Central Nervous System: Structure, Function, and Development (Chapter 12 Study Guide)

Central Nervous System (CNS): Structure, Function, and Development

Embryonic Development of the Brain

The human brain develops from the embryonic neural tube, which forms three primary brain vesicles that further differentiate into five secondary vesicles. These structures give rise to the major regions of the adult brain.

• Primary Brain Vesicles: Prosencephalon (forebrain), Mesencephalon (midbrain), Rhombencephalon (hindbrain)

• Secondary Brain Vesicles: Telencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon

• Adult Brain Structures:

  • Telencephalon: Cerebrum (cortex, white matter, basal nuclei)

  • Diencephalon: Thalamus, Hypothalamus, Epithalamus

  • Mesencephalon: Midbrain

  • Metencephalon: Pons, Cerebellum

  • Myelencephalon: Medulla oblongata

• Brain Flexures: Two bends (cephalic and cervical) shape the brain during development.

Main Structures of the Adult Brain

The adult brain consists of six main structures, each with distinct origins and functions.

• Cerebrum

• Diencephalon

• Midbrain

• Pons

• Medulla oblongata

• Cerebellum

Cerebrum: Anatomy and Function

The cerebrum is the largest part of the brain, divided into two hemispheres and five lobes, each with specialized functions.

• Hemispheres: Left and right, connected by the corpus callosum

• Lobes:

  • Frontal: Motor control, reasoning, problem-solving

  • Parietal: Sensory perception, spatial processing

  • Temporal: Auditory processing, memory

  • Occipital: Visual processing

  • Insula: Taste, visceral sensation

• Folding: Gyri (ridges) and sulci (grooves) increase surface area for cortical neurons

• Layers:

  • Cerebral cortex: Gray matter, pyramidal cells

  • White matter: Myelinated tracts

  • Basal nuclei: Deep gray matter clusters

Functional Regions of the Cerebrum

• Central Sulcus: Separates frontal and parietal lobes

• Precentral Gyrus: Primary motor cortex; controls voluntary movements

  • Motor Homunculus: Map of body regions; larger areas for fine control

• Postcentral Gyrus: Primary somatosensory cortex; receives sensory input

  • Sensory Homunculus: Map of sensory input distribution

• Motor Association Areas:

  • Premotor Cortex: Plans movements

  • Broca's Area: Speech production; usually left hemisphere

  • Frontal Eye Field: Controls voluntary eye movements

  • Prefrontal Cortex: Higher cognitive functions

• Sensory Areas:

  • Somatosensory Association Cortex: Integrates sensory input

  • Visual Areas: Occipital lobe; primary and association areas

  • Auditory Areas: Temporal lobe; primary, association, Wernicke's area

  • Vestibular Area: Balance

  • Olfactory Cortex: Smell; linked to limbic system

  • Gustatory Area: Taste

  • Visceral Sensory Area: Internal organ sensation

• Multimodal Association Areas:

  • Anterior Association Area: Prefrontal cortex; complex learning, personality

  • Posterior Association Area: Integration of sensory input, recognition

  • Limbic Association Area: Emotional processing; cingulate gyrus, hippocampus

• Cerebral Dominance: Lateralization of function; e.g., language (left), spatial abilities (right)

Cerebral White Matter Pathways

White matter tracts connect different regions of the brain, facilitating communication.

• Association fibers: Connect areas within the same hemisphere (e.g., corona radiata)

• Commissural fibers: Connect hemispheres (e.g., corpus callosum)

• Projection fibers: Connect cortex with lower CNS (e.g., internal capsule)

Basal Nuclei (Corpus Striatum)

Basal nuclei are clusters of gray matter deep within the cerebrum, involved in motor control.

• Caudate nucleus

• Lentiform nucleus: Putamen and Globus pallidus

• Functions: Regulate movement, inhibit unnecessary motion

Diencephalon

The diencephalon is located deep within the brain and consists of three main structures.

• Thalamus: Relay station for sensory information; lateral and medial geniculate nuclei (vision, hearing), ventral posterolateral nucleus (sensory input)

• Hypothalamus: Controls autonomic functions, endocrine system, homeostasis

  • Mammillary bodies: Olfactory relay

  • Preoptic nucleus: Thermoregulation

  • Suprachiasmatic nucleus: Circadian rhythms

  • Seven main functions: Autonomic control, emotional response, body temperature, food intake, water balance, sleep-wake cycles, endocrine regulation

• Epithalamus: Contains pineal gland; secretes melatonin, regulates sleep

Ventricles and Cerebrospinal Fluid (CSF)

The brain contains four ventricles filled with CSF, which cushions and nourishes neural tissue.

