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Step 1 > Neurology- embryology, neural tube defects, sleep > Flashcards

Neurology- embryology, neural tube defects, sleep Flashcards

0
Q

What does the neural plate give rise to?

A

neural tube and neural crest cells

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1
Q

What causes the differentiation of ectoderm into neuroectoderm?

A

Signals from the notochord induce the overlaying ectoderm to differentiate into the neuroectoderm and form the neuroplate
-begins at about 18 days

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2
Q

What is the derivative of the notochord in adults ?

A

nucleus pulposus of the intervertebral discs

Recall: nucleus pulposus is inner gel-like center, surrounded by outer thick fibrous, anulus fibrosus

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3
Q

From what structure do the primary vesicles develop?

A

neural vesicles are the result of rapid growth of the cranial region of the neural tube

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4
Q

What are the primary vesicles?

A

There are three primary vesicles

  1. Prosencephalon - forebrain
  2. Mesencephalon-Midbrain
  3. Rhombencephalon- hindbrain
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5
Q

What are the secondary vesicles?

A

There are five secondary vesicles:

  1. Prosencephalon–> telencephalon & diencephalon
  2. Mesencephalon –> mesencephalon
  3. Rhombencephalon –> metecephalon, myelcephalon
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6
Q

Telencephalon

A
  • neocortex, basal ganglia, limbic system, olfactory system

- lateral ventricles

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7
Q

Diencephalon

A
  • thalamus, hypothalamus, subthalmus, epithalamus

- third ventricle

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8
Q

Mesencephalon

A
  • midbrain

- cerebral aqueduct

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9
Q

Metencephalon

A
  • pons, cerebellum

- upper fourth ventricle

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10
Q

Myelcephalon

A
  • medulla

- lower fourth ventricle

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11
Q

What cell types develop from the neuroectoderm?

A

CNS neurons, ependymal cells, oligodendroglia, astrocytes

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12
Q

What cell types develop from the neural crest cells?

A

PNS neurons, schwann cells

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13
Q

Microglia develop from what germ layer?

A

Mesoderm

hint: like macrophages

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14
Q

From what structure does the spinal cord develop?

A

From the caudal portion of the neural tube

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15
Q

Alar plate

A

posterior portion of neural tube –> sensory structures of spinal cord
“alar is like alarm for sensory”

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16
Q

Basal plate

A

the anterior portion of the spinal cord —> motor structures of the spinal cord

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17
Q

What separates the basal plate from the alar plate?

A

Sulcus limitans

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18
Q

Spina bifida occulta

A

: failure of posterior vertebral arch to close but no structural herniation; usually in lower vertebral levels, dura is intact
-associated w/tuft of hair or dimple at the level of the bony defect

  • neural tube defect = elevated AFP in amniotic fluid and maternal serum, elevated AChE in amniotic fluid
  • associated with low folic acid intake before conception and during pregnancy
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19
Q

Meningocele

A

:meninges but not the spinal cord herniate through the bony defect

  • neural tube defect = NORMAL AFP, elevated AChE in amniotic fluid
  • associated with low folic acid intake before conception and during pregnancy
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20
Q

Meningomyelocele

A

:meninges and spinal cord herniate through spinal defect

  • neural tube defect = elevated AFP in amniotic fluid and maternal serum, elevated AChE in amniotic fluid
  • associated with low folic acid intake before conception and during pregnancy
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21
Q

Anencephaly

A

: malformation of anterior neural tube resulting in no forebrain, open calvarium (skull)

  • elevated AFP, polyhydraminos (no swallowing center in brain)
  • associated with maternal DM I
  • maternal folate supplementation decreases the risk
22
Q

Holoprosencephaly

A

:failure of left and right hemispheres to separate; occurs in 5-6 wk

  • may be related to sonic hedgehog signaling pathway
  • moderate form has cleft lip/palate, most severe form results in cyclopia
23
Q

Arnold Chiari malformation (Chiari II)

A

: significant herniation of cerebellar tonsils and vermis through foramen magnum with aqueductal stenosis and hydrocephalus.

  • often associated with meningomyelocele and paralysis below the defect
24
Q

Dandy Walker

A

:angenesis of cerebella vermis and cystic enlargement of the 4th ventricle; huge dilated 4th ventricle in posterior fossa

-associated with spina bifida and hydrocephalus

25
Q

Cerebral aqueduct stenosis

A

:congenital stenosis of the cerebral aqueduct which leads to hydrocephalus
- presents are enlarging head circumference in an infant

26
Q

Wallerian degeneration

A

:degeneration distal to injury and axonal retraction proximally; allows for regeneration of axon if in the PNS

27
Q

Nissl substance

A

stains RER of dendrites, RER not in axons

28
Q

Astrocytes

A

: physical support, repair, K metabolism, removal of excess NT, component of BBB, glycogen fuel reserve buffer

  • reactive gliosis (proliferation and hypertrophy) in response to neuronal injury
  • astrocyte marker GFAP (glial fibrillary acidic protein)
  • derived from neuroectoderm
29
Q

Microglia

A

:CNS phagocytes; respond to tissue damage by differentiating into large phagocytic cells

  • derived from mesoderm; part of the mononuclear phagocyte system
  • HIV infected microglia fuse to form giant cells in CNS
30
Q

Nodes of Ranvier

A

unmyelinated portions of axons that contain high concentrations of Na channels
-myelin + nodes of ranvier = saltatory conduction

31
Q

What is the effect of myelin on signal conduction?

