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USMLE Step1 Neuro Anatomy Kaplan


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Neural Crest Derivatives?
1) Adrenal Meduall
2) Ganglia (Sensory + Autonomic)
3) Pigment Cells (Melanin)
4) Schwann Cells
5) Meninges (Pia + Arachnoid)
6) Pharyngeal Arches
7) Odontoblasts
8) Parafollicular (C) Cells
9) Aorticopulmonar Septum
10) Endocardial Cushions
Asymptomatic defect in vertebtral arches
Spina Bifida Occulta
Meninges project through the vertebral defect
Spina Bifida w/ Meningocele
What Labx do you ask for in Spina Bifida?
Alfa-feto protein (increased)
What happens in meningmyelocele?
Meninges and spinal cord project through vertebral defect
What are the FOUR sympathetic ganglions?
1) Superior Cervical Ganglion
2) Middle Cervcial
3) Vertebral
4) Cervicothoracic
What level does the Lateral Horn of the Sympathetic system comprises?
What are the Four cranial ganglia of the Parasympathetic System?
1) Ciliary ganglion
2) Submandibular
3) Pterygopalatine
4) Otic
What cranial nerves are Parasympathic?
1) III
2) VII
3) IX 3,7,9
What controls the foregut and midgut in the parasympathetic?
Vagus X, at terminal ganglia
What Parasympathetic controls the Hindgut?
Pelvic Splachnic Nerves S2-S4
Ciliary Ganglion controls what CN and muscle?
Parasymp. CN III
Ciliary m.
Submandibular galgion controlled by?
Parasymp. CN VI
Submandibular and sublingual glands
Pterygopalatine ganglion is in control of?
Lacrimal glands
Otic Ganglion controls what?
Parasymp. CV IX
Parotid Gland
Decrease in Alfa-feto Protein in Pregnancy equals?
Down Syndrome
Forebrain TEL
Midbrain MES
Hindbrain MET
Telecephalon? CNS Structure + what ventricle is formed?
Cerebral Hemis. Lat. Ventri
Diecephalo? makes what structure in CNS and what Ventricles?
Thalamus, Pineal Third Vent
Gland, neurohypo
physis, hypotha-
lamus, retina
Mesencephalon? CNS/Ventricle
Midbrain Cerebral Acued.
PONS Cerebellum 4th Ventri
Medulla 4th Ventri
Who makes the PONS Bridge?
What makes Craniopharyngiomas?
Remannts of Rathke's Pouch that compress optich chiasm
Anterograde movement by?
Retograde movement in CNS?
These viruses affect retrograde movement?
Oligodendrocyte vs Schwan?
Oligo can myelinate more than 1 cell, sometimes up to 50 cells!
Hair cells are derived from what layer?
Substantia Nigra derives from with plate? Alar or Basal?
Polyhydramnios caused by?
Potter's Syndrome (Bilateral Renal Agenesis), Oligohydramnios causes limb deformities and pulmonary hipoplasia
What connects the lateral ventricles?
Foramen of Monroe (Mon Roe)
What connects the 3rd ventricle with the 4th?
Acueduct of Sylvius
What connects the ventricles and the subarachnoid space? And where is this located?
Located in the 4th ventricle
Three openings:
1) Two Lateral formaina of Luschka
2) Median foramina of Magendie
Normal pH of CSF?
CSF has higher concentrations of ____ than blood?
Cl-, Ca2+, HCO3- and glucose
How are protein levels in CSF compared to blood?
How are Sodium levesl in CSF compared to blood?
Same about 138 mEq/L
Are PMN normal in CSF?
No!!! Bacterial Meningitis
What does it mean when there is an increase in protein in CSF?
Possibly a CNS tumor
Define Hydrocephalus?
Increase in volume (excess) or pressure of CSF producing ventricular dilation
Communicating Hydrocephalus
What are the underlying causes?
It is due to oversecretion of CSF by:

