Central Nervous System: Structure and Composition

Central Nervous System

CNS Composition

The central nervous system (CNS), which includes the brain and spinal cord, is composed of two main types of matter: white matter and gray matter. Understanding their structure and function is essential for medical terminology and neuroanatomy.

• White Matter: Consists primarily of myelinated axons, which are responsible for transmitting signals rapidly across different regions of the CNS.

• Gray Matter: Contains neuron bodies and dendrites, and is involved in processing and integrating information.

Brain: The outer layer is gray matter (cerebral cortex), while the inner regions are white matter.

Spinal Cord: The central core is gray matter, surrounded by an outer layer of white matter.

Type of Matter	Main Function
White Matter	Signal transmission (myelinated axons)
Gray Matter	Information processing (neuron bodies)

Example: White matter is essential for transferring signals because it is more insulated, while gray matter is crucial for processing and integrating information.

Major Regions of the Brain

Brain Organization

The brain coordinates most body activities and serves as the center for thought, memory, judgment, and emotion. It is divided into four major regions, each with distinct functions.

• Cerebrum: Largest part, responsible for thought, memory, and voluntary movement.

• Cerebellum: Controls balance and coordination.

• Brainstem: Regulates vital involuntary functions such as breathing and heart rate.

• Diencephalon: Relays sensory information and controls autonomic functions.

Region	Main Function
Cerebrum	Thought, memory, voluntary movement
Cerebellum	Balance, coordination
Brainstem	Vital involuntary functions
Diencephalon	Sensory relay, autonomic control

Example: The cerebrum is the most superior part of the brain and is responsible for higher cognitive functions.

Lobes of the Cerebrum

Cerebral Lobes and Their Functions

The cerebrum consists of four lobes, each named after the cranial bones that overlie them. Each lobe has specialized functions:

• Frontal Lobe: Voluntary movement, planning, reasoning, consciousness, and personality.

• Parietal Lobe: Sensation, temperature, pain, touch, spatial perception.

• Temporal Lobe: Hearing, smell, memory.

• Occipital Lobe: Visual association.

Lobe	Main Function
Frontal	Movement, planning, decision making
Parietal	Sensation, spatial perception
Temporal	Hearing, memory
Occipital	Vision

Example: The occipital lobe is the most posterior part of the cerebrum and controls visual processing.

CNS: Spinal Cord

Spinal Cord Structure and Function

The spinal cord is a column of nervous tissue with a central core of gray matter surrounded by white matter. It contains bundles of nerve fibers (tracts) that transmit information between the brain and the rest of the body.

• Ascending Tracts: Carry sensory information to the brain.

• Descending Tracts: Transmit motor information from the brain.

• Dura Mater: Tough membrane that encases the spinal cord.

Tract Type	Direction	Main Function
Ascending	To brain	Sensory information
Descending	From brain	Motor information

Example: Descending tracts are responsible for the transmission of motor signals, while ascending tracts carry sensory information.

Directional Terms in Neuroanatomy

Superior, Inferior, Anterior, Posterior

Directional terms are used to describe the location of brain regions:

• Superior: Above or higher

• Inferior: Below or lower

• Anterior: Toward the front

• Posterior: Toward the back

Example: The cerebrum is the most superior part of the brain, while the cerebellum is located inferiorly and posteriorly.

Additional info: These notes expand on the brief points in the original material, providing definitions, examples, and tables for clarity and completeness.