Summary of Nervous System Organization and Function

Overview of the Nervous System

  • Divided into Central Nervous System (CNS) and Peripheral Nervous System (PNS)
  • CNS comprises the brain and spinal cord; PNS includes all other nervous components

Neurons

  • Functional units of the nervous system, carrying electrical signals
  • General structure includes:
    • Cell body (soma): contains nucleus, organelles, and DNA
    • Dendrites: handle inputs, increase surface area
    • Axon: single output from cell, may branch

Types of Neurons

  • Functional Classification:
    • Sensory (afferent) neurons
    • Interneurons (CNS)
    • Efferent neurons
  • Structural Classification:
    • Multipolar
    • Bipolar
    • Pseudounipolar
    • Anaxonic

Myelination

  • Myelin sheath surrounds some axons, increases speed of action potential conduction
  • Composed of lipid layers from Schwann cells (PNS) and oligodendrocytes (CNS)

Nervous Tissue Organization

  • Gray matter contains cell bodies and dendrites; white matter consists of myelinated axons
  • Glial cells support neurons, including astrocytes, oligodendrocytes, microglia, and ependymal cells

Nerve Definitions

  • 'Nerve' refers to both individual nerve cells (neurons) and bundles of axons (nerve trunks)

Afferent & Efferent Nerves

  • Afferent nerves: transmit sensory information to CNS
  • Efferent nerves: transmit motor commands from CNS
    • Divided into Somatic motor and Autonomic nervous systems

Autonomic Nervous System (ANS)

  • Comprises three divisions: Sympathetic, Parasympathetic, and Enteric
  • Regulates involuntary bodily functions

Action Potentials

  • Electrical impulses propagating along neurons
  • All-or-none event; speed varies with fiber diameter and myelination

Information Flow

  • Frequency coding used to communicate the strength of signals via varying action potential rates.