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How does the spinal cord work?

Medicine & HealthLesson on requestFree to readयह पेज हिंदी में पढ़ें

Quick answer

The spinal cord is a bundle of nerves that connects the brain to the body. Sensory nerves bring signals up to the brain, and motor nerves carry commands down to muscles. It also handles reflexes, which are quick, automatic responses that do not need the brain to start them.

The spinal cord works by carrying electrical signals between the brain and the rest of the body through bundles of nerve fibres. Sensory information travels up to the brain, while motor commands travel down to muscles and organs.

Step by step

  1. Sensory receptors in the skin, muscles, and organs detect a stimulus such as touch, heat, or pain.
  2. Sensory neurons carry electrical impulses from these receptors into the spinal cord through the dorsal roots.
  3. The spinal cord transmits the signals upward to the brain, which processes the information.
  4. The brain sends a response down the spinal cord through motor neurons in the ventral roots.
  5. Motor neurons carry the command to muscles or glands, which carry out the response.
  6. In a reflex, sensory neurons connect to motor neurons in the spinal cord, directly or via interneurons, skipping the brain to act faster.

Key things to understand

  1. The spinal cord is a long, thin bundle of nervous tissue that extends from the base of the brain down inside the backbone to the lower back.
  2. It is made of grey matter in the centre, containing neuron cell bodies, and white matter on the outside, containing nerve fibres.
  3. Sensory neurons carry signals from the skin, muscles, and organs into the spinal cord, which then sends them up to the brain.
  4. Motor neurons carry commands from the brain down the spinal cord and out to muscles, causing them to contract.
  5. The spinal cord also controls reflexes, which are rapid, automatic responses that bypass the brain to save time.

Labelled diagram

  1. Sensory receptor

    Detects a stimulus such as touch or heat in the skin or organ.

  2. Sensory neuron

    Carries the signal from the receptor into the spinal cord.

  3. Spinal cord

    Relays the signal upward to the brain or directly to a motor neuron.

  4. Brain

    Processes the information and decides on a response.

  5. Motor neuron

    Carries the command from the spinal cord out to a muscle.

  6. Muscle

    Contracts or relaxes to produce movement in response.

How signals travel through the spinal cord

Real-world examples

  • When you touch a hot pan, sensory neurons in your hand send a signal to your spinal cord, which quickly triggers a reflex to pull your hand away.
  • During a routine check-up, a doctor may tap your knee with a small rubber hammer to test the knee-jerk reflex, which involves the spinal cord.
  • A person with a spinal cord injury at the neck may lose the ability to move their arms and legs because signals from the brain cannot reach those muscles.
  • When you decide to walk, your brain sends motor commands down the spinal cord to the leg muscles, which then contract in a coordinated pattern.

Common mistake

✗ Myth: The spinal cord is just a passive cable that simply connects the brain to the body.

✓ Fact: The spinal cord is an active processing centre. It contains neural circuits that can generate reflexes and modulate signals on their own, without waiting for instructions from the brain.

People also ask

What does the spinal cord do?
The spinal cord carries signals between the brain and the body. It sends sensory information from the body up to the brain and motor commands from the brain down to muscles and organs. It also contains reflex circuits that produce fast, automatic responses without involving the brain.
How does the spinal cord send messages?
The spinal cord sends messages through electrical impulses that travel along neurons. Sensory neurons bring signals in through the back of the spinal cord, and motor neurons send signals out through the front. These signals travel up and down the cord in bundles of nerve fibres called tracts.
Why is the spinal cord important?
The spinal cord is important because it is the main pathway for communication between the brain and the body. Without it, the brain could not control movement or receive sensations from most of the body. It also enables reflexes that protect us from harm, such as pulling away from a hot object.
What happens if the spinal cord is injured?
Damage to the spinal cord can block the flow of signals between the brain and the body. This may cause loss of movement or feeling below the injury. The exact effect depends on where and how severe the injury is. See a doctor immediately for any suspected spinal injury.
How is the spinal cord protected?
The spinal cord is protected by the vertebrae of the spine, which form a bony canal around it. Inside, three layers of membranes called meninges cushion it, and cerebrospinal fluid provides a watery shock absorber. This layered protection helps prevent damage from everyday movements.
What is the difference between the spinal cord and the spine?
The spine is the bony column of vertebrae that supports the body and protects the spinal cord. The spinal cord is the soft nervous tissue that runs inside the spine. The spine is bone; the spinal cord is nerve tissue.
Can the spinal cord repair itself?
The spinal cord has very limited ability to repair itself after serious injury. Unlike some other body tissues, neurons in the spinal cord do not readily regrow. Research into treatments continues, but currently, damage is often permanent.

Part of the guide: How Your Body Works →