Neurology And Special Senses Flashcards by Emily Acton

Notochord induces overlying ectoderm to differentiate into ———
And form ———.

1. Neuroectoderm

2. Neural plate

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Notochord becomes ——— in adults.

Nucleus pulposus of intervertebral disc

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Neural plate gives rise to:

Neural tube and neural crest cells

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Lateral walls of neural tube are divided into:

Alar and basal plates

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What are the functions and locations of the alar and basal plates, and what are they induced by?

Alar plate (dorsal): sensory; induced by bone morphogenetic proteins (BMPs)

Basal plate (ventral): motor; induced by sonic hedgehog (SHH)

(Same orientation as spinal cord)

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Three primary vesicles of neural tube:

1. Forebrain (prosencephalon)
2. Midbrain (mesencephalon)
3. Hindbrain (rhombencephalon)

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Five secondary vesicles of neural tube (and primary vesicles they come from):

Forebrain (prosencephalon):
1. Telencephalon
2. Diencephalon

Midbrain (mesencephalon) :
3. Mesencephalon

Hindbrain (rhombencephalon):
4. Metencephalon
5. Myelencephalon

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Walls that are adult derivatives of neural tube (and primary/secondary vesicles they come from):

Forebrain (prosencephalon)/ Telencephalon:
1. Cerebral hemispheres
2. Basal ganglia

Forebrain (prosencephalon)/ Diencephalon:
3. Thalamus
4. Hypothalamus
5. Retina

Midbrain (mesencephalon)/ Mesencephalon
6. Midbrain

Hindbrain (rhombencephalon)/ Metencephalon:
7. Pons
8. Cerebellum

Hindbrain (rhombencephalon)/ Myelencephalon:
9. Medulla

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Cavities that are adult derivatives of neural tube (and primary vesicles they come from):

Forebrain (prosencephalon):
1. Lateral ventricle
2. Third ventricle

Midbrain (mesencephalon) :
3. Cerebral aqueduct

Hindbrain (rhombencephalon):
4. Fourth ventricle

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Neuroepithelia in neural tube origins for:

CNS neurons and CNS glial cells (astrocytes, oligodendrocytes, ependymal cells)

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Neural crest origins for:

PNS neurons (dorsal root ganglia, autonomic ganglia [sympathetic, parasympathetic, enteric]), PNS glial cells (Schwann cells, satellite cells), and adrenal medulla

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Mesoderm origin for what CNS glial cell?

Microglia (like macrophages).

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Definition for neural tube defects:

Failure of neural tube to close completely by week 4 of development

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Neural tube defects associated with ——— during pregnancy

Maternal folate deficiency

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Neural tube defects diagnosed by:

Ultrasound,
Maternal serum alpha-fetoprotein (AFP) (increased in open NTDs)

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List major open and closed neural tube defects:

Closed NTDs:
Spina bifida occulta

Open NTDs:
Meningocele
Myelomeningocele
Myeloschisis
Anencephaly

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Spina bifida occulta characterization, location, and associated symptoms:

Characterization:
- Failure of caudal neural tube to close, but no herniation
- Dura is intact

Location:
- Usually seen at lower vertebral levels

Associated Symptoms:
- Tuft of hair or skin dimple at level of bony defect

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Meningocele characterization:

- Meninges (but no neural tissue) herniate through bony defect
- Skin defect/thinning

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Myelomeningocele characterization:

- Meninges and neural tissue (eg, cauda equina) herniate through bony defect
- Skin thin or absent

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Myeloschisis characterization:

Exposed, unfused neural tissue without skin/meningeal covering

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Anencephaly characterization and presentation:

Characterization:
- Failure of rostral neuropore to close
- No forebrain, open calvarium

Presentation:
- Polyhydramnios (decreased fetal swallowing due to lack of neural control)

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Holoprosencephaly characterization, occurrence time, associated mutation, associated conditions, and presentation:

Characterization:
- Failure of forebrain (prosencephalon) to divide into 2 cerebral hemispheres

Occurrence Time:
- Developmental field defect usually occurring at weeks 3–4 of development

Associated Mutation:
- SHH mutation

Associated Conditions:
- Patau syndrome (trisomy 13)
- Fetal alcohol syndrome

Presentation: (Midline defects)
- Monoventricle
- Fused basal ganglia
- Cleft lip/palate
- Hypotelorism
- Cyclopia
- Proboscis
- Risk for pituitary dysfunction (eg, diabetes insipidus)

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Lissencephaly characterization and presentation:

Characterization:
- Failure of neuronal migration
- Smooth brain surface that lacks sulci and gyri

Presentation:
- Dysphagia
- Seizures
- Microcephaly
- Facial anomalies

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Do neurons divide in adulthood?

