Introduction to the Structure of the Nervous System

Main Divisions of the Nervous System

• Central Nervous System (CNS)
  • Made up of the brain and spinal cord
  • Brain:
    • Mainly located in the head
    • Divided into different parts:
      • Cerebrum: Largest part, located on top
        • Divided into left and right cerebral hemispheres
      • Brain Stem: Connects cerebrum to spinal cord
        • Divided into three parts:
          • Midbrain
          • Pons
          • Medulla (medulla oblongata)
      • Cerebellum: Located behind and connected to the brain stem
  • Spinal Cord:
    • Long, thin tube-like structure in the spine

Embryonic Development of the Brain

• Forebrain (Prosencephalon): Becomes the cerebrum
• Midbrain (Mesencephalon): Becomes the midbrain part of the brain stem
• Hindbrain (Rhombencephalon): Becomes the pons, medulla, and cerebellum

Peripheral Nervous System (PNS)

• Structures outside the CNS
• Components of PNS:
  • Nerves: Long stringy structures carrying the axons of neurons
  • Ganglia: Lumps attached to nerves containing the somas of neurons

Neurons and Nervous System Communication

• Afferent Neurons: Carry information into the CNS
• Efferent Neurons: Carry information away from the CNS

Types of Nerves

• Cranial Nerves:
  • Exit the skull or cranium
  • 12 pairs
• Spinal Nerves:
  • Exit the spinal cord
  • 31 pairs
  • Formed from spinal nerve roots:
    • Afferent neurons: Travel through the back roots
    • Efferent neurons: Travel through the front roots
  • Mix of afferent and efferent neurons in the spinal nerves

Nerve Structure

• Nerves branch repeatedly from proximal (close to the center of the body) to distal (far from the center of the body) parts
• Proximal nerves are large and visible to the naked eye
• Distal branches become microscopic

Additional Notes

• Cranial nerves pass through the skull
• Overview is a basic introduction; more details will be discussed in later videos