Somatosensory and somatic motor pathways LO3, LO4

Question 1

Three main somatosensory pathways

Answer 1

1. Spinothalamic pathway
2. Posterior column pathway
3. Spinocerebellar pathway

Question 2

Spinothalamic Pathway

Answer 2

Conducts sensations of crude touch, deep pressure, pain & temperature.
First-order neurons:
- conduct sensory input from receptors into a posterior gray horn
synapse with
Second-order neurons (within a sensory nucleus)
- conduct sensory input to the thalamus
- ascend spinal cord in a/an: anterior spinothalamic tract or lateral spinothalamic tract
synapse with
Third-order neurons (in the thalamus)
- conduct sensory input to the primary somatosensory cortex (PSC)

Question 3

Posterior Column Pathway

Answer 3

Conducts sensations of fine touch, light pressure, vibration & proprioception.
First-order neurons
- conduct sensory input into a posterior gray horn and up to the medulla oblongata
- ascend spinal cord in a fasciculus gracilis or fasciculus cuneatus tract
synapse with
- Second order neuron (in medulla oblongata)
- conduct sensory input to the thalamus
synapse with
Third-order neurons (in the thalamus)
- conduct the sensory input to the PSC

Question 4

Spinocerebellar Pathway

Answer 4

Conducts sensations of proprioception
First-order neurons
- conduct sensory input from proprioceptors into a posterior gray horn
synapse with
Second-order neurons (within a sensory nucleus)
- conduct sensory input to the cerebellum
- ascend spinal cord in an anterior or posterior spinocerebellar tract

Question 5

Somatic Motor Pathways

Answer 5

Conduct somatic motor output
from the primary motor cortex (PMC) to skeletal muscles
1. Lateral corticospinal pathway
2. Anterior corticospinal pathway

Question 6

Lateral Corticospinal Pathway

Answer 6

Conducts the somatic motor output that controls the skeletal muscles of the limbs.
Upper motor neurons:
- conduct somatic motor output from the PMC to an anterior gray horn
- descend spinal cord in a lateral corticospinal tract
synapse with
Lower motor neurons (in a motor nucleus)
- conduct somatic motor output to skeletal muscles of the limbs

Question 7

Anterior Corticospinal Pathway

Answer 7

Conducts the somatic motor output that controls the skeletal muscles of the trunk (axial skeleton).
Upper motor neurons:
- conduct somatic motor output from the PMC to an anterior gray horn
- descend the spinal cord in an anterior corticospinal tract
synapse with
Lower motor neurons (in a motor nucleus)
- conduct somatic motor output to skeletal muscles of the trunk