Spinal Cord & Spinal Nerves

Question 1

What are the following subdivisions of the nervous system?

Answer 1

Question 2

What is the difference between grey and white matter?

Answer 2

Grey matter:

• collection of nerve cell bodies

White matter:

• axons with glial sheath (myelin)
• myelin is a fatty substance that appears white

Question 3

Where is grey matter located within the CNS and PNS?

Answer 3

CNS:

• in the cortex - the outer layer of the hemispheres
• in the nuclei deep in the cortex

PNS:

• within the ganglia

Question 4

What occurs within the gray matter?

Answer 4

Synapses occur within the gray matter

Question 5

What is the difference between white matter in the CNS and PNS?

Answer 5

CNS:

• it is located in a pathway
• e.g. Tracts, fascicles, bundles

PNS:

• peripheral nerves

Question 6

What is the purpose of the vertebral column?

Answer 6

It contains and protects the spinal cord and beginning of the spinal nerves

Question 7

What are the different types of vertebrae within the vertebral column?

Answer 7

• 7 cervical
• 12 thoracic
• 5 lumbar
• sacrum (5 fused)
• coccyx (3-4 fused)

Question 8

What is significant about the spinal cord with respect to the vertebral column?

Answer 8

The spinal cord narrows at the end

It ends before the vertebral column ends

Question 9

What are the roles of the spinal cord?

Answer 9

• Part of the CNS
• Reflex centre
• Conduction pathway between the brain and the body

Question 10

Where does the spinal cord extend from and to?

Answer 10

It extends from the foramen magnum of the occipital bone

it is continuous with the medulla oblongata

it runs to the vertebral levels LI - LII, where it terminates as the conus medullaris

Question 11

What happens when the spinal cord terminates as the conus medullaris?

Answer 11

Single nerves leave from the region of the conus medullaris as the cauda equina

this gives rise to spinal nerves (PNS)

Question 12

Label the components of the spinal cord

Answer 12

Question 13

What is the filum terminale?

Answer 13

A small extension of pia mater that attaches the spinal cord to the coccyx

this gives stability

Question 16

What are the roles of the cervical and lumbosacral enlargements?

Answer 16

They are thicker, larger regions of the spinal cord

they give rise to nerves that innervate the upper and lower limbs

Question 17

In order to see the spinal cord, which layer must be opened?

Answer 17

The dural sac

Question 18

What is the composition of the spinal cord like from top to bottom?

Answer 18

• 8 cervical segments (C1 - C8)
• 12 thoracic segments (T1 - T12)
• 5 lumbar segments (S1 - S5)
• 1 coccygeal segment (Co1)
• conus medullaris
• cauda equina
• filum terminale

Question 19

What is meant by a ‘segment’ of the spinal cord?

How many spinal nerve segments are they and what do they form?

Answer 19

A segment refers to a pair of spinal nerves

there are 31 spinal nerve segments, each giving rise to a pair of segmental spinal nerves

31 pairs of spinal nerves form the PNS

Question 20

Which features of the spinal cord are shown here?

Answer 20

Lumbar cistern:

• expansion of subarachnoid space that surrounds the cauda equina

Dural sac:

• extends to the level of S1

Filum terminale:

• this is an extension of the pia
• it extends to attach to the coccyx

Question 21

Where is the conus medullaris located?

Answer 21

This is the termination of the spinal cord

It is situated between L1 and L2

Question 22

What nerves are found within the cervical enlargement?

Answer 22

The brachial plexus (C1 - C8)

this supplies the upper limb

Question 23

What nerves are found within the lumbosacral enlargement?

Answer 23

The lumbosacral plexus (L1 - S4)

this supplies the lower limb

Question 24

What nerves are found within the cauda equina?

Answer 24

Dorsal and ventral roots of lower lumbar, sacral and coccygeal spinal nerves

Question 25

What is meant by the spinal nerve transition zone?

