Spinal cord

• From where does the spinal cord extend?

  From the medulla oblongata to the region of T12
• What is located below T12?

  The cauda equina
• In which regions do enlargements of the spinal cord occur?

  In the cervical and lumbar regions
• How long is the spinal cord?

  17 inches
• What is the function of the exterior white matter of the spinal cord?

  It contains conduction tracts
• What is primarily found in the internal gray matter of the spinal cord?

  Mostly cell bodies
• What do the dorsal (posterior) horns of the spinal cord do?

  Sensory information passes through
• What do the anterior (ventral) horns of the spinal cord do?

  Motor information passes through
• What is the central canal of the spinal cord filled with?

  Cerebrospinal fluid
• What covers the spinal cord?

  The meninges
• At what level do nerves leave the spinal cord?

  At the level of each vertebrae
• What is the dorsal root associated with?

  The dorsal root ganglia
• What are dorsal root ganglia?

  Collections of cell bodies outside the central nervous system
• What is the ventral root responsible for?

  Carrying motor impulses away from the CNS
• What does the peripheral nervous system consist of?

  Nerves and ganglia outside the central nervous system
• What is a nerve?

  A bundle of neuron fibers
• How are neuron fibers bundled?

  By connective tissue
• What surrounds each neuron fiber?

  Endoneurium
• What binds groups of neuron fibers into fascicles?

  Perineurium
• What binds fascicles together?

  Epineurium
• What are the classifications of nerves?

  • Mixed nerves: both sensory and motor fibers
  • Afferent (sensory) nerves: carry impulses toward the CNS
  • Efferent (motor) nerves: carry impulses away from the CNS
• How many pairs of cranial nerves are there?

  12 pairs
• What is the primary function of cranial nerves?

  They mostly serve the head and neck
• What type of nerves are most cranial nerves?

  Most are mixed nerves
• How are cranial nerves numbered?

  In order, front to back
• How many cranial nerves are sensory only?

  Three
• How many pairs of spinal nerves are there?

  31 pairs
• How are spinal nerves formed?

  By the combination of the ventral and dorsal roots of the spinal cord
• How are spinal nerves named?

  For the region from which they arise
• What are the major plexus nerves and their regions?

  • Cervical C1-C4: Phrenic
  • Brachial C5-T1: Axillary, Radial, Musculocutaneous, Ulnar, Median
  • Lumbosacral L1 to S4: Obturator, Femoral, Tibial, Common fibula
• What do dorsal rami serve?

  They serve the skin and muscles of the posterior trunk
• What do ventral rami form?

  A complex of networks (plexus) for the anterior
• What is the autonomic nervous system?

  The involuntary branch of the nervous system
• What does the autonomic nervous system consist of?

  Only motor nerves
• What are the two divisions of the autonomic nervous system?

  1. Sympathetic division
  2. Parasympathetic division
• What are the differences between somatic and autonomic nervous systems?

  1. Nerves:

  • Somatic: one motor neuron
  • Autonomic: preganglionic and postganglionic nerves

  1. Effector organs:

  • Somatic: skeletal muscle
  • Autonomic: smooth muscle, cardiac muscle, and glands

  1. Neurotransmitters:

  • Somatic: always use acetylcholine
  • Autonomic: use acetylcholine, epinephrine, or norepinephrine
• Where does the sympathetic division originate?

  From T1 through L2
• Where are the ganglia located in the sympathetic division?

  At the sympathetic trunk (near the spinal cord)
• What type of neurons are involved in the sympathetic division?

  Short pre-ganglionic neuron and long postganglionic neuron
• What neurotransmitters are used in the sympathetic division?

  Norepinephrine and epinephrine