Spinal Cord Morphology Flashcards
(22 cards)
What are the three major pathways?
Association pathways - axons connect different corical areas within a hemisphere
Commissural pathways - axons connect ares on boths sides of the brain (generally homotopic)
Projection pathways - Axons connect different areas, ascending or descending
What are afferent pathways?
Input for example sensory
What are efferent pathways?
Output for example motor
Where are the two enlargements of the spinal cord?
Cervical - C5 to T1
Lumbar - L2 - S3
What is the pyramidal decussation?
Region where some descending pathways cross
What are the three columns of white matter that surround the gray matter?
Anterior funiculus
Lateral funiculus
Posterior funiculus
Where is the coricospinal tract located within the spinal cord?
Descends the cord within the lateral funiculus
Principal targets are neurons concerned with the activation of skeletal muscles
What is the distribution of segments in the human spinal cord?
8 cervical
12 thoracic
5 lumbar
5 sacral
1 Coccygeal
What levels of the spinal cord is there a lateral horn (gray matter) present?
The 12 thoracic and upper two or three lumbar levels
Where do axons pass from one side of the spinal cord to the other?
Anterior white and gray commissures
What are fasiciculi composed of?
Central processes of peripheral sensory neurons supplying muscles, joints and skin
What is Lissauer’s tract?
Compact bundle of small fibers, part of the pain pathway, that lies on the periphery of the spinal cord
Where is the proportion of gray matter to white matter the greatest?
Lumbar and Cervical enlargements
Describe the gray matter in the cervical region
The dorsal gray column is comparatively narrow and the ventral column is broad and expansive
Describe the gray mater in the thoracic region
Both dorsal and ventral columns are narrow
A lateral column is present
Describe the gray matter in the lumbar region
The dorsal and ventral columns are broad
Describe the blood supply to the spinal cord.
Two posterior spinal arteries supply the dorsal horns
One anterior spinal artery territory supplies the ventral horns
Describe the stretch reflex
Muscle spindles are excited and in turn excite synergistic alpha motor neurons
Reciprocal inhibition occurs
How is autogenic inhibition manifested clinically in certain pathological conditions?
Clasp-knife reflex
Mediated by Ib fibers from golgi tendon organs
Why can only noxious stimuli illicit the flexor reflex?
Descending influences normally hold the reflex in a somewhat inhibited state
What are the two ways the flexor reflex pathway spreads over multiple spinal segments?
Primary afferent fibers bifurcate on entering, and their processes then extend in both directions
The interneuron itself may have processes extending over severeal segments
Why doesn’t the flexor reflex cause falling over?
The contralateral limb is stimulated to extend to support the weight of the body