1) Choroid Plexus Papilloma
2) Tumor in Subarachnoid space
3) Meningitis (limits absorption into superior saggital sinus)
Noncommunicating Hydrocephalus
undersecretion/ obstruction of CSF flow
1)tumor blocking foramen Monro, cerebral aqueduct, 4th ventricle or Fomanina Magendie or Lushka.
Mechanism of Normal Pressure hydrocephalus?
- CSF not absorbed by arachnoid villi
- ventricles enlarged
- ventricles press agains cortex and skull
Symptoms of NPH (normal pressure hydrocephalus)?
1) confusion
2) gait apraxia
3) urinary incontinence

stiff legs, dementia
confused with Alzheimer
like magnetic feet stuck to the ground
Blood-brain barrier regulated by what type of cells? What type of junctions?
- Tight Junctions in the capillary endothelium
- Astrocytes
Where is CSF produced?
Choroid Plexus
What part of hypothalamus is controlled by sympathetic?
Posterior Hypothalamus...
remember to use your posterior to be sympathetic w/ someone
Sympathetic Response? Think of the tiger chasing you
- Eyes open wide + pupil dilation (to see better)
- Perspire (to slip from it)
- Hair Sticks up (to look ferocious)
- Sphincters close (don't wanna go to the bathroom in the middle of the chase)
- Increase HR
- Epinephrine increase adrenalin
- liver increase degradation of glycogen to glucose
- pancreas
increase glucagon
decrease insulin
- Stress causes diabetes!
Horner Sx is an attack to sympathetic. What are the symptoms?
- Miosis enophthalmos
- pseudotosis
- Anhydrosis (can't sweat)
- lack of piloerection
What kind of neurons does the ventral horn contains?
What kind of neurons does the dorsal horn control?
Sensory neurons
What 2 motorneurons does the ventral horn have?
Alpha and Gamma
What do alpha motorneurons control?
skeletal muscle (extrafusal fibers)
What do gamma motorneurons control?
muscle spindle contractile intrafusal fibers
Neural Systems
3 Major Neural Systems
Motor Systems composed of?
1) Upper Motorneuron
2) Lower Motorneuron
Where are the bodies of the upper motor neurons found?
1) Red nucleus
2) Reticular Formation
3) Lateral Vestibular Nuclei of the brain stem.
4) Cerebral Cortex (Most Important)
What tract are the upper motor neurons run in?
Corticospinal Tract
Where is the motor cortex located in the brain? What lobe of the brain?
1) Precentral Gyrus of the Frontal Lobe
2) Premotor Area both 60%
3) 1ry + 2ry somatosensory cortical areas of parietal lobe 40% of fibers
Where do corticospinal tract fibers exit the cerebral cortex?
In the Internal Capsule
Dorsal Horns transmit what type of stimulus?
Ventral Horns transmit which type of stimulus?
Motor (Remember S&M)
What happens to the corticospianl tract at the lower medulla?
They cross the decussation of the pyramids continue contralaterally
Decorticate rigiditiy is caused by?
Lesions above the midbrain
A lesion below the midbrain causes what type of rigidity?
Decerebrate Rigidity
What reflexes are lost in an Upper Motorneuron Lesion?
Reversal of Reflexes
1) Babinski Reflex (extension instead of flexion)
2) Abdominal Reflex Lost
3) Cremasteric Reflex Lost
What are the two sensory systems?
1) Dorsal Column-Medial Meniscal System

2) Anterolateral (Spinothalamic) System
Where is the 1st order neuron for the Sensory Systems?
Dorsal Root Ganglion (Pseudounipolar neuron)
Where is the 2nd order neuron?
Brain stem or Spinal Cord before crossing
Where is the 3rd order neuron?
Thalamus (T for Third)
It already has crossed to the other side
What does the Dorsal Column-medial leminiscal system convey? (DC-ML)
Propioception and Stereoception
- sensory info. for discriminatory touch
- joint position
- vibratory
- pressure sensation from trunk and limbs
What type/class of fibers does the Dorsal Column (DC-ML) system have?
Class II or A-beta
Which part of the Dorsal Column is located medially? (Which Fasciculus)
Fasciculus Gracilis
What does the fasciculus gracilis control? (Closest to the midline)
Lower Extremities

