Chemical control of ventilation

Introduction:

During emotion and exercise increase respiratory rate and force. But the pattern of respiration is come back to normal, within a short time by some regulatory mechanisms in the body.

Chemical mechanism of regulation of respiration is operated through the chemoreceptors.

Chemoreceptors are the sensory nerve endings, which give response to changes in chemical constituents of bloód

which Stimulate Chemoreceptors ?( In blood)

1.Central chemoreceptors

2.Peripheral chemoreceptors

Central chemoreceptors are present in the brain.

Situation:

Central chemoreceptors are located in deeper part of medulla oblongata, close to the dorsal respiratory group of neurons.

This area is called as chemosensitive area and the neurons are called chemoreceptors.

Mechanism of action : central chemoreceptors:

Central chemoreceptors

Central chemoreceptors are stimulated by hydrogen ions, however the blood hydrogen ions doesn't stimulated central chemoreceptors because the Blood H ions doesn't cross through the blood brain barrier and blood cerebrospinal fluid barrier.
In other way the invreased blood CO2 able to cross the blood brain barrier and blood cerebrospinal fluid barrier and enter into interstitial fluid of brain or cerebrospinal fluid
The CO2 combine with H2O to form carbonic acid, Since carbonic acid is unstable, it immediately dissociates into hydrogen ion and bicarbonate ion

H- ions stimulate the central chemoreceptors. From chemoreceptors, the excitatory impulses are sent to dorsal respiratory group of neurons(DGN).

result of increased ventilation (increased rate and force of breathing). Because of this, excess carbon dioxide is washed out and respiration is back to normal.
Lack of Oxygen does not have significant effect on the central chemoreceptors, except that it generally depresses the overall function of brain.

Peripheral chemoreceptors

Peripheral chemoreceptors are the chemoreceptors present in carotid and aortic region.

Mechanism Of Action:

Peripheral chemoreceptors

peripheral chemoreceptors O2 sensitive potassium channels in the glomus cells of peripheral chemoreceptors.'

( Hypoxia) decrease O2 level cause closure of O2 sensitive potassium channels and prevents potassium efflux.

This efflux cause depolarization of glomus cells (receptor potential) and generation of action potentials in nerve ending.

These impulse pass through aortic and Hering nerves and excite the dorsal group of neurons. Dorsal group of neurons (DGN) in turn, send excitatory impulses to respiratory muscles, resulting in incréased ventilation.