The muscular system of a cat gives it approximately half of its body weight and is one of the largest systems in the body. The cat’s skeletal muscles are very similar to those of the human system, which is why cats are often dissected by anatomy students. The muscular system accounts for a cat’s athletic and hunting abilities, giving the cat the opportunity to swiftly stalk and capture its prey.
According to Virginia Wells’ article, "Structure and Function of the Muscular System in Cats," cats have three types of muscle tissue. Smooth muscles are located in the internal organs, such as the stomach, and are controlled by the autonomic nervous system. Skeletal muscles, also known as striated muscles, are attached to the skeleton and are used for voluntary actions such as walking or eating. Cardiac muscles are also striated, but they are attached to the heart and are involuntarily controlled.
Muscles are mainly used to provide movement to the cat’s body, either by moving individual body parts or the body as a whole. Muscles give stability to joints so that they can hold up when bearing a load. Smooth muscles push food through the bowels and regulate the bladder. If the cat is cold, its muscles will contract and relax, causing shivering that creates heat. Muscles control extension and flexion of the cat’s paws, wrists and toes. Muscles that perform more functions are often smaller and more complex than those that perform a singular function.
Voluntary muscles work in pairs to flex and extend because they cannot push--they can only contract. Flexor muscles bend the joints to lift the limbs, while the extensor muscles contract, lowering the limbs back down. Another muscle pair is made up of abductor muscles, which move the limbs away from the midline, and the adductor muscles, which move the limbs back toward the midline.
Muscles are composed of multiple cells held together by tissues and attached to bones by elastic tendons. When muscle fibers receive nerve impulses, the chemical energy becomes mechanical energy, and the muscle contracts. Muscles require a large quantity of oxygen, particularly when undergoing endurance activities such as running. Tiny capillaries deliver oxygen to the muscles, and blood vessels travel through connecting arteries to maintain blood supply in the muscles.
When the muscular system is affected by a disease, it is unable to function properly. Feline polymyositis is a muscle inflammation that leads to weak, lame muscles. Feline polymyopathy results from extremely low potassium levels, which cause muscle pain and weakness. Potassium is essential for optimum muscle function. Cancerous lesions called neoplasia sometimes occur on muscles, usually in adult cats.