Spinal Cord

Question 1

Mammal spinal cord

Answer 1

Have Brain and Spinal Cord
Central
Spine and spinal cord are segmented and specialized
Reflex Pathways, Conduit, Central Pattern Generators

Question 2

Properties of cord segments

Answer 2

Each major region has characteristic cross-sectional anatomy: the anatomy reflects the # of neurons (both cell bodies and axons) found throughout the cord

The efferent regions get smaller going down

Always less white matter in the sacral cord than in the cervical cord.

Thus it makes sense that the cervical cord is the largest; more things going out AND coming in. Very large dorsal horns.

Question 3

Where the cord ends is called

Answer 3

the conus medullaris

Question 4

Properties of the cervical cord

Answer 4

oval
gray matter: enlarged ventral horn
white matter: large W:G ratio, post. intermediate sulcus

Question 5

properties of thoracic cord

Answer 5

round
lateral horn, narrow dorsal and ventral horns
large W:G ratio, post. intermediate sulcus

Question 6

properties of lumbar cord

Answer 6

round
large dorsal and ventral horns
W:G = 1:1

Question 7

properties of sacral horn

Answer 7

round
almost continuous dorsal– ventral horns
Small W:G ratio

Question 8

Major landmarks of the spinal cord, clockwise from noon

Answer 8

Posterior median sulcus
Lissauer's tract
Central canal
Anterior median fissure
Anterior white commissure
Posterolateral sulcus
Posterior intermediate sulcus

Question 9

Things for pain and temp

Answer 9

Lissauer’s tract
Substantia gelatinosa
Anterior white commissure

Question 10

vertebral arteries in the cervical region

Answer 10

Each vertebral artery gives rise to an anterior spinal artery which fuses into a single vessel and travels along the anterior median fissure

Each posterior inferior cerebellar artery gives rise to a posterolateral (posterior) spinal artery which travels along each posterolateral sulcus

Question 11

Vertebral arteries below the cervical region

Answer 11

The spinal cord is largely supplied by radicular arteries

Throughout the cord, venous drainage occurs through a series of veins that feed into radicular veins which drain into the epidural venous plexus. The anterior and posterior spinal veins travel along their respective fissures/sulci.

Question 12

Neuropathy

Answer 12

dysfunction from a particular nerve or set of nerves (PNS)

Both sensory and motor, localized

Question 13

Radiculopathy

Answer 13

impingement of a given spinal root

Sensory OR motor, follows dermatome or myotome

Question 14

Myelopathy

Answer 14

a spinal cord disorder resulting in loss of nerve function

sensory OR motor loss. Lots of different presentations. May involve more than one limb or more than one side.

Question 15

Afferent Tract Neurons

Answer 15

The major ascending pathways. Both soma (for pain + temp and for proprioception) in the gray matter and myelinated axons (for all somatosensory modalities) in the white matter.

Different diameters of neurons dictate different pathways

Question 16

Interneurons

Answer 16

Have short processes in the cord, often glycinergic, part of many central pattern generators and reflexes

Question 17

Motor neurons

Answer 17

The axons of upper motor neurons (UMN) are found in the white matter. The cell bodies of lower motor neurons (LMN) are found in the gray matter, in specialized LMN pools

Question 18

Propriospinal neurons

Answer 18

Neurons that provide communication between cord segments. All different lengths

act like interneurons

Question 19

Lissaue fusciulus- what kind of neurons

Answer 19

pain and temp

thin diameter fibers

Question 20

Renshaw cells

Answer 20

provide negative feedback on LMNs at level of spinal cord

Constant inhibition is needed
Lots of “microcircuits” in the spinal cord, must coordinate flexor/extensor activation and inactivation at each segment
Glycinergic (like GABA in the brain)
– Large amounts in jaw and facial musculature
Blocked by strychnine
– Convulsions

Question 21

Motorneurons

Answer 21

Neurons are upper or lower motor neurons

LMN = a neuron directly innervating muscle
*UMN = a neuron in a series of neurons in the brain that will innervate a LMN

Question 22

Where we find propriospinal neurons and what they’re like

Answer 22

Ascending
Descending
Travel in Propriospinal tract (“Fasciculus Proprius”)
Bilateral or unilateral
Can be short, medium or long axons

Question 23

Lamina I

Answer 23

Marginal Zone (Pain and Temp Primary Afferent terminals, 2nd order cell bodies)

marginal zone of waldeyer:nociceptive, thermoreceptive, itch

at all levels

Question 24

Lamina II

Answer 24

Substantia Gelatinosa (Interneurons that receive input from Pain and Temp Fibers)

Lamina II S.G. of Rolando (pain fibers)

at all levels

Question 25

Lamina III-IV

Answer 25

Nucleus Proprius (Interneurons that receive input from non-nociceptive fibers)

mechanoreceptive (nucleus proprius)

at all levels. Sensory processing

Question 26

Lamina V

Answer 26

Terminals of GVAs, 2nd order cell bodies

pain (referred pain here)

Question 27

Lamina VI

Answer 27

Terminals of proprioceptive afferents, 2nd order cell bodies

proprioceptive

Question 28

Lamina VII

Answer 28

Contains both:
IML/Lateral horn (T1-L2, S2-S4)
Cell bodies of preganglionic autonomic cell bodies
Nucleus Dorsalis of Clarke (C8-L3)
Terminals of proprioceptive afferents, 2nd order cell bodies

from the notes:
proprioception (lateral horn included). Nucleus dorsalis of clarke C8-L3)…also sacral autonomic nucleus

Question 29

Lamina VIII

Answer 29

Interneurons and propriospinal neurons that receive input from UMN’s

Question 30

Lamina IX

Answer 30

LMN’s that receive input from UMN’s

Question 31

Lamina X

Answer 31

Mostly interneurons

Question 32

The LMN pools in RL IX show anatomic and functional segregation

Answer 32

α-MNs and γ-MNs are scattered in different LMN pools
Flexors and extensors are segregated (relatively) dorsal to ventral
Humuncular organization from axial muscles to extremeties, medial to lateral

Question 33

crossed extension reflex

Answer 33

A flexor reflex involves several segments of the spinal cord, activating multiple LMNs. Interneurons and propriospinal neurons modulate these effects.

In a crossed-extension reflex, the flexor reflex is activated, and contralaterally, the antagonist muscles are activated

Complex, coordinated movements can be completely controlled by the spinal cord

Question 34

myotactic reflex

Answer 34

reflex works within spinal circuits: Clinical Clues

In the patellar tendon reflex, stretching the muscle spindle leads to a direct activation of LMN through the stretching of the quadriceps

Question 35

Central Pattern Generators in the Spinal Cord of Humans?

Answer 35

Lobectomized kids are not paraplegic
Paraplegic humans cannot regain function as cats
Central Pattern Generator without sensory input hasn’t yet been established