Organization of the Central Nervous System

Study Notes

The central nervous system consists of the brain and spinal cord.
The brain plays a central role in controlling most bodily functions, including awareness, movements, sensations, thoughts, speech, and memory.

The spinal cord is connected to the brainstem and runs through the spinal canal.
Cranial nerves exit the brainstem.
Nerve roots exit the spinal cord to both sides of the body.
The spinal cord carries signals between the brain and peripheral nerves.
Cerebrospinal fluid surrounds the brain and spinal cord, circulating within cavities called ventricles.
The leptomeninges surround the brain and spinal cord.
The cerebrospinal fluid circulates between the pia matter and arachnoid meningeal layers.
The outer, thicker layer serves as a protective shield and is called the dura matter.

The formation of the neural tube is known as neurulation, achieved by the end of the fourth week of development.
In the fifth week, swellings appear at the cranial end of the neural tube, forming three primary vesicles that develop into five secondary vesicles.
These vesicles give rise to all brain and cerebellum structures.

The five secondary vesicles and their derivatives are:
- Telencephalon: cerebral hemispheres and globus pallidus
- Diencephalon: thalamus, hypothalamus, and epithalamus
- Mesencephalon: midbrain
- Metencephalon: pons and cerebellum
- Myelencephalon: medulla
Neuroderm cells differentiate into neurons and glial cells, migrating throughout the brain to form axons, dendrites, and synapses.

The caudal end of the neural tube develops to form the spinal cord.
A fatty material called myelin coats nerve cells to insulate and facilitate quick communication.

The cerebrum is the largest part of the brain, controlling voluntary actions, speech, senses, thought, and memory.
The cerebral cortex has grooves (sulci) and infoldings, with the largest being termed fissures.
The cerebrum is divided into two halves (right and left hemispheres), connected by the corpus callosum.
Each hemisphere has four lobes: frontal, parietal, occipital, and temporal.

The frontal lobes are responsible for voluntary movement, speech output, organizational skills, and certain aspects of behavior, mood, and memory.
The primary motor cortex is located in the frontal lobe, controlling movement.

The parietal lobes are located above the occipital lobes and behind the frontal lobes.

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