Spinal Cord: Organization and Neural Systems (Dr. White) Flashcards
Hold on to your butts. (Didn't make flash cards for charts on the last two slides, but those are probably important.)
What’s in the ventral columns?
Bundles of axons organized into tracts or fasiculi.
If a dorsal root nerve fiber is classified using Roman numerals, what does that tell you about the sensory information it carries?
Its info is coming from skeletal muscle proprioception (muscle spindles and Golgi-tendon organs)
What type of fibers do muscle spindles use?
Ia
What kind of information to Ia fibers carry?
Info from muscle spindles.
What type of fibers do Golgi tendon bodies use?
Ib
Are lower or higher Roman numeral fibers more heavily myelinated?
lower number Roman numeral fibers are more heavily myelinated (proprioception needs to be conducted quickly)
What kind of information do Ib fibers carry?
info from Golgi tendon bodies
If a dorsal root fibers are classified alphabetically, what does that tell you?
The fibers are carrying info from skin.
What type of fiber is used for touch, vibration, and pressure?
A-beta
What info is carried by A-beta fibers?
touch, vibration, pressure
What type of fiber is used for pain and temperature from the skin?
A-delta, C
What info is carried in A-delta and C type fibers?
temperature and pain (nociception)
Where do Ia / Ib (proprioception fibers) go when they enter the spinal cord? (2 places)
They enter the dorsal horn - most are interested in synapsing in the ventral horn for reflexes. Some enter dorsal columns to provide info to the CNS.
Where II and A-beta (touch, vibration, pressure) fibers go when they enter the spinal cord? (2 places, mainly)
Medial division ignores dorsal nerve -> goes up dorsal column to CNS.
Most form synapses in ventral horn for reflexes.
Where do A- delta / C fibers (pain and temp.) go when they enter the spinal cord?
They love the dorsal horn.
What’s the myelination of A-delta / C fibers like?
They’re small and thinly myelinated or unmyelinated.
What’s the most important tract for voluntary muscle contraction? Where in the spinal cord is it located?
The corticospinal tract. (coming from the motor cortex). It’s dorsal and lateral.
What different functions do alpha and gamma motor neurons serve?
Alpha motor neurons make muscle contract.
Gamma motor neurons increase the sensitivity of muscle spindles (especially when the muscle is contracting)
If a motor neuron innervates a muscle in the trunk, were is its cell body going to be located in the ventral horn? What’s the pattern to remember? What does this mean for segments of spinal cord sending motor neurons to the limbs?
Medially. There’s a proximal -> distal gradient of muscle innervation where neurons to the proximal muscles have their cell bodies more medial. If sending motor axons to the limbs, the ventral horns will extend further laterally.
How many neurons do you need to make a skeletal muscle contract? Where do these neurons have their cell bodies? Where do they synapse?
Two. Upper motor neuron that has its cell body in the primary motor cortex and synapses ventral horn. Lower (alpha) motor neuron that has cell body in the ventral horn and synapses at the NMJ.
Where does the upper motor neuron (UMN) cross the midline?
In the pyramidal decussation aka. caudal medulla-spinal cord junction. (then it travels down the lateral corticospinal tract)
What’s the pyramidal tract?
It’s the same thing as the corticospinal tract.
Is the lower motor neuron’s cell body ipsilateral or contralateral to the muscle it innervates?
Ipsilateral. (Recall that the crossing over is done by the UMN at the pyramidal decussation.)
What’s the significance of the reticulospinal tracts?
These carry fibers that innervate extensor muscles for postural support, bilaterally.