- Remember that you are graceful when you walk
- Also, gracilis muscle is on the medial aspect of the leg/thigh
What part of the brainstem is the 2nd order neuron located?
Does the second order neuron for sensory pathway cross the midline?
NO! It crosses at the 3rd order neuron in the Thalamus
Where do 2nd order Dorsal Column cells synapse?
Nucleus Gracilis
Nucleaus Cuneatus
Where do 3rd order of the Dorsal Column-Medial Leminiscus System (DC-MLS) cells synapse?
Medial Leminiscus like its name
Part of the Thalamus
in the Ventroposterolateral Nucleus (VPL)
Where can you find 2nd order neuron in the Dorsal Column pathway? What Nuclei?
- Medulla
Nucleus Gracilis
Nucelus Cuneatus
What pathway crosses the midline in the sensory pathways?
The 2nd order neuron always crosses... need two lines to make a cross
Where is the 3rd order neuron located in the Dorsal Column Medial Leminiscus (DC-MLS) Pathway? Which nucleus?
- Thalamus
- At the medial lemniscus like its name
- It is found in the Ventroposterolateral Nucleus
Where do the 3rd order Neurons project in the Dorsal Column Pathway?
To the ANTERIOR portion of the PARIETAL Lobe
- Primary somethetic (somatosensory) area
- located in the Postcentral gyrus
How do you determine a lesion to the Dorsal Column?
Loss of Joint sensation
- vibratory
- pressure sensation
- two-point discrimination
- loss of the ability to identify characteristics of an object
What is asterognosis?
- shape
- size
- consistency
- form
of an object using the sense of TOUCH
How do you diagnose Dorsal Column Pathway lesion?
ask patient to close his eyes and place feet together
- positive if patient sways

- if patient sways with eyes open then the lesion/damage is at the cerebellum and not dorsal column
What is another name for the Anterolateral System?
Spinothalamic Tract System
What does the Anterolateral System sense?
- pain
- temperature
- crude touch sensations
Via what fibers do the dorsal root ganglia enter the spinal cord?
Dorsal Root Fibers
- via A-Delta
- Class III
- Class IV
What is the backup of the Corticospinal Tract Lesions?
The backup is that 20% of the fibers do not cross
- the conscious crosses
unconscious doesn't cross
What do direct fibers that do NOT cross controll?
They control proximal pathways giving function to the proximal extremities
What is a picture of a Monkey's Bottom w/ flowers?
Medulla Oblongata IX, X, XII
What is the function of a bipolar neuron?
They are responsible for special senses
- vision
- smell
- taste
Function of a pseudounipolar neuron?
It is a scanning neuron
Where are 3ry (Tertiary) neurons of the Dorsal Column Systems located?
Thalamus (Remember T is for Third/Tertiary and Thalamus)
They cross
What happens to all the lesions that are unilateral in the Spinal Cord or the Brain Stem?
They result in a contralateral loss of pain and temperature
Where is the 2nd Neuron located for the Anterolateral (Spinothalamic) System?
Dorsal HORN Gray Matter
What order neuron crosses in the Anterolateral AL-SpT tract?
2nd order neuron
Where do the axons of the 2nd order neuron enter?
Ventral White Commissure
Where does the analgesia begin after a lesion of the anterolateral/spinothalamic tract?
1 or 2 segments below the contralateral side of the lesion.
What information does the spinocerebellar pathways carry?
Unconscious propioceptive input from muscle spindles and GTOs to cerebellum
What two major spinocerebellar pathways are there?
Dorsal and Cuneocerebellar
(Dorsal and Ventral)
Where are the 2nd order neuron from the Dorsal Spinocerebellar tract found?
(What nucleus)
At what level?
- Clarke Nucleus

