Cranial Nerve Branches and CNS Development Stages

Vocabulary flashcards covering vagus nerve branches, their functions, and the six stages of central nervous system development along with their associated timelines, processes, and disorders.

Pharyngeal Branch

Controls pharynx muscles and soft palate elevation (velopharyngeal mechanism); helps with swallowing and prevents air from escaping through the nose during oral speech sounds.

Superior Laryngeal Branch

Controls the cricothyroid muscle, which adjusts vocal fold tension and helps control pitch.

Recurrent Laryngeal Branch

Controls most intrinsic laryngeal muscles, which move the vocal folds for voice production and airway protection during swallowing.

Dorsal Induction

The first stage of CNS development ($3\text{--}7$ weeks) in which neurulation occurs, forming the neural tube that develops into the brain and spinal cord.

Anencephaly

A disorder occurring during dorsal induction when the top of the neural tube fails to close, preventing normal brain development.

Ventral Induction

The second stage of CNS development ($2\text{--}3$ months) during which the brain and face develop, and the forebrain separates into two hemispheres.

Holoprosencephaly

A disorder occurring during ventral induction when the forebrain does not divide properly into two hemispheres.

Alobar Holoprosencephaly

A classification of holoprosencephaly characterized by no separation between the hemispheres.

Semilobar Holoprosencephaly

A classification of holoprosencephaly characterized by partial separation between the hemispheres.

Lobar Holoprosencephaly

A classification of holoprosencephaly where the forebrain is mostly separated into hemispheres.

Neural Proliferation

The third stage of CNS development ($3\text{--}4$ months) where neurogenesis occurs, producing new neurons at approximately $250{,}000$ per minute.

Microcephaly

A disorder occurring during neural proliferation when the brain develops abnormally small.

Neuronal Migration

The fourth stage of CNS development ($3\text{--}5$ months) where neurons move outward to form the six layers of the cortex.

Reelin

A chemical or signal that helps tell neurons where to stop during neuronal migration.

Gyri

The hills or elevated ridges of the brain.

Sulci

The valleys or grooves of the brain.

Schizencephaly

A disorder occurring during neuronal migration that causes abnormal clefts or openings in the brain.

Cortical Organization and Synapse Formation

The fifth stage of CNS development ($5$ months to years after birth) where neurons form connections through synaptogenesis, and unused connections are removed through pruning.

Synaptogenesis

The process occurring during cortical organization where neurons form connections with one another.

Pruning

The process during cortical organization where unused neuronal connections are removed.

Polymicrogyria

A disorder occurring during cortical organization that causes too many small, abnormal folds in the brain.

Myelination

The sixth stage of CNS development (birth to years after birth) where myelin forms around axons, allowing nerve signals to travel faster.

Hypomyelination

A disorder occurring when insufficient myelin develops during the myelination stage.