Spinal Cord

Question 1

The spinal cord is a segmental structure that is involved in _______neural activity

Answer 1

lower integrative

Question 2

The spinal cord lies in

Answer 2

the spinal canal of the vertebral column

Question 3

there are _ cervical segments of the spinal cord

Answer 3

8

Question 4

there are _ thoracic segments of the spinal cord

Answer 4

12

Question 5

there are _ lumbar segments of the spinal cord

Answer 5

5

Question 6

there are _ sacral segments of the spinal cord

Answer 6

5

Question 7

there are _ coccygeal segments of the spinal cord

Answer 7

1

Question 8

Each segment of the spinal cord has

Answer 8

~a pair of spinal nerves with motor and sensory axons inn each pair

Question 9

What extra is in the thoracolumbar spinal nerves?

Answer 9

There is still motor and sensory axons, but these spinal nerves also have autonomic axons

Question 10

the spinal cord has a tapering cylindrical shape with two enlargements:

Answer 10

~Cervical enlargement that is associated with spinal nerves of the upper extremity
~Lumbar enlargement that is associated with spinal nerves of the lower extremity

Question 11

the spinal cord ends at the _____ between ___ and ___ vertebrae

Answer 11

Conus Medularis; between L1 and L2

Question 12

The very end of the spinal cord is the ____, which is

Answer 12

Filum terminale

~this is a continuation of pia mater to end of spinal canal

Question 13

Numbering of C1-8 spinal nerves in relation to the vertebra

Answer 13

~C1-7 exits above the same numbered vertebra

~C8 exits below C7

Question 14

Numbering of spinal nerves (other than cervical)

Answer 14

~the rest of the spinal nerves exit below the same numbered vertebrae
~sacral nerves exiting through the sacral foramina
~coccygeal spinal nerve exiting just lateral to the coccyx bone
*the lower lumbar, sacral, and coccygeal spinal nerves descend together in the spinal canal as the cauda equina to each exit where they should

Question 15

Dorsal superficial features of the spinal cord (3)

Answer 15

~dorsal median sulcus
~dorsal intermediate sulcus
~dorsal lateral sulcus

Question 16

Dorsal lateral sulci of the spinal cord

Answer 16

Where dorsal roots enter the spinal cord

Question 17

Dorsal intermediate sulci of the spinal cord

Answer 17

The division between two parts of dorsal columns of each side

Question 18

Dorsal median sulcus of the spinal cord

Answer 18

Divides spinal cord into two halves

Question 19

Ventral superficial features of the spinal cord (2)

Answer 19

~Ventral lateral sulci

~Ventral median fissure

Question 20

Ventral lateral sulci of the spinal cord

Answer 20

where ventral roots exit spinal cord

Question 21

Ventral median fissure of the spinal cord

Answer 21

divides spinal cord into two halves

Question 22

Spinal cord dimensions

Answer 22

*most people overestimate the size of the spinal cord since it carries so many tracts and has so many nuclei, but it is really quite small
~Overall dimension of spinal cord is 7-8 mm dorsal-ventral axis and 12mm medial-lateral axis

Question 23

Gray matter

Answer 23

its cell bodies and dendrites in the center of the spinal cord

Question 24

White matter

Answer 24

~surrounds the gray matter

~ascending and descending tracts of myelinated axons

Question 25

Gray matter is organized to regions (3)

Answer 25

~dorsal (posterior) horn ~ventral (anterior) horn ~lateral horn

Question 26

Dorsal horn of the gray matter

Answer 26

sensory relay nuclei

Question 27

Ventral horn of the gray matter

Answer 27

motor nuclei

Question 28

Lateral horn of the gray matter

Answer 28

sympathetic efferent pre-ganglionic nuclei in the thoracic and upper lumbar spinal cord

Question 29

Variable size of horns at different levels of spinal cords

Answer 29

~Larger size of ventral gray horns in cervical (C5--T1) and lumbar-sacral (L4-S2) enlargements ~Larger size of dorsal gray horns in cervical (C5-T1) and lumbar-sacral (L4-S2) enlargement areas ~Lateral horn really only seen in thoracic and upper lumbar segments ~small dorsal and ventral horns in upper cervical and thoracic spinal cord

Question 30

Why are the ventral gray horns larger in certain areas of the spinal cord?

Answer 30

~larger due to the large number of lower motor neurons needed to innervate limb musculature of the upper and lower extremities

Question 31

Why are the dorsal gray horns larger in certain areas of the spinal cord?

Answer 31

~larger due to the larger amount of sensory input from limbs and need for sensory tract cell bodies in the dorsal horns

Question 32

Why are lateral horns only seen in the thoracic and upper lumbar segments?

Answer 32

~this is the only area where the sympathetic efferents neurons reside

Question 33

Why are there small dorsal and ventral horns in the upper cervical and thoracic spinal cord?

