Spinal Cord [13.3 - 13.4]

• What do the anterior horns of the spinal cord contain?


  Somatic motor nuclei
• What do the posterior horns of the spinal cord contain?


  Somatic and visceral sensory nuclei
• Where are visceral motor nuclei located in the spinal cord?


  In the lateral horns
• What is the function of the gray commissures in the spinal cord?


  They contain axons that cross from one side of the cord to the other
• How are sensory and motor nuclei organized in the spinal cord?


  They are spatially organized and may extend along the length of the spinal cord
• What do the anterior horns in the cervical enlargement control?


  Muscles of the upper limbs
• How are somatic motor nuclei organized in relation to muscle control?


  They are organized from medial to lateral based on the muscles they control
• What happens to motor neurons that control flexor muscles in the spinal cord?


  They are grouped separately from those that control extensor muscles
• What is the structural organization of white matter in the spinal cord?


  It is divided into three regions called columns
• What are the three regions of white matter in the spinal cord?

  Posterior white columns, anterior white columns, and lateral white column
• What is a tract in the context of the spinal cord?


  A bundle of axons in the CNS that relays the same type of information
• What do ascending tracts in the spinal cord do?


  They carry sensory information toward the brain
• What do descending tracts in the spinal cord do?


  They convey motor commands to the spinal cord
• What is the significance of the organization of spinal tracts?


  Damage to one tract produces a characteristic loss of sensation or motor control
• What are the three spinal meninges?


  Dura mater, arachnoid mater, and pia mater
• What is the role of sensory nuclei in the spinal cord?


  They receive and relay sensory information from peripheral receptors
• What is the role of motor nuclei in the spinal cord?


  They issue motor commands to peripheral effectors
• What is a dermatome?


  A specific bilateral region of the skin surface monitored by a single pair of spinal nerves
• Why are dermatomes clinically important?


  Damage to a spinal nerve produces a loss of sensation in the corresponding skin region
• What is peripheral neuropathy?


  A regional loss of sensory and motor function often resulting from nerve trauma or compression
• How does the structure of spinal nerves relate to their function?


  Spinal nerves are wrapped in connective tissue layers that protect and support their function
• What happens when a peripheral axon is severed but not displaced?


  Normal function may eventually return as the cut stump grows across the site of injury
• What complicates repairs made after an entire peripheral nerve has been damaged?


  Problems with axon alignment and regrowth
• What is the role of connective tissue sheaths in peripheral nerves?


  They are continuous with those of spinal nerves and provide support
• What is the outermost layer surrounding a spinal nerve called?

  Epineurium
• What is the middle layer surrounding a spinal nerve called?

  Perineurium
• What is the innermost layer surrounding a spinal nerve called?

  Endoneurium
• How do blood vessels relate to the connective tissue layers of spinal nerves?


  Arteries and veins penetrate the epineurium and branch within the perineurium
• What is the significance of the overlap in adjacent dermatomes?


  It provides clues to the location of injuries along the spinal cord
• What is the relationship between spinal nerves and peripheral nerves?


  Spinal nerves branch and interconnect to form peripheral nerves
• What is the role of Schwann cells in peripheral nerves?

  They support and insulate axons
• What happens to the function of a spinal nerve if it is damaged?


  It can produce a loss of sensation in the corresponding region of the skin
• What is the significance of the central canal in the spinal cord?


  It is surrounded by gray matter and contains cerebrospinal fluid
• How does the organization of gray matter relate to its function?


  Masses of gray matter are organized into nuclei that perform specific functions
• What is the relationship between the spinal cord and the brain regarding tracts?


  Longer tracts connect the spinal cord with the brain
• What is the role of the anterior white commissure?


  It is a region where axons cross from one side of the spinal cord to the other
• What is the function of the posterior median sulcus?


  It separates the two posterior horns of gray matter
• What is the function of the anterior median fissure?


  It separates the two anterior horns of gray matter
• What is the role of the pia mater?


  It is the innermost layer of the meninges that directly covers the spinal cord
• What is the role of the arachnoid mater?


  It is the middle layer of the meninges that surrounds the spinal cord