Organization of the spinal cord and the brainstem Flashcards
Dr. Mokha
Brainstem:
Pons
Medulla
Midbrain
T/F: Right thalamus will receive sensory information from the right side of the body?
False. The right thalamus will receive sensory information from the left side of the body
Principle of 2nd order axons:
Axons of 2nd order neurons in sensory pathways crossover contralaterally
How does somantosensory initially travel?
From the peripheral nerve fibers to the spinal cord then finally arriving at the CNS
Sensory function Proprioception:
Receptor type: Muscle spindle
Sensory function: Touch
Receptor type: Merkel, meissner, pacinian, and ruffini cells
Sensory function: Pain, temperature
Receptor type: free nerve ending
Where is the medial leminiscus located?
Inside the middle portion of the medulla
Where is the Gracile nucleus located?
Inside the frontal portion of the medulla
Where is the Cuneate nucleus located?
Inside the temporal portion of the medulla
Spinal nerve:
Dorasal root (sensory)
Ventral root (motor)
Spinal cord:
31 pairs of spinal nerves:
C=8
T=12
L=5
S=5
C=1
Where does the spinal cord end?
Causally end between L1 and L2
What spinal nerves are good for obtaining CSF and epidural injections?
Cauda Equina L2-S4. Only spinal nerves and no spinal cord tissue
Anterolateral system (ALS):
Pain, temperature, and itch pathway
Damage to the Lateral corticospinal tract:
Spastic paralysis, babinski sign, loss of motor movement
Dorsal columns:
Touch and proprioception
What are the lateral motor columns?
C5-T1
L1-S3
Lateral motor column C5-T1:
Innervates muscles of the upper extremity
Lateral motor column L1-S3:
Innervates muscles of the lower extremity
Dorsal nucleus of Clarke:
Spinal level C8-L3
Nucleus of origin of the dorsal spinocerebellar
Medial motor columns:
All levels; lower motor neurons innervating axial musculature
Lateral motor columns:
C5-T1; lower motor neurons innervating muscles of the upper extremity
Lesions in the rostral medulla, pons, midbrain, internal capsule (posterior limb) and cortex:
Will produce symptoms contralaterally
Corticospinal tract:
-Originates from the primary cortex (precentral gyrus) (upper motor neurons)
-Crosses at the level of caudal medulla
- Lesions in the spinal cord causes ipsilateral (same side) symptoms: Spastic paralysis, Babinski sign
Fas Cuneatus:
T6 and above; upper extremities
Fas Gracilis:
Lower extremities
Two point discrimination:
The ability of the brain to discern between two closely located touch like stimuli; the smaller the difference the larger the number of receptors
T/F: Right thalamus receives sensory information from the left side of the body
True.
Dorsal column medial lemniscal (DCML):
Touch pathway (non-painful)
Where are the first neurons that synapse for DCML located?
First order neurons will synapse in the relay nuclei and have their cell bodies located in the dorsal root ganglion
Where does decussation (cross over) occur in DCML?
2nd order neuron inside the caudal medulla
2nd order neuron for DCML:
2nd order neuron will synapse in the VPL, will have their cell bodies located in the cuneatus and gracilis nuclei
Lesions above the sensory decussation (above the 2nd order neuron) for DCML:
Loss of tactile (touch) non-painful sensations- contralateral
Lesions at or below the spinal cord (above the 2nd order neuron) for DCML:
Loss of tactile (touch) sensations; non-painful; ipsilateral
3rd order neurons for DCML:
Will synapse in the primary somatosensory cortex, and have their cell bodies in the VPL nucleus of the thalamus. Will terminate @ the cortex
Where is decussation (crossing over) located for pain and temperature?
Contained within the spinal cord (ALS specific)
What are some functions of the DCML system?
Morphosynthesis
Graphesthesia
Two-point discrimination
Texture discrimination
Vibration
Proprioception
Is DCML an ascending or descending pathway ?
Ascending pathway
First order neurons for ALS:
1st order neurons that synapse in lamina I, II, or V will have their cell bodies in the dorsal root ganglion
Second order neurons for ALS:
2nd order neurons that synapse in the VPL have their cell bodies in lamina I, II, or V
Third order neurons for ALS:
3rd order neurons that synapse in somatosensory cortex, cell bodies in the VPL of the thalamus (termination)
Where does decussation occur for ALS?
At the spinal cord
Lesions for ALS:
At or below the spinal cord; ipsilateral
Above the spinal cord; Contralateral loss of pain and temperature below the lesion after a few (2 or 3) spinal segments
Horner’s Syndrome:
-Miosis: Decreased pupillary size
-Ptosis:Drooping of the upper eyelid
-Anhidrosis: Decreased sweating of the ipsilateral face and neck
-Loss of sympathetic innervation
C fibers termination:
II, I
A delta fibers termination:
I , V
Spinothalamic tract neurons located in:
Lamina I, V
Lamina neurons II:
Interneurons (excitatory or inhibitory) modulate transmission
Where does the sensory information from the thalamus (pain, touch, and temp leave from
Leaves via thalamo-cortical projections; located in the posterior limb of the internal capsule
Brown sequard syndrome:
-DCML lesion; touch and proproioception ipsilateral
-ALS lesion; pain and temp contralateral
-Corticalspinal tract lesion; Babinski sign and Spastic paralysis ipsilaterally. Loss of volitional control of movement ipsilaterally
