Pain Pathways

Pain Pathways

Question 1. Describe origin, course and function of corticospinal. (or) Functions of pyramidal tract.
Answer:

• Pyramidal tract is also called corticospinal tract.

Corticospinal Functions:

1. The pyramidal tracts are concerned with voluntary movement of the body.

• Lateral corticospinal tract.
  • Convey motor impulses to control voluntary movements specially of the distal limb muscles.
  • Concern with fine, precise movements.
• Anterior corticospinal tract.
• Convey motor impulses to control movements of trunk and proximal portions of the limb.

2. Forms part of pathway for superifcial reflexes

3. Fibers of this tract are concerned with sensory motor coordination.

Question 2. Describe the pain pathway. (or) Pathway of pain.
Answer:

• Lateral spinothalamic tract carries the pain sensation from the peripheral parts of the body to the CNS.

Pain Pathway Origin:

• Pain fibers arises from free nerve endings that are distributed throughout the body.

Pain Pathway Course:

1. First order neurons – posterior nerve root ganglia cells.

• Dendrites of these neurons receive the impulses and their axons carry them to the spinal cord.
  • Fibers for fast pain.

2. Fibers for slow pain.

2. Second order neuron – marginal cells and substantia gelatinosa cells.

1. Fast pain.

2. Slow pain.

Pain Pathway Termination:

1. Fast pain fibers

• Majority of fibers terminate in ventral posterolateral nucleus of thalamus.
• Few fibers terminate in ascending reticular system of brainstem.

2. Slow pain fibers.

• One-fifth of fibers terminate in ventral posterolateral nucleus of thalamus.
• Remaining fibers terminate in either of the following.
  1. Reticular formation of brainstem.
  2. Tectum of midbrain
  3. Grey matter around aqueduct of sylvius.
• These terminating sites form third order neuron.
• Axons from these neurons reach the sensory area of the cerebral cortex.