CHAPTER 13

• What are reflexes?

  Quick, automatic responses triggered by specific stimuli
• What are spinal reflexes?

  Reflexes controlled by the spinal cord alone without input from the brain
• What are the two main divisions of the nervous system?

  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)
• What does the central nervous system consist of?

  Brain and spinal cord
• What is the role of the peripheral nervous system?

  It includes cranial nerves and spinal nerves for sensory input and motor response pathways
• What is the spinal cord made of?

  Nervous tissue, housed within protective membranes and vertebral column
• What is the function of the spinal cord?

  It carries sensory and motor information between the brain and most other parts of the body
• How many regions does the spinal cord have?

  Four regions: cervical, thoracic, lumbar, and sacral
• What is the significance of the gray matter in the spinal cord?

  It contains neuronal cell bodies
• What does the white matter in the spinal cord consist of?

  Myelinated axons
• What divides the spinal cord into left and right sides?

  Grooves
• What is the central canal in the spinal cord?

  An internal passageway that contains cerebrospinal fluid (CSF)
• What is the conus medullaris?

  The tapered, conical end of the spinal cord below the lumbar enlargement
• What is the cauda equina?

  Nerve roots extending below the conus medullaris
• What is the filum terminale?

  A thin thread of fibrous tissue at the end of the conus medullaris
• What are spinal nerves formed from?

  The union of the anterior and posterior roots
• What type of nerves are spinal nerves?

  Mixed nerves containing both afferent (sensory) and efferent (motor) fibers
• What is the role of the white ramus communicans?

  Contains myelinated axons that innervate glands and smooth muscle
• What does the gray ramus communicans contain?

  Unmyelinated fibers that innervate glands and smooth muscle
• What is the dura mater?

  The outer layer of the spinal meninges
• What is meningitis?

  A viral or bacterial infection of the meninges
• What is the epidural space?

  The space between the vertebrae and the dura mater
• What is the function of the subarachnoid space?

  It contains cerebrospinal fluid (CSF) that carries dissolved gases, nutrients, and wastes
• What are dermatomes?

  Specific bilateral regions of skin monitored by a single pair of spinal nerves
• Why are dermatomes clinically important?

  Damage or infection of a spinal nerve or spinal ganglion produces loss of sensation in the corresponding dermatome
• What is a nerve plexus?

  A complex, interwoven network of nerve fibers formed from blended fibers of the anterior rami of adjacent spinal nerves
• What are the four major nerve plexuses?

  1. Cervical plexus
  2. Brachial plexus
  3. Lumbar plexus
  4. Sacral plexus
• What does the cervical plexus innervate?

  The scalp behind the ear, the neck, and the diaphragm
• What is the major nerve of the cervical plexus that controls the diaphragm?

  Phrenic nerve
• What does the brachial plexus innervate?

  The pectoral girdle, upper back, and upper limbs
• What are the major nerves of the brachial plexus?

  Musculocutaneous, radial, median, and ulnar nerves
• What is carpal tunnel syndrome?

  Compression of the median nerve, usually when adjacent tendons are swollen
• What is the lumbar plexus responsible for?

  Innervating the pelvis and lower limb
• What is the function of the anterior ramus?

  Innervates the ventrolateral structures of the trunk and the limbs
• What is the role of the posterior ramus?

  Innervates the skin/muscles of the back
• What is the anterior white commissure?

  A structure that interconnects anterior white columns and where axons cross from one side of the spinal cord to the other
• What is the difference between ascending and descending tracts?

  Ascending tracts carry sensory information up toward the brain, while descending tracts carry motor commands down to the spinal cord
• What are the connective tissue layers surrounding spinal nerves?

  Epineurium, perineurium, and endoneurium
• What is the function of the epineurium?

  It is the outermost layer that provides protection and support to the nerve
• What is the role of the perineurium?

  It separates the nerve into fascicles (bundles of axons)