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Neuro > Nervous System Anatomy, Embryology > Flashcards

Nervous System Anatomy, Embryology Flashcards

1
Q

what produces cerebrospinal fluid?

A

choroid plexus in the brain ventricles

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2
Q

where can a spinal tap be collected in adults vs children?

A

adult spinal cord ends at L1-L2

child spinal cord ends at L3-L4

CSF can be collected via spinal tap caudal (below) these levels

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3
Q

_____ cells line the brain ventricles and spinal cord central canal for regulation of CSF production and flow

A

ependymal cells

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4
Q

name 4 infective agents with which Guillain-Barré Syndrome is associated?

A
  1. campylobacter jejuni
  2. mycoplasma pneumoniae
  3. cytomegalovirus (CMV)
  4. Epstein-Barr

molecules produced mimic myelin gangliosides —> antibodies produced demyelinate peripheral nerves

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5
Q

unmyelinated nerve fibers in the [PNS/CNS] are engulfed/nested within [Schwann cells/oligodendrocytes] ?

A

unmyelinated nerve fibers in the PNS are engulfed/nested within Schwann cells

unmyelinated fibers in the CNS are not invested by oligodendrocytes

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6
Q

what shape are efferent vs afferent neurons?

A

efferent/motor: multipolar (soma on one end, surrounded by dendrites)

afferent/sensory: pseudounipolar (soma in middle, dendrites and axons on opposite ends)

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7
Q

what is contained within the dorsal root ganglion of the spinal cord?

A

pseudounipolar (soma in middle) cell bodies of sensory neurons

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8
Q

where are unmyelinated axons found within the CNS?

A

gray matter = cell bodies, unmyelinated axons

white matter = myelinated axons

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9
Q

in which segments of the spinal cord are sympathetic vs parasympathetic neurons found?

A

sympathetic: T1-L2 (“thoracolumbar”) spinal cord, somas within gray matter’s lateral horn

parasympathetic: brainstem + S2-S4 (“craniosacral”), somas within grey matter nuclei

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10
Q

the preganglionic neuron of [para/sympathetic] is longer than the postganglionic neuron

A

parasympathetic: long preganglionic neuron, short post-ganglionic neuron

sympathetic: short preganglionic neuron, long post-ganglionic neuron

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11
Q

what receptor types are found on the target tissues of somatic vs parasympathetic vs sympathetic neurons?

A

somatic —> nicotinic 1 (N1) cholinergic receptors

parasympathetic —> muscarinic receptors

sympathetic —> adrenergic receptors

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12
Q

preganglionic sympathetic motor neuron cell bodies are located in…

A

lateral horns of T1-L2 (thoracic vertebrae only)

axons exit ventral root —> spinal nerve —> ventral ramus —> white ramus communication (T1-L2 only) —> sympathetic chain

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13
Q

how does the location of motor sympathetic synapses differ for innervation of sweat glands/ arrector pili/ vascular smooth muscle at T1-L2 level vs beyond?

A

for motor innervation at level of T1-L2, preganglionic sympathetics immediately synapse in the paravertebral ganglion of the sympathetic chain

for motor innervation outside of T1-L2, preganglionic sympathetics ascend or descend the sympathetic chain, then synapse at the ganglion

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14
Q

what are the 2 ways by which sympathetic motor neurons innervate internal organs?

A
  1. preganglionic sympathetics synapse in the sympathetic chain and postganglionic sympathetic motor neuron axons exit medially via visceral nerves to reach internal organs
  2. preganglionic sympathetics pass through sympathetic chain and synapse at prevertebral ganglia in the abdomen
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15
Q

which cranial nerves and which spinal cord nerves give parasympathetic innervation?

A

CN III, CN VII, CN IX —> head/neck

CN X (vagus) —> thoracic, abdominal

S2-S4 (pelvic splanchnic nerves) —> distal GI and pelvic organs

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16
Q

postganglionic parasympathetic neuron cell bodies are located in…

A

organ walls

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17
Q

what are the embryonic brain vesicles and what do they become? (3)

A
  1. prosencephalon (forebrain): divides into telencephalon (cerebral hemispheres, CN I) and diencephalon (optic cups, pineal gland, thalamus, hypothalamus, posterior pituitary, CN II)
  2. mesencephalon (midbrain): associated with CN III, IV
  3. rhombencephalon (hindbrain): divides into metencephalon (pons, cerebellum, CN V, VI, VII, VIII) and myelencephalon (medulla, CN IX, X, XI, XII)
18
Q

what are the 2 components into which the prosencephalon (forebrain) divides, and what do these respectively become?

A
  1. telencephalon: cerebral hemispheres, lateral ventricles, associated w CN I
  2. diencephalon: optic cups, pineal gland, thalamus, hypothalamus, posterior pituitary, 3rd ventricle, associated w CN II
19
Q

what are the 2 components into which the rhombencephalon (hindbrain) divides, and what do these respectively become?

