Central Nervous System -

Topics Covered

• General Anatomical Overview

• CNS Embryology and Development

• Grey vs. White Matter

• Ventricles

• Brain Structures: Cerebrum, Thalamus, Cerebellum

• Brain Stem: Midbrain, Pons, Medulla

• Spinal Cord

CNS Anatomy Overview

• Composed of:

  • Brain:

    • Cerebrum

    • Thalamus

    • Cerebellum

    • Brain Stem (Midbrain, Pons, Medulla)

  • Spinal Cord

CNS Embryology

• Neural Tube Development:

  • Begins as a tube with rostral (anterior) and caudal (posterior) pores.

  • Prenatal vitamins (B9 - folic acid) help prevent birth defects due to tube closure issues.

Primary Brain Vesicles

• Formed from closing neural tube:

  • Prosencephalon (Forebrain)

  • Mesencephalon (Midbrain)

  • Rhombencephalon (Hindbrain)

Secondary Brain Vesicles

• Primary vesicles divide into:

  • Telencephalon

  • Diencephalon

  • Mesencephalon

  • Metencephalon

  • Myelencephalon

Structures of Secondary Vesicles

• Telencephalon: Cerebral Hemispheres (white matter and basal nuclei)

• Diencephalon: Thalamus, Hypothalamus, Retina

• Mesencephalon: Midbrain

• Metencephalon: Pons

• Myelencephalon: Medulla Oblongata

Grey vs. White Matter

• Grey Matter:

  • Unmyelinated, short axons, neuron cell bodies

  • Found in cortex, islands within white matter

• White Matter:

  • Myelinated, long axons

  • Surrounds grey matter in brain and spinal cord

Ventricles

• Fluid-filled spaces providing nutrients via cerebrospinal fluid (CSF).

• Components:

  • 4 Ventricles in the brain:

    • Lateral Ventricles (1st & 2nd)

    • 3rd Ventricle

    • 4th Ventricle

  • Central Canal in Spinal Cord

• Choroid Plexus: Produces CSF.

Brain Coverings (Meninges)

• Dura Mater: Outermost, tough layer

• Arachnoid Mater: Middle, thin layer

• Pia Mater: Innermost, delicate layer adhering to brain and spinal cord

Cerebrum Overview

• Divided into two hemispheres (left/right) and four lobes:

  • Frontal

  • Parietal

  • Temporal

  • Occipital (Insular lobe is hidden)

• Major Landmarks:

  • Longitudinal Fissure (divides hemispheres)

  • Corpus Callosum (connects hemispheres)

  • Central Sulcus (divides frontal from parietal)

  • Pre-Central Gyrus (primary motor cortex)

  • Post-Central Gyrus (primary sensory cortex)

• Functions of Lobes:

  • Frontal: Higher order processes, motor initiation

  • Temporal: Speech and language

  • Parietal: Sensory information integration

  • Occipital: Vision

  • Insular: Taste

Functional Areas of Cerebral Cortex

• Primary Cortices:

  • Motor: Pre-central gyrus, frontal lobe

  • Somatosensory: Post-central gyrus, parietal lobe

  • Auditory: Temporal lobe

  • Visual: Occipital lobe

  • Gustatory: Insular lobe

Broca's and Wernicke's Areas

• Broca's Area: Speech production

  • Damage affects speech production but not comprehension.

• Wernicke's Area: Speech understanding

  • Damage affects comprehension but not production.

Associations Within the Brain

• Brain functions are integrative, utilizing multiple systems for processes like vision and hearing.

• Brain can form new connections for recovery after damage (e.g., PET scans).

Brain Stem

• Components: Midbrain, Pons, Medulla Oblongata, Reticular Formation.

• Functions: Integrates visual/auditory stimuli, controls heart rate, respiration, and alertness.

Midbrain Structures

• Superior Colliculus (vision)

• Inferior Colliculus (hearing)

• Substantia Nigra (motor control, dopamine production)

• Functions include relaying visual/auditory info and motor control.

Pons Structures

• Relays info between cerebrum and cerebellum

• Coordinates respiration with medulla

• Integrates sensory and motor functions (Cranial Nerves V, VI, VII)

Medulla Oblongata Functions

• Controls heart rate, blood pressure, respiration, vomiting, and other autonomic functions (Cranial Nerves VIII, IX, X, XII).

Reticular Formation

• Functional system maintaining wakefulness and filtering stimuli.