Brain and Spinal Cord Flashcards
What is A?
Dentate nucleus
What is B?
Spinal nucleus
What is C?
Tract of trigeminal nerve
What is D?
Medial lemniscus
What is E?
Inferior olivary nucleus
What is F?
Pyramid
What is G?
Pontine nuclei
What is H?
Middle cerebellar peduncle
What is I?
Glossopharyngeal nerve
What is J?
Cochlear nerve
What is K?
Inferior cerebellar peduncle
What are the origin cells of neurons?
Ependymal cells
What are the immune cells of the nervous system?
Microglia
What do olgiodendrocytes do?
Form myelin sheaths in the CNS
What is the function of the pineal gland?
Circadian rhythms
What is the function of the area postrema?
Monitors blood for toxins and triggers the emetic reflex
What are the main functions of dorsal column neurons? Are they ipsilateral or contralateral?
Touch, pressure, vibration, position sense
Ipsilateral in cord
medial lemniscus large fiber pathway
What are the main functions of the anterolateral system small fiber pathway? Is it ipsilateral or contralateral?
Pain and temperature sense
Contralateral
What are the main functions of the corticospinal tract? Is it ipsilateral or contralateral?
Voluntary control of limbs + distal extremities
Ipsilateral
Whats the difference between decussation sites of the dorsal column medial lemniscal system and the anterolateral system?
The dorsal column system decussates in the medulla but is ipsilateral in the spinal cord. The anterolateral system decussates immediately in the spinal cord and is contralateral the whole way.
What is Brown-Sequard syndrome?
A condition that occurs after hemisection of spinal cord. Leads to ipsilateral lose of tactile and limb position sense at lesion level and below (dorsal columns) and contralateral loss of pain and temperature senses a few segments below lesion (anterolateral system).
this occurs because the anterolateral system decussates in the spinal cord a few vertebrae above their starting point
What is Central Cord Syndrome/Syringomyelia?
A syndrome caused by crushing of the cervical region in the center of the spinal cord that affects the anterolateral system (pain and temperature) that leads to reduced pain/temperature sensation in the arms and chest.
What is the central nervous system?
The brain and spinal cord
What is the peripheral nervous system?
Nervous system outside the brain and spinal cord
What is the spinal column?
Bones and ligaments surrounding and protecting the spinal cord
What is the spinal cord?
The cylindrical bundle of nerves made from ascending (sensory info from body to brain) and descending (motor info from brain to body) tracts that is housed within the spinal column from the foramen magnum to the L1 vertebral level
What is the conus medullaris?
Tapered caudal end of spinal cord around L1
What is the cauda equina?
A bundle of spinal nerves and rootlets that arise caudally from the conus medullaris - consists of second through fifth lumbar nerve pairs, first through fifth sacral nerve pairs, and the coccygeal nerve
What is white matter?
Outer area of the spinal cord, appears white due to myelinated axons
What is Gray matter?
Central area of spinal cord with a predominance of cell bodies, shaped like an H or butterfly
What are spinal tracts?
Bundles of nerve fibers organized according to ascending (seonsory) or descending (motor) pathways.
In the picture below, which label represents white matter?
C
D
E
F
Answer: C
In the picture below, which label represents motor nerve fibers?
E
J
F
C
Answer: J
Which spinal cord tract carries motor information from the brain to the peripheral nervous system?
a) spinocerebellar tract
b) spinothalamic tract
c) corticospinal tract
d) dorsal column
c) corticospinal tract
Occlusion of the anterior spinal artery causing anterior cord syndrome would cause damage to which of the following pathways?
a) gracile fasciculus
b) spinocerebellar
c) cuneate fasciculus
d) dorsal column medial leminiscus
b) spinocerebellar
What exits through the intervertebral foramen between the C6 and C7 vertebrae?
a) the C5 cervical spinal nerve
b) the C6 cervical spinal nerve
c) the C7 cervical spinal nerve
d) the C8 cervical spinal nerve
c) the C7 cervical spinal nerve
How many vertebrae are in the vertebral column?
