Overview of the Nervous System Development

Overview of the Nervous System

Cervical Plexus

Supplies the skin of the neck and a deep one that supplies most of the muscles of the neck and the diaphragm muscle.

Brachial Plexus

Three primary trunks:

• 1^st primary trunk: C5-C6
• 2^nd primary trunk: C7
• 3^rd primary trunk: C8-T1

Three secondary trunks:

• External anterior trunk
• Internal anterior trunk
• Posterior trunk

Lumbar Plexus

Gives side branches to the psoas muscle.

Terminal branches:

• Obturator nerve, which serves the thigh.
• Femoral nerve, which extends the knee (quadriceps).

The innervation of this plexus territory does not pass the knee.

Sacral Plexus

Gives collateral branches to the muscles of the hip.

Delivers a single terminal branch, the thickest nerve, called the sciatic nerve.

Innervates the hamstrings and all muscles below the knee.

Neural Crest

Gives rise to part of the peripheral nervous system:

1. Sensory neurons, nerve ganglia, spinal and cranial nerves.
2. Post-ganglionic neurons of the ANS.
3. Schwann cells.

Auditory System and Language Areas

Language Areas

Broca's Area

Motor programs for the generation of language.

Wernicke's Area

Mechanisms for language decoding.

Mechanisms of language development.

Both areas are interconnected through the arcuate fasciculus.

Embryology

Germ Layers

• Ectoderm: Skin and nervous system.
• Mesoderm: Muscles, bones, blood vessels.
• Endoderm: Gastrointestinal tract and associated glands.

3^rd Week

A neural plate forms and begins to bend inward to form the neural groove. The edges are called neural folds. A longitudinal furrow in the ectoderm is called the neural plate.

4^th Week

Full closure of the neuropore. The neural folds fuse, giving rise to the neural tube. As the fusion occurs, clusters of cells separate from the neural folds, forming the neural crest.

Day 22: The fusion of neural folds begins in the cervical region and spreads towards the ends like a zipper.

The neural tube and its total independence from the ectoderm give rise to the CNS. Its cavity becomes the ventricular system. A longitudinal groove forms on the side wall of the neural tube. This groove is called the limiting sulcus. The top of it is called the alar plate. The lower limiting sulcus is called the basal plate, which gives rise to the anterior horn (motor).

Primary Vesicles

The primary vesicles are the forebrain, midbrain, and hindbrain.