1. Sensory and Motor Pathways in the Spinal Cord

2. Objectives
Basic understanding of how information is conveyed between the cortex and spinal cord
Understand the significance of decussations
Have a general idea about where sensory and motor tracts are in the spinal cord

3. Big Picture Functional organization of each lobe Sensory receptors
Sensory pathways
Motor pathways
Upper motor neurons
Lower motor neurons
We have discussed how the cortex is organized by function: sensory and motor. We covered how we take in sensory information: touch, proprioception, auditory and vestibular. Now we are going to put those two together to describe the full sensory pathway from receptor to cortex. Then we will start looking at the motor system in more detail. Today we will talk about how efferent signals travel from cortex to the spinal cord in general. In coming lectures we will go into more detail about how the brain modulates movement (upper motor neurons) and what happens once efferent signals leave the CNS (lower motor neurons).

4. Looking at cross sections to identify sensory and motor tracts

5. Sensory Tracts Anterolateral: detect harmful stimuli
Spinocerebellar
Spinothalamic (Ventral and Lateral)
2. (Medial) Lemniscal: tactile and proprioceptive
Fasciculus Gracilis
Fasciculus Cuneatus
Dorsal columns
Tract names: origin and then destination

6. Lower Motor Neuron Cell Bodies
Upper Motor Tracts
Lateral Corticospinal Tract and Rubrospinal Tract: Distal limb
Vestibulospinal Tract and Reticulospinal Tract: Posture and Proximal
Lower Motor Neuron Cell Bodies
Located in the ventral horn and are the target of the upper motor tracts
Cell bodies are in the cortex or brainstem. Primarily excitatory but if connect to interneuron in spinal cord depends on the neurotransmitter released by the interneuron
The more ventral or anterior motor tracts originate from vestibular nuclei, the reticular formation and the superior colliculus and provide a stable base of control for more distal limb movements.

7. SLTC: sacral lumbar thoracic cervical
PD: proximal, distal EF: extensor, flexor
Fasciculus- bundle of axons going to the same place
Notice that the sensory input from the upper part of the body is located more medially. Its like the lower sensory nerves got on the bus first so they took the seats closest to the window and the cervical nerves had to take the aisle seats. Also, this is a diagram- in actuality the tracts are not so neatly contained.

8. https://youtu.be/5B87zsAKmWc
Overview of spinal cord organization

9. Sensory Pathways

10. https://youtu.be/70Kg4uPem4U
Dorsal column pathway

11. https://youtu.be/QpoEh9VQ7so

12. Upper Motor Pathways

13. https://youtu.be/dZ5H6PesskA

14. Corticospinal tract lesions

15. Draw it yourself!
Gheysens, K., Lebeau, R., & Glendinning, D. (2017). Spinal cord neuroanatomy: An interactive, step-wise module. MedEdPORTAL: Journal of Teaching and Learning Resources,  13 (Jun 8). DOI /mep_ URL:

16. Spinal Cord Section
Here is an image of spinal cord section with the three major tracts labeled for your review:
Whenever you are looking at spinal cord slices, remember that R will be on your left and the L side of the cord will be on your R. It’s like a person facing you. Helps to get used to this since your client will be facing you many times.

17. Pain and Temperature
Here is an image of consecutive sections to demonstrate how nerves carrying pain and temperature travel up the spinal cord:
Spinothalamic tract
*regardless of where a nerve enters, it will travel approximately 2-3 cord levels on the ipsilateral side before synapsing and decussating to the contralateral side
Purple

18. Vibration and Position Sense
A nerve carrying vibration and position has been added to the sections to demonstrate how it enters and travels up the spinal cord: Dorsal column medial lemniscus tract
orange

19. Motor
A nerve carrying motor information has been added to the sections to demonstrate how it descends, synapses in the motor horn, and travels out the spinal cord: Corticospinal tract
Green