- Spinal Cord level (T1-L2)
Where are the bodies of the cuneocerebellar tact found? (What nucleus)
At what level?
- External Cuneate Nucleus
- Medulla
What information is gathered from the dorsal spinocerebellar pathway?
Input from lower extremities and lower trunk
What information is gathered by the Cuneocerebellar tracts?
Propioceptive input to the cerebellum from upper extremities and upper trunk
What disease atacks the Spinocerebellar tract?
Friederich's Ataxia
What form of inheritance is Friederich's Ataxia?
Autosomal Recessive
What are the symptoms in a hemisection of the spinal cord?
1) ipsilateral spastic paresis below injury
2) ipsilateral loss of joint position sense, tactile discrimination and vibratory sensations below lesion
3) contralateral loss of pain and temperature starting 1 or 2 segments below lesion
What is another name for hemisection of the spinal cord?
Brown-Sequard Sx
What pathways are interrupted by a hemisection?
1) corticospinal
2) dorsal columns
3) spinothalamic (anterolateral)
What spinal cord lesion is caused by Vitamin B12 Deficiency?
Subacute Combined Degeneration
What other Diseases cause Subacute Combined Degeneration (SCD)?
- Vitamin B12
- Pernicious Anemia
What pathway is damaged in Polio?
What pathway is damaged in Tabes Dorsalis?
Dorsal Column
What Pathway is damaged in Amyotrophic Lateral Sclerosis?
- Corticospinal Tract
What pathways are damaged in Anterior Spinal Artery occulsion (ASA)?
- Spinothalamic tract (SpTh)
- Corticospinal tract (CST)
Except Dorsal Column (DC) is spared
What pathways are damaged in Subacute combined degeneration?
- Corticospinal Tract (CT)
- Dorsal Column
- Spinocerebellar Tract
What sign do we find on Dorsal Column lesion?
Romberg's Sign (+)
What tract is damaged in Syringomyelia?
- Spinothalamic (SpTh)
What is a late complication of Syringomyelia?
Horner Syndrome (ptosis, miosis, anhydrosis)
What tracts are damaged in Hemisection: Brown-Sequard Sx?
- DC
- SpTh
All of them!
If lesion is above T1 then Horner Sx. (Ipsilateral)
Which side is affected in Horner Sx lesion at T1-T4?

Above T1?
Contralateral side

Above T1 is ipsilateral side
What happens in Vitamin B12 Def?
Demyelination of Spinal Cord Tracts
What tracts are affected by Vitamin B12 deficiency?
- Dorsal Columns (DC)
- Spinocerebellar Tracts
- Corticospinal Tracts (CTS)
Patient with paresthesias, bilateral spastic weakness, Babinksi sign and antibodies to intrinsic factor? Diagnosis Dx:?
Dx: Subacute combined degeneration
Intrinsic Factor is deficient and wont let the ileum absorb Vitamin B12
How are Multiple Sclerosis, Vitamin B 12 deficiency and Subacute Combined Degeneration similar?
They are all conditions where CNS is demyelinated
What cells are within the white matter of spinal cord?
- they create the myelin for all axons inside the CNS and tracts of white matter
What tract is injured in a patients with signs of UMN and LMN?
Amyotrophic Lateral Sclerosis (ALS)
Which cells regenerate in the PNS? Why?
Cells in the Ventral Root
- they contain myelin from Schwann Cells which promote regeneration of cut axons.
What are the three Ps of Tabes Dorsalis?
1) Pain
2) Paresthesia
3) polyuria
Argyll Robertson Pupils
Last P is Pupil Defect!
What structures degenerates in MS?
Myelin containing nerves
i.e. Optic Nerves, formed by oligodendrocytes not schwann(PNS)
What test do you find positive in MS?
Heterogeneous Immunoglobulin G Staining w/ oligoclonal banding
Charactestic of Syringomyelia?
Bilateral loss of pain and temperature
What level does the fasciculus cuneatus begins?
T5 segment
What cells are affected in LMN lesions?
Alpha motor neurons in the ventral horns
What cells manage the reflex contraction of muscle and extension of oposite muscles?
Muscle Spindles
What are does the anterior spinal artery supply?
Ventrolateral 2/3's of the spinal cord
- DC are spared
- NO problems in pain and temp.
What is affected if the spinothalamic tract on the left side is affected?
Pain and temperature sensations on the right leg
Where do axons of fasciculus cuneatus have their bodies in?
Dorsal Root Ganglia
The Brain Stem
pg. 363
What three parts make the Brainstem?
1) midbrain
2) pons
3) medulla
What cranial nerves arise from the midbrain?
1) oculomotor III
2) trochlear IV

3 and 4
What cranial nerves enter or exit the pons?

