulation of arterioles and veins.

The result of this action is vasoconstriction and an increased blood pressure.