Spinal Cord Organization

Question 1

What are the main functions of the spinal cord?

Answer 1

1. communicates with the brain
2. connects with spinal nerves
3. gives rise to spinal reflexes

Question 2

How does he spinal cord communicate with the brain?

Answer 2

by means of ascending and descending pathways that form tracts in spinal white matter

Question 3

How does the spinal cord connect with the spinal nerves?

Answer 3

through afferent and effort axons in spinal roots

Question 4

Describe the gross anatomy of the spinal cord.

Answer 4

1. a cylinder of the CNS

2. exhibits subtle cervical and lumbosacral enlargements

Question 5

What produces the cervical and lumbosacral enlargements of the spinal cord?

Answer 5

extra neurons within segments that innervate limbs

Question 6

What is the conus medullaris?

Answer 6

the region of the spinal cord caudal to the lumbar enlargement

Question 7

Define a segment in terms of the spinal cord

Answer 7

a portion of the spinal cord that gives rise to a pair (right and left) of spinal nerves.

Question 8

How are spinal nerves attached to the spinal cord?

Answer 8

each spinal nerve is attached to the spinal cord by means of dorsal and ventral roots

Question 9

How are spinal segments, spinal roots, and spinal nerves identified?

Answer 9

numerically by region

Question 10

What is the caudal equine?

Answer 10

it is composed of sacral and caudal spinal roots, which surround the conus medullar is and terminal filament streaming caudally to reach intervertebral foramina

Question 11

What envelops the spinal cord and spinal roots?

Answer 11

the meninges within the vertebral canal

Question 12

Are the spinal roots CNS or PNS?

Answer 12

PNS

Question 13

What type of cells is the central canal lined by?

Answer 13

ependymal cells

Question 14

What is the central canal filled with?

Answer 14

cerebrospinal fluid

Question 15

What is the central canal derived from?

Answer 15

the embryonic neural cavity

Question 16

What is the gray matter derived from?

Answer 16

the embryonic mantle layer

Question 17

Describe the gray matter

Answer 17

1. it is butterfly shaped
2. it has a high density of neuron cell bodies and gliocytes
3. high capillary density
4. sparse myelinated fibers

Question 18

What are the gray matter regions?

Answer 18

• dorsal horn
• ventral horn
• intermediate substance (lateral horn)

Question 19

What is white matter derived from?

Answer 19

embryonic marginal layer

Question 20

Describe white matter

Answer 20

1. it is located superficially to the gray matter
2. it is composed of concentrated myelinated fibers
3. gliocytes
4. low capillary density

Question 21

What are the white matter regions?

Answer 21

dorsal funiculus, ventral funiculus, lateral funiculus, and white commissure

Question 22

What are the methods for organizing gray matter?

Answer 22

1. spinal laminae

2. spinal nuclei

Question 23

Describe spinal laminae organization

Answer 23

spinal gray matter is organized into ten laminae

Question 24

What is the advantage of spinal laminae organization?

Answer 24

all the neurons are included

Question 25

What is the disadvantage of spinal laminae organization?

Answer 25

the laminae are difficult to distinguish

Question 26

Describe spinal nuclei organization

Answer 26

recognizable clusters of cells are identified as nuclei

Question 27

What is the advantage of the spinal nuclei organization?

Answer 27

the advantage is that the distinct nuclei are generally detectable

Question 28

What is the disadvantage of the spinal nuclei organization?

Answer 28

the numerous nuclei outside the distinct nuclei are not included

Question 29

What type of neurons are found in the gray matter?

Answer 29

all of the neurons are multipolar cell bodies

Question 30

What are the three major types of spinal neurons?

Answer 30

1. efferent neurons 2. projection neurons 3. interneurons

Question 31

Describe efferent neurons

Answer 31

Send axons to the ventral root

Question 32

Where are the cell bodies of efferent neurons located?

Answer 32

in the ventral horn or in intermediate substance

Question 33

Where are the somatic efferent neurons?

Answer 33

in the ventral horn

Question 34

Where are the visceral efferent neurons?

Answer 34

in the intermediate substance

Question 35

What are the types of somatic efferent neurons?

Answer 35

alpha and gamma

Question 36

Define alpha motor neurons

Answer 36

innervate ordinary skeletal muscle fibers (motor units); neuron size is proportional to motor unit size

Question 37

Define gamma motor neurons

Answer 37

innervate intrafusal muscle fibers (within muscle spindles)

Question 38

Describe visceral efferent neurons

Answer 38

preganglionic sympathetic and parasympathetic neurons

Question 39

Projection Neurons

Answer 39

send axons into spinal white matter to travel to the brain (or to a distant part of the spinal cord)

Question 40

True or False: Projection neuron axons form tracts associated with descending spinal pathways and all share the same function

Answer 40

FALSE: ascending pathways' many different functions

Question 41

How are projection neurons categorizes?

Answer 41

according to the types of stimulation that ultimately excites them (thermal, somatic, visceral stimuli)

Question 42

Define Interneurons

Answer 42

have axons that remain within spinal gray matter; they are interposed between pineal input and spinal output

Question 43

What determines inherent reflex responses of the spinal cord?

Answer 43

interneurons --> by establishing local circuits, interneurons hardwire input to output =spinal reflexes

Question 44

What is a primary afferent neuron?

Answer 44

the fist neuron in a spinal reflex or ascending spinal pathway

Question 45

What type of cell bodies are found in primary afferent neurons?

Answer 45

unipolar cells bodies in spinal ganglia