Answer 25

At vertebral levels C1 - C7, the spinal nerve leaves **_above_** the corresponding vertebra C8 leaves **_below_** the corresponding vertebra all nerves below this level leave **_below_** their respective vertebra

Question 26

What is the difference in the way the cervical spinal nerves leave the spinal cord?

Answer 26

**Spinal nerves C1 - C7:** * leave the vertebral column **_superior_** to their corresponding vertebra * C1 from above CI, C2 from above CII.... **C8 spinal nerve:** * leaves from above TI * there are only 7 cervical vertebrae

Question 27

How do spinal nerves T1 - C0 leave the spinal cord?

Answer 27

They leave from **_below_** their corresponding vertebra ALL spinal nerves leave the spinal cord via the **intervertebral foramina**

Question 28

Label the meninges and features of the spinal cord

Answer 28

Question 29

What are the denticulate ligaments?

Answer 29

Extensions of pia that attach the spinal cord to the outer meningeal layers this secures the spinal cord laterally

Question 30

What are the subdural and subarachnoid spaces of the spinal cord?

Answer 30

**Subdural space:** * this is a potential space between the dura and arachnoid mater **Subarachnoid space:** * this is a real space between the pia and arachnoid * it is filled with CSF

Question 31

What happens to the spinal nerves as they leave the vertebral canal?

Answer 31

As each spinal nerve leaves the vertebral canal it takes with it the meningeal coverings these go on to form the **epineurium** this is a protective outer sheath of connective tissue

Question 32

What are the main differences between the spinal and cranial dura?

Answer 32

* Cranial dura has an inner meningeal layer and outer periosteal layer * Spinal dura only has a **meningeal layer** * the epidural space in the cranium is a potential space * it can become a pathological space if there is bleeding * the epidural space in the spinal cord is a real space * it is filled with fat

Question 33

Label the differences of the spinal and cranial dura

Answer 33

Question 34

How does the spinal cord change in length during development? Why?

Answer 34

During development, the dural sac grows along the vertebrae but not the spinal cord the bones of the vertebral column grow faster than the spinal cord, leading to regression of the spinal cord

Question 36

What is the consequence of changes in spinal cord length on spinal nerve roots?

Answer 36

The spinal nerve roots show disparity between their segmental attachment to the cord and the corresponding vertebral levels within the cervical region, the nerves close to the vertebrae leave close to their point of origin nearer the end of the spinal cord, the nerves travel down to leave below their vertebra these form the cauda equina

Question 37

Label the diagram and the position of the needles for performing certain procedures

Answer 37

Question 38

What is the role of the ligamentum flavum?

Answer 38

It connects the lamina of adjacent vertebrae the needle for lumbar puncture passes between the vertebrae through the ligamentum flavum to reach the dural sac and obtain CSF

Question 39

Where should the needle be inserted for lumbar puncture? How should the patient be positioned?

Answer 39

The needle is inserted between **LIV and LV** the needle is inserted into the **lumbar cistern** due to the cauda equina, the nerve roots move out of the way when the needle is inserted the patient should be hunched over or in the foetal position to stretch the space between the vertebrae

Question 40

Where should the needle be inserted for epidural anaesthesia?

Answer 40

Within the lumbar region or sacral hiatus the needle is only inserted into the epidural space

Question 41

Label the sulci of the spinal cord What structures pass through them?

Answer 41

**Blood vessels** travel in the posterior median sulcus and anterior median fissure **rootlets** that form spinal nerves travel in the posterior lateral sulcus and anterior lateral sulcus

Question 42

Label the arterial supply to the spinal cord Where do the vessels originate from?

Answer 42

The anterior and posterior spinal arteries are branches of the **vertebral artery** the segmental spinal artery arises from a branch of the aorta (depending on the location within the spinal cord) The segmental spinal artery gives rise to the **medullary artery** the medullaris artery give rise to the **anterior & posterior radicular arteries** which supply the roots of nerves

Question 43

What are the different segmental spinal arteries depending on the location within the spinal cord?

