Chapter 12 (Part 2): The Central Nervous System - Spinal Cord

Question 1

Spinal Cord

Answer 1

• CNS tissue inclused in vertebral column
• epidural space: between vertebrae and dural sheath (dura matter) filled with fat and network of veins
• foramen to L1

Question 2

Conus medullaris

Answer 2

termina portion of spinal cord

Question 3

Cauda equina

Answer 3

collection of nerve roots at inferior end of vertebral column

Question 4

filum terminale

Answer 4

fibrous extension of the pia mater, anchors spinal cord to coccyx

Question 5

denticulate ligaments

Answer 5

“shelves” of pia mater that attach the spinal cord to vertebrae

Question 6

cervical and lumbar enlargements

Answer 6

sites where nerves serving the upper and lower limbs emerge

Question 7

organization of gray matter

Answer 7

• cell bodies
• dorsal half: sensory roots and ganglia
• ventral half: motor roots
• they fuse laterally to form spinal nerves

Question 8

white matter organization

Answer 8

• axons, fibers
• fibers in 3 directions: ascending, descending, transverse
• 3 funiculi (columns): posterior, lateral, anterior
• pathways decussate (crossover) and are paired (one on each side)

Question 9

ascending (input) pathways

Answer 9

• first order neurons
• some=spinal cord reflexes
• others synapse with second order neurons and ascend to thalamus
• three types
  1. nonspecific and 2. specific send impulses to sensory for touch, conscious proprioception
  3. spinocereballar tracts send impulses to cerebellum, do not directly contribute to sensory perception

Question 10

Anterior and posterior spinocerebellar tracts

Answer 10

• type of ascending pathway
• muscle and tendon stretch
• do not decussate
• muscle spindles, specialized proprioceptors

Question 11

descending spinal cord tracts

Answer 11

• output
• direct: pyramidal
• indirect: essentially all other tracts
• motor pathways require two neurons (upper and lower)

Question 12

direct (pyramidal) pathways

Answer 12

• originate pyramidal neurons (upper motor)
• sent through corticalspinal tracts
• stimulation of anterior horn neurons (lower motor) activates skeletal muscles
• fast and fine (skilled) movements

Question 13

indirect (extrapyramidal) path

Answer 13

• complex and multisynaptic
• posture and balance
• coarse movements of proximal limbs
• head, neck, and eye movement

Question 14

Flaccid paralysis

Answer 14

• damage to lower motor neurons
• impulses do not reach muscles
• no voluntary or involuntary control of muscles

Question 15

spastic paralysis

Answer 15

• only upper motor neurons are damaged
• spinal neurons intact, muscles stimulated irregularly
• no voluntary control of muscles

Question 16

transection spinal cord injury

Answer 16

• cut spinal cord
• total motor and sensory loss below cut
• paraplegia: transection between T1 and L1
• quadriplegia: transection in cervical region

Question 17

ALS

Answer 17

• Lou Gehrig’s disease
• neuromuscular condition
• destruction of ventral horn motor neurons, fibers of pyramidal tract
• loss of ability to speak, swallow, breathe
• death within 5 years
• linked to malfunctioning genes for glutamate transporter and/or superoxide dismutase