33: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 5 coccygeal
What are the components of the meninges?
Dura + arachnoid + pia mater
Where do nerve roots exit relative to their numbered vertebra?
Thoracic, lumbar, and sacral regions: exit caudally (below) the corresponding vertebra
Cervical: exit rostrally (above) the corresponding vertebra
this is because there is an extra cervical vertebra
What is the function of the nerves in the posterior funiculi?
2 components:
Fasciculi gracilis - sensory information (vibration, deep touch, etc) from the legs to the brain
Fasciculi cuneatus - sensory information (fibration, deep touch, etc) from the arms to the brain
What is the path of decussation for ascending sensory tracts?
They ascend the spinal cord ipsilaterally to their respective nuclei. Then the second-order neurons cross the midline in the caudal medulla. Third motor neurons begin in the thalamus and terminate in the contralateral sensorimotor cortex.
What is the function of the dorsal spinocerebellar tract? Where does it run?
It carries afferent information from muscle spindles and golgi tendon organs to the cerebellum for coordination of grouped muscle movement for postural control and ambulation.
This tract runs with nerves from L3 to C8 in the dorsal portion of the lateral funciculus
What is the path of neurons in the dorsal spinocerebellar tract?
They ascend ipsilaterally to the inferior cerebellar peduncle and terminate in the cerebellar vermis of the anterior lobe.
What is the function of the ventral spinocerebellar tract? Where does it run?
Carries afferent information regarding whole limb movements and postural adjustments to the cerebellum - nerves arise from golgi tendon organs within the muscles.
It runs in the ventral portion of the lateral funiculus
What is the path of nerves of the ventral spinocerebellar tract?
They arise from golgi tendon organs within muscles and synapse in the dorsal root nerve –> sends a second-order neuron n contralaterally to through the medulla to the pons –> joins superior cerebellar peduncle, crosses midline again (now back to ipsilateral) and terminates in the vermis of the cerebellum
What is the function of the spinothalamic tract? What region is it in?
Transmits afferent information about pain, temperature, and nondiscriminative touch to the primary sensory cortex.
It is within the anterolateral funiculus
What is the result of injury to one side of the spinal cord in the spinothalamic pathway?
Contralateral loss pain and temperature sense and tactile stimulation at and below the site of injury
What is the path of the corticospinal tract?
Arises from cerebral cortex –> converges in the corona radiata –> descends through the internal capsule and brainstem –> decussates in the caudal medulla to the contralateral side –> terminates in spinal cord as lateral corticospinal tract
What is the function of the corticospinal tract?
Controlling flexor motor systems and fine motor control of limbs
What is the effect of damage ot the spinocerebellar tract?
Loss of voluntary motor control and flaccid muscle tone at first, and then spasticity and hyperreflexicity
What are the main blood supplies to the spinal cord?
Two posterior spinal arteries, one anterior spinal artery (arises from vertebral arteris and radicular arteries)
Where do the posterior spinal arteries run? What do they supply?
Descend along the posterolateral spinal cord, just medial to dorsal roots.
Supplies the posterior one third of the spinal cord.
Where does the anterior spinal artery go? What does it innervate?
It goes along the midline of the spinal cord.
It supplies the anterior 2/3 of the spinal cord
What is the course of radicular arteries in the spinal cord?
They arise from segmental levels all along the spinal cord and are supplied by the thoracic and abdominal aorta
What is the largest radicular artery? What does it supply?
Artery of Adamkiewicz
It supplies the caudal 2/3 of the spinal cord (with the other small radicular arteries)
Which two areas of the spinal cord are at increased risk of hypoperfusion and infarction?
T1-T4 and L1
Describe venous drainage through the spinal cord.
It is through a series of venous plexuses that empty into the anterior and posterior epidural venus plexuses
What is A?
Lateral corticospinal tract
What is B?
Anterior corticospinal tract
What is 1?
Pyramidal tracts
What is C?
Cuneate fasciculus
What is D?
Gracile fasciculus
What is 2?
