Week 5 Lecture 11: Spinal cord and spinal nerves

Question 1

Is the somatic nervous system voluntary or involuntary?

Answer 1

voluntary

Question 2

Is the autonomic nervous system voluntary or involuntary?

Answer 2

involuntary

Question 3

What is white matter made of?

Answer 3

axons with glial sheath (myelin)

Question 4

What is the conus medullaris?

Answer 4

the point of termination of the spinal cord

Question 5

Where does the brainstem become continous with the spinal cord?

Answer 5

foramen magnum

Question 6

What are cauda equina?

Answer 6

after the spinal cord ends at conus medullaris, the spinal nerves continue to emerge at lower levels as longer nerves leave below their intravertebral foramina

Question 7

Which parts of the spinal cord are thinner, and which are thicker?

Answer 7

• cervical cord is thicker
• thoracic cord is thinner
• lumbar cord is thicker

Question 8

What are filum terminale?

Answer 8

• extends from tip of conus medullaris all the way to the coccyx and provides an inferior attachment to the spinal cord
• secures it into the coccyx to prevent excessive movement of the cord

Question 9

Which meningeal layers are the spinal cord covered with?

Answer 9

all of them - dura, arachnoid, pia

Question 10

What is the cauda equina bathed in?

Answer 10

CSF as dural sac extends lower than the terminaion of the spinal cord so it is continous with the cauda equina and the inside of the dural sac is filled with CSF

Question 11

What is the lumbar cistern?

Answer 11

a region filled with CSF between conus medullaris and filum terminale

Question 12

How many spinal nerve segments (and therefore how many pairs of spinal nerves) are there?

Answer 12

31

Question 13

What is a spinal nerve segment?

Answer 13

each gives rise to 1 pair of segmental spinal nerves

Question 14

Where in the spinal cord does the dural sac extend to?

Answer 14

S1 or S2

Question 15

Why is the cervical region of the spinal cord thicker?

Answer 15

because of all the motor neuronal cell bodies that are going to innervate our upper limbs including all the nerves that go onto form the brachial plexus

Question 16

Why do we see lumbosacral enlargement in the lumbar region?

Answer 16

because of the motor neurones that emerge from the spinal cord to innervate our lower limbs, forming the lumbosacral plexus

Question 17

Why are there 8 cervical spinal nerves but only 7 cervical vertebrae?

Answer 17

• C1 spinal nerve leaves above C1 vertebrae
• C2 spinal nerve leaves above C2 vertebrae
• C8 spinal nerve leaves above the T1 vertebrae
• at this point there is a transition where the spinal nerves emerge below their corresponding vertebrae
• e.g T1 spinal nerve emerges below T1 vertebrae

Question 18

How many pairs of spinal nerves are there in the C-spine?

Answer 18

8

Question 19

How many pairs of spinal nerves are there in the T-spine?

Answer 19

12

Question 20

How many pairs of spinal nerves are there in the lumbar spine?

Answer 20

5

Question 21

How many pairs of spinal nerves are there in the sacral spine?

Answer 21

5

Question 22

How do spinal nerves C1-7 leave the VC with respect to their corresponding vertebrae?

Answer 22

superior to their corresponding vertebrae e.g CII from above C2

Question 23

Where does the C8 spinal nerve leave the column?

Answer 23

above T1

Question 24

How do spinal nerves T1-C0 leave the VC with respect to their corresponding vertebrae?

Answer 24

leave from below their corresponding vertebrae

Question 25

What are denticulate ligaments?

Answer 25

lateral extensions of the pia that secure the spinal cord on each side to prevent excessive movement they are interspersed within spinal nerve roots

Question 26

What is the epineurium?

Answer 26

- as each spinal nerve leaves the vertebral canal it takes the meningeal coverings with - these form the epineurium - a protective sheath of connective tissue for each spinal nerve

Question 27

What is the difference between spinal dura and cranial dura?

Answer 27

- cranial dura is made of the meningeal layer and the periosteal layer - only the meningeal layer continues through the foramen magnum - so the dura around the spinal cord is only the meningeal layer

Question 28

What is between the vertebrae and the dura mater?

Answer 28

real epidural space filled with fat

Question 29

Why does the spinal cord end before the vertebral column ends?

Answer 29

at birth: vertebral column grows faster than spinal cord, so the spinal cord regresses and grows upward

Question 30

At birth, what vertebral level does the spinal cord end at?

Answer 30

L3

Question 31

What is the relationship between the spinal cord and the vertebrae in a 2-3 month foetus?

Answer 31

spinal cord extends all the way along the vertebrae

Question 32

What is the clinical significance of the cauda equina?

Answer 32

enables us to perform procedures such as lumbar puncture

Question 33

Where do we insert the needle when doing a lumbar puncture?

Answer 33

anywhere below L3

Question 34

How does a lumbar puncture allow us to collect CSF?

Answer 34

Nerve roots of the cauda equina move out of the way when a needle is inserted

Question 35

Why can an LP not be performed if a patient has increased intracranial pressure?

Answer 35

CSF would escape as a jet because a pressure differential is created so the brain could herniate

Question 36

Where is the needle inserted through in an LP?

Answer 36

Ligamentum flavum

Question 37

What are the reasons to take CSF?

Answer 37

- shouldn't be blood in CSF but if there is could indicate subarachnoid haemorrhage - can analyse cell composition in CSF for meningitis - can inject specific medications and drugs

Question 38

Where would you inject anaesthesia?

Answer 38

- Into the epidural space (not as deep as LP) but you still puncture the ligamentum flavum - anything downwards from the point of injection will be anaesthetised

Question 39

How are epidurals used during childbirth?

Answer 39

they are injected into the sacral region to numb the nerves around the perineum

Question 40

Where is the anterior spinal artery found and what does it supply?

Answer 40

- along the anterior median fissure of the spinal cord | - descends down to supply the anterior aspect of the spinal cord

Question 41

Which artery is the anterior spinal artery and posterior spinal artery reinforced by?

Answer 41

segmental spinal artery

Question 42

As the segmental spinal artery approaches the cord laterally, which artery branches off?

Answer 42

medullary artery, which reinforces the ASA

Question 43

Which arteries does the medullary artery give rise too and what do these supply?

Answer 43

- anterior and posterior radicular arteries | - supply the spinal nerve rootlets

Question 44

What is the difference between the arrangement of white and grey matter in the spinal cord and in the brain?

Answer 44

in the brain: grey matter generally resides in the outside with white matter underlying in the cord: grey matter confined to inside of the cord with white matter outside

Question 45

Give 3 features of grey matter inside the spinal cord

Answer 45

- dorsal horn of grey matter - lateral