Dorsal Root Ganglion: Function & Definition

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  • 0:00 Nervous System Essentials
  • 1:16 Dorsal Root Ganglion…
  • 1:59 Dorsal Root Ganglion Function
  • 4:03 Lesson Summary
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Lesson Transcript
Instructor: Taormina Lepore

Taormina has taught advanced high school biology, is a science museum educator, and has a Master's degree in museum paleontology.

All along our spinal cord, we have specialized nerves that send and receive messages to and from various parts of our body. There are particular nerve cell clusters called dorsal root ganglia that are present in the root of these spinal nerves. In this lesson, we'll discuss the function and definition of a dorsal root ganglion.

Nervous System Essentials

If you stick the tip of your finger with a thumbtack, your body will tell you immediately: 'Hey! Stop that!'

Pain is a fundamental evolutionary feature, something we sense to help our bodies avoid harm. Running throughout our body is a highway of nerves that helps transmit these sensory messages to the brain, and in response, sends motor messages back to our extremities to make them move away from the source of the pain.

Our nervous system is made up of two main sub-systems: the central nervous system, which is comprised of the brain and the spinal cord; and the peripheral nervous system, which is comprised of all the nerves that branch out from the spinal cord.

Let's think of the word 'peripheral.' It makes us think of things that are on the edges, like images in our peripheral vision. These peripheral nerves spread out to the edges, or extremities, of the body to the organs, and to the surface of the skin. Unlike the central nervous system, peripheral nerves aren't protected by the spinal column or the skull. The peripheral nervous system makes direct contact with the mechanical and sensory world around us.

Let's talk about one particular way in which our body senses and registers pain using the peripheral nervous system.

Dorsal Root Ganglion Definition

Within the peripheral nervous system, there are special nerve cell clusters called dorsal root ganglia that help transmit the sensory messages of pain and touch. Dorsal root ganglia are also known as spinal ganglia, or posterior root ganglia.

The dorsal root ganglion lies at the base of individual branching spinal nerves, very close to the spinal cord itself. The ganglion forms a little bulge at the base of each spinal nerve. The ganglion collects and transmits messages of pain and touch very quickly to the spinal cord, rather than all the way back to the brain. This shorter distance allows for a very rapid response to a painful stimulus. It allows you, for example, to quickly pull your hand away from a hot stove or a thumbtack.

Dorsal Root Ganglion Function

Even though dorsal root ganglia are a part of the system of peripheral nerves, they lie very close to the spine, and therefore to the central nervous system. That makes them an important connection between the two systems. These nerve clusters help transmit messages toward the brain.

In order to understand how dorsal root ganglia function, we'll need to define a couple of terms: afferent nerves, which send messages toward the brain; and efferent nerves, which send messages away from the brain. Using these terms, we can think more deeply about how messages of pain and touch are sent to our brain indirectly by the dorsal root ganglia along our spine.

We can start by using that mental image of touching a thumbtack again. When you touch a painful stimulus, the message of that pain travels through your finger and arm along the long axon, a threadlike projection of a nerve cell, toward the brain. The message is clear: hurry and move your finger away from the harmful thing.

We call these nerves afferent, or sensory nerves, because they send that message toward the brain. But pain can't wait long, and your body wants to react quickly to avoid damage. The message of pain doesn't have to travel all the way up to the brain. Instead, the long, thin axon funnels the message from your finger to the dorsal root ganglion at the base of your spinal vertebrae.

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