Structure and Function of the Muscular System in Cats
Smooth muscle. Smooth muscles are found within the internal organs such as the intestines, stomach, and bladder. They are involuntary muscles and are under the control of the autonomic nervous system.
What Is the Muscular System?
The muscular system is one of the largest systems in the cat's body. It is composed of units of tissue that have the power to contract, and hence to produce movement. The musculoskeletal system provides the basic framework for cats' athletic prowess and the light bone structure and lithe muscles give the cat tremendous abilities. The cat's skeletal muscles are similar to many other species, including humans. The triceps, biceps, gluteal muscles, deltoids and trapezius are some of the commonly known skeletal muscles.
Where Are Muscles Located?
Skeletal muscles are found throughout the entire skeletal system. They are attached to bones, other muscles and skin. They account for about half the weight of an animal. Parts of the walls of hollow internal organs such as the heart, stomach and intestines, and blood vessels are composed of smooth muscles.
What Is the General Structure of Muscles?
The cat possesses a highly evolved muscle system that is capable of producing swift and agile movements. The muscle system of a cat enables it to catch prey and escape from potential threats.
Muscles can be under voluntary or involuntary control. Voluntary muscles, such as those found in the arms and legs, can be controlled by thought. Involuntary muscles are those that are automatically controlled by the nervous system and cannot be moved at will. Examples of involuntary muscles are the muscles of the heart, diaphragm, and intestines.
There are three types of muscle tissue:
Skeletal muscle. These muscles are also called striated muscles. They predominately attach to portions of the skeleton and are voluntary muscles. They are involved with such things as walking, eating, tail motion and eye movement.
Cardiac muscle. Cardiac muscle fibers are found in the heart and are involuntary muscles. Cardiac muscle is unique in that it is striated muscle, like skeletal muscle, but is not under voluntary control.
Each individual muscle is composed of many cells held together by connective tissue. Skeletal muscles attach to bones by means of connective tissue tendons, which are elastic and strong. When muscles contract, they pull on the tendons, which then pull on the bones and cause the limbs to move.
Each muscle fiber receives its own nerve impulses, which trigger various motions. Once a signal or an impulse travels down the nerve to the muscle, the muscle fiber changes chemical energy into mechanical energy, and the result is muscle contraction.
Muscles receive a generous blood supply from neighboring blood vessels. The arteries supplying a muscle enter at rather definite places and often connect within the muscle. A rich capillary (the smallest of all blood vessels) distribution helps to deliver oxygen to muscles. High intake of oxygen by the muscles is necessary for endurance running, or other types of performance. Veins also accompany the arteries. During contraction, blood is circulated by being forced into the larger veins.
What Is the Function of Muscles?
The primary function of muscles is to bring about movement to all or a part of the cat's body. Muscle is used to stabilize joints to prevent their collapse under a load. Smooth muscles maintain continence of the bladder and propel food through the bowel. Muscles also help to generate heat by shivering.
Voluntary muscles can contract and pull, but they cannot push, so they must work in pairs that flex and extend. Extensor muscles straighten the limbs and attach to the bones, so the bones act as levers. The flexor muscles, which bend the joints, act to pick up the limb. Their partners, the extensor muscles, in turn contract to bring the limb back down. The abductor muscles move the limbs away from the midline, and the adductor muscles move the limbs toward the midline.
What Are Common Diseases of Muscles?
Congenital muscler disorders. Congenital, inherited diseases of the muscles are extremely rare in cats. Congenital myotonia has been seen in the cat. This disease of skeletal muscle is characterized by involuntary active contraction of a muscle that persists after some sort of voluntary effort or stimulation of the muscle.
Feline polymyositis. This disease is believed to be an immune-mediated inflammation of multiple muscles through out the body. It causes muscle weakness, lethargy, decreased appetite, bizarre gait abnormalities and lameness.
Myositis ossificans. This is a rare, progressive disease associated with cartilage and bone formation in skeletal muscles. Signs include firm masses in the affected muscles and adjacent soft tissues, limb weakness, stiffness, decreased range of motion of joints, muscle pain and immobility.
Myositis caused by infections. Infectious agents such as bacteria, protozoa and some parasites may cause localized or generalized inflammation of the muscles.
Feline polymyopathy. This disorder occurs when potassium levels fall to a dangerously low level within the body. Potassium is needed for normal muscle function, and low potassium causes widespread muscle weakness, inability to hold the head up, reluctance to walk and possible muscle pain.
Neoplasia. Primary cancer lesions of muscles are rare and usually occur in adult or older animals.
What Types of Diagnostic Tests Are Used to Evaluate Muscles?
Serum muscle enzymes – These tests measure the enzymes of muscles that are released into the blood stream when the tissue is damaged or inflamed or when a lot of muscle activity has occurred.
Electromyography (EMG) – This test assesses the electrical properties of skeletal muscle.
Muscle biopsy – Biopsy is the removal and microscopic examination of muscle tissue. It is used to detect inflammation and infection within the muscle and to determine whether a tumor of muscle is malignant or benign.
Radiography – X-rays do not reveal much information about muscles, but can detect abnormalities in the surrounding bony structures.