Nervous System
Nervous
The neurological system represents one of the communication mechanisms in the dog’s body. The nervous system includes the brain, spinal cord, and branching nerves that conduct signals throughout the entire body.
Anatomically, the nervous system consists of two main areas: central, the brain and spinal cord; and peripheral, the nerves coming from the brain and spinal cord to innervate areas of the body. The control of the nervous system falls into two separate categories: the somatic and autonomic nervous systems. The somatic nervous system relays voluntary (conscious) signals to activate skeletal muscle movement to allow your pet to navigate its surroundings. In contrast, the autonomic nervous system relays involuntary (unconscious) signals to regions of the body to control your pet’s internal organs, such as the lungs, heart, and intestinal tract.
Indications that your pet may have a neurologic problem include seizures, weakness, inability to rise/walk, incontinence, sudden blindness, behavior changes, and pain.
Common conditions that affect the nervous system in dogs include:
- Epilepsy , a seizure disorder of unknown causes
- Intervertebral disc disease, a prolapse of disc material that cushions the bones of the spine
- Congenital abnormalities, such as hydrocephalus (also known as, water in the brain)
- Infectious causes, such as Distemper virus
Brain
Brain
The dog’s brain, weighing only 2-3 ounces, contains hundreds of millions of nerve connections to control and coordinate specific functions in the body. Nerves travel directly from the brain or down the spinal cord to transmit signals back and forth to the rest of the body. The skull provides protection for this delicate organ. Problems within the brain manifest in a variety of ways depending on the region of the brain affected. Behavior changes, mental dullness, incoordination, and seizures are some common indications of brain disease.
Vertebrae
Vertebrae
As the skull protects the brain, the bony spine protects the spinal cord. The spinal cord passes through multiple vertebrae to provide a neurologic highway that connects the brain to the rest of the body. Muscles intimately attach to the spine and allow movement and activity. Disorders of the spinal column may involve the bony structures of the spinal column (e.g.: arthritis), the muscles that attach to it (e.g.: trauma), or the nerves that pass through (e.g.: intervertebral disc disease or a “slipped disc”). Symptoms of spinal injury include: pain along the spine, weakness, inability to walk or stand, and restlessness. Spinal injury requires immediate veterinary attention.
Intervertebral Disc Disease
The spinal cord is protected by bony vertebrae. To allow shock absorption and flexion of the spine, the vertebrae are separated by soft cushions (intervertebral discs). These cushions are similar to jelly donuts: they have a firm exterior and a soft middle. Due to age or genetics, the outer portion degenerates and the soft center is pushed out (ruptured) without warning when the spine moves. When the disc ruptures, the center is expelled with high velocity and force, bruising the spinal cord that lies above it. The spinal cord swells from the impact and becomes compressed by the surrounding bone. Pressure on the spinal cord impairs nerve conduction along the spinal column. Symptoms of intervertebral disc disease range from acute pain to paralysis. The area of the body affected depends on the location of the disc rupture. Diagnosis of IVDD requires physical examination to localize the lesion followed by imaging studies with a myelogram (radiographs with contrast material) or MRI. Treatment depends on the severity of the signs. Mild cases benefit from strict rest and pain management. Patients with acute paralysis require emergency surgery to restore normal nerve conduction and prevent permanent nerve damage.