Dog Nervous System: Brain, Spinal Cord & Sensory Functions

The Brain and Spinal Cord: Controlling Movement and Sensation

A dog’s nervous system is the command centre of their body, coordinating everything from voluntary movements to involuntary reflexes. At the core of this system are the brain and spinal cord, which together form the central nervous system (CNS). This intricate network oversees countless processes, from walking and running to interpreting sensations and responding to the environment.

• The Brain:
  The dog’s brain can be divided into several major regions, each responsible for different functions.
  • Cerebrum: The largest part of the brain, the cerebrum, handles voluntary actions, complex thinking, and sensory interpretation. It processes visual and auditory signals, allows dogs to solve problems, and helps them recognise patterns and familiar faces.
  • Cerebellum: Located at the back of the brain, the cerebellum coordinates movement, balance, and posture. When a dog runs, jumps, or navigates uneven terrain, the cerebellum ensures their actions are smooth and well-coordinated.
  • Brainstem: The brainstem controls many of the body’s automatic functions, such as breathing, heart rate, and blood pressure. It also plays a key role in reflexes, such as rapidly pulling back a paw when it touches something hot.
  • Limbic System: This area governs emotions, memory, and instinctual behaviours. It explains why dogs form strong bonds, remember training commands, or exhibit fear or joy in certain situations.
• The Spinal Cord:
  The spinal cord is a long, cylindrical structure encased in the vertebrae. It serves as the primary communication highway between the brain and the rest of the body. Nerves branch out from the spinal cord, reaching every muscle, organ, and limb. These nerves carry motor commands from the brain to the muscles and relay sensory information, such as pressure, temperature and pain, back to the brain for processing.

When a dog moves, the brain sends electrical signals down the spinal cord and through peripheral nerves, instructing specific muscles to contract or relax. Simultaneously, sensory nerves send feedback about the dog’s environment, helping them adjust their movements and respond to changes around them. This constant communication ensures that dogs can walk without tripping, leap gracefully, and react quickly if they sense danger.

How Dogs See, Hear, Smell, Taste, and Feel

Dogs rely on a combination of senses to explore and interact with the world. While humans often depend heavily on vision, dogs are more attuned to smells, sounds, and touch. Each sense plays a distinct role in how dogs perceive their surroundings.