Dorsal column medial lemniscus system
What is E?
Posterior spinocerebellar tract
What is F?
Anterior spinocerebellar tract
What is 3?
Spinocerebellar tract
What is G?
Lateral spinothalamic tract
What is H?
Anterior spinothalamic tract
What is 4?
Anterolateral system
What is I?
Spino-olivary fibers
What is the origin of the third order sensory neurons of the spinothalamic tract?
Ventral posterolateral nucleus of thalamus
What is the function of the extrapyramidal tracts?
Rubrospinal = flexion and fine control of arms
Reticulospinal and vestibulospinal = postural and complex body movements
Whats the difference between the lateral and anterior corticospinal tract?
The lateral tract decussates in the medulla, the anterior tract doesn’t decussate until the anterior white commisure
What is the path of the lateral and anterior corticospinal tracts from the brain to the muscle?
Lateral: cerebral cortex –> decussate in medulla –> descend –> synapse on motor neuron in anterior horn –> spinal nerve –> muscle
Anterior: cerebral cortex –> descends –> decussates at anterior white commissures –> synapse on motor neuron anterior horn –> spinal nerve –> muscle
Where are the synapses of the first/second/third order neurons of the dorsal column-medial lemniscal pathway?
First and second order synapse together in the dorsal column nuclei (ipsilateral)
Second and third synapse together in the thalamus (contralateral)
What is the effect of complete spinal cord transection?
Loss of pain/temperature, proprioception, and motor movement below the level of the lesion
What is the effect of posterior column syndrome?
Loss of proprioception, vibration, and two point discrimination only below the level of the lesion
affects dorsal column medial lemniscus system
What would you expect to see in unilateral posterior spinal artery infarction?
Ipsilateral loss of proprioseption, vibration, and two point discrimination below the level of the lesion
wipes out dorsal column medial lemniscus system before it decussates in the medulla
What are the effects of anterior cord syndrome?
Loss of motor function below the level of the lesion bilaterally; loss of pain and temperature below level of lesion bilaterally; preservation of two point discrimination, vibration, and proprioception bilaterally
knocks out pyramidal tracts, spinocerebellar tracts, and anterolateral system (spinothalamic tracts) on both sides
What do you see clinically in Brown-Sequard syndrome?
Ipsilateral motor loss below level of lesion; ipsilateral proprioceptive and vibratory loss at and below level of lesion; contralateral pain and temperature loss 1-3 levels below the lesion
- corticospinal tracts and dorsal column medial lemniscal system have not yet decussated (they decussate at the medulla)*
- spinothalamic tracts decussate 1-3 levels above where it enters the spinal cord, so the lesion would knock out the contralateral nerves 1-3 levels below and all the way down*
What is the effect of central cord syndrome?
Loss of motor function in upper limbs and partial loss in trunk
center of spinal cord are nerves in cervical region (and then progresses outwardto thoracic, lumbar, and sacral)
What is the difference between tetraplegia/quadriplegia vs. paraplegia?
Tetraplegia = impairment or loss in motor and/or sensory function in cervical segments
Paraplegia = impairment or loss in motor and/or sensory function in thoracic, lumbar, or sacral segments (arm function spared)
Where is the junction of the spinal cord and medulla?
Upper rootlet of the first cervical nerve at the level of the foramen magnum
What are the components of the medulla?
Closed portion (continuation of the central canal of the spinal cord) and open portion (contining caudal half of fourth ventricle)
What are the contents of the medullary pyramids?
Corticospinal (pyramidal) tract
What is the result of medial medullary syndrom on motor function?
It results in contralateral hemiparesis
it wipes out the corticospinal tract above the site of decussation in the medulla
Where do olivocerebellar fibers decussate?
Opposite inferior cerebellar peduncle
What is the function of the inferior olive/inferior olivary nuclei?
Motor learning
What nerves lie in the trigeminal tubercle? Where is the trigeminal tubercle?