Answer 33

~because of the innervation to the neck and trunk only need little sensory and motor input

Question 34

Posteromarginal nucleus of the spinal cord

Answer 34

~along the most dorsal end of the dorsal horn ~receives primary and secondary input from posterolateral tract (fasciculus of Lissauer) ~relays this information related to pain and temperature sensation into the spinothalamic (anterolateral) pathways

Question 35

Substantia gelatinosa of the spinal cord

Answer 35

~a crescent shaped nucleus near tip of dorsal horn just ventral to the posteromarginal nucleus ~receives a large number of C-fibers primary afferent nociceptive (pain) fibers from the peripheral nerves ~relay pain sensation as tract neurons for antrerolateral system ~these are cell bodies which contribute axons which form parts of the spinothalamic (anterolateral) pathways ~have a large density of mu and kappa opiod receptors ~these receptors are probably related to enkephalinergic descending pain control pathways and may be site of this control of afferent nociceptive signals in the spinal cord

Question 36

Nucleus proprius of spinal cord

Answer 36

~in the dorsal horn jus ventral to the substantia gelinosa ~receives and relays non-noxious inputs from the periphery ~has neurons that project to other spinal neurons which are tracts neurons ~are tract neurons that project to other supraspinal relay centers including the midbrain, thalamus, and hypothalamus

Question 37

Base of the dorsal horn of the spinal cord

Answer 37

~in thoracic and lumbar spinal cord in this area is the dorsal nucleus of Clarke (Clarke's cloum) or just nucleus dorsalis ~axons from the dorsal nucleus of Clarke ascend as the dorsal spinocerebellar tract ~adjacent cells give rise to the ventral spinocerebellar tract ~in the cervical spinal cord, these cells give rise to the rostral spinocerebellar tracts

Question 38

Intermediate cell column of spinal cord

Answer 38

~most clearly seen in the lateral aspect in T1-L2 levels of spinal cord and forms the interomediolateral cell column ~it is seen grossly as the lateral horn of the gray matter from T1-L2 ~contains autonomic efferent neurons forming preganglionic fibers of the sympathetic divisions

Question 39

Ventral Motor nuclei of the spinal cord

Answer 39

~Lateral motor nuclei and medial motor nuclei ~Upper cervical lower motor neurons innervate only intrinsic neck muscles ~thoracic lower motor neurons innervate only trunk (proximal) muscles ~there are more distal muscles, there is no need for a lateral motor neuronal nucleus

Question 40

Lateral motor nuclei of the ventral motor nuclei

Answer 40

~lower motor neuron that innervate distal muscles of the limbs

Question 41

Medial motor nuclei of the ventral motor nuclei

Answer 41

~lower motor neurons that innervate proximal limbs and trunk muscles *only the medial motor nucleus exits in the upper cervical and thoracic spinal cord

Question 42

White matter is arranged into regions (3)

Answer 42

~dorsal columns ~lateral columns ~ventral columns *each region contains "tracts" which are groups of ascending or descending axons

Question 43

Dorsal Column of the white matter

Answer 43

ascending (sensory) tracts

Question 44

Lateral Column of the white matter

Answer 44

descending (motor) tracts

Question 45

Ventral Column of the white matter

Answer 45

both ascending (sensory) and descending (motor) tracts

Question 46

White matter: variable size

Answer 46

~greater amount of white matter in rostral compared with caudal spinal cord levels

Question 47

Why is there a greater amount of white matter in the rostral compared to caudal area?

Answer 47

~most axons in the descending tracts have ended before you reach the more caudal spinal cord segments ~most axons in the ascending tracts have not yet begun until you get to the more rostral spinal cord

Question 48

Fasciculus Gracilis & Cuneatus | (dorsal columns) of the spinal cord

Answer 48

~these tracts carry discriminate (fine) touch and proprioception from the lower extremity and from the upper extremity (respectively) ~rise ipsilaterally to the end in the caudal medulla ~dorsal intermediate sulcus lies in between them

Question 49

Lateral Column of the spinal cord: Dorsal and ventral spinocerebellar tract

Answer 49

~ascend in the lateral funiculus and carry proprioceptive information to cerebellum ~Dorsal spinocerebellar tract rises ipsilaterally ~Ventral spinocerebelalr ascends contralaterally

Question 50

Lateral spinothalamic tract (lateral column) of the spinal cord

Answer 50

~contralateral nociceptive (pain) and temperature pathway

Question 51

Anterior spinothalamic tract (lateral column) of the spinal cord

Answer 51

~contralateral pathway but carries non-discriminative (crude) touch and pressure information

Question 52

Lateral and anterior corticospinal tracts (lateral and ventral column) of the spinal cord

Answer 52

~descending tracts are in the lateral and ventral funiculi | ~the crossed and uncrossed fine motor control from pathway the cerebral motor cortex to spinal lower motor neurons

Question 53

Lateral (medullary) and Medial (pontine) reticulospinal tracts (lateral and ventral columns) of the spinal cord

Answer 53

~both uncrossed and bilateral descending motor pathways from the reticular formation of medial and pons ~medial- plays an important role in maintaining posture ~lateral- interrupts postural sets to allow for movements

Question 54

Rubrospinal tract (lateral and ventral column) of spinal cord

Answer 54

~a very small, crossed motor pathways to primarily cervical spinal cord from red nucleus ~plays a role in fine motor control by the upper extremities

Question 55

Tectospinal tract (lateral and ventral) spinal cord

Answer 55

~descends from the midbrain tuctum to lower motor neurons in the cervical spinal cord ~originating in the superior and inferior colliculi of midbrain plays a role for visual and auditory reflexes involving neck movements (orientation to sights and sounds)

Question 56

Dorsolateral funiculus (Lissaur's fasciculus) of the spinal cord

Answer 56

~allows for intersegmental connections within the spinal cord for primary and secondary nociceptive (pain) transmitting axons

Question 57

Anterior white commissure of the spinal cord

Answer 57

~composed of decussating axons of secondary spinothalamic tract neurons as part of the anterolateral pathway