A
  1. metencephalon: pons, cerebellum, associated w CN V, VI, VII, VIII
  2. myelencephalon: medulla, associated w CN IX, X, XI, XII
20
Q

neurons in nuclei associated with cranial nerves form from ________, while neurons in ganglia associated with cranial nerves form from ________

A

neurons in nuclei associated with cranial nerves form from neuroepithelium of the neural tube,

while neurons in ganglia associated with cranial nerves form from neural crest cells and ectodermal placodes

21
Q

the lumen of the developing neural tube eventually becomes…

A

the ventricular system, whose choroid plexus produces CSF

22
Q

formation of the neural tube is complete by the end of week ___

A

four

23
Q

describe how the neural tube forms (neurulation)

A
  1. induction of ectoderm into neuroectoderm via signals from underlying notochord mesoderm
  2. neuroectoderm cells organize in midline as thickening called neural plate
  3. neural plate buckles to form depression called neural groove with raised bilateral neural folds
  4. neural folds fuse to form neural tube, which detaches from epidermis-forming ectoderm
  5. caudal end of neural tube becomes spinal cord, cranial end becomes brain

[note the notochord becomes the nucleus pulposus of intervertebral discs]

24
Q

craniorachischisis

A

“cleft skull and spine”

Defective closure of the entire CNS neural tube is seen as an open furrow on the dorsal surface of the head and body and results in a fatal deformity

25
Q

spina bifida occulta vs cystica

A

spina bifida occulta: mild defect (no disability, incidental finding), defect in fusion of vertebral arches (usually S1-S2) without herniation

spina bifida cystica: severe defect in fusion of vertebral arches with involvement of underlying neural tissue/meninges protruding through (appear cyst-like), neurological deficits (but not usually intellectual disability)

26
Q

how are severe neural tube defects (NTDs) screened for?

A

at 15-20 weeks, alpha-fetoprotein (AFP) is measured in maternal blood - if elevated, this suggests AFP has passed into amniotic fluid via NTD or abdominal wall defect

27
Q

what does high vs low alpha-fetoprotein (AFP) indicate in prenatal screening?

A

elevated - suggests AFP has passed into amniotic fluid via NTD or abdominal wall defect

low - suggests chromosomal abnormality such as trisomy 21 or 18

28
Q

what does acetylcholinesterase (AChE) in amniotic fluid suggest?

A

open neural tube defect (NTD) - AChE is normally not found in amniotic fluid (primarily active in CNS)

29
Q

why is folic acid recommended for potentially childbearing women?

A

most neural tube defects (NTDs) can be prevented with sufficient amounts of folic acid

neurulation (week 4) often occurs before awareness of pregnancy, so folic acid is recommended to women trying to become pregnant

30
Q

main signals for development of ventral vs dorsal neural tube, respectively?

A

ventral neural tube - sonic hedgehog (SHH) via notochord

dorsal neural tube - TGF-beta family via surface ectoderm (developing skin epidermis)

31
Q

the dorsal horns of the spinal cord arise from the ____ plates, while the ventral horns arise from the ____ plates

A

alar plates —> dorsal horns (sensory)

basal plates —> ventral horns (motor)

32
Q

the expression of Hox genes in developing neural tube cells is dependent on ______ [chemical], which is more concentrated in the head region and determines rostral-caudal organization of the neural tube

thus, deficiency or excess can be teratogenic

A

retinoic acid (vit. A)

33
Q

the pons and cerebellum develop from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

b. metencephalon (division of rhombocephalon)

34
Q

the medulla oblongata develops from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

a. myelencephalon - division of the rhombencephalon

35
Q

the choroid plexus develops from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

a. myelencephalon - division of the rhombencephalon

36
Q

Dandy-Walker Syndrome

A

congenital malformation of the
cerebellum, which may result from cystic enlargement of the 4th ventricle and leads to developmental delays, defective muscle tone, poor coordination and balance (ataxia), and sometimes hydrocephalus.

37
Q

the Edinger-Westphal nucleus develops from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

c. mesencephalon

Edinger-Westphal nucleus: in the midbrain, sends axons fibers through CN III to the innervate pupillary sphincter/constrictor muscle and ciliary muscle.

38
Q

the cerebral aqueduct (of Sylvius) develops from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

forms from the lumen of the (c.) mesencephalon

39
Q

the hypothalamus and thalamus develop from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

d. diencephalon - division of prosencephalon

40
Q

the cerebral hemispheres develop from the:
a. myelencephalon
b. metencephalon
c. mesencephalon
d. diencephalon
e. telencephalon

A

e. telencephalon - division of the prosencephalon

41
Q

which endocrine cells are of neural crest origin? (3)

A
  1. thyroid parafollicular cells
  2. parathyroid chief cells
  3. adrenal medulla chromaffin cells
42
Q

cause of Hirschsprung’s Disease/Congenital Megacolon

A

defective neural crest cell migration (due to mutation in RET gene for tyrosine kinase receptor, essential for migration)

—> distention and hypertrophy of intestinal segments proximal to the aganglionic segment because of efforts to overcome obstruction resulting from defective persistalsis. Aganglionosis is found in the rectum in nearly all cases

Neuro (50 decks)

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