Neuroanatomy and Physiology of the Spinal Cord

Question 1

What region of the neural tube lies ventral to the sulcus limitans?

Answer 1

Basal plate

Question 2

What region of the neural tube lies dorsal to the sulcus limitans?

Answer 2

Alar plate

Question 3

What part of the spinal cord contains primarily motor neurons (efferent)?

Answer 3

Basal plate

Question 4

What part of the spinal cord contains primarily sensory neurons (afferent)?

Answer 4

Alar plate

Question 5

Is the spinal cord longer in men or women?

Answer 5

Men (45cm compared to the 42cm in women)

Question 6

What is the approximate diameter of the spinal cord?

Answer 6

1.0-1.5cm

Question 7

In adults, the spinal cord ends at what vertebral level?

Answer 7

L1-L2

Question 8

There are 2 observable enlargements that occur in the spinal cord. Where do these occur?

Answer 8

• cervical

- lumbar/sacral

Question 9

The 2 observable enlargements of the spinal cord mark what?

Answer 9

mark the areas of the spinal cord that contain the neurons concerned with the upper and lower extremities, respectfully

Question 10

Rostrally, the spinal cord is continuous with what part of the brainstem?

Answer 10

medulla oblongata

Question 11

Caudally, the spinal cord tapers into what structure?

Answer 11

conus medullaris

Question 12

The dorsal and ventral roots of the lower lumbar and sacral segments continue caudally to exit where?

Answer 12

exit through their appropriate intervertebral foramina

Question 13

What makes the dorsal and ventral roots so long?

Answer 13

due to the differential growth of the spinal cord versus the spine

Question 14

The collection of these long dorsal and ventral roots is known as?

Answer 14

cauda equina

Question 15

What are the three layers of meninges that cover the spinal cord?
–> these coverings of the spinal cord vary somewhat to that surrounding the brain

Answer 15

1) dura mater
2) arachnoid
3) pia

Question 16

Which layer of the spinal cord consists only of a meningeal layer?

Answer 16

Dura mater

Question 17

The periosteal layer ends where?

Answer 17

foramen magnum

Question 18

The epidural space is filled with what?

Answer 18

fat

Question 19

The arachnoid mater acts as the limiting component to contain what substance?

Answer 19

CSF

Question 20

When does the CSF get into the subarachnoid space of the spinal cord?

Answer 20

after leaving the foramina of Luschka and Magendie

Question 21

Since the spinal cord ends at the level of L1-L2, that leaves a large pocket of subarachnoid space below the caudal tip of the cord….this space is known as what?

Answer 21

lumbar cistern

Question 22

In what space is it safe to perform lumbar punctures (spinal tap)?

Answer 22

lumbar cistern - subarachnoid space below the caudal tip of the cord

Question 23

What are the 2 components of the pia mater?

Answer 23

1) pia intima

2) denticulate ligaments

Question 24

Which component of the pia mater is adhered directly to the spinal cord, much the same as with the brain?

Answer 24

pia intima

Question 25

Extensions that protrude from the lateral sides of the cord and pierce the arachnoid to attach to the dura mater are called what?

Answer 25

denticulate ligaments

Question 26

What is the function of the denticulate ligaments?

Answer 26

help anchor and stabilize the spinal cord in the vertebral canal

Question 27

At the caudal end of conus medullaris, what ligament extends to anchor the spinal cord?

Answer 27

filum terminale

Question 28

What is the filum terminale made up of ?

Answer 28

- pia - glial elements - some remnants of coccygeal neuronal elements

Question 29

What is the filum terminale termed, as it extends through and becomes encased with the dura mater attached to the coccyx?

Answer 29

coccygeal (sacral) ligament

Question 30

What is the function of the coccygeal (sacral) ligament?

Answer 30

anchors the end of the cord in the spinal canal

Question 31

Why is it safe to perform a lumbar puncture (spinal tap) in the lumbar cistern?

