A: Balance and orientation in space are controlled by the vestibular system with some help from visual clues. The vestibular system which is located in the inner ear is composed of several fluid-filled compartments arranged at right angles to each other. Movement of fluid within these compartments stimulates nerves within the brain signaling the position of the head. The direction of head movement and the speed of position changes are also detected.
Cats, being natural climbers, have evolved a sequence of reflex movements to ensure an upright landing should they fall. Vestibular and visual inputs allow the cat first to level its head in relation to gravity. Spinal cord reflexes then result in a series of movements which jackknife the body into an upright position. The cat lands safely using bent legs and its tail to cushion the impact.
Q: Why do cats have such good night vision?
A: The night vision in cats is far superior to that present in most mammals. Cats need just 16 percent of the light required by humans to see as well in the dark. In bright light, the muscles of the feline iris are able to contract the pupil down to a very narrow slit allowing only optimum light to reach the retina. By contrast, at night, the pupils will dilate allowing as much light into the eye as possible to stimulate the photographic cells in the retina.
Cats also have a well-developed reflective layer of tissue located behind the retina called the tapetum. Light which has already passed through the retina is reflected by the tapetum back into the retina layer of the eye. The photographic cells responsible for picking up the image in the retina are therefore stimulated twice. Light reflected by the tapetum is responsible for the yellow-green glow you notice when looking into cat’s eyes at night.