EC

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.