What's the physiology of a cat's purr?

Answer 1

Hi Linda...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 2

wow seattle I am very impressed by your answer. I have always believed that there is a deeper "reason" as to why cats purr, but your post explained it perfectly.

Because the weirdest thing is, i have seen a cat shorttly before it died and it was just purring away, that was a long time ago but I thought it would be okay, but unfortunately it passed on shortly thereafter.
So your post makes perfect sense

kudos

Answer 3

they say a cat purrs when he's happy, but a cat can also purr when he's sick as it helps him to calm down. scientists say that it may be connected to a hormone, endorphins, which humans release when they're happy and stressed.

Answer 4

Although it is tempting to state that cats purr because they are happy, it is more plausible that cat purring is a means of communication and a potential source of self-healing.
http://cats.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=cats&zu=http%3A%2F%2Fwww.sciam.com%2Faskexpert_question.cfm%3FarticleID%3D0005CB0D-82FC-1E31-82FC809EC5880000

Answer 5

Air rubs against their missing vocal chords in the larynx as they breathe.

Answer 6

It is a sign of contentment and affection.

Answer 7

It means that they are happy, know that they are loved, content and satisfied.

Answer 8

I think it means that they are happy and rested.

Answer 9

happiness