The nervous system is made up of the cerebrum, cerebellum, midbrain, spinal cord, twelve pair of cranial nerves, and paired sets of peripheral nerves that extend from the spinal cord to all parts of the body. There are many functions governed by the nervous system, including learning, reasoning, memory, and judgment. Involuntary action, which is controlled by the cerebrum, is also considered a part of the nervous system. Blood pressure, respiratory rate, and heart rate are monitored by the midbrain and so also contained within the nervous system.

The endrocine system comprises the glands that secrete hormones into the bloodstream. The most important gland, sometimes referred to as the master gland, is the pituitary, located at the very base of the brain. The pituitary gland, in addition to producing growth-stimulating hormone, controls the activities of the other glands, including the thyroid, adrenal gland, and the testicles or ovaries of the cat. In turn, these glands control the activities of the body.

The respiratory system includes the nose, throat, larynx (voice box), trachea (windpipe), bronchial tubes, and lungs. This system is vitally important to the cat as a cat at rest completes 25 to 30 breaths a minute. This is approximately twice as many as a human completes. In the cat, inhaling takes about half as long as exhaling.

The lymphatic system is one of the main defenses of the cat's body. It is a network of vessels that transport lymph, which is made up up excess tissue fluids, protein, and other substances. This system functions without the benefit of a pump and carries out its mission through the venous side of the circulatory system. Lymph nodes, another important component of the lymphatic system, filter out foreign particles found throughout the body.  Lymph nodes contain lymphocytes, a types of white blood cell, which produce antibodies that neutralize bacterial poisons.

The digestive system comprises the mouth, teeth, esophagus, stomach, small and large intestines, liver, pancreas, and rectum. Of all the carnivores, cats have the fewest number of teeth, barely 30. These teeth were not made for chewing, but rather for killing prey ad tearing their flesh. Therefore, cats tear off chunks of food and swallow them whole.

The kidneys, ureters, bladder, and urethra make up with urinary or excretory system in both sexes. Closely related to the urinary system is the reproductive system. The testicles and sperm ducts comprise the male reproductive system with the fallopian tubes, uterus, womb, and vagina are part of the female reproductive system.

The other systems mentioned here, such as the circulatory and musculoskeletal, are complex systems deserving of elaboration. The musculoskeletal systems is the bedrock of conformation and body type at its most elementary. The circulatory system is the medium through which many of the body's other systems function. However, the details of these two systems are deserving of their own articles and will be covered in detail in coming weeks.