Question

Using specific examples found in the special senses, describe the difference between chemoreceptors and mechanoreceptors. What stimuli do each respond to and how do they transduce this stimuli into an action potential?

Answer 1

chemoreceptors are of two types- central and peripheral.

Central chemoreceptors are present in Brian. These receptors are connected with the respiratory centres. These are responsible for 70-80%of increased ventilation through chemical regulatory mechanism.

Chemoreceptors respond to change in chemical composition. The main stimuli for Central chemoreceptors is the increased hydrogen ion concentration. But this hydrogen ion cannot cross blood brain barrier. So carbon dioxide combines with water to form carbonic acid and this a I'd dissociate to from hydrogen ion and bicarbonate ion. Now this hydrogen ion stimulate the central chemoreceptors.

Mechanism of action- from chemoreceptors, the excitatory impulses are sent to dorsal respiratory group of neurons, resulting in increased ventilation.

Peripheral chemoreceptors are present in carotid and aortic region.

Hypoxia is the main stimulus for activation of peripheral chemoreceptors. Hypoxia cause closure of potassium channels and prevent potassium efflux. This leads to depolarization and generation of nerve impulses.

mechanomechanoreceptors- receptors present in the skin are called cutaneous or mechanoreceptors. These respond to mechanical stimuli such as touch, pressure and pain. Some examples of these type of receptors are Meissner corpuscles for touch, Merkel disk for touch, Pacinian corpuscles for pressure etc.

Mechanism of action- when any mechanical stimuli comes, it cause opening of mechanical gated sodium channel which cause development of receptor potential. This cause opening of voltage gated sodium channels in node of Ranvier. Sodium enters the cell and generate action potential in nerve fibre.