Spinal Cord & Tracts Flashcards
What muscles are activated during a reflex motion?
Ipsilateral synergists are activated and antagonists are inactivated to prevent opposition to the flexor motion
What is the function of lamina VII-IX?
Motor
What stimuli is transmitted via the spinocerebellar tract?
Proprioception
What stimuli is transmitted via the anterior spinothamalic tract?
Crude touch
UMNs for what tract are found in the superior colliculus?
Tectospinal tract
What is the function of lamina X?
Visceral touch, pain, temperature
What are the three types of nerve fibers in white matter of the spinal cord?
Long, ascending fibers
Long, descending fibers
Short, propriospinal fibers
This group of axons is located only in the cervical spinal cord and transmits stimuli from the upper body.
Fasciculus cuneatus
Where does crossing over of information take place in the spinal cord?
Anterior white commissure
What stimuli is detected by Meissner’s corpuscles?
Fine and discriminative touch
The dorsal horn houses what types of neurons?
Sensory
The C7 spinal nerve is associated with what reflex?
Triceps reflex
What is the conus medularis?
The end of the spinal cord at L1/L2
What stimuli are carried by the medial lumniscus tract?
Fine/discriminative touch, pressure and touch, vibration, proprioception, muscle stretch
What group of axons transmits stimuli from the lower body?
Fasciculus gracilis
True/False. Damage to an upper motor neuron will cause the muscle to atrophy.
False. The muscle may become more diffuse, but it will not atrophy due to increased reflex arc. LMN damage will cause muscle atrophy.
C fibers transmit dull, non-localized pain. What are the primary stimuli for these fibers?
Chemical stimuli (H+, K+, bradykinin)
Describe the somatotrophic arrangement of the internal capsule.
In the internal capsule, axons of neurons associated with the lower limbs are more lateral, while axons of the upper limbs and head are more medial. This arrangement is opposite that of homunculus where the lower limbs are found medially within the longitudinal fissure and the head is more medial near the lateral fissure.
What spinal cord nerve is associated with the achilles reflex?
S1
What is the Tract of Lissauer?
Axons of the spinothalamic tract in the lateral white column ascend/descend 2-3 spinal levels before crossing over and continuing on the tract
Briefly describe the pathway of the corticospinal tract.
Axons from the corona radiate funnel through the posterior limb of the internal capsule and enter the brainstem via the crus cerbri of the cerebral peduncles. Fibers move through the pontine nuclei and pass through the pyramids of the medulla. Contralateral fibers of the lateral tract will cross at the pyramidal decussation and continue descending. Ipsilateral fibers of the anterior tract will descend and cross in the anterior white commissure at the level of their target.
Describe the dorsal spinocerebellar tract.
First-order neurons are located in the DRG between T1-L2 and synapse on Clarke’s nuclei in the dorsal root. The axon ascends ipsilaterally via the dorsal aspect of the lateral white column and exits the spinal cord at the inferior peduncles to enter the cerebellum.
What receptor detects fine touch and superficial pressure?
Merkel’s discs
What test can be used to assess for UMN damage?
Babinski’s sign - stimulation to the sole of the foot causes the big toes to rise. A positive test is only normal in infant.
The lateral horn is only found between what spinal levels?
T1-L2
Where does the spinal cord end?
L1/L2
What is the difference between the ipsilateral and contralateral pathways?
The ipsilateral pathway crosses over in the brain, white the contralateral pathway crosses over in the spinal cord
The C6 spinal nerve is associated with what reflex?
Brachioradialis
What types of neurons synapse on extrafusal muscle fibers?
Alpha motor neurons
Proprioceptive stimuli from what parts of the body is transmitted via the cuneocerebellar tract?
Head, neck, upper limbs
Describe the lateral spinothamalic tract.
First-order neurons are located int he DRG and synapse on a second-order neurons in the dorsal root. Prior to synapsing on the second-order neuron, axons from the first-order neuron may ascend/descend the spinal cord via the Tract of Lissauer. The axons then cross over in the anterior white commissure. Most C fibers terminate in the reticular formation, with the rest ascending to the intralaminar nuclei of the thalamus. Most A-delta fibers ascend to the ventroposterior lateral and ventroposterior infection nuclei of the thalamus. Fourth-order neurons for C and A-delta fibers are in the post-central gyrus.