No
Permanent cells—do not divide in adulthood

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What part of neurons receives input and what part sends output?

Dendrites receive input and axons send output

What does Nissl staining stain, and which part of neurons visible on Nissl stain?

Nissl staining stains RER Cell bodies and dendrites can be seen on Nissl staining (RER is not present in the axon)

Neuron markers:

neurofilament protein and synaptophysin

Largest and most abundant glial cell in CNS?

Astrocytes

Astrocytes derived from:

Neuroectoderm

Astrocyte marker:

GFAP

6 functions of Astrocytes:

- Physical support - Repair - Removal of excess neurotransmitter - Component of blood-brain barrier - Glycogen fuel reserve buffer - Reactive gliosis in response to neural injury

——— fuse to form multinucleated giant cells in CNS in ———

- HIV-infected microglia - HIV-associated dementia

Microglia are———— with activation in response to———, leading to release of———

- Phagocytic scavenger cells of CNS - Tissue damage - Inflammatory mediators (eg, nitric oxide, glutamate)

Microglia apperence on Nissl stain:

Not readily discernible

Describe appearance and location of Ependymal cells:

Appearance: - Ciliated simple columnar glial cells Location: - Lining ventricles and central canal of spinal cord

Apical surfaces of ependymal cells are covered with ——— (which ———) and ——— (which help with ———)

- Cilia (which circulate CSF) - Microvilli (which help with CSF absorption)

Specialized ependymal cells (location:———) produce ———

- Choroid plexus - CSF

Ependymal cells derived from:

Neuroectoderm

Function of myelin:

Increases conduction velocity of signals transmitted down axons

Myelin yields ——— conduction of action potential at the ———, where there are high concentrations of ———

- Saltatory - Nodes of Ranvier - Na+ channels

In CNS (including CN ———), myelin is synthesized by———; in PNS (including CN ———), myelin is synthesized by ———

- CN II - Oligodendrocytes - CN III-XII - Schwann cells -

Myelin wraps and insulates axons leading to increases or decreases in: - Membrane capacitance - Membrane resistance - Space (length) constant - Time constant

- Membrane capacitance: decreased - Membrane resistance: increased - Space (length) constant: increased - Time constant: decreased

Schwann cells promote:

Axonal regeneration

Schwann cells derived from

Neural crest

Schwann cell marker:

S100

Schwann cells injuried in what disease?

Guillain-Barré syndrome

Each Schwann cell cell myelinates ——— PNS axon.

Each “Schwone” cell myelinates only 1 PNS axon

Predominant type of glial cell in white matter?

Oligodendrocytes

Each oligodendrocyte can myelinate ———

Many axons (∼ 30)

Oligodendrocytes derived from:

Neuroectoderm

Oligodendrocytes appearance histologically:

“Fried egg”

Oligodendrocytes injured in:

- Multiple sclerosis - Progressive multifocal leukoencephalopathy (PML) - Leukodystrophies

Of the spinal tracts, which synapse and then cross VS cross and then synapse?

Spinothalamic tract and dorsal column synapse and then cross Corticospinal tract crosses and then synapses

Which spinal tracts are the ascending vs descending tracts?

Spinothalamic tract and dorsal column = ascending tracts Corticospinal tract = descending tract

Function Spinothalamic tract?

Pain and temperature

Function Dorsal column?

Pressure, vibration, fine touch, proprioception (conscious)

Function Corticospinal tract?

Voluntary movement

First order neurons of Spinothalamic tract?

Sensory nerve ending (Aδ and C fibers) of pseudounipolar neuron in dorsal root ganglion —> enters spinal cord

First synapse of Spinothalamic tract?

Posterior horn (spinal cord)

Second order neurons of Spinothalamic tract?

Decussates in spinal cord as the anterior white commissure --> ascends contralaterally

Second synapse of Spinothalamic tract?

VPL (thalamus)

Third order neurons of Spinothalamic tract?

Projects to 1° somatosensory cortex

First order neurons of the dorsal column?

Sensory nerve ending of pseudounipolar neuron in dorsal root ganglion —> enters spinal cord and ascends ipsilaterally in dorsal columns

First synapse of the dorsal column?

Nucleus gracilis, nucleus cuneatus (ipsilateral medulla) (Fasciculus graciLis (Lower body, legs) and Fasciculus cUneatus (Upper body, arms) )

Second order neurons of the dorsal column?

Decussates in medulla —> ascends contralaterally as the medial lemniscus

Second synapse of the dorsal column?