• Sight:
  A dog’s vision is adapted for detecting motion and seeing well in low-light conditions.
  • Field of View: Dogs have a wider field of view than humans, allowing them to see more of their surroundings without turning their heads. This is particularly true for breeds with long snouts, as their eyes are set farther apart.
  • Colour Perception: Dogs see fewer colours than humans, roughly equivalent to a human with red-green colour blindness. They primarily perceive shades of blue and yellow, while reds and greens appear more muted.
  • Night Vision: Dogs have more rods and light-sensitive cells in their retinas, enabling them to see in dim light. A reflective layer behind the retina, called the tapetum lucidum, further enhances their night vision by reflecting light through the retina, increasing sensitivity in low-light conditions.
    While not as colour-rich or sharp as human vision, a dog’s sight is highly tuned for detecting movement and tracking prey or objects from a distance.
• Hearing:
  Dogs have a remarkable sense of hearing that far surpasses human capabilities.
  • Frequency Range: Dogs can hear higher-pitched sounds, often up to 65,000 Hz or more, compared to the human upper limit of about 20,000 Hz. This allows them to detect subtle sounds, such as a squeak from a far-off toy or the faint rustle of an animal in the grass.
  • Directional Hearing: Their mobile ears can swivel and tilt independently, helping them pinpoint the exact source of a sound. This ability is particularly useful for hunting, as dogs can quickly locate prey even if it’s hidden.
  • Sensitivity to Volume: Dogs are sensitive to loud noises, so many react strongly to fireworks, thunderstorms, or other sudden, high-volume sounds.
• Smell:
  The sense of smell is a dog’s most influential and well-developed sense.
  • Olfactory Receptors: Dogs have up to 300 million scent receptors in their noses, compared to a human’s five million. This incredible sensitivity enables them to detect scents at concentrations as low as parts per trillion.
  • Jacobson’s Organ: Dogs also have a specialised organ, known as the vomeronasal organ or Jacobson’s organ, located in the roof of the mouth. This organ detects pheromones and other chemical signals, helping dogs gather information about other animals, such as their reproductive status or emotional state.
  • Scent Memory: A dog’s ability to remember and distinguish scents is unparalleled. This is why dogs are used for tasks such as tracking, search and rescue, and detecting medical conditions like diabetes or certain cancers.
    A dog’s nose constantly gathers information, allowing them to identify individuals, detect changes in its environment, and even sense subtle changes in a person’s mood or health.
• Taste:
  Dogs have fewer taste buds than humans, about 1,700 compared to a human’s 9,000. However, their sense of taste is still important, especially when combined with their sense of smell.
  • Preference for Meat and Fat: Dogs are more attuned to the taste of meat, fats, and certain minerals. They tend to prefer savoury and umami flavours rather than sweet ones.
  • Smell-Taste Connection: Because their sense of smell is so acute, a dog’s perception of flavour is strongly influenced by scent. Food that smells appealing will likely be more eagerly eaten, even if its taste is subtle.
• Touch:
  The sense of touch begins at birth when puppies rely on tactile contact with their mother and littermates to find warmth and comfort. As dogs mature, touch remains an essential form of communication and a way to navigate the environment.
  • Whiskers: Dogs have vibrissae (called whiskers) on their face, above their eyes, and near their muzzle. These highly sensitive whiskers help dogs detect nearby objects, air currents, and changes in their surroundings.
  • Skin Sensitivity: Dogs can feel pressure, vibration, pain, and temperature through their skin. Their sensitivity to touch varies across different body parts, with some areas, like the belly or paws, more responsive to gentle strokes or irritation.
    Touch is a sensory experience for dogs and a key element in bonding with humans. Gentle petting, scratching, or grooming can soothe and relax them, reinforcing trust and affection.

Understanding Neurological Issues and Sensory Impairments

While the nervous system and senses function seamlessly in healthy dogs, certain conditions can disrupt this harmony. Recognising the signs of neurological or sensory problems can help owners seek timely medical care and maintain their dog’s quality of life.

• Common Neurological Disorders:
  • Seizures and Epilepsy: Some dogs experience seizures, which can range from mild twitching to full-body convulsions. Epilepsy is a chronic condition that may require medication to manage.
  • Intervertebral Disc Disease (IVDD) occurs when the cushioning discs between the vertebrae degenerate or rupture, pressing on the spinal cord. Dogs with IVDD may show signs of pain, difficulty walking, or even paralysis.
  • Vestibular Disease: Affecting balance and coordination, vestibular disease can cause a dog to tilt their head, stumble, or appear dizzy. It often has a sudden onset and may be related to inner ear problems or age.
  • Degenerative Myelopathy: A progressive condition affecting the spinal cord, degenerative myelopathy leads to weakness in the hind legs, difficulty walking, and eventually paralysis. It is most common in older dogs, especially certain breeds like German Shepherds and Corgis.
• Sensory Impairments:
  • Hearing Loss: Age-related hearing loss is common in older dogs. Some breeds are also prone to congenital deafness. Signs include not responding to sounds, sleeping more deeply, and being startled when approached.
  • Vision Problems: Conditions such as cataracts, progressive retinal atrophy (PRA), or glaucoma can impair a dog’s sight. Signs include bumping into objects and reluctance to move in dim light or visible eye changes.
  • Olfactory Disorders: Although rare, certain diseases or infections can reduce a dog’s sense of smell, affecting their appetite and ability to interact with the environment.

By understanding the structure and function of the nervous system and senses and recognising potential problems early on, owners can provide better care and ensure their dogs maintain healthy and happy lives.