The Nervous System

• Function of Nervous System:

  • Receive sensory input
  • Integrate information
  • Motor function
  • Maintain homeostasis
  • Establish and maintain mental activity
• The Peripheral Nervous System can be divided into two divisions:

  • Structural Division
  • Functional Division
• Structural Division:


  • Cranial Nerves
  • Spinal Nerves
• Functional Division: 


  • Sensory (Afferent) Division
  • Motor (Efferent) Division
• Sensory (Afferent) Division - conducts action potentials (impulses) from PNS to the CNS.
• Motor (Efferent) Division - conducts action potentials (impulses) from the CNS to the PNS.
• Motor (Efferent) Division:


  • Autonomic Nervous System
  • Somatic Nervous System
• Cells of the Nervous System:

  • Neurons
  • Neuroglia
• Neurons - the fundamental units of the nervous system.
• Neurons - receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs.
• Neurons - do not undergo cell division.
• Neurons - responsible for the reception of stimuli and transmission of impulses.
• Dendrites - multiple branches that transmit impulse towards the cell body.
• Axon - long, single that transmit impulse away from the cell body to other neuron.
• How are the new neurons produced if neurons cannot divide?

  Because of neuroblasts. Neuroblasts undergo mitosis while neurons cannot.
• Neuroglia - nonneuronal cells of the CNS and PNS.
• Neuroglia - supporting cells for the nourishment, protection, and insulation of the neurons.
• Neuroglia - undergo cell division, thus may cause brain tumor.
• Types of Neuroglia:


  • Astrocytes
  • Microglia
  • Ependymal cells
  • Oligodendrocytes
  • Scwhann cells
• Astrocytes - star-shaped neuroglia located between neurons and capillaries.
• Astrocytes - major supporting tissue in the CNS.
• Astrocytes - contribute with the blood-brain barrier (BBB).
• Microglia - acts as immune cells of the CNS (protects against infection).
• Microglia - help protect the brain by removing bacteria and cell debris (phagocytes).
• Ependymal cells - line the fluid-filled cavities (ventricles) of the Central Nervous System.
• Ependymal cells - some form choroid plexus to produce cerebrospinal fluid (CSF), and others, with cilia on the surface, help move the CSF through the CNS.
• Oligodendrocytes - cell processes form myelin sheaths around the axons or enclosed unmyelinated axons in the CNS.
• Schwann cells - form the myelin sheath around axons or enclose unmyelinated axons in the PNS.
• Both the CNS and PNS contain areas of gray matter and white matter.
• Gray matter - consists of groups of neuron cell bodies and their dendrites.
• Cortex - a gray matter on the surface of the brain in the CNS.
• Ganglion - a cluster of neuron cell bodies in the PNS.
• White matter - consists of bundles of parallel axons with their myelin sheaths, which are whitish in color.
• Nerve tracts - white matter forms conduction pathways in the CNS.
• Nerves - bundles of axons and their connective tissue sheaths in the PNS.
• In the Brain:

  • Gray matter is outside; white matter is inside.
• In the Spinal Cord:

  • White matter is outside; gray matter is inside.
• Synapse - a junction where the axon of one neuron interacts with another neuron or with an effector organ.
• Spinal Cord - extends from the foramen magnum at the base of the skull to the second lumbar vertebra.
• Electrical and Neural Pathways:

  • Resting Membrane
  • Action potential
  • Synapse