Centrals Nervous System Overview

Introduction

• Overview of the central nervous system (CNS) and its division from the peripheral nervous system (PNS).
• Focus on embryological development of the brain.

Embryological Development

• The CNS develops from the neural tube.
  • Surrounding cells called the neural crest will form the PNS.
• The process begins with the neural tube, which lasts about three weeks, during which it enlarges into three primary vesicles:
  • Prosencephalon (forebrain)
  • Mesencephalon (midbrain)
  • Rhombencephalon (hindbrain)

Primary Vesicles

• Prosencephalon:
  • Divides into:
  • Telencephalon (cerebrum)
  • Diencephalon (thalamus, hypothalamus, etc.)
• Mesencephalon remains unchanged.
• Rhombencephalon:
  • Divides into:
  • Metencephalon (pons, cerebellum)
  • Myelencephalon (medulla oblongata)

Main Parts of the Brain

• CNS consists of brain and spinal cord only.
• Major divisions:
  • Brain Stem: Includes midbrain, pons, and medulla oblongata.
  • Functions: Cranial nerve origin, visual and auditory relay centers.
  • Cerebellum:
  • Role in balance, equilibrium, and coordination of voluntary skeletal movement.
• Diencephalon: Key components are the thalamus (sensory relay) and hypothalamus (homeostasis regulation).
• Cerebrum: Largest brain area; involved in decision making, emotions, sensory integration, etc.

Brain Structure

• Cortex Composition:
  • Gray Matter: Cell bodies (decision making).
  • White Matter: Axons (information transport).
  • Gyri (ridges) and sulci (grooves) serve to increase surface area for cognitive processing.
  • Fissures: Longitudinal fissure separates the two hemispheres; central sulcus separates the frontal and parietal lobes.

Functional Areas and Cortical Mapping

• Precentral Gyrus: Motor control center.
• Postcentral Gyrus: Somatosensory area for processing sensory information.
• Broca's Area: Located in the frontal lobe; responsible for speech production.
• Wernicke's Area: Located in the temporal lobe; responsible for speech comprehension.

Spinal Cord Structure

• Spinal cord terminates at L1-L2 level:
  • Conus Medullaris: The tapered end of the spinal cord.
  • Cauda Equina: Nerve roots extending from conus medullaris, resembling a horse's tail.
  • Filum Terminale: A fibrous extension anchoring the spinal cord to the coccyx.
• Gray Matter Organization:
  • Organized into anterior, lateral, and posterior horns.
  • Anterior horn: Motor information; posterior horn: Sensory information.
  • Interneurons: Located in the gray matter, processing information locally.

Blood Supply and Venous Drainage of the Brain

• Blood supply through the internal carotid and vertebral arteries forming the Circle of Willis.
• Venous drainage through dural sinuses:
  • Major sinuses include the superior sagittal sinus, inferior sagittal sinus, and confluence of sinuses draining into the jugular vein.

Meninges of the CNS

• Meningeal Layers:
  • Dura Mater: Outermost, dense fibrous layer.
  • Arachnoid Mater: Middle layer, web-like structure where cerebrospinal fluid (CSF) circulates in the subarachnoid space.
  • Pia Mater: Innermost layer, adheres closely to the brain and spinal cord.

Cerebrospinal Fluid (CSF)

• Production Location: Choroid plexus within the ventricles of the brain.
• Ventricular System:
  • Including two lateral ventricles, third ventricle, and fourth ventricle.
  • Contains choroid plexus for CSF production; CSF flows through ventricles and into the central canal of the spinal cord.

Key Takeaways

• Understanding the embryological development and functional anatomy of the central nervous system is crucial in fields such as neurology, nursing, and rehabilitative therapies.
• Integration of the structural knowledge of the brain and spinal cord with their major functions will aid in recognizing clinical conditions and understanding health sciences.