Vosko- Review of Neuroscience, Deck 2 Flashcards
Mesencephalon: Midbrain
(Following the eyes and ears)
Contains inferior and superior colliculi
Auditory
Eye control (TRACKING, not all things visual; a lesion here –> still can see)
Contains VTA and substantia nigra: Dopamine centers in the brain
Contains Crus Cerebri (Cerebral Peduncles)
Contains Periaqueductal Grey (Pain modulation)
parkinson’s disease
when the substantia nigra ceases to function as it should; substantia nigra is a midbrain portion that feeds into the basal ganglia
Metencephalon: Pons
(The bridge of the brain)
Contains: Locus ceruleus Micturition center (involuntary clearance) Cranial nerve nuclei Reticular Formation
Usually will find 3 cranial nerve nuclei at this location. V, VI, little bit of VII
Metecephalon: Cerebellum
(The CNS Quality Control Dept.)
hemispheres (regulates coordinated movements like walking), vermis (spinocerebellum- regulates posture. All those terrible pathways are here), and the ancient flocculonodular lobe (vestibular cerebellum: regulates metrics of eye tracking)
Receives unconscious, proprioceptive input
Coordinates complex movements
Measures muscle positions relative to targets
Responsible for normal gait and posture
Myelencephalon: Medulla
(Vital function controls housed here)
Respiratory center Cardiac center Consciousness center Pathway for all ascending and descending info from the spinal cord Contains cranial nerve nuclei
reticular are responsible for keeping you out of a coma
CN VII, IX, X and XII
nissel and silver stains
Nissel stains gray matter
silver stains white matter
Spinal cord anatomical features: The Bell-Magendie Law
dorsal horns- sensory
ventral horns- motor
Dorsal columns
white matter of spinal cord
inside the dorsal funniculus
ascending basic tactile and conscious proprioceptive information
Lateral funniculus/ anterior funiculus
White matter of spinal cord
gemisch of both motor and sensory information, both up and down
Lamina II
substantia gelatinosa
Modulates transmission of pain and temperature information
Lamina VII
has clarke’s nucleus (posterior spinocerebellar tract cells),
intermediolateral column (has preganglionic sympathetic neurons
Lamina IX
all of lower motor neurons sit here.
two enlargements in the spinal cord
lumbar enlargement: huge ventral horns to innervate the legs
cervical enlargement: in part, lower motor neurons going to fingers, but also has a lot of white matter (ratio of white to gray matter is largest here)
conus medullaris level
L2
caudal to that we can take a spinal tap
around the conus medullaris is where we start to see the cauda equina
shapes of the spinal cord
cervical– looks oval
thoracic– tiny, little love handles that are the IML (intermedial lateral cell column)
lumbar– giant ventral horns, very round
sacral– like lumbar but much smaller
dorsal column medial lemniscus pathway
how we localize basic touch and conscious proprioception
Info travelling either in the fasciculus cuneatus (info from upper part of body) or the fasciculus gracilis (more central- stuff from lower part of body)
Someone grabbing your left hand
Dorsal Column Medial Lemniscus pathway
activating a mechanical receptor
a primary sensory afferent neuron: pseudounipolar. Brushes by dorsal horn without entering gray matter; ascends up through the cord to synapse on the Nucleus Cuneatus.
2nd order neurons go through internal arcuate fasciculus and decussate
ascends through medial lemniscus to 3rd order neuron in VPL of thalamus: sends its axon into the primary somatosensory cortex to receive info from contralateral side of the body
someone grabbing your right foot
Dorsal Column Medial Lemniscus pathway
activating a mechanical receptor
a primary sensory afferent neuron: pseudounipolar. Brushes by dorsal horn without entering gray matter; ascends up through the cord to synapse on the Nucleus Gracilis.
2nd order neurons go through internal arcuate fasciculus and decussate
ascends through medial lemniscus to 3rd order neuron in VPL of thalamus: sends its axon into the primary somatosensory cortex to receive info from contralateral side of the body
Anterolateral system/ spinothalamic
= neothalamic
carry pain, temp, light touch (crude, not well localized)
uses slower conducting axons (smaller)
synapses happen in the spinal cord and in the VPL of thee thalamus
Pain on the hand
free nerve ending (major pain receptor)
pseudounipolar neuron, goes through early lamina into spinal cord. First synapse here.
- 2nd order neuron decussates right away in anterior white commissure. Fibers settle in lateral region of the spinal cord and ascends up to the VPL of the thalamus.
Spinocerebellar tracts
transmit unconscious proprioception of the body.
Most of these are 2-neuron pathways and ipsilateral. No thalamus involved (unconscious)
Divided into fine and gross
Fine- C and D:
- Cuneocereballar (upper body)
- Dorsal Spinocerebellar (lower body)
Gross– entire limb:
Ventral spinocerebellar (does a double decussation) Rostral spinocerebellar (we don't care about this)
Cuneo relates to
upper body
cerebellar pathway from the upper limb
muscle spindle
pseudounipolar neuron
no synapse; travels through fasciculus cuneatus (hitching a ride) until the lateral cuneatus (accessory/ external cuneate nucleus)- synapse.