Answer 31

At the level of the lumbar cistern the nerve roots are suspended in CSF and therefore float away from the pressure of the needle.

Question 32

What are the 4 segments of embryological segmental organization? (similar to segmental development of the spinal cord)

Answer 32

- somites - dermatomes - myotomes - sclerotomes

Question 33

How many pairs of spinal nerves are there?

Answer 33

31 (32) nerves - 8 cervical - 12 thoracic - 5 lumbar - 5 sacral - 1 (2) coccygeal

Question 34

During development of the cord, what happens to the segmental arrangement of the spinal cord?

Answer 34

the segmental arrangement of the spinal cord gets obscured

Question 35

What are the 2 subdivisions of the spinal cord and CNS?

Answer 35

gray matter and white matter

Question 36

What is the central "butterfly" shaped area that consists of neuron cell bodies and glial cells?

Answer 36

gray matter

Question 37

What is the area surrounding the gray matter and contains myelinated axons?

Answer 37

white matter

Question 38

Which subdivision of the spinal cord contains both ascending and descending fiber tracts or pathways?

Answer 38

white matter

Question 39

The ascending and descending fiber tracts of the white matter of the spinal cord can be divided into what three general funiculi?

Answer 39

- dorsal (posterior) funiculus - lateral funiculus - ventral (anterior) funiculus

Question 40

What is the general term for an area of white matter?

Answer 40

funiculus

Question 41

Gray matter is composed of what?

Answer 41

nerve cell bodies and their dendritic processes, and glial cells

Question 42

The lateral horn present from segments S1-S3 of the spinal cord is the location of what type of neurons?

Answer 42

preganglionic parasympathetic neurons for the lower parts of the body

Question 43

The lateral horn present from segments T1-L2 of the spinal cord is the location for what type of neurons?

Answer 43

preganglionic sympathetic neurons

Question 44

Gray matter is divided into various nuclei or divisions. This is referred to as what?

Answer 44

Lamina of Rexed

Question 45

The substantia gelatinosa of the dorsal horn is given what roman numeral (Lamina of rexed)?

Answer 45

Lamina II

Question 46

The dorsolateral tract of Lissauer is known as what?

Answer 46

Lissauer's tract

Question 47

The nucleus proprius of the dorsal horn is given what roman numeral (Lamina of rexed)?

Answer 47

Lamina III, IV

Question 48

The dorsal nucleus of Clarke (segmental levels T2-L2) is given what roman numeral (Lamina of rexed)?

Answer 48

Lamina VII, in part

Question 49

The dorsal nucleus of Clarke is made primarily of what?

Answer 49

interneurons

Question 50

The intermediolateral cell column or lateral horn (segmental levels C8/T1 - L2; S1-S3) is given what roman numeral (Lamina of rexed)?

Answer 50

Lamina IX

Question 51

The ventral horn of the spinal cord is given what roman numeral (Lamina of rexed)?

Answer 51

Lamina IX

Question 52

The ventral horn is made primarily of what?

Answer 52

lower motor neurons that innervate extrafusal fibers

Question 53

The dorsal horn of the spinal cord receives what kind of information?

Answer 53

incoming sensory information

Question 54

What type of fibers enter the dorsal horn more medially, where the spinal cord is myelinated?

Answer 54

large diameter, heavily myelinated (Ia/b, A-alpha, II) fibers coming from encapsulated nerve endings

Question 55

What type of fibers enter the dorsal horn more laterally?

Answer 55

small diameter, non-myelinated C fibers and A-delta fibers coming from free nerve endings

Question 56

What two fiber types enter the spinal cord at Lissauer's tract?

Answer 56

Fibers A-delta and C

Question 57

Lissauer's tract contains axons that carry what kind of information into the dorsal horn of the spinal cord?

Answer 57

pain and temperature information

Question 58

The ventral horn of the spinal cord contains what kind of neurons?

