AP 2 2.2: The Spinal Cord

Question 1

spinal cord

Answer 1

The spinal cord is about 17 inches in length and is protected by the surrounding vertebral column. The spinal cord extends from the brainstem to the first lumbar vertebra where it officially terminates as the conus medullaris. The extension of the cord beyond L1 is a collection of nerve roots called the cauda equina, which runs to its end at the coccyx. The spinal cord and the extension of the cauda equina is how all electrical impulses travel between the brain and the rest of the body.

Question 2

conus medullaris

spinal cord

Answer 2

The spinal cord extends from the brainstem to the first lumbar vertebra where it officially terminates as the conus medullaris

Question 3

cauda equina

spinal cord

Answer 3

The extension of the cord beyond L1 is a collection of nerve roots called the cauda equina, which runs to its end at the coccyx . The spinal cord and the extension of the cauda equina is how all electrical impulses travel between the brain and the rest of the body.

Question 4

vertebral column

Answer 4

Like the brain, the spinal cord is protected by the bony vertebral column, meninges, and cerebrospinal fluid. The three meninges in the spinal cord are continuous with the meninges of the brain, as discussed earlier.

Question 5

spinal dura mater

Answer 5

In the spinal cord, a single layer sheath called the spinal dura mater is separated from the vertebral column by a cushioning fat-filled epidural space

Question 6

epidural space

Question 7

spinal tap

Answer 7

The cerebrospinal filled subarachnoid space inferior to the end of the spinal cord at L1 is the location chosen to perform a spinal tap, a is removal of fluid for diagnostic testing. This region is chosen because there is a less risk of damaging the spinal cord from the insertion of the long needle.

Question 7

filum terminale

Answer 7

The space between the middle arachnoid and inner pia mater meninges is filled with cerebrospinal fluid. An extension of pia mater called the filum terminale runs from the conus medullaris to the coccyx where it provides the inferior anchor for the spinal cord.

Question 8

surface of the spinal cord has two grooves:

Answer 8

The surface of the spinal cord has two grooves: the **anterior median fissure **and the shallower posterior median sulcus. The central canal is an opening that runs the length of the spinal cord and is filled with cerebrospinal fluid

Question 9

tract

Answer 9

In the central nervous system, a bundle of axons is called a tract. All the tracts cross over to the opposite side in the spinal cord. This crossing-over of information makes the left side of the brain control the right side of the body and the right side of the brain control the left side of the body.

Question 9

white matter

Answer 9

The outer white matter is composed of myelinated and unmyelinated nerve fibers organized into regions called columns. In the central nervous system, a bundle of axons is called a tract.

Question 10

ascending tracts

Answer 10

The white matter fibers of the spinal cord are mostly composed of ascending tracts that proceed up to the brain carrying sensory inputs and descending tracts that proceed down to (or within) the cord carrying motor outputs with a few commissural tracts across the cord.

Question 11

descending tracts

Answer 11

The white matter fibers of the spinal cord are mostly composed of ascending tracts that proceed up to the brain carrying sensory inputs and descending tracts that proceed down to (or within) the cord carrying motor outputs with a few commissural tracts across the cord.

Question 12

dorsal root

Answer 12

Recall the dorsal root of a spinal nerve carries incoming afferent (sensory) neurons

Question 13

dorsal root ganglion (DRG)

Answer 13

The dorsal root ganglion (DRG) contains the cell bodies of those afferent neurons.

Question 14

ventral root

Answer 14

The ventral root contains the axons of motor neurons. The dorsal and ventral roots on each side of the spinal cord come together to form a spinal nerve

Question 15

spinal nerve

Answer 15

The dorsal and ventral roots on each side of the spinal cord come together to form a spinal nerve

Question 16

gray matter

Answer 16

The interior gray matter of the cord is composed of a mixture of the cell bodies of neurons (Figure 2.21). The gray matter is organized into regions called horns. There are two posterior (dorsal) horns and two anterior (ventral) horns.

Question 17

anterior (ventral) horns

gray matter

Answer 17

The anterior (ventral) horns contain somatic motor neurons whose axons serve as efferent pathways to skeletal muscles by way of the ventral roots of the spinal cord

Question 18

posterior (dorsal) horns

gray matter

Answer 18

The posterior (dorsal) horns serve as one of the afferent pathways from receptors by way of the dorsal roots of the spinal cord.

Question 19

two lateral horns

Answer 19

The two lateral horns (Figure 2.21) of the gray matter are located primarily at the thoracic level of the spinal cord. The lateral horns contain autonomic sympathetic motor neurons whose axons serve as efferent pathways to visceral organs. The efferent pathways exit via the ventral roots of the spinal cord along with those of the somatic motor neurons.