The nervous and sensory systems of the cat are essential to his health and well-being. Perceptions and reactions to his environment are dependent on his senses; movement is controlled via the central nervous system brain and spinal cord; and the endocrine system hormone-producing glands controls his behaviour patterns. The five faculties by which a cat’s body perceives his surroundings are on the checklist.
The central nervous system
This controls and co-ordinates the cat’s everyday activities. Information received by the sensory organs is constantly monitored by the system and dealt with according to its importance: it is acted upon immediately, discarded or stored away for future use, as appropriate. The brain has three clearly defined regions: the fore-brain, the mid-brain and the hind-brain.
This area is concerned with the sense of smell via the olfactory lobe, memory and intelligence. It also contains the thalamus which responds to impulses travelling from the spinal cord and the hypothalmus which controls the internal regulatory processes.
This contains the optic lobes and deals with signals stimulated by light; therefore it is responsible for sight.
Here, the cerebellum controls balance and the enlarged end of the spinal cord forms the medulla, controlling the respiratory and circulatory systems. The pituitary gland which produces hormones is situated in this region, as is the limbic system that controls digestion. Unsurprisingly,
this part of the brain is vital for the survival of the cat.
The pupil of the eye opens very wide to admit more light, which passes through the transparent cornea and lens to the retina at the back of the eye. Any light not absorbed by the retina bounces back to a layer of cells known as the tapetum lucidum, which reflects it back to the retinal cells, reinforcing the information transmitted to the brain by the nerves there. Any reflecting light still not absorbed creates the effect of the cat’s eyes shining yellow, green or red at night. Their eyes can open slightly wider than ours. This enables the cat to be accurate in judging distances for jumping, or springing and pouncing when hunting.
Cats need only one-sixth of the light humans need in order to distinguish the same detail of shape and movement. The eyes face forwards, allowing fields of vision to overlap and giving stereoscopic vision that is slightly wider than ours. This enables the cat to be accurate in judging distances for jumping, or springing and pouncing when hunting.
Being comparatively large, and set in deep skull sockets, feline eyes do not move freely, so the cat turns his head to bring objects into sharp focus. Cats are not colour-blind, but see the world in more subtle shades of colour than we do. Their eyes are protected from strong light by the iris the sharpness of vision is enhanced. In addition to the upper and lower eyelids, there is a third eyelid, called the nictitating membrane haw. This is a thin sheet of pale tissue tucked away in the corner of the eye. Its function is to remove dust and dirt from the cornea by moving across the surface of the eyeball during a inward movement, and also to keep it moist and lubricated.