Central Nervous System: Structure and Organization (Anatomy & Physiology Study Notes)

Central Nervous System (CNS)

Definition and Components

The central nervous system (CNS) is the primary control center of the body, consisting of the brain and spinal cord. It integrates sensory information and coordinates bodily functions.

• Brain: The organ responsible for higher neural functions and control of most bodily activities.

• Spinal Cord: The main pathway for information connecting the brain and peripheral nervous system.

Directional Terms Unique to the CNS

• Rostral: Toward the nose (anterior in the brain).

• Caudal: Toward the tail (posterior in the brain).

The Brain

Basic Functions

The brain is responsible for regulating vital bodily functions and complex behaviors.

• Controls: Heart rate, respiratory rate, blood pressure.

• Autonomic Nervous System: Regulates involuntary functions.

• Endocrine System: Influences hormone secretion.

• Innervation of the Head: Via cranial nerves.

Complex Neural Functions

• Intelligence: Ability to learn, reason, and solve problems.

• Consciousness: Awareness of self and environment.

• Memory: Storage and retrieval of information.

• Sensory-Motor Integration: Coordination of sensory input and motor output.

• Emotion, Behavior, Socialization: Regulation of feelings, actions, and social interactions.

Embryonic Development of the Brain

Formation of Brain Regions

During embryonic development, the brain forms distinct regions and internal cavities.

• Brain Stem: Includes the midbrain, pons, and medulla oblongata.

• Ventricles: Formed by enlargement of the neural tube's central cavity.

Growth and Structural Changes

• The brain grows rapidly, causing changes in the relative position of its parts.

• Cerebral Hemispheres: Envelop the diencephalon and midbrain.

• Wrinkling (Gyri and Sulci): Increases surface area, allowing more neurons to fit within limited space.

Basic Parts and Organization of the Brain

Major Regions

The brain is classified into four main regions, each with distinct functions.

• Brain Stem: Midbrain, pons, and medulla oblongata.

• Cerebellum: Coordinates movement and balance.

• Diencephalon: Includes structures such as the thalamus and hypothalamus (not detailed in these slides).

• Cerebrum: Composed of two central hemispheres, responsible for higher cognitive functions.

Ventricles of the Brain

Structure and Function

The ventricles are interconnected cavities within the brain, filled with cerebrospinal fluid (CSF) and lined with ependymal cells.

• Expansions of Central Cavity: Allow circulation of CSF.

• Cerebrospinal Fluid (CSF): Cushions and nourishes the brain.

• Ependymal Cells: Line the ventricles and help produce CSF.

• Ventricles are continuous with each other and with the central canal of the spinal cord.

Types of Ventricles

• Lateral Ventricles: Located in the cerebral hemispheres; horseshoe-shaped due to the bending of the hemispheres.

• Third Ventricle: Lies in the diencephalon; connected to lateral ventricles by the interventricular foramen.

• Cerebral Aqueduct: Connects the third and fourth ventricles.

• Fourth Ventricle: Located in the hindbrain; connects to the central canal of the spinal cord.

Summary Table: Brain Regions and Key Features

Region	Main Components	Primary Functions
Brain Stem	Midbrain, Pons, Medulla Oblongata	Basic life functions, cranial nerve origin
Cerebellum	Anterior, Posterior, Flocculonodular lobes	Coordination, balance
Diencephalon	Thalamus, Hypothalamus (not detailed)	Relay, homeostasis
Cerebrum	Left and Right Hemispheres	Higher cognitive functions

Key Terms and Definitions

• Cerebrospinal Fluid (CSF): Clear fluid found in the brain and spinal cord, providing cushioning and nutrient transport.

• Ependymal Cells: Glial cells lining the ventricles, involved in CSF production.

• Gyri: Ridges on the cerebral surface.

• Sulci: Grooves between gyri.

• Interventricular Foramen: Channel connecting lateral and third ventricles.

• Cerebral Aqueduct: Narrow channel connecting third and fourth ventricles.

Additional info:

• The diencephalon includes the thalamus and hypothalamus, which are important for sensory relay and homeostasis.

• Wrinkling of the cerebral hemispheres (gyri and sulci) is a key adaptation for increasing neural capacity.