Spinal Cord

Front 1

How many total segments make up the spinal cord?

Back 1

31

Front 2

How many cervical segments are in the spinal cord?

Back 2

8

Front 3

How many thoracic segments are in the spinal cord?

Back 3

12

Front 4

How many lumbar segments are in the spinal cord?

Back 4

5

Front 5

How many sacral segments are in the spinal cord?

Back 5

5

Front 6

How many coccygeal segments are in the spinal cord?

Back 6

1

Front 7

When do you transition from brain to spinal cord in the CNS?

Back 7

as soon as you pass through the foramen magnum

Front 8

What are the names of the three supporting layers of the spinal cord?

Back 8

1. dura mater (toughest)

2. arachnoid membrane

3. pia mater (unable to pull off spinal cord tissue)

Front 9

Where does the spinal cord end and what is the ending called?

Back 9

conus medullaris @ ~L2

(but NOT end of nerve roots!)

Front 10

What is the name of the extensions of pia mater that pass laterally between the dorsal and ventral roots to support the spinal cord and help tether it in place?

Back 10

denticulate ligaments

Front 11

What is the name for an extension of pia mater that supports the spinal cord by extending inferiorly from the conus medullaris to the first segment of the coccyx?

Back 11

filum terminale

Front 12

C1-C7 spinal nerves exit where?

Back 12

above their respective vertebra

Front 13

C8 spinal nerve exits where?

Back 13

below C7 vertebra

Front 14

What is the cauda equine and what are its levels?

Back 14

continuation of nerve roots at the end of the spinal cord that descend in the vertebral canal (L2-Co1)

Front 15

What are the two spinal cord enlargements and their levels?

Back 15

1. cervical enlargement (C4-T1)

2. lumbar enlargement (L2-S3)

Front 16

What do the spinal cord enlargements represent and why?

Back 16

areas of increased neuronal density as they supply the limbs through nerve plexi

Front 17

The cervical spinal cord enlargement is associated with what plexus?

Back 17

brachial plexus - upper limb

Front 18

The lumbar spinal cord enlargement is associated with what plexus?

Back 18

lumbosacral plexus - lower limb

Front 19

What is a plexus?

Back 19

an area where at least 2 neuronal structures come together and can leave/re-branch; can combine different spinal cord levels

Front 20

What are the three main longitudinal arterial supplies of the spinal cord?

Back 20

posterior spinal aa. (2)

anterior spinal artery (1)

Front 21

From what artery do the main spinal cord longitudinal arteries arise?

Back 21

vertebral artery

Front 22

The anterior spinal artery and its branches supply what part of the spinal cord?

Back 22

anterior 2/3 of the spinal cord

Front 23

The posterior spinal arteries and its branches supply what part of the spinal cord?

Back 23

posterior 1/3 of the spinal cord

Front 24

What does each vertebral level receive in order to supplement the longitudinal arteries?

Back 24

a pair of segmental arteries

Front 25

What artery creates a watershed region of vascular supply to the lower thoracic and lumbosacral regions of the spinal cord?

Back 25

the great radicular artery (of Adamkiewicz)

Front 26

What type of artery is the great radicular artery and where is it located?

Back 26

very large and critically important segmental artery (T10-T12)

Front 27

What is a watershed region?

Back 27

an area of the body that receives dual blood supply from the most distal branches of two arteries; blood supply from the two vessels does not overlap

Front 28

What is the transition point from CNS to PNS?

Back 28

AS SOON AS YOU LEAVE THE SPINAL CORD

Front 29

What makes up a spinal nerve?

Back 29

at each segment, paired dorsal roots (sensory) and paired ventral roots (motor) that merge to form a nerve of mixed fibers

Front 30

What will a typical spinal nerve bifurcate into?

Back 30

a dorsal ramus and a ventral ramus

Front 31

What fibers are responsible for the innervation of a strip of skin referred to as the dermatome?

Back 31

the somatosensory fibers in the dorsal and ventral rami of each spinal nerve

Front 32

In regards to fiber types, ROOTS are ______ or _______ while NERVE is ______.

Back 32

Roots are sensory OR motor.

Nerve is mixed.

Front 33

What are the two possible fates of a spinal nerve?

Back 33

1. go out to join a plexus

2. go to segmentally innervate something

(ex: intercostal nerve)

Front 34

Where is the synapse for afferent fibers coming into the CNS/spinal cord? Why is this important?

Back 34

IN the CNS; NOT in the dorsal root ganglion!

Need for speed!

Front 35

Where is the CBO for somatosensory neurons?