A

Increases the space constant and conduction velocity

32
Q

Oligodendroglia

A

:myelinates the axons of neurons of the CNS.

  • each oligodendrocyte can myelinated many axons
  • predominant type of glial cell in the white matter
  • Fried egg appearance on H & E stain
33
Q

Schwann cells

A

:myelinated axons in PNS

-each schwanna cell myelinates only 1 PNS axon

34
Q

What are the components of the BBB?

A
  1. tight junctions between non-fenestrated capillary endothelial cells
  2. thick basement membrane
  3. astrocyte foot processes
35
Q

How do glucose and amino acids cross the BBB?

A

cross slowly via carrier-mediated transport

36
Q

What kind of substances readily cross the BBB by diffusion

A

non-polar/lipid soluble substances cross the BBB rapidly via diffusion

37
Q

What are the circumventricular organs?

A

:structures in the brain that lack normal BBB; allow blood-borne substances to be in contact with the brain and these organs can communicate with the periphery via hormones
“Mild SOAP”
1. Median eminence: part of the hypothalamic-hypophyseal portal system; allows hypothalamus secrete releasing/inhibitory molecules into portal system to reach anterior pituitary
2. Subfornical organ: wall of 3rd ventricle; contains receptors for angiotensin II –> induces thirst
3. Organum vasculosum of laminal terminalis (OVLT): osmotic sensing
4. Area postrema: wall of 4th ventricle, close to nucleus solitarius; chemorecpetor trigger zone for vomiting in response to GI toxins including after chemo
5. Pinel gland: 3rd ventricle; senses darkness to secrete melatonin
6. Posterior pituitary: oxytocin and ADH

38
Q

Vasogenic edema

A

:results from the destruction of tight junctions of the endothelial cells that make up the BBB
-often destroyed in infarction or neoplasm —> leakage of fluid and intravascular proteins into extracellular space of brain

39
Q

What regulates the circadian rhythm?

A

The hypothalamus via the suprachiasmatic nucleus (“need sleep to be charismatic”)

SCN –> norepinephrine release –> pineal gland –> melatonin

-SCN is regulated by retinal light sensing cells

40
Q

What hormones are released as a result of circadian rhythm control?

A

noctural ACTH, prolactin, melatonin, norepinephrine

41
Q

What controls extraocular movements during REM sleep?

A

PPRF (conjugate gaze center)

42
Q

How often does REM sleep occur? How does it change throughout the night?

A

occurs every 90 minutes and increases through the night

43
Q

What drugs are associated with decreased REM sleep and delta wave sleep?

A

EtoH, benzodiazepines, barbituates

-Norepinephrine associated with decreased REM sleep

44
Q

How do you treat bedwetting?

A

oral desmopressin acetate (DDAVP) which mimics ADH; preferred over imipramine d/t adverse effects

45
Q

What drug class if useful for night terrors and sleep walking?

A

benzodiazapines

46
Q

What is the EEG wave pattern of the sleep cycle?

A

“BATS Drink Blood”

Beta, Alpha, Theta, Sleep spindles and K complexes, Delta, Beta

47
Q

EEG sleep: beta

A

: highest frequency, lowest amplitude

-during awake eyes open

48
Q

EEG sleep: alpha

A

Awake eyes closed

49
Q

EEG sleep: Theta

A

Non-REM stage N1; light sleep (5% of sleep cycle)

50
Q

What stage does bruxism occur? What waveform is expected on EEG?

A

Bruxism= teeth grinding

EEG: sleep spindles and K complexes (45% of sleep cycle)

51
Q

What EEG waveform is seen in the deepest non-REM sleep stage?

A

:delta- lowest frequency, highest amplitude =slow wave sleep (25% of sleep cycle)
-when sleep walking, night terrors, and bedwetting occur

52
Q

What happens during REM sleep?

A

loss of motor tone, increase in brain O2 use, increase in variable pulse and blood pressure
-when dreaming and clitoral tumescence (engorgement) occur

53
Q

Tongue development

A
  • Anterior 2/3 develops from 1 & 2 branchial arches _> sensation from V3, taste via CN VII
  • posterior 1/3 develops from 3 & 4 branchial arches -> sensation and taste mainly from IX, extreme posterior va CN X
  • motor innervation from CN XII
  • muscles of the tongue derived from occipital myotomes

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