Vibrissae
Vibrissae are hairs specialized for detection of movement, commonly called whiskers. In general, vibrissae are hairs which grow around the nostrils or other parts of the face in many mammals, usually specialized for tactile sensation. They are thicker and stiffer than other types of hair, and they can also be found on the wrists of the forelegs of cats. The term is also used in reference to the stiff feathers near the mouths of some birds.
Vibrissae consist of inert material and contain no nerves. What makes vibrissae different from other hairs is that they are implanted in a special follicle sealed by a capsule of blood, called a blood sinus. Touching a vibrissa causes it to bend and the blood in the sinus is pushed to one side or the other. The blood amplifies the movement and allows the nerves at the base to detect extrememly small sensations. In some mammals, the follicles of vibrissae are surrounded by a highly developed sheath of muscle tissue which can be used to move the whiskers.
Whiskers can grow extremely long; the whiskers of a chinchilla can be up to a third of its body length. Vibrissae offer an advantage to animals that don't always have sight to rely on to navigate, or to find food, or when the usefulness of non-tactile senses is limited. A large part of the brain of many mammals is devoted to processing the nerve impulses from vibrissae because it is important to their survivial. Mammals use a lot of energy to keep the follicles housing their whiskers warm and ready to use.
Note: The singular form is vibrissa.
Categories: Zootomy