Back 35

dorsal root ganglion

Front 36

What are two other names for the ventral horn?

Back 36

somatomotor neuron

lower motor neuron (LMN)

Front 37

Why is the ventral horn also called the LMN?

Back 37

because it is the final common pathway used to innervate skeletal muscle

Front 38

What is the white matter of the spinal cord composed of?

Back 38

bundles of ascending or descending myelinated fibers

Front 39

What is the gray matter of the spinal cord composed of?

Back 39

neurons

(also: butterfly shaped, surrounded by white matter)

Front 40

The dorsal (posterior) horn of the spinal cord contains neurons that receive what type of input and from where?

Back 40

synaptic input from primary afferent fibers (central processes of spinal ganglion neurons)

Front 41

The lateral horn of the spinal cord contains what type of neurons?

Back 41

preganglionic neurons of the sympathetic division of the autonomic nervous system (IML - intermediolateral cell column)

Front 42

The ventral (anterior) horn contains what type of neurons?

Back 42

somatomotor neurons that innervate extrafusal and intrafusal muscle fibers in skeletal muscle

Front 43

How do we organize the gray matter of the spinal cord?

Back 43

by nuclear regions

Front 44

What 3 nuclear regions are present THROUGHOUT the spinal cord?

Back 44

1. substantia gelatinosa

2. nucleus proprius

3. medial nucleus of ventral horn

Front 45

Substantia Gelatinosa is located where and is the site of termination for what fibers?

Back 45

location: posterior horn

site of termination: for nociceptive (pain) fibers

Front 46

Nucleus Proprius is located where, is the site of termination for what fibers, and contains what other type of neurons?

Back 46

location: posterior horn

site of termination: for general sensory afferent fibers (NOT pain)

other type of neurons: many interneurons

Front 47

What type of fibers does the Medial Nucleus of the Ventral Horn contain?

Back 47

somatomotor neurons that innervate axial skeletal muscles (maintain postures)

Front 48

A patient with problems in the Medial Nucleus the Ventral Horn would present how?

Back 48

postural control issues; off balance

Front 49

What 6 nuclear regions are present in RESTRICTED regions of the spinal cord?

Back 49

1. Doral Nucleus of Clarke

2. Intermediolateral Cell Nucleus (Column)

3. Lateral Nucleus of Ventral Horn

4. Accessory Nucleus

5. Phrenic Nucleus

6. Sacral Parasympathetic Nucleus

Front 50

What are the levels of the Dorsal Nucleus of Clarke and what type of neurons does it contain?

Back 50

(C8-L2)

contains neurons that relay proprioceptive information to the cerebellum (non-conscious)

Front 51

What are the levels of the Intermediolateral Cell Nucleus and what type of neurons does it contain?

Back 51

(T1-L2)

contains preganglionic neurons of the sympathetic nervous system

Front 52

What are the levels of the Lateral Nucleus of the Ventral Horn and what type of neurons does it contain?

Back 52

contains somatomotor neurons that project to the upper and lower limb

(C5-T1) upper limb, cervical plexus

(L1-S3) lower limb, lumbar plexus

Front 53

What are the levels of the Accessory Nucleus and what type of neurons does it contain?

Back 53

(C1-C4)

somatomotor neurons that innervate sternocleidomastoid and trapezius (CN XI)

Front 54

What are the levels of the Phrenic Nucleus and what type of neurons does it contain?

Back 54

(C3-C5)

somatomotor neurons that innervate the thoracic diaphragm

Front 55

What are the levels of the Sacral Parasympathetic Nucleus and what type of neurons does it contain?

Back 55

(S2-S4)

neurons for caudal portion of the parasympathetic fibers

Front 56

What is the other system of organization for the gray matter of the spinal cord? Why?

Back 56

series of 10 lamina called "Rexed's Lamina"

histologically, the spinal cord has "laminated" appearance/layers/morphology, broken down and each associated with different functions

Front 57

How are the Rexed's Lamina arranged?

Back 57

layered from the posterior horn to the anterior horn

Front 58

Lamina 1 is the target of what type of fibers?

Back 58

c fibers

Front 59

Where is lamina 1 located and what type of neurons does it contain?

Back 59

location: caps the posterior horn

neurons: receive nociceptive and thermal input from primary afferent fibers from the same level or levels above and below via the dorsolateral fasciculus

Front 60

Projections from lamina 1 contribute to what tract?

Back 60

spinothalamic tract

(pain from spinal cord --> brain)

Front 61

Where is lamina 2 located, to what structure is it a direct equivalent, and what type of neurons does it contain?

