Why do cats purr? What is happening to a cat's body when it is purring?

Answer 1

Here you go :-)

According to veterinarian Bruce Fogle, author of The Cat's Mind, the original function of purring was to enable a kitten to communicate with his mother that things are well. A kitten is able to purr by the second day of life, and although he can't meow and nurse at the same time, he can purr and nurse. And the mother cat often purrs back, probably to reassure the kitty.

There are many theories to explain how the purr is generated. One study determined that purring involves activation of nerves within the voice box. These nerve signals cause vibration of the vocal cords while the diaphragm serves as a piston pump, pushing air in and out of the vibrating cords, thus creating a musical hum. Veterinarian Neils C. Pederson, author of Feline Husbandry, believes that purring is initiated from within the central nervous system and is a voluntary act. In other words, cats purr only when they want to.

Purring is an integral part of the feline communication system and occurs for a variety of reasons. It is classified with the “murmur vocalization” group, which involves sounds produced by a cat while the mouth is closed. In addition to purring, this group of sounds includes grunting, calling, and acknowledgment murmurs. Domestic cats and some wild cats, like pumas and mountain lions (almost any big cat that cannot roar), are all able to purr.

As the cat matures the meaning of the purr changes. Some cats purr to indicate contentment or pleasure, but badly frightened cats and severely ill cats also purr, and so do females while they are delivering their kittens. It is not uncommon for cats to purr when they are close to death. This final purring may indicate a state of anxiety or possibly euphoria, states that have also been described in terminally ill people.

Animal behaviorists believe that when cats purr under stressful circumstances, they are reassuring or comforting themselves, much as humans may sing to themselves or hum when they are nervous. Frightened cats may purr to communicate submissiveness or non-aggressive intentions. A feral cat may purr to signal that he will not attack and other cats need not feel threatened. Older cats may purr when they play or approach other cats, signaling that they are friendly and want to come closer.

A more recent theory about purring is that it is caused by the release of nature's own morphine-like substances (endorphins) in the brain. Since endorphins are released under circumstances of pain and pleasure, this would explain the seemingly ambiguous expression of purring. This theory jives with Pederson's reasoning, that purring is initiated in the brain, and is also compatible with the more mechanical explanations for purring, as endorphins activate one of the main action systems in the brain (so thought is translated into movement). Whatever the explanation for purring, it seems to indicate cats' contentment and is associated with improvement in their affect at times of stress. Purring is one of cats' most endearing qualities.

Answer 2

Hi Caroline...The reason is psychological as well as physiological--the two are not mutually exclusive of one another. Cat's purr whenever they feel content, extremely frightened and some will purr when they are dying as well.

How cats purr:
One study determined that purring involves activation of nerves within the voice box. These nerve signals cause vibration of the vocal cords while the diaphragm serves as a pump, pushing air in and out of the vibrating cords, thus creating a musical hum. Some veterinarians believes that purring is initiated from within the central nervous system and is a voluntary act. In other words, cats purr only when they want to.

The other theory is that the sound comes more from vibrating blood vessels than in the voicebox itself. The larger the vocal chords the softer the purr whereas the smaller the louder.
Source: http://cats.about.com/cs/catmanagement101/a/why_cats_purr.htm

The Scientific Reason WHY cats purr:

Some scientists believe when cats purr the frequency of their purring will help heal damaged bones and body organs as well as help heal humans.

All the cats had purr frequencies between 20 Hz and 200 Hz. With the exception of the cheetah, which had frequencies 2 Hz from the rest, all the species had frequencies, notably 25 Hz, 50 Hz, 100 Hz, 125 Hz, and 150 Hz, that correspond exactly with the best frequencies determined by the most recent research for bone growth, fracture healing, pain relief, relief of breathlessness, and inflammation. All of the cats' purrs, including the cheetah, had frequencies 4 Hz from the entire repertoire of low frequencies known to be therapeutic for all of the ailments.

That fact that the cats in this study produced frequencies that have been proven to improve healing time, strength and mobility could explain the purr's natural selection. After a day or night of hunting, purring could be likened to an internal vibrational therapeutic system, a sort of "kitty massage" that would keep muscles and ligaments in prime condition and less prone to injury. Additionally, the purr could strengthen bone, and prevent osteodiseases. Following injury, the purr vibrations would help heal the wound or bone associated with the injury, reduce swelling, and provide a measure of pain relief during the healing process.
Source: http://www.sciam.com/askexpert_question.cfm?articleID=0005CB0D-82FC-1E31-82FC809EC5880000&catID=3&topicID=3.

Answer 3

It was once thought that the purr was produced from blood surging through the inferior vena cava, but as research continues it seems that the intrinsic (internal) laryngeal muscles are the likely source for the purr. Moreover, there is an absence of purring in a cat with laryngeal paralysis. The laryngeal muscles are responsible for the opening and closing of the glottis (space between the vocal chords), which results in a separation of the vocal chords, and thus the purr sound. Studies have shown, that the movement of the laryngeal muscles is signaled from a unique “neural oscillator” in the cat’s brain.

Answer 4

purring is a sign of a cat being happy and contented

Answer 5

They purr, because of being joyfilled at having a cozy home to live in, delighted by something or, happy because of being loved

Answer 6

Cats also purr when they are ill or unhappy.