CNS spinal cord

SPINAL CORD 

A. Provide a description of the general longitudinal anatomy of the spinal cord  (conus medullaris, cauda equina, and filum terminale). 

Conus Medullaris: The cone-shaped end of the spinal cord located between L1-L2 vertebrae.

Cauda Equina: A "horse-tail" of nerve roots that extend below the conus medullaris.

Filum Terminale: A thin extension of pia mater that anchors the spinal cord to the coccyx.

B. Name the three actual and potential spaces associated with the spinal meninges  and their clinical significance to performing an epidural or spinal anesthesia, and collection of CSF.  

Epidural Space:

• Between vertebrae and dura mater. Contains fat and blood vessels.

• Clinical Use: Epidural anesthesia is delivered here.

Subdural Space (Potential Space):

• Between dura and arachnoid mater.

• Clinical: Potential site for hematomas (bleeding).

** Subarachnoid Space:

• Between arachnoid and pia mater; contains CSF.

• Clinical Use: Lumbar puncture (CSF collection) and spinal anesthesia occur here.

C. Identify the location in the spinal cord and describe the function of the neurons in  the following areas (anterior horn, lateral horn, posterior horn). 

Anterior Horn:

• Location: Front of gray matter.

• Function: Contains somatic motor neurons for skeletal muscle control.

Lateral Horn:

• Location: Side of gray matter (T1-L2 region).

• Function: Contains autonomic neurons for smooth muscle, cardiac muscle, and glands.

Posterior Horn:

• Location: Back of gray matter.

• Function: Contains sensory neurons for processing incoming sensory signals.

D. Identify the location in the spinal cord and describe the function of the following  (anterior funiculus, posterior funiculus, lateral funiculus). 

Anterior Funiculus:

• Location: Front (ventral) white matter.

• Function: Motor pathways for voluntary movement.

Lateral Funiculus:

• Location: Sides of the spinal cord.

• Function: Contains both motor and sensory pathways (e.g., spinothalamic tract).

Posterior Funiculus:

• Location: Back (dorsal) white matter.

• Function: Sensory pathways for touch and proprioception.

E. Describe the general locations and functions of first-, second-, and third-order  neurons in the posterior column, spinothalamic (antereolateral) and  spinocerebellar ascending pathways. 

Posterior Column:

• Function: Carries touch and proprioception signals.

• Neurons:

  • 1st Order: From sensory receptors to medulla.

  • 2nd Order: Crosses over at medulla to thalamus.

  • 3rd Order: Thalamus → Somatosensory cortex.

Spinothalamic Pathway– going UP to the brain:

• Function: Carries pain and temperature signals.

• Neurons:

  • 1st Order: Sensory receptors → Posterior horn.

  • 2nd Order: Crosses over in the spinal cord → Thalamus.

  • 3rd Order: Thalamus → Somatosensory cortex.

Spinocerebellar Pathway:

• Function: Carries unconscious proprioception signals.

• Neurons:

  • 1st Order: Sensory receptors → Posterior horn.

  • 2nd Order: Ends in cerebellum.

F. Describe the general locations and functions of the upper and lower motor  neurons in the corticospinal descending pathway. 

Upper Motor Neurons:

• Location: Start in the primary motor cortex.

• Function: Controls voluntary movement.

• Decussates (crosses) in the medulla → Ends in anterior horn.

Lower Motor Neurons:

• Location: Start in the anterior horn.

• Function: Innervates skeletal muscles.

G. Explain why damage to left side of the brain affects the right side of the body,  and vice versa. (Use knowledge on how decussation occurs in sensory and  motor pathways).

Decussation: Sensory and motor pathways cross over to the opposite side of the body.

• Motor Pathway: Crosses at the medulla (corticospinal tract).-- always going down and out (Descending)  

• Sensory Pathway: The spinothalamic tract crosses in the spinal cord, while posterior column crosses in the medulla.

Therefore, damage to the left brain affects the right body