Nerves: spinal tract of the trigeminal nerve, nucleus of spinal tract
Location: between the olive and dorsolateral sulcus
What are the nerve contents of the spinal tract of the trigeminal nerve? What is the function?
Primary afferent fibers, transmits pain and temperature sensations from the face
What is the course of trigeminal nerve fibers?
They synapse on second order neurons in the spinal nucleus and then travel (and mostly cross) to the ventral posteromedial (VPM) thalamic nucleus where they synapse with third order neurons that project into the post-central gyrus
What are the dorsal structures of the medulla?
Fasciculus gracilis and cuneatus
Gracile tubercle
Cuneate tubercle
Medial lemniscus
What is the gracile tubercle? Cuneate tubercle?
Gracile: rostral end of fasciculus gracilis, produced by nucleus gracilis
Cuneate: rostral end of fasciculus cuneatus, produced by nucleus cuneatus
What forms the medial lemniscus?
Axons of cells in the dorsal column nuclei that have crossed/decussated to the contralateral side
What is the function of the lateral reticular area?
Small neurons that coordinate reflexes and simple stereotyped movements mediated by cranial nerves (i.e. eating and eye movements)
What is the function of the medial reticular area?
Large neurons that form long ascending and descending projection systems for pain sensations, movement and posture, autonomic and endocrine functions, and arousal and consciousness
What is A?
Medial longitudinal fasciculus
What is C?
Anterior longitudinal fasciculus
What is D?
Fourth ventricle
What is E?
Trigeminal nerve
What is B?
Superior cerebellar peduncle
What is F?
Spinothalamic tract
What is G?
Transverse pontine (pontocerebellar) fibers
What is H?
Pontine nuclei
What is I?
Corticospinal tract
What is J?
Medial lemniscus
What is K?
Central tegmental tract
What is L?
Middle cerebellar peduncle
What is the function of the basal portion of the pons?
It is a large relay station between the cerebral cortex and the opposite cerebellar cortex
What are the three general components of the basal pons?
Longitudinal fiber bundles, transverse fibers, and collections of pontine nuclei between fibers
What are the components of the longitudinal bundles of the basal portion of the pons?
Corticobulbar (corticonuclear) fibers, corticospinal fibers, and corticopontine fibers
Where do corticobulbar (corticonuclear) fibers in the pons go?
They synapse bilaterally on lower motor neurons in the motor nuclei of cranial nerves
Where do corticospinal fibers in the pons go?
Pass through the pons to the pyramids of the medulla
Where do corticopontine fibers in the pons go?
They come from all four lobes and synapse on neurons in the pontine nuclei of the same side
What are the components of the pontocerebeller/transverse fibers in the pons? Where do they go?
They are axons of neurons in the pontine nuclei. They decussate to the contralateral side and enter the cerebellum through the middle cerebellar peduncle.
What are the contents of the tegmentum of the pons?
ascending and descending tracts, nuclei of cranial nerves, reticular formation
What are the four main parts of the midbrain?
Tectum, tegmentum, substantia nigra, and crus cerebri
Where is the the tectum of the midbrain? What are its components?
Location: dorsal to cerebral aqueduct
Contents: inferior and superior colliculi, inferior andsuperior brachium, and the periaqueductal gray
What is the function of the inferior colliculus?
Relay nucleus on the auditory pathway to the thalamus
What is the functionof the inferior brachium?
It is formed by fibers from the inferior colliculus that synapse in the medial geniculate nucleus of the thalamus
What is the function of the superior colliculus?
A reflex center for saccadic (jerky/simulatneous) eye movements and movements of eyes/head in response to visual, auditory, and cutaneous stimuli
reflexes mediated by tectobulbar and tectospinal tracts
What is the function of the superior brachium?
Formed by fibers from the visual cortex of the occipital lobe and from retina that synapse in the superior colliculus and pretectal area. They also function for visual reflexes (pupillary light reflex, accomodation, eye movements)
What is the function of periaqueductal gray?
It is a pain control center.
What is the pathway of pain control from the periaqueductal gray?