VPL (thalamus)

Third order neurons of the dorsal column?

Projects to 1° somatosensory cortex

First order neurons of the Corticospinal tract?

UMN: 1° motor cortex —> descends ipsilaterally (through posterior limb of internal capsule and cerebral peduncle), decussates at caudal medulla (pyramidal decussation) descends contralaterally

First synapse of the Corticospinal tract?

Anterior horn (spinal cord)

Second order neurons of the Corticospinal tract?

LMN: leaves spinal cord

Second synapse of the Corticospinal tract?

NMJ (skeletal muscle)

Basal ganglia are important in what two things:

voluntary movements and adjusting posture

Basal ganglia receives ——— input, provides ——— feedback to cortex to modulate ———

- cortical - negative - movement

Striatum composed of:

putamen (motor) caudate nucleus (cognitive)

Lentiform nucleus composed of:

putamen globus pallidus

In basal ganglia: Direct pathway ——— movement (D#?)

facilitates D1 (D1 Receptor = D1Rect pathway)

In basal ganglia: Indirect pathway ——— movement (D#?)

Inhibits D2 (INdirect (D2) = INhibitory)

Dopamine from ——— (ie, ———pathway) stimulates the ———pathway (by binding to ——— receptor) and inhibits the ——— pathway (by binding to ——— receptor); therefore ——— motion

SNc nigrostriatal direct D1 indirect D2 Increasing

Medial longitudinal fasciculus (MLF) is a pair of tracts that interconnect:

CN VI and CN III nuclei

MLF coordinates:

both eyes to move in same horizontal direction

MLF is highly ——— (must communicate ———)

myelinated quickly so eyes move at same time

MLF lesions may be unilateral or bilateral (latter classically seen in ———)

multiple sclerosis, stroke

Lesion in MLF =

internuclear ophthalmoplegia (INO), a conjugate horizontal gaze palsy

INO = lack of communication such that when ——— activates ———, contralateral ——— does not stimulate ——— to contract; thus Abducting eye displays ——— (———overfires to stimulate ———); ——— normal

CN VI nucleus ipsilateral lateral rectus CN III nucleus medial rectus nystagmus CN VI CN III Convergence

Notmally: When looking left, the left nucleus of ——— fires, which contracts the ——— and stimulates the ——— nucleus of ——— via the ——— to contract the ———

CN VI left lateral rectus contralateral (right) CN III right MLF right medial rectus

In INO, the directional term (eg, right INO, left INO) refers to the eye that is:

unable to adduct

INO mnemonic:

Ipsilateral adduction failure, Nystagmus Opposite

When the eye is abducted, the ——— muscles are the prime vertical movers. Elevation is due to the action of the ———, and depression is due to the action of the ———. When the eye is adducted, the ——— muscles are the prime vertical movers. Elevation is due to the action of the ——— muscle, while depression is due to the action of the ——— muscle. The ——— muscles are also primarily responsible for torsional movements

rectus superior rectus inferior rectus oblique inferior oblique superior oblique oblique Obliques go Opposite (left SO and IO tested with patient looking right) IOU: IO tested looking Up

Blowout fracture is a ——— fracture; usually caused by ———; risk of ——— muscle and/or ——— entrapment; May lead to ———

orbital floor direct trauma to eyeball or intraorbital rim IR orbital fat infraorbital nerve injury

UMN vs LMN lesions: weakness

Both

UMN vs LMN lesions: atrophy

LMN lesion (LMN = everything lowered (less muscle mass, muscle tone, reflexes, downgoing toes); Upper motor neuron (UMN) = everything up (tone, DTRs, toes))

UMN vs LMN lesions: fasciculations

LMN lesion

UMN vs LMN lesions: reflexes

UMN: increased LMN: decreased (LMN = everything lowered (less muscle mass, muscle tone, reflexes, downgoing toes); Upper motor neuron (UMN) = everything up (tone, DTRs, toes))

UMN vs LMN lesions: tone

UMN: increased LMN: decreased (LMN = everything lowered (less muscle mass, muscle tone, reflexes, downgoing toes); Upper motor neuron (UMN) = everything up (tone, DTRs, toes))

UMN vs LMN lesions: babinski

UMN lesion (LMN = everything lowered (less muscle mass, muscle tone, reflexes, downgoing toes); Upper motor neuron (UMN) = everything up (tone, DTRs, toes))

UMN vs LMN lesions: spastic paresis

UMN lesion

UMN vs LMN lesions: flaccid paresis

LMN lesions

UMN vs LMN lesions: clasp knife spasticity

UMN lesion

Positive Babinski is normal in:

infants