Spinal Cord 2 Flashcards
What function does the corticospinal system control?
Voluntary motor function
What tracts are involved in voluntary motor control?
Lateral and anterior corticospinal tracts
What tracts are involved in fine touch and proprioception?
Dorsal column with posterior funiculus
What tracts are involved in pain, temp, and crude touch?
Anterolateral system
Which motorneurons come from the precentral gyrus?
Uppermotor neurons
Any cranial nerve that does motor function is considered what?
Lowermotor neurons
What are the cranial nerves that are lowermotor neurons?
3,4,5,6,7,9,10,11,12
In cranial nerve nuclei and spinal cord, there is a synapse that provides communication for what?
Between upper and lower motor neurons
The corticospinal tract divides into what two tracts? Where does it split? Which one crosses the midline?
- anterior and lateral corticospinal tract
- in the medulla
- lateral corticospinal tract crosses the midline (lateral tract is bigger)
The lateral CST controls what? How does it terminate?
- upper and lower limbs
- terminates ipsilaterally (on opposite side where it originates)
The anterior CST does what? How does it terminate?
- head and neck (axial)
- terminates bilaterally
In the anterior horn, where are flexor and where are extensor?
Flexor are more towards the center and the extensor are more towards the edge
How are anterior horn motor neurons organized?
In vertical (rostral caudal) columns
How does the lateral CST run?
- descends through body in lateral funiculus
- synapse in anterior horn (on opposite side)
- serves limbs contralateral to cortex
- serves limbs ipsilateral to tract
What is the excitatory NT in corticospinal projections? Inhibitory?
Glutamate is excitatory
GABA is inhibitory
What happens when CST are damaged rostral to pyramidal decision?
-produces limb paralysis on side contralateral to lesion (left side damage means right side weakness)
what happens when the LATERAL CST has damage CAUDAL to pyramidal decussation?
-produces weakness ipsilateral to the lesion (left side damage means left side weakness)
Damage to the lateral CST produces what kind of deficits?
- level down
- suprasegmental deficits
- damage to uppermotor neurons
Damage to ventral hor, ventral roots, and peripheral nerves produce what kind of deficits?
- lower motor damage
- segmental deficits
- only damage at that level, not down
Which tract can compensate for the other when it is damaged and result in no significant deficit?
The lateral can compensate for the anterior.
Describe what happens to strength when there is lowermotor damage. Uppermotor Damage?
Lower: decreased
Upper:decreased
Describe what happens to muscle tone when there is lowermotor damage. Uppermotor?
Lower: decreased
Upper: increased
What happens to stretch reflexes when there is damage to the lowermotor neuron? Upper?
Lower: decreased
Upper: increased! Clonus! You took out the inhibitory effect from descending inputs
Damage to what kind of motorneuron shows severe atrophy?
Lowermotor neuron damage
What are fasciculations?
-spontaneous contractions of a group of muscle fibers visible as muscle twitches
What are fibrillation?
-spontaneous contraction of individual muscle fibers, not grossly visible, but detectable
Damage to which motorneurons causes fibrillation and fasciculation?
Lowermotor neuron damage
What is babinskis sign? What kind of motorneurons is damaged?
- foot should show dorsal flexion when touched on dorsal side, but instead you see extension and the toes fan out
- uppermotor neuron damage
Uppermotor neuron signs are also called…
Spastic weakness
- NO atrophy
- increased muscle tone
- exaggerated reflexes
- clonus
Lowermotor signs are also called….
Flaccid weakness
- muscle atrophy
- decreased muscle tone
- decreases ref;exes
- fasciculation
In order for UMN signs to occur, what must the LMN be?
- LMN must be intact in order to see lowermotor neuron signs
- if they are both damaged, patient shows LMN signs
What is discriminative sense?
- fine spatial/temporal resolution
- able to detect what the stimulus is
What is position sense>
- conscious proprioception
- tell where your limbs are in space
So sensory fibers synapse in the spinal cord?
Nah
-they enter posterior funiculus and go to contralateral cortex
The posterior column system is an ascending system that ends where?
In cortex
Third order neurons in ___________ project to somatosensory cortex (postcentral gyrus)
Thalamus
Second order neurons in posterior column system synapse where?
In thalamus
What supplies all of the sensory innervation for the face?
The trigeminal nerve joins the posterior column system
Where do first order neurons from posterior dorsal column system synapse?
In the medulla
What kind of deficit is there when there is damage to fasciculus gracilis and fasciculus cuneatus?
- level down sensory loss(ipsilateral to legion)
- fine/discriminative touch and conscious proprioception
- NO LOSS OF PAIN OR TEMP!!! THAT IS A DIFFERENT SYSTEM
Does the posterior/dorsal column system cross the midline?
Nope!! Right lesion always means right sensory loss
What does the anterolateral system control?
Pain/temp/crude touch
Is there a midline cross in the anterolateral system?
Yes! At the anterior white commissure
Where do the sensory fibers synapse in the anterolateral system?
Synapse in the posterior/dorsal horn before they cross the midline
An intramedullary tumor damaging the cord from medial to lateral is more likely to cause damage to what?
-cervical region
(Medial to lateral)
- cervical
- thoracic
- lumbar
- sacral
An extramedullary tumor compressing the cord from lateral to medial is most likely to cause damage to what?
-sacral!
Visceral innocuous sensory receptors project via what nerves to the spinal cord?
Parasympathetic
Visceral nociception project via what nerves to the spinal cord?
Sympathetic
What is referred pain?
Convergence of somatic and visceral pain sensation in the spinal cord.
-cross talk between somatosensory and viscerosensory
What kind of information does the spinocerebellar pathway provide?
Non-conscious proprioception to cerebellum
-check balance and coordination
What is Friedreich’s ataxia? What pathway would you see damage in?
- impaired coordination of walking
- unsteady during standing with eyes closed(Romberg’s sign)
- degeneration in dorsal columns, dorsal cerebellar tracts, lateral CST
What is tabes dorsalis?
- degeneration of dorsal roots and dorsal column
- impaired somatosensation and conscious proprioception loss
- Tabetic gait: high stepping and foot flapping when foot strikes ground
What is subacute combined degeration?
-degeneration of dorsal roots, dorsal columns, LCST
Gimme some examples of dermatomes
- diaphragm (C3,4,5)
- Heart(T1-T4)
- Stomach (T6-T9)
What is stereognosis? Graphesthesia?
- coin identification
- trace letters on patient
-testing fine touch and posterior/dorsal pathway
The lowermotor neuron in corticospinal system has an axonal projection that….
-projects out of the spinal cord, into subarachnoid space, and through the intervertebral foramen
