16 Questions
Which part of the body do the Gracile fassiculus primary sensory neurons carry information from?
Legs and trunk
Where do the axons in fasciculus cuneatus synapse?
Nucleus Cuneatus
What is the function of the internal arcuate fibers in the sensory pathway?
To decussate and form the medial lemniscus
What type of information does the medial lemniscus tract carry?
Vibration, proprioception, fine touch
Where do the second order sensory neurons cross midline in the caudal medulla?
Internal arcuate fibers
What is the role of first order neurons in the sensory pathway?
Ascend to caudal medulla
Which part of the body do the Cuneate fasciculus primary sensory neurons carry information from?
Neck and arms
"Maintains somatotopic organization" refers to:
"Arms being lateral and legs being medial"
Which sensory receptor provides proprioception?
Muscle spindles
What type of information do Bare nerve endings provide?
Pain and temperature
Which nerve root innervates the upper portion of the arm/shoulder area?
C5
Which nerve root is associated with the sensation in the chest area around the nipple?
T4
In which ascending sensory pathway do large diameter myelinated axons carrying proprioception information enter the spinal cord?
Posterior column medial lemniscus pathway
Which nerve innervates the small toe, lateral foot, and side of the calf?
S1
What type of touch is provided by the Merkel receptor?
Superficial touch
Which region is innervated by nerve root L4?
Medial part of lower leg
Study Notes
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.
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