Nervous System

What system includes the brain and spinal cord, and is protected by the cranium and vertebral column?

Central Nervous System (CNS)

What system includes neurons outside CNS as well as cranial nerves, spinal nerves (and associated ganglia) which connect the brain and spinal cord with peripheral structures?

Peripheral nervous system (PNS)

What system has parts in the other two and consists of neurons that innervate smooth muscle, cardiac muscle, glandular epithelium and combinations of these tissues?

Autonomic nervous system (ANS)

What is neuralation? When and where does it begin?

formation of neural plate and neural tube, beginning during the 4th week in region of 4th-6th pair of somites

What differentiates into the CNS?

Neural tube

What forms most of the PNS and ANS?

Neural crest cells

What forms the neural tube at the 5th somite? Where does it begin and what direction does it proceed in?

Fusion of neural folds, begins in middle and expands in cranial and caudal directions

What coincides with the establishment of vascular circulation for the neural tube?

Closure of neuropores

What is the ventricular zone?

Give rise to all neurons and macroglial cells (astrocytes and oligodendrocytes)

What is the marginal zone? What grows into it?

White matter of spinal cord; axons grow into it from nerve cell bodies

What is the intermediate zone?

Mantle layer, neuroblasts become neurons

What are glioblasts? Where do they migrate from and to?

Supporting cells of the CNS, migrate from ventricular to intermediate and marginal zones

What are microglia? What are they derived from? Where do they originate from?

Scattered throughout grey and white matter of spinal cord, derived from mesenchymal cells, originating in bone marrow

What are megines? What is the difference between the external and internal layer?

Membranes covering the spinal cord; external layer thickens to form dura mater, internal layer composed of pia mater and arachnoid mater

What is the filum terminale?

dura mater and arachnoid mater end at the S2 vertebra in adults, pia mater forms this long fibrous thread, which indicates original level of caudal end of embryonic spinal cord and end of embryonic development

When do myelin sheaths develop?

Begin to form during late fetal period and continue through 1st postnatal year

Do motor roots or sensory roots myelinate first?

motor roots

What is the sacral dimple? What does it represent?

Indicated region of closure of caudal neuropore at the end of 4t week; last place of separation between surface ectoderm and neural tube

What are neural tube defects?

Failure of one or more neural arches of developing vertebrae during 4th week

What is the embryonic basis of NTDs?

failure of closure of rostral and caudal neuropores

What is meroencephaly (meroanecephaly)?

complete absence of cranium results in residual mass of brain tissue left completely unprotected

What are 3 conditions caused by defective closure of caudal neuropore?

1. myeloschisis

2. meningomyelocele

3. spina bifida occulta

What is myeloschisis?

NTD where spinal cord and nerve tissue exposed directly to outside without covering sac or skin

What is Meningomyelocele? What can it cause?

NTD where spinal cord and meninges do not fully close during fetal development; causes hydrocephalus (build up of CSF)

What is spina bifida occulta?

NTD where there is a small gap or opening in spina that doesn’t extend through skin

What are the etiologies of NTDs?

nutritional factors, environmental factors, genetic syndromes and chromosomal disorders

What supplement do we recommend for NTDs?

folic acid (0.4 mg or 400 mcg) or (4 mg) if h/o NTD

What is Pallister-Killian Syndrome (PKS)?

caused by tetrasomy 12p (4 copies of genes on 12p)