In this video, I describe the three main pathways of the anterolateral system: the spinothalamic, spinoreticular, and spinomesencephalic tracts. I follow the route pain information takes along each of these tracts, from nociceptors to the somatosensory cortex, reticular formation, or periaqeuductal grey (depending on the tract).

For an article (on my website) that explains the spinothalamic tract more in-depth, click this link: https://neuroscientificallychallenged.com/posts/know-your-brain-spinothalamic-tract

TRANSCRIPT:

Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss pain and the anterolateral system.

Pain begins at nociceptors, cutaneous receptors that are specialized to detect noxious stimuli like extreme pressure, very hot or cold temperatures, or tissue damage. When activated, nociceptors send a signal to the spinal cord; the signal will be sent to the brain on pathways that make up what is known as the anterolateral system.

The anterolateral system consists of three major pathways: the spinothalamic, spinoreticular, and spinomesencephalic tracts.

The spinothalamic tract can be considered the main pathway for transmitting pain information to the cerebral cortex; it is involved in the awareness and recognition of where in the body a painful stimulus is occurring. Neurons in the spinothalamic tract carry pain information from nociceptors to the spinal cord, then immediately synapse with a second neuron that quickly decussates, or crosses over to the other side of the spinal cord before traveling up the spinal cord. These fibers proceed to the ventral posterolateral nucleus of the thalamus, where they synapse with another neuron that carries the pain information to the somatosensory cortex.

The function of the spinoreticular tract is not very clearly defined, but it may be involved in changes in the level of attention in response to pain. The fibers of the spinoreticular tract follow the same path as the spino thalamic tract, but they also project to areas in the reticular formation, which is a network of neurons found throughout the brainstem that are involved in a wide range of functions including attention and consciousness.

The spinomesencephalic tract, also known as the spinotectal tract, plays an important role in the control and inhibition of pain. Fibers in the spinomesencephalic tract follow the same path as the spinothalamic tract but they synapse in an area of the midbrain called the periaqueductal gray. When neurons in the periaqueductal gray are stimulated, they can activate a natural pain suppression system that involves the release endogenous opioids, which are substances that are produced by the body and have painkilling effects. The release of endogenous opioids and other neurotransmitters leads to inhibition of the pain signal in the spinal cord and naturally-produced analgesia.

REFERENCE:

Nolte J. The Human Brain: An Introduction to its Functional Anatomy. 6th ed. Philadelphia, PA. Elsevier; 2009.