Answer 43

* Vertebral artery * deep cervical artery * posterior intercostal artery * lumbar arteries * lateral sacral artery

Question 44

What is the main difference in the grey and white matter in the CNS?

Answer 44

**Brain:** * grey matter is found in the cortex and nuclei - the **outside** * white matter is found on the **inside** **Spinal cord:** * grey matter is found on the **inside** * white matter is found on the **outside** of the spinal cord

Question 45

How is grey matter organised within the spinal cord?

Answer 45

It is organised into **horns** 1. Dorsal horn 2. Ventral horn 3. Lateral horn - only present T1-L2 and S2-S4

Question 46

What is significant about the lateral horn?

Answer 46

It only exists between T1 - L2 and S2 - S4

Question 47

How is white matter organised within the spinal cord?

Answer 47

It is organised into **columns** 1. Dorsal white column 2. Ventral white column 3. Lateral white column 4. Ventral white commisure

Question 48

What is the ventral white commisure?

Answer 48

An area of white matter that connects the left and right sides of the spinal cord

Question 49

What horns/columns are represented in this transverse section of the spinal cord?

Answer 49

Question 50

label the transverse section of the spinal cord

Answer 50

Question 51

What are the 2 types of fibres within the peripheral nervous system?

Answer 51

The PNS is all the connections outside of the brain and spinal cord **sensory (afferent) fibres:** * these send information from the periphery **_towards_** the CNS **motor (efferent) fibres:** * these send information **_away from_** the CNS and towards the periphery

Question 52

How is the spinal cord connected with the PNS?

Answer 52

Via nerve rootlets each spinal level gives rise to 1 pair of spinal nerves these spinal nerves are part of the PNS

Question 53

Label the components of a spinal nerve

Answer 53

Question 54

Where do the dorsal and ventral rootlets of the spinal cord leave from?

Answer 54

**dorsal rootlets:** * leave from posterolateral sulcus **ventral rootlets:** * leave from anterolateral sulcus

Question 56

Label the transverse section of the spinal cord and spinal nerve

Answer 56

Somatic and visceral sensory fibres travel through the dorsal root ganglion and dorsal root somatic motor fibres travel through the ventral root visceral motor fibres travels through the ventral horn and into the spinal nerve

Question 57

What is the purpose of the reflex arc?

Answer 57

When there is no time to pass through the normal pathway a sensory neurone connects directly to a motor neurone for a rapid response via an interneurone

Question 58

How does the amount of white matter change as you go through the spinal cord?

Answer 58

The amount of white matter increases as you ascend the cord i.e. there is more white matter in the cervical cord than the lumbar cord

Question 60

What is significant about the size of the ventral grey horn in certain locations of the spinal cord?

Answer 60

The ventral grey horn is enlarged where motor fibres to limbs arise these are the cervical and lumbosacral enlargements they contain cell bodies from motor neurones innervating the upper and lower limbs

Question 61

What are the dorsal columns of white matter present on either side of the midline in the spinal cord? How do these change as you ascend the spinal cord?

Answer 61

**Gracile fascicle:** * This is located medially * it runs the entire length of the spinal cord * it carries sensory information from the **lower limb** **Cuneate fascicle:** * this is located laterally * it is only present **_above segment T6_** * it carries sensory information from the **upper limb**

Question 62

Label the sections of the spinal cord

Answer 62

Question 63

What are the functions of the cuneate and gracile tubercles?

Answer 63

Tubercles contain cell bodies The gracile and cuneate fascicles terminate as the gracile and cuneate tubercle these are part of the dorsal column pathway the **cuneate tubercle** carries **sensory information from the upper limb** the **gracile tubercle** carries **sensory information from the lower limb**

Question 64

Is this section from above or below T6? How can you tell?

Answer 64

**Above T6** this is a thoracic vertebral section as the **lateral grey horn** is present here there is also a **small ventral grey horn**

Question 65

How is spinal grey matter divided?

Answer 65

The grey matter is divided into regions called **Rexed's laminae** these are sites of sensory or motor nuclei