Neuroanatomy Lecture Notes

Introduction to the Nervous System

• Main Components:
  • Central Nervous System (CNS)
    • Brain
    • Spinal Cord
  • Peripheral Nervous System (PNS)
• Divisions:
  • CNS collects sensory information and sends motor responses.
  • PNS transmits information to/from the CNS.

Central Nervous System (CNS)

• Components:
  • Brain: processes sensory inputs, integrates information, and sends motor outputs.
  • Spinal Cord: transmits information to and from the brain.
• Functions:
  • Collect sensory information.
  • Compare new information with stored information.
  • Decide on and send motor responses.

Peripheral Nervous System (PNS)

• Motor:
  • Voluntary responses (skeletal muscles).
  • Involuntary responses (smooth muscles, gland secretion).
    • Divisions: sympathetic (fight/flight) and parasympathetic (rest/digest).
• Sensory:
  • General sensations: touch, temperature, pain, proprioception.
  • Special sensations: vision (eyes), olfaction (nose), taste (tongue), hearing (ears), balance (vestibular apparatus in the inner ear).
  • Information flow direction: sensory input to CNS, motor output from CNS.

Sensory System

• Special vs. General Sensations:
  • Special: from specific body locations (e.g., eyes for vision).
  • General: from multiple body locations (e.g., touch from skin).
• Proprioception:
  • Awareness of body position and movement through sensory inputs from muscles, joints, and tendons.

Motor System

• Voluntary:
  • Somatic responses (e.g., limb movement).
• Involuntary:
  • Autonomic responses (e.g., heart rate, gland secretion).

Functional Divisions of the Brain

• Forebrain:
  • Cerebral Cortex (gray matter).
  • Diencephalon.
• Midbrain:
  • Mesencephalon.
• Hindbrain:
  • Pons, Medulla, Cerebellum (gray matter on the surface of the cerebellum).

Cells in the Nervous System

• Neurons:
  • Functional cells conducting electrochemical signals (action potentials).
  • Structure: cell body and axon.
• Glial Cells:
  • Supportive cells for neurons.

Gray Matter vs. White Matter

• Gray Matter:
  • Composed of neuronal cell bodies.
  • Present in the CNS as cortex (surface) and nuclei (deep structures).
• White Matter:
  • Composed of axons.
  • Bundles of axons known as tracts (within CNS) and nerves (within PNS).
• Reticular Formation:
  • Mixed gray and white matter within the brainstem due to sensory and motor crossings.

Functional Pathways

• Tracts:
  • Ascending Tracts: carry sensory information upward.
  • Descending Tracts: carry motor responses downward.
• Commissural Fibers:
  • Connect right and left parts of the CNS.
  • Example: Corpus Callosum.
• Association Fibers:
  • Connect anterior and posterior parts of the CNS.

Nerve vs. Tract

• Tract: Bundle of axons in the CNS.
• Nerve: Bundle of axons in the PNS.
• Myelination:
  • CNS: Oligodendrocytes.
  • PNS: Schwann Cells.

Summary

• The nervous system is divided into the CNS and PNS, each responsible for specific types of input and output processing.
• CNS (brain and spinal cord) processes sensory inputs and motor outputs, while PNS transmits information to/from the CNS.
• Understanding structure (gray and white matter, tracts, fibers) and functions (voluntary and involuntary responses) is crucial in neuroanatomy.

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