Dermatomes Quiz: Test Your Knowledge of Sensory Innervation

Which part of the body do the Gracile fassiculus primary sensory neurons carry information from?

Where do the axons in fasciculus cuneatus synapse?

What is the function of the internal arcuate fibers in the sensory pathway?

What type of information does the medial lemniscus tract carry?

Where do the second order sensory neurons cross midline in the caudal medulla?

What is the role of first order neurons in the sensory pathway?

Which part of the body do the Cuneate fasciculus primary sensory neurons carry information from?

"Maintains somatotopic organization" refers to:

Which sensory receptor provides proprioception?

What type of information do Bare nerve endings provide?

Which nerve root innervates the upper portion of the arm/shoulder area?

Which nerve root is associated with the sensation in the chest area around the nipple?

In which ascending sensory pathway do large diameter myelinated axons carrying proprioception information enter the spinal cord?

Which nerve innervates the small toe, lateral foot, and side of the calf?

What type of touch is provided by the Merkel receptor?

Which region is innervated by nerve root L4?

Primary Sensory Neurons

Gracile fasciculus (thin) carries information from legs and trunk (medial portions)
Axons in fasciculus gracilis synapse on nucleus gracilis
Cuneate fascicules (wedge shape) carry information from neck and arms
Axons in fasciculus cuneatus synapse on nucleus cuneatus

Somatotopic Organization

Maintains somatotopic organization
Legs = medial
Arms = lateral

Second Order Sensory Neurons

Cross midline in caudal medulla and synapse in thalamus
Decussate as internal arcuate fibers
Form the medial lemniscus on the other side of the medulla

Third Order Sensory Neurons

From thalamus to somatosensory cortex
Pathway: vibration, proprioception, fine touch
Goes into dorsal root ganglion through the cervical spinal cord
Primary sensory neurons synapse on the dorsal root entry

Sensory Information

Muscle spindles and GTO provide proprioception
Meissner corpuscle and Merkel receptor provide superficial touch
Pacinian corpuscle and Ruffini ending provide deep touch, and vibration
Bare nerve endings provide pain and temperature information

Dermatomes

Know major dermatomes for legs & feet, arms and hands, and trunk
Useful in identifying site of lesion
Sensory regions of the skin are innervated by a nerve root

Dermatome Chart

C2 = greater and lesser occipital nerve (head)
C3 = neck
C4 = top of shoulder (collarbone)
C5 = upper portion of arm/shoulder area
C6 = upper half of lower arm
C7 = upper half of lower arm, hands
C8 = Palm of hands
T4 = nipple area (chest area)
T10 = belly button
L3 = knee
S1 = small toe, lateral foot, side of the calf
L4 = medial part of lower leg

Ascending Sensory Pathways

Posterior column medial lemniscus pathway
Large diameter myelinated axons carrying information about proprioception, vibration, light/fine touch
Enter the spinal cord via the medial portion of the dorsal root entry level/zone via the dorsal root ganglion through the cervical spinal cord

Test your knowledge of sensory information, such as proprioception and tactile sensations, as well as major dermatomes for different regions of the body. Learn about the innervation of sensory regions of the skin and the trigeminal nerve's role in facial sensation.