Back 61

location: immediately deep to lamina 1

lamina 2 = substantia gelatinosa

neurons: mostly interneurons (receiving nociceptive inputs from primary afferent fibers)

Front 62

Projections from lamina 2 go where?

Back 62

involved with local spinal cord circuits; either ascend or descend multiple segments in the fasciculus proprius

(interneurons connect spinal cord levels, but do not travel very far - like 1 or 2)

Front 63

Where is lamina 3 located, what structure does it correspond with, and what type of neurons does it contain?

Back 63

location: deep to lamina II

corresponds with: nucleus proprius

neurons: interneurons targeted by larger diameter sensory afferents

Front 64

Projections from lamina 3 go where?

Back 64

involved with local spinal cord circuits and either ascend or descend multiple spinal cord segments in the fasciculus proprius

Front 65

What two lamina do we chunk together and what broad category of neurons do we associated with them?

Back 65

lamina 3 & 4 - general target of sensory neurons coming into spinal cord

Front 66

Where is lamina IV located, what other structure is it a part of, and what is it the target of?

Back 66

location: deep to lamina III

also part of: nucleus proprius

target of: larger diameter sensory afferents

Front 67

Where is lamina V located, and what two things is it associated with?

Back 67

location: base of the dorsal horn

*general sensory & pain*

Front 68

More specifically, what are the two neuronal functions of lamina V?

Back 68

1) its neurons receive direct inputs from A-delta pain fibers

2) dendrites of this lamina extend into lamina III and IV and thus are also targeted by large diameter sensory fibers

Front 69

Projections from lamina V go where?

Back 69

contribute to the spinothalamic tract

(sending to brain cortex to sort out subtle differences in pain stimuli)

Front 70

Where is lamina VI most clearly defined?

Back 70

at cervical and lumbosacral enlargements

Front 71

What type of fibers are associated with lamina VI?

Back 71

receives afferent fibers from muscle stretch receptors

Front 72

Where is lamina VI located?

Back 72

base of the dorsal horn

Front 73

To what structure is lamina 7 equivalent?

Back 73

the intermediate gray matter

Front 74

What does lamina 7 contain?

Back 74

*source of autonomic sympathetics*

medially: Dorsal Nucleus of Clarke

laterally: IML

Front 75

Where is lamina 8 located?

Back 75

base of the anterior horn

Front 76

What type of neurons does lamina 8 contain (and what is their job)?

Back 76

mostly interneurons that receive input from primary motor cortex which then project to somatomotor neurons of lamina 9

Front 77

What is located in lamina 9?

Back 77

location of somatomotor neurons of the anterior horn

Front 78

Where is lamina 10 located and what type of fibers is it associated with?

Back 78

encircles the central canal of spinal cord

receives visceral afferent fiber innervations

Front 79

What are the two methods of organization of afferent fibers coming into the spinal cord?

Back 79

1) somatotopic organization - spatial pattern of sensory receptors in your skin is preserved as the fibers enter the spinal cord in a point to point fashion

2) size - larger fibers passing more medially and terminating in deeper layers

Front 80

What are the 2 possible fates of primary afferent fibers?

Back 80

1) synapse in the dorsal/posterior horn of the spinal cord at the level in which they enter

2) ascend multiple levels to synapse in more rostral levels of the spinal or brainstem

Front 81

What is the purpose of the local circuits of the spinal cord?

Back 81

reflex - "the need for speed"

local circuits connect sensory and motor without a need for the brain, but not perfectly - kind of ballistic in nature

Front 82

What is the myotatic reflex?

Back 82

stretch reflex - the basis of the knee jerk reflex and is one example of a local circuit

Front 83

How does the myotatic reflex work?

Back 83

when you tap the patellar tendon, the thigh muscles (quads) are stretched briefly

Ia fibers that innervate the muscle spindle synapse directly on motor neurons of the ventral horn, eliciting contraction of the muscle

Ia fibers will also synapse on interneurons in nucleus proprius to inhibit antagonistic muscles

Front 84

Broadly speaking, how does the withdrawal reflex work?

Back 84

excites efferents to flexor muscles

inhibits efferents to extensor muscles

Front 85

In more detail, how does the withdrawal reflex work?

Back 85

-harmful stimulus applied to skin, stimulating free nerve endings

-resulting impulses are conducted through small-diameter afferent fibers (type C) to the dorsal horn of the spinal cord (lamina I, II, and V) and directly on LMN of the ventral horn

-ipsilateral flexors contract and antagonistic extensors relax