Spinal Cord

Question 1

Spinal nerves contain both sensory and motor fibers except

Answer 1

C1- strictly motor and coccygeal

Question 2

Two plexus/enlargements

Answer 2

Cervical and lumbarsacral. No thoracic plexus.

Question 3

External spinal cord features

Answer 3

Spinal cord exits foramen magnum. Two enlargements: cervical and lumbar sacral.

As the spinal cord comes to an end, it merges to form the conus medularris in the upper lumbar region.
Cauda equine branch off the conus medularris and travel to the coccygeal. The fibers form a single strand called the film terminale and travel through the vertebral canal.

Question 4

Origin of the fibrum terminale is made completely of

Answer 4

Pia. The rest is composed of dura, arachanoid, and pia.

Question 5

Is the dura matter loosely or closely attached to the wall of the vertebral canal? What about the brain?

Answer 5

Dura loosely connected to vertebral canal. Allows for movement.
Tightly attached to brain.

Question 6

Where does dura matter terminate

Answer 6

S2.

Question 7

How can you determine the anterior side of the spinal cord vs the posterior side of the spinal cord.

Answer 7

Anterior side has median fissure

Posterior side has medial sulus (not as deep)

Question 8

The spinal cord is supplied mainly by which two main arteries

Answer 8

Vertebral and descending aorta via the posterior intercostals.

Question 9

What are the major branches off the posterior intercostals that take blood to the spinal cord from the vertebral and descending aorta?

What are the minor branches that do this?

Answer 9

Major: Segmental arteries
Minor: Longitudinal arteries. One anterior, two posterior.

Segmental arteries feed into the longitudinal arteries. Lots of anastomosing.

Question 10

Plexuses drain into what to reach the superior vena cava

Answer 10

Drain into the anterior or posterior spinal vein. These two drain into the radicular veins, which drain into vertebral veins, which drains into the superior vena cava.

Question 11

Blood below the heart makes its way back by the

What about blood above the heart?

Answer 11

below- Azygous and inferior vena cava

Above- superior vena cava

Question 12

Funiculi

Answer 12

Nerve tracts

Question 13

Functions of large spinal neurons

Answer 13

Motor supply to skeletal muscles, motor supply to muscle spindles

Question 14

Interneurons of the spinal cord are located where

Answer 14

Located in the grey matter horn. Reflex arc, spinal reflexes. Connects sensory to motor neurons without sending an impulse to the brain. Quick and short.
Both excitatory and inhibitory.

Question 15

Where is the substantial gelatinosa and what is its role in the afferent PNS

Answer 15

Apex of the posterior horn. Afferent PNS fibers transmit touch, pain, and temperature to the CNS.

Question 16

Where is the nucleus proprius and what is its role

Answer 16

Area of large neurons in the posterior horn. Deals with proprioception, two point discrimination and vibration.

Question 17

3 somatosensory cell columns

Answer 17

1. Substantia gelatinosa
2. Nucleus proprius
3. Nucleus dorsalis

Question 18

If name of a tract starts with “spino,” then its ____ and if it ends with “-spinal,” then its ___

Answer 18

Sensory

Motor (think corticospinal is a motor pathway)

Question 19

Another name for anterolateral pathway

Answer 19

Spinothalamic

Question 20

Another name for medial lemniscal pathway

Answer 20

Posterior column

Question 21

3 major afferent tracts

Answer 21

2 are somatic:
Medial lemniscal/dorsal column
Anterolateral/Spinothalamic

1 proprioceptive:
Spinocerebellar

Question 22

Sensory tract organization: Sensory modality

Answer 22

Different sensations carried in different tracts. Ex: fine touch in one tract, pain in another.

Question 23

Sensory tract organization: somatotopic

Answer 23

Ascending tracts are arranged mapped according to site of origin of the sensation.

Question 24

Medial-lateral rule of sensory tract organization

Answer 24

Sensory neurons that enter at a lower level are more medially located within the cord.

Sensory neurons that enter at a higher level of the cord are located more laterally within the cord.

Info from the trunk between the two.

Question 25

Medial lemiscal/dorsal column sensations

Anterolateral/spinothalmic sensations

Answer 25

1. Medial lemiscus is touch, pressure, and vibration

2. Anterolateral is pain, temp, and crude touch.

Question 26

Medial lemiscal pathway synapses in the gracilis and cuneatus of the medulla. What is the difference with the information each receives?

Answer 26

Both still receive info about pressure, vibration, and touch.

Difference:
The Gracilis carries info from the lower extremities such as the hips and legs.
Cuneatus carries info from the arms and trunk.

The fibers will travel up further in the medulla and then decussate.

Question 27

In the medulla, which is more inner. The gracile tubercle or the cuneate tubercle?

Answer 27

The gracile is more inner.

Both are in the lowest segment of the medulla.

Question 28

Describe the spinothalamic/anterolateral pathway

Answer 28

Axons synapse in the posterior gray horn and then cross at all segment levels. The axons, after crossing, then ascend either in the anterior funiculus tract (coarse touch) or lateral funiculus tract (pain and temp)

Question 29

After the spinothalamic/anterolateral fibers decussate in the spinal cord, they either ascend in the anterior funiculus tract or the lateral funiculus tract. Which fibers go where

Answer 29

The fibers carrying coarse touch info goes to the anterior funiculus

The fibers carrying pain and temp info goes to the lateral funiculus tract.

Question 30

Anterolateral/spinothalmic pathway.

Lesion of fibers on the left side of the body will affect ___

Answer 30

The right side of the body, starting several segments BELOW the lesion because of oblique path of fibers crossing at the commissure.

Question 31

There are two descending corticospinal tracts. Which one is dominant

Answer 31

The lateral tract, which carries pain and temp, is dominant. There are more tracts.

80-90% of the lateral fibers decussate at the medulla.
10-20% stay ipsilateral

The other tract is the anterior (uncrossed) tract

Question 32

The lateral corticospinal tract sends info to which areas of the body

Answer 32

upper and lower extremities

Question 33

The anterior corticospinal tract sends info to which areas of the body

Answer 33

The trunk

Question 34

Corticospinal tract originates mainly in the

Answer 34

primary motor cortex.

Question 35

Vestibulospinal tract main function

Answer 35

Involved with the VOR. Retinal image stabilization. Critical pathway for this.