Through cerebellar peduncle into the cerebellum.
all other cerebellar pathways will synapse in the cord, in Lamina VII (Clarke’s Nucleus)
most input to the cerebellum goes through
the inferior cerebellar peduncle
the one exception is the ventral spinocerebellar, it goes through the superior peduncle
mossy fibers
2nd order neurons after they get into the cerebellum.
They synapse on granule cell –> synapse on purkinje cells –> synapse on deep cerebellar nuclei
Ventral trigeminothalamic tract
sensation of the face- pain and temp pathway + ear info on VII, IX and X
free nerve ending neuron- CN V- descends to spinal trigeminal nucleus –> synapse, decussate, ascends to VPM, –> synapse to Primary somatosensory cortex
Trigeminal nerve- goes to 3 parts
midbrain
pons
down to medulla
Lateral movement of head activates the
medial longitudinal fasciculus (MLF)
Head moves to the right, eyes move to the left
This is the vestibulo ocular reflex (VOR)
The VOR also affects gaze in the upward/downward direction, uses the
riMLF, the bilateral elevator muscles, ipsilateral inferior rectus, and contralateral superior oblique
Right head turn activates
Left abducens (via decussation)
Double decussation causes ipsilateral (Right) oculomotor nucleus to be activated
what innervates the muscles of the face and throat?
corticobulbar projections
at level of eyes and higher, as well as throat– bilaterally
lower half of the face– contralateral innervation
lateral corticospinal tract
originates around M1 (primary motor cortex)
descends through corono radiata, internal capsule, crus cerebri, pons, medullary pyramids–> decussate
synapse in lamina IX, leave through ventral root to muscle.
Cortico-bulbo-spinal pathway
Collaterals come off that pathway about level of pons, synapse bilaterally and go to face above eyes’’
a different pathway has a decussation and goes to face below eyes
A combination of pyramidal and extrapyramidal pathways control skeletal muscle
Lateral Corticospinal
Anterior Corticospinal- bilateral, posture
Tectospinal- coordinating movements of head neck etc. at the same time. Contralateral.
Rubrospinal- decussates. Seems to be involve with flexion of hands/ thumbs.
Reticulospinal- ipsilateral, supplemental.
Vestibulospinal- ipsilateral, supplemental
Anterior spinal syndrome
all you have left is basic touch
ALS
first: upper motor neurons die (positive Babinski sign, spastic paralysis). Next: lower moter neurons die. (flaccid paralysis, areflexia, no Babinski sign)
Brown sequard syndrome
spinal cord injury on one side. Basic tactile sensation- ipsilateral deficiency. Corticospinals have already decussated, so ipsilateral motor control. Contralateral deficit in pain and temperature. Some pain fibers trying to cross at this level will not be able to, so on that particular level you will have bilateral pain and temp deficit.
Basal Ganglia- indirect pathway
inhibition pathway
Motor cortext activates the striatum via glutamate –> Globus Pallidus External inactivation via GABA–> Disinhibits subthalamic nucleus via decreased GABA–> more glutamate to globus pallidus internal (more GABA to Thalamus)–> less excitatory signal to motor cortex.
Basal Ganglia- direct pathway
movement pathway
Motor cortex –> excitatory signal via glutamate. Activates Striatum (caudate + putamen, GABA-ergic–> inactivates Globus Pallidus Internal –> disinhibited signal (less GABA) to Thalamus –> motor cortex. (circuit going)
Substantia nigra pars compacta releases Dopamine onto the Striatum– gives us the oomph we need to get everything to go smoothly. (Parkinson’s–lose this)
Substantia nigra pars reticulata does eye movement instead of the GPI
huntington’s disease
indirect pathway of basal ganglia is damaged; can’t stop the movements.
visual pathway
rods and cones (receptors on retina) release neurotransmitter on bipolar cells –> retinal ganglion cells (first action potential takes place). Parvocellular is for fine detail, Magnocellular for overall shape, etc.–> lateral geniculate–> primary visual cortex
EACH LGN contains fibers from BOTH EYES.
Each LGN has 4 layers of parvocellular pathway and 2 layers of magnocellular
Visual fields sent to contralateral brain
left visual fields of both eyes go to the right ride of the retina and then to the right side of the brain.
decussation happens in optic chiasm
damage in fovea of retina
–> scotoma (loss of center of visual field)
like macular degeneration, MS,
compression/ damage at optic chiasm –>
bitemporal hemianopsia
lesion in optic tract (say, on the right side)
–> loss of the entire left visual field
quadrantanopsia
pie in the sky
loss of the superior or inferior quadrant of one visual field (this happens after the optic chiasm, and inferior fibers carry superior quadrant information)
fall down on occipital pole –>
lose foveal represenation of visual fields on both sides (bilateral scotoma)