• Ventricles: Lateral (2), third, fourth

• Choroid Plexus: Produces CSF

• CSF Flow: Lateral ventricles → third ventricle → cerebral aqueduct → fourth ventricle → central canal/spinal cord → subarachnoid space → arachnoid villi → dural venous sinus → circulation

• Blood-Brain Barrier: Protects brain from harmful substances

• Hydrocephaly: Excess CSF accumulation

Meninges

The brain is protected by three connective tissue layers called meninges.

• Dura mater: Tough, outer layer

• Arachnoid mater: Middle, web-like layer

• Pia mater: Delicate, inner layer

Brainstem: Midbrain, Pons, Medulla

The brainstem controls vital functions and houses most cranial nerve nuclei.

• Midbrain:

  • Cerebral peduncles: Motor tracts

  • Corpora quadrigemina: Superior colliculi (visual reflexes), inferior colliculi (auditory reflexes)

  • Substantia nigra: Dopamine production; Parkinson's disease

  • Red nucleus: Motor coordination (rubrospinal tract)

• Pons: Connects cerebellum, relays information, cranial nerve nuclei

• Medulla oblongata:

  • Pyramids: Motor tracts; decussation (crossing)

  • Olives: Relay sensory information

  • Dorsal columns: Cross at medulla; nucleus cuneatus (arms), nucleus gracilis (legs)

  • Homeostatic functions: Cardiovascular, respiratory, vomiting

Cerebellum

The cerebellum coordinates movement and balance.

• Structure: Two hemispheres, cortex, arbor vitae (white matter)

• Function: Fine-tunes motor activity

• Four-step processing:

  1. Receives motor plan from cortex

  2. Receives sensory input about movement

  3. Compares intent with actual movement

  4. Sends corrective feedback to cortex

Cranial Nerves

There are 12 pairs of cranial nerves, each with specific functions and origins.

Roman #	Name	Function	Origin
I	Olfactory	Smell	Cerebrum
II	Optic	Vision	Diencephalon
III	Oculomotor	Eye movement	Midbrain
IV	Trochlear	Eye movement	Midbrain
V	Trigeminal	Facial sensation, chewing	Pons
VI	Abducens	Eye movement	Pons
VII	Facial	Facial expression, taste	Pons
VIII	Vestibulocochlear	Hearing, balance	Pons/Medulla
IX	Glossopharyngeal	Taste, swallowing	Medulla
X	Vagus	Autonomic control	Medulla
XI	Accessory	Neck muscles	Medulla
XII	Hypoglossal	Tongue movement	Medulla

Functional Brain Systems

Brain systems integrate functions across multiple regions.

• Limbic System: Emotional processing, memory

  • Amygdala: Anger, fear

  • Cingulate gyrus: Physical emotions

  • Hippocampus: Memory formation

• Reticular Activating System (RAS): Maintains consciousness, filters stimuli

  • Location: Brainstem

  • Three nuclei groups: Raphe, medial, lateral

  • Three-step flow: Sensory input → RAS → cortex

  • Damping: Filters extraneous stimuli

Memory and Levels of Consciousness

• Memory:

  • Short-term (STM): Temporary storage

  • Long-term (LTM): Permanent storage; requires processing

  • Declarative: Facts

  • Procedural: Skills

• EEG Waves: Four types; alpha, beta, theta, delta (vary in speed and function)

Sleep and Wake Cycles

• REM Sleep: Dreaming, rapid eye movement

• NREM Sleep: Non-dreaming, restorative

• Glymphatic System: Cleanses brain during sleep

Brain Disorders

Common disorders include infections, trauma, and degenerative diseases (e.g., Parkinson's, hydrocephaly).

Summary Table: White Matter Communication Patterns

Type	Direction	Main Structure	Function
Association	Within hemisphere	Corona radiata	Connects cortical areas
Commissural	Between hemispheres	Corpus callosum	Integrates left/right
Projection	Cortex to lower CNS	Internal capsule	Links cortex to body

Example Questions

• List the 7 functions of the hypothalamus

• Describe the division of labor in the cerebrum

• Name the 5 main areas of the adult brain

• Briefly describe the location and function of the 5 lobes of the cerebrum

• Explain the three different white matter communication patterns in the cerebrum

• Describe the RAS system and its functions

• Trace CSF flow and its function

Additional info: Academic context and expanded explanations were added to clarify brief points and ensure completeness for exam preparation.