Stimulation –> release neuropeptide enkephalin –> activates neurons in nucleus raphe magnus in medulla –> descends spinal cord –> inhibits pain entering the dorsal horn
What is A?
Superior colliculus
What is B?
Central/periaqueductal gray
What is C?
Cerebral aqueduct
What is D?
Brachium of inferior colliculus
What is E?
Medial lemniscus
What is F?
Red nucleus
What is G?
Pontine fibers
What is H?
Corticospinal tract
What is I?
Corticobulbar fibers
What is J?
Frontopontine fibers
What is K?
Third nerve
What is L?
Substantia nigra
What is M?
Crus cerebri
What is N?
Tegmentum
What is O?
Tectum
What are the contents of the tegmentum of the midbrain? Where is it located?
Contents: ascending and descending tracts, nuclei of cranial nerves, reticular formation, and the red nucleus
location: continuation of the tegmentum of the pons, ventral to cerebral aqueduct
What is the function of the mesencephalic nucleus of the trigeminal nerve?
proprioception from receptors in muscles of mastication, TMJ, and teeth
Where do the central processes from the mesencephalic nucleus of the trigeminal nerve synapse?
in the trigeminal motor nucleus, cerebellum, and on second order neurons in adjacent reticular formation (sends axons to crossed trigeminal lemniscus)
What is the path of the rubrospinal tract?
It forms from the magnocellular portion of the red nucleus and immediately decussates to the contralateral side
What is the function of the substantia nigra?
Produces dopamine (and melanin as a byproduct)
What are the components of the crus cerebri?
Corticospinal, corticobulbar, and corticopontine fibers
What does cerebral peduncle mean?
One half of the midbrain (minus the tectum)
Where does the oculomotor nerve emerge from the brainstem?
Side of the interpeduncular fossa (midbrain)
Where does the trochlear nerve emerge from the brainstem?
Dorsal surface of the midbrain immediately below the inferior colliculus
Where does the trigeminal nerve emerge from the brainstem?
Attached to the lateral surface of the brainstem at the boundary between the pons and the middle cerebellar peduncle
Where does the abducens nerve emerge from the brainstem?
Pontomedullary junction between pyramid and pons
Where do the facial and vestibulocochlear nerves emerge from the brainstem?
Attached tot he lateral surface at the pontomedullary junction (facial nerve more medially)
Where do rootlets of the glossopharyngeal and vagus nerves emerge from the brainstem?
They attach to the medulla along the retro-olivary groove between the olive and trigeminal tubercle
Where do rootlets of the hypoglossal nerve emerge from the brainstem?
Ventrolateral sulcus (pre-olivary groove) of the medulla between the pyramid and the olive
A lesion of the ventral area of the medulla on one side will most likely result in:
a) ipsilateral hemiparesis of the body
b) contralateral loss of pain and temperature from the body
c) contralateral hemiparesis of the body
d) ipsilateral loss of pain and temperature from the face
c) contralateral hemiparesis of the body
ventral area of the medulla contains the corticospinal tract after decussation
A patient presents with loss of pain and temperature from right side of the face. Where is the most likely site of the lesion?
a) right spinothalamic tract
b) left spinal nucleus of V
c) left spinothalamic tract
d) right spinal tract of V
e) left spinal tract of V
d) right spinal tract of V
this region tract brings pain and temperature sensations to the face, ipsilateral because lesion is pre-decussation
The cell bodies of the first order neurons for proprioception from the face are located in the:
a) trigeminal ganglion
b) reticular formation
c) principal (main) sensory nucleus
d) spinal nucleus of V
e) mesencephalic nucleus
e) mesencephalic nucleus
A lesion in the tegmentum of the midbrain would most likely affect which of the following structures?
a) red nucleus
b) corticospinal tract
c) periaqueductal gray
d) superior brachium
e) corticopontine tract
a) red nucleus
Which cranial nerves would you expect to be damaged by midbrain lesions?
a) I and II
b) III and IV
c) V, VI, VII, and VIII
d) IX, X, XI, and XII
b) III and I
