Hair and Skin
The Muscular System
The Nervous System
The Digestive System
The Urinary System
The Reproductive System
THE DOG'S NERVOUS SYSTEM
Like all mammalian nervous systems, that of the dog is complex. Basically, the dog's nervous system is composed of the peripheral and central nervous systems. The peripheral system consists in part of sensory fibers and motor neurons. These are gathered together in bundles and are called nerves. The central system has segregated neurons and lies within the skull and spinal cavities. The central nervous system is divided into two main parts: the brain and the spinal cord. The brain has an important role in complex behavior, since it governs learning, motivation, perception, etc. The function of the spinal cord is twofold: it acts as a conductor to and from the brain and it effects reflex actions.
All of the above are true for other mammals, including man. It is in the area of reflex action that the dog's nervous system differs from man. The dog has a highly developed reflex-action mechanism. His reflexes are very important to his daily life. They play a major part in his everyday behavior. For example, reflexes are responsible for the dog's blinking when something strikes his eye, for scratching when he has an itch, for making his hair stand up on end when he sights or smells something strange, and for making his ears twitch when he hears various sounds. These and many other reflexes are well developed in the dog.
The dog's reflexes have been the subject of study for many years. Much of the information obtained from studying the dog's reflexes can be applied to man. Perhaps one of the most publicized experiments involving the reflexes of the dog was that done by the Russian scientist Ivan P. Pavlov (1849-1936). Pavlov introduced the concept of the conditioned reflex. The conditioned reflex involves a simple response to a particular action or stimulus.
In a very simplified version, Pavlov's experiment went something like this: He set a pan of food in front of a dog. At the sight of the food, the dog's saliva began to flow. This act of salivating at the sight of food, Pavlov called an unconditioned response or reflex. He next varied the experiment by ringing a bell before setting down the pan of food. After a time, the dog salivated when he heard the bell ring and without seeing the food. Pavlov called the ringing of the bell a conditioned stimulus and the dog's flow of saliva at hearing the bell, a conditioned response or reflex.
The dog's nervous system can be damaged by disease. Distemper and rabies are diseases that involve the central nervous system. The majority of dogs that recover from distemper are usually left with an impairment of the central nervous system. In the case of rabies, there are no survivors.