Nervous System

• Nervous System


  One of the two main divisions of the human body's control and communication systems

  
• Divisions of the Nervous System

  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)

  
• Central Nervous System (CNS)

  • Consists of the brain and spinal cord

  
• Peripheral Nervous System (PNS)


  • Consists of all the nervous tissues outside the CNS (nerves and ganglia)
  • Functions to link the CNS with the various parts of the body

  
• Cells of the Nervous System

  • Neurons
  • Glial Cells

  
• Neurons


  Nerve cells that receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs
• Parts of a Neuron

  • Cell Body
  • Dendrites
  • Axon

  
• Types of Neurons


  • Multipolar
  • Bipolar
  • Pseudo-unipolar
• Glial Cells


  Primarily supportive cells of the CNS and PNS that do not conduct action potentials
• Types of Glial Cells

  • Astrocytes
  • Ependymal
  • Microglia
  • Oligodendrocytes
  • Schwann Cells
• Nervous System


  One of the two main divisions of the human body's control and communication systems

  
• Divisions of the Nervous System

  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)

  
• Astrocytes


  • Highly branched cells that provide structural support, regulate neuronal signaling, contribute to blood brain barrier, and help with neural tissue repair

  
• Central Nervous System (CNS)

  • Consists of the brain and spinal cord

  
• Ependymal Cells


  • Epithelial-like cells that line the ventricles of the brain and central canal of the spinal cord, circulate cerebrospinal fluid, and form choroid plexuses

  
• Peripheral Nervous System (PNS)


  • Consists of all the nervous tissues outside the CNS (nerves and ganglia)
  • Functions to link the CNS with the various parts of the body

  
• Microglia


  • Small, mobile cells that protect the CNS from infection and become phagocytic in response to inflammation
• Cells of the Nervous System

  • Neurons
  • Glial Cells

  
• Oligodendrocytes


  • Cells with processes that can surround several axons and form myelin sheaths around axons or enclose unmyelinated axons in the CNS

  
• Neurons


  Nerve cells that receive stimuli, conduct action potentials, and transmit signals to other neurons or effector organs

  
• Schwann Cells


  • Single cells surrounding axons that form myelin sheaths around axons or enclose unmyelinated axons in the PNS

  
• Parts of a Neuron

  • Cell Body
  • Dendrites
  • Axon

  
• Myelin Sheaths


  Specialized layers that wrap around the axons of some neurons and act as an excellent insulator to increase the speed and efficiency of action potential generation

  
• Types of Neurons


  • Multipolar
  • Bipolar
  • Pseudo-unipolar
• Nodes of Ranvier


  Gaps in the myelin sheath where ion movement can occur
• Glial Cells


  Primarily supportive cells of the CNS and PNS that do not conduct action potentials
• Types of Glial Cells

  • Astrocytes
  • Ependymal
  • Microglia
  • Oligodendrocytes
  • Schwann Cells

  
• Spinal Cord


  • Extends from the foramen magnum at the base of the skull to the second lumbar vertebrae
  • Spinal nerves communicate between the spinal cord and the body
  • The inferior end of the spinal cord and the spinal nerves existing there resemble a horse's tail and are collectively called the Cauda Equina

  
• Astrocytes


  • Highly branched cells that provide structural support, regulate neuronal signaling, contribute to blood brain barrier, and help with neural tissue repair

  
• Spinal Nerves


  • Arise along the spinal cord from the union of the dorsal root and ventral roots
  • All spinal nerves contain axons of both sensory and somatic motor neurons (mixed nerves)
  • Spinal nerves are categorized by the region of the vertebral column from which they emerge

  
• Ependymal Cells


  • Epithelial-like cells that line the ventricles of the brain and central canal of the spinal cord, circulate cerebrospinal fluid, and form choroid plexuses

  
• Structure of the Spinal Cord

  • Consists of a superficial white matter portion and a deep gray matter portion
  • The white matter consists of myelinated axons, and the gray matter is mainly a collection of neuron cell bodies
  • The gray matter is shaped like the letter H, with posterior and anterior horns
  • The white matter in each half of the spinal cord is organized into 3 columns
  • The central canal is a fluid filled space in the center of the cord

  
• Microglia


  • Small, mobile cells that protect the CNS from infection and become phagocytic in response to inflammation
• Spinal Nerve Roots


  • Spinal nerves arise from numerous rootlets along the dorsal and ventral surfaces of the spinal cord
  • The ventral and dorsal roots unite just lateral to the spinal cord to form the spinal nerve
  • The cell bodies of pseudo-unipolar sensory neurons are in the dorsal root ganglia
  • Somatic motor neurons are in the anterior horn, and autonomic neurons are in the lateral horn
  • Dorsal root contains sensory axons, and the ventral root contains motor axons

  
• Oligodendrocytes


  • Cells with processes that can surround several axons and form myelin sheaths around axons or enclose unmyelinated axons in the CNS

  
• Brain


  • The major regions of the brain are the brainstem, the cerebellum, diencephalon, and the cerebrum
• Schwann Cells


  • Single cells surrounding axons that form myelin sheaths around axons or enclose unmyelinated axons in the PNS

  
• Brainstem


  • Connects the spinal cord to the remainder of the brain
  • Consists of the medulla oblongata, pons, and midbrain
  • Damage to small areas of the brainstem can cause death, whereas damage to relatively large areas of the cerebrum or cerebellum often do not
  • Contains several nuclei involved in vital body functions, such as the control heart rate, blood pressure, and breathing
• Myelin Sheaths


  Specialized layers that wrap around the axons of some neurons and act as an excellent insulator to increase the speed and efficiency of action potential generation

  
• Medulla Oblongata


  • The most inferior portion of the brainstem and is continuous with the spinal cord
  • Extends from the level of the foramen magnum to the pons
  • Contains the ascending and descending nerve tracts
  • Contains discrete nuclei with specific functions, such as regulation of the heart rate and blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, balance and coordination
  • Contains two large enlargements called the pyramids that consist of descending nerve tracts involved in the conscious control of movement