Ontogeny and Spinal Nervous System Development – Lecture Notes

A set of Question-and-Answer flashcards covering key concepts from embryology of the nervous system, including gastrulation, germ layers, neural plate/neural tube formation, neural crest, neurulation, spinal cord organization, somites, radiculopathy, disc herniation, and brain vesicle development.

What is ontogeny in the context of this lecture?

Embryology of the nervous system.

What does gastrulation produce in embryology?

A trilaminar embryonic disc with ectoderm, mesoderm, and endoderm.

Which germ layer gives rise to the nervous system?

Ectoderm.

What induces the formation of the neural plate and neural tube?

The notochord (axial mesoderm) induces neural plate to form the neural tube.

What happens to the notochord after neural development?

Notochord remnants form intervertebral discs; it also induces neural tissue formation above it.

What are neural crest cells and what do they form?

Cells that migrate from the neural folds to become sensory neurons, autonomic neurons, Schwann cells, adrenal medulla, melanocytes, and some non-neural derivatives.

What is neurulation?

Formation of the neural tube from the neural plate by folding and fusion; neural crest cells migrate away.

What is the sulcus limitans?

A groove in the neural tube that separates the alar (dorsal) and basal (ventral) plates.

What do the alar plate and basal plate become?

Alar plate becomes dorsal/sensory structures; basal plate becomes ventral/motor structures; separated by the sulcus limitans.

What does Bell-Magendie law state?

Sensory afferents enter the dorsal root; motor efferents exit via the ventral root.

What are the dorsal and ventral horns of the spinal cord?

Dorsal horn contains sensory interneurons; ventral horn contains motor neuron cell bodies.

What are somites and their three components?

Paraxial mesoderm blocks; sclerotome (vertebra), myotome (muscle), dermatome (dermis).

What is the fate of the sclerotome and notochord?

Sclerotome forms vertebrae; remnants contribute to intervertebral discs; vertebral column develops around the neural tube.

What is radiculopathy?

Pathology of a spinal nerve root with sensory/motor signs in the corresponding dermatomes/myotomes and radicular pain.

What is the most common cause of radiculopathy?

Herniation of an intervertebral disc compressing a nerve root.

Cervical disc herniation example: which nerve is affected?

C5-6 disc typically affects the C6 nerve; C6-7 disc typically affects the C7 nerve; generally the nerve below the upper vertebra in the adjacent pair.

Lumbar disc herniation example: which nerve is affected?

Typically the nerve corresponding to the lower of the two adjacent vertebrae; e.g., L4-5 disc often affects L5; L5-S1 disc often affects S1.

What are the three primary brain vesicles?

Prosencephalon, Mesencephalon, Rhombencephalon.

What are the five secondary brain vesicles?

Telencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon.

What does the telencephalon become?

Cerebral hemispheres; lateral ventricles.

What does the diencephalon become?

Thalamus, hypothalamus, epithalamus; third ventricle.

What does the mesencephalon become?

Midbrain; cerebral aqueduct.

What does the metencephalon become?

Pons and cerebellum; upper part of the fourth ventricle.

What does the myelencephalon become?

Medulla; lower part of the fourth ventricle.

What is the orientation change that occurs due to telencephalon rotation?

Rostral becomes anterior; caudal becomes posterior; dorsal becomes superior; ventral becomes inferior (for the forebrain).