Central Nervous System: Structure and Function (Ch. 12 Study Notes)

Central Nervous System: Structure and Function

White Matter vs. Gray Matter

The central nervous system (CNS) is composed of two distinct types of tissue: white matter and gray matter. Understanding their differences is fundamental to neuroanatomy.

• Gray Matter: Contains neuron cell bodies, dendrites, and unmyelinated axons. It is the site of synaptic integration and processing.

• White Matter: Consists mainly of myelinated axons, which facilitate rapid transmission of electrical signals between different CNS regions.

• Location: In the brain, gray matter forms the outer cortex and some deep nuclei, while white matter lies beneath. In the spinal cord, this arrangement is reversed.

• Example: The cerebral cortex is gray matter; the corpus callosum is white matter.

CNS Anatomy: Sulcus, Gyri, and Fissures

The surface of the brain is highly folded, increasing its surface area for neural processing.

• Gyrus (plural: Gyri): Elevated ridges on the brain's surface.

• Sulcus (plural: Sulci): Shallow grooves between gyri.

• Fissure: Deep grooves that separate major brain regions.

• Important Examples:

  • Central Sulcus: Separates the frontal and parietal lobes.

  • Lateral Sulcus (Sylvian fissure): Separates the temporal lobe from the frontal and parietal lobes.

  • Longitudinal Fissure: Divides the two cerebral hemispheres.

Primary Auditory Cortex Location

• The primary auditory cortex is located in the superior temporal gyrus of the temporal lobe.

• It is responsible for processing auditory information from the ears.

Structures of the Limbic System

The limbic system is a group of interconnected structures involved in emotion, motivation, and memory.

• Amygdala: Processes emotions such as fear and pleasure.

• Hippocampus: Essential for memory formation.

• Cingulate gyrus: Involved in emotional regulation and pain processing.

• Hypothalamus: Regulates autonomic and endocrine functions.

• Mammillary bodies: Involved in recollective memory.

• Fornix: A fiber tract connecting parts of the limbic system.

Parts of the Brain Stem

The brain stem connects the brain to the spinal cord and controls vital functions.

• Midbrain

• Pons

• Medulla oblongata

Location of Intellect, Cognition, Recall, and Personality

• These higher-order functions are primarily located in the prefrontal cortex of the frontal lobe.

• The prefrontal cortex is involved in decision-making, problem-solving, and social behavior.

Functions of the Midbrain, Medulla, and Pons

• Midbrain: Controls visual and auditory reflexes, and coordinates motor movements.

• Pons: Relays signals between the cerebrum and cerebellum; regulates breathing.

• Medulla oblongata: Controls autonomic functions such as heart rate, blood pressure, and respiration.

Functions of Broca’s and Wernicke’s Areas

• Broca’s Area: Located in the frontal lobe (usually left hemisphere); responsible for speech production.

• Wernicke’s Area: Located in the temporal lobe (usually left hemisphere); responsible for language comprehension.

Function of the Hypothalamus

• The hypothalamus regulates homeostasis by controlling the autonomic nervous system and endocrine system.

• It influences body temperature, hunger, thirst, sleep, and emotional activity.

Basic Parts of the CNS

• Brain: Includes the cerebrum, cerebellum, diencephalon, and brain stem.

• Spinal Cord: Extends from the brain stem and transmits neural signals between the brain and the body.

Arbor Vitae

• The arbor vitae is the distinctive, tree-like arrangement of white matter in the cerebellum.

• It facilitates communication between different regions of the cerebellum and the rest of the CNS.

Dorsal Root Ganglion

• The dorsal root ganglion is a cluster of sensory neuron cell bodies located in the dorsal root of a spinal nerve.

• It transmits sensory information from the periphery to the spinal cord.

Function of the Basal Nuclei

• The basal nuclei (also called basal ganglia) are deep gray matter structures in the cerebrum.

• They regulate voluntary motor movements, procedural learning, and routine behaviors.

• Dysfunction can result in movement disorders such as Parkinson’s disease.