Answer 58

lower motor neurons

Question 59

What are the two types of lower motor neurons (LMN) found in the ventral horn?

Answer 59

- alpha-motor neurons | - gamma-motor neurons

Question 60

The neurons situated most medially in the ventral horn innervate what part of the body?

Answer 60

axial musculature (trunk, neck, etc.)

Question 61

The neurons situated most laterally in the ventral horn innervate what part of the body?

Answer 61

the muscles of the extremities

Question 62

The lower motor neurons situated posteriorly in the ventral horn are concerned with what muscles?

Answer 62

muscles of flexion

Question 63

The lower motor neurons situated anteriorly in the ventral horn are concerned with what muscles?

Answer 63

muscles of extension

Question 64

What regions of the spinal cord are concerned with the extremities?

Answer 64

lumbar and cervical spine

Question 65

What region of the spinal cord is NOT concerned with the extremities?

Answer 65

Thoracic spine

Question 66

What forms the spinal nerve?

Answer 66

the merging of the dorsal and ventral roots away from the spinal cord

Question 67

Prior to the merging of the dorsal and ventral roots, the dorsal root is entirely ________ and the ventral root is entirely _______.

Answer 67

dorsal --> sensory | ventral --> motor

Question 68

Once the merging of the dorsal and ventral roots occurs, the spinal nerve becomes what kind of nerve?

Answer 68

mixed nerve -- has both motor and sensory components

Question 69

Each spinal nerve then branches into a number of branches to reach what?

Answer 69

its specific dermatomal segment or muscle of innervation

Question 70

What is associated with the spinal nerves at spinal cord levels T1-L2 is a series of what?

Answer 70

autonomic ganglia

Question 71

Autonomic ganglia are the location of what?

Answer 71

the postganglionic cell bodies for the sympathetic nervous system

Question 72

The preganglionic cell bodies are located where?

Answer 72

in the lateral horn in the spinal cord (intermediolateral) cell column

Question 73

What are specific, stereotyped motor responses to an adequate (appropriate) stimulus?

Answer 73

reflexes

Question 74

Reflexes require a series of structures consisting of a minimum of what four components?

Answer 74

- receptor - afferent limb - efferent limb - effector organ

Question 75

A stretch reflex or deep tendon reflex (DTR) are also classified as what?

Answer 75

myostatic or monosynaptic

Question 76

What is an example of a deep tendon reflex (DTR)?

Answer 76

patellar ligament or knee jerk

Question 77

A deep tendon reflex demonstrates what principle?

Answer 77

autogenic facilitation with a small amount of reciprocal inhibition

Question 78

What is autogenic inhibition?

Answer 78

When the Golgi tendon organ (GTO) detects an increased tension while the muscle is contracting, the stimulus generates an inhibitory influence to the alpha motor neurons that are driving the contracting muscle. The muscle can now relax, releasing the tension.

Question 79

What is reciprocal facilitation?

Answer 79

Through the interneuronal pool, the antagonistic muscle can be activated to facilitate the release of tension

Question 80

What are the names of two complex reflexes? They involve more than just two neurons and the reciprocal inhibition of the antagonist/opposing muscle must occur.

Answer 80

- Flexor Withdrawal Reflex | - Crossed Extension Reflex

Question 81

What is being inhibited during reciprocal inhibition?

Answer 81

antagonistic muscle

Question 82

What is being inhibited during recurrent inhibition?

Answer 82

same muscle and synergists

Question 83

What is being inhibited during non-reciprocal inhibition?

Answer 83

inhibits agonists, synergists and antagonists (coordination of various movements)

Question 84

What does segmental loss include and NOT include?

Answer 84

Include: the structures that are present at the specific segmental level -- gray matter areas of the cord and to some extent the dorsal and ventral root components that are bringing in sensory information and/or sending out motor information NOT include: the additional involvement of ascending and descending white matter pathways that are also involved