Neuroanatomy Sensory Paths - Nociception: Quintothalamic Tract

What does the quintothalamic tract do?

Handles pain and head areas

The GSA function in the head and face region is served by what cranial nerve?

CN V (trigeminal n.)

What kind of nucleus is associated with the trigeminal nerve?

(a very large) sensory nucleus

The sensory nucleus associated with the trigeminal nerve extends through which of the brainstem divisions?

1. Mesencephalon (midbrain)

2. Metencephalon (pons)

3. Myelencephalon (medulla)

What three parts is the sensory nucleus associated with the trigeminal nerve broken into?

1. Mesencephalic nucleus

2. Pontine nucleus

3. Spinal nucleus of trigeminal nerve

Mesencephalic nuelcus

Handles proprioception and is mostly rostral

Trigeminal ganglion

Where the sensory nerve bodies of the first order are located. This is located on the floor of the cranial cavity

Where do nociceptors in the head and face travel through to get to the trigeminal ganglion?

Trigeminal n.

What are the two portions of the quintothalamic tract?

1. Cranial reflex arc

2. quintothalamic tract for relay to higher centers

Cranial reflex arc of quintothalamic tract

Multi-synaptic and involves sensory input into the CNS resulting in an observable motor response

Does the cranial reflex arc of the quintothalamic tract involve conscious awareness?

No, not unless the stimulus is intense enough to activate the relay portion of the path

1st neuron of cranial reflex arc

Trigeminal ganglion

Describe the axonal movement of the 1st neuron of the cranial reflex arc

Axons ascend and descend a short distance forming hte spinal tract of the trigeminal nerve

2nd neuron of cranial reflex arc

Location depends on modality of sensation:

• Pontine sensory nucleus: mechanical type of sensation

• Spinal nucleus of the trigeminal nerve: thermal type of sensation

What is the location of the 2nd neuron of the cranial reflex arc when the there is a mechanical type of sensation?

Pontine sensory nucleus

What is the location of the 2nd neuron of the cranial reflex arc when there is a thermal type of sensation?

Spinal nucleus of the trigeminal nerve

Describe the axonal movement of the 2nd neuron of the cranial reflex arc

Axons synapses in brainstem on motor nuclei of appropriate cranial nerves

3rd neuron of the cranial reflex arc

Any motor neuron of the appropriate cranial nerve

Describe the axonal movement of the 3rd neuron of the quintothalamic tract

Axon leaves brainstem through a cranial nerve to reach peripheral target

What is the typical peripheral target of the 3rd neuron of the cranial reflex arc?

Skeletal muscles of the face

When is the quintothalamic tract for relay to higher centers invoked?

When a noxious stimulus has a higher degree of intensity, leading to conscious awareness

1st neuron of QTRHC

trigeminal ganglion

Axonal movement of 1st neuron of QTRHC

Axons ascend and descend a short distance forming the spinal tract of the trigeminal nerve

2nd neuron of QTRHC

Location depends on modality of sensation:

• Pontine sensory nucleus: mechanical type of sensation

• Spinal nucleus of the trigeminal nerve: thermal type of sensation

Axonal movement of the 2nd neuron of the QTRHC

Axons immediately cross to the opposite side and ascend contralaterally as the trigeminal lemniscus

3rd neuron of the QTRHC

Ventral caudal medial nucleus of the thalamus VCM

Axonal movement of the 3rd neuron of the QTRHC

Axons contribute to the formation of the internal capsule and synapse in the appropriate part of the cerebral cortex