What three cranial nerves enter or exit from the medulla?
Are Motor Nuclei located medially or lateral?
Medial M=Medial M=Motor
What are some of the symptoms for a pineal tumor?
Parinaud Sx:
1) paralisis of upward gaze
2) noncummunicating hydrocephalus
What cranial nerve is affected in Neurofibromatosis II?
VIII, associated with Schwannomas
What happens to a lesion of the nucleus ambiguus?
Ipsilateral paralysis of the soft palate
- uvula deviates away from the lesion
- nasal regurgitation of liquids
- hoarseness
- difficulty swallowing
What does the solitary nucleus control?
solitary sounds like salivary and taste.
- it controls the taste and visceral sensory neurons
What cranial nerve does the spinal nucleus control?
Trigeminal nerve V
What is the major parasympathetic nucleus in the brain stem? Where is it located?
Dorsal motor nucleus in the 4th ventricle
What cranial nerves does the nucleus solitarius control?

What nerve is NOT affected when there is an intramedullary lesion?
Spinal Accesory Nerve (XI)
What muscles does the spinal accesory nerve innervate?
1) sternocleidomastoid
2) trapezius
Where is the abducens nucleus found?
Floor of the 4th ventricle
- lateral to the MLF
What happens when the abducens nucleus has a lesion?
- ipsilateral facial paralisis of the VII nerve
- inability to look to the side of the lesion
Where does the facil nerve exit the brain?
pontomedullary junction
What is the superior olivary nucleus responsible for?
It receives auditory impulses from both ears by cochclear nuclei.
- cochclear nuclei at pontomedullary junction
Where are vestibular nuclei found?
posterior surface of pons
What three structures are found in the pontomedullary junction?
- Facial motor nucleus exits fibers
- cochlear nuclei
What four nerves emerge from the pons?
at the pontomedullary junction
What is another name for midbrain?
What structures pass through the midbrain?
- cerebral acueduct
- superior colliculi
- inferior colliculi
What is the function of the inferior colliculi?
processes auditory information received bilaterally from cochlear nuclei
What is the function of superior colliculi?
help direct movement of both eyes in gaze
What two nerve emerge from midbrain?
oculomotor III
trochlear IV
What do the cerebral peduncles contain?
Corticospinal fibers
corticobulbar fibers
How do oculomotor nucleus exists the midbrain?
ventrally in the interpenducular fossa
How do trochlear nerves exit?
posterior midline inferior to the inferior colliculi
How does the ear protect itself against damage to the inner ear from loud sounds?
It contracts the stapedius and tensor tympani muscles
What happens to the Upper Face and Lower Face in a corticobulbar lesion?
The Upper Face has normal function since it has a bilateral innervation.

The Lower Face is affected contralaterally since there is only one set of fibers going there.
What are the components of the ear?
1) external ear
2) middle ear
3) inner ear
What structures make up the external ear?
External Auditory Meatus
What makes up the middle ear?
- Temporal Bone
- tympanic membrane
- connecting it to the oval window
What bones are included in the middle ear?
What makes up the inner ear?
- labyrinth
- channels (semicircular ducts and cochlear duct)
What is the characteristic of endolymph?
It contains the same characteristics as intracellular fluid
What is the characteristic of perilymph?
It is ionically extracellular fluid
How does sound travel from the ear to the brain?
hair cells in the organ of Corti are conected to the spiral ganglion.
- to cochlear part of CN VIII
- ventral cochlear nuclei --> Superior Olivary N. --> Inferior Colliculus --> Midbrain
What is stimulated in low-frequency sounds?
Apex of of the cochlea
What is stimulated in high-frequency sounds?
Base of the cochlea
Does perilymph move towards or away the direction of movement?
How does endolymph move?
Against the direction of movement
Static Laberynth is made up of?
How can you tell if there is excitation from the kinocillium?
They are pointing toward the striola
What are the components of the dynamic laberynth?
Ampulla, endolymph, hair cells, crystals
What consists in a Pinealoma Sydrome?
Insomnia, headache and can't look up
What is the mechanism of damage in a pinealoma?
- Damage to the superior colliculus center for upward gaze
- pupillary constriction for accomodation
- decrease in melatonin
- decrease in sleep patterns
- headache from tumor compression
- Can't follow Upward gaze
- Hydrocephalus
- Headache
- Pupils Accomodate but not react
Pinnealoma/Parinaud Sx
What nerve is intact when you have good convergence?
III adducts well
Patient difficulty swallowing and palata droopped, what center is affected?
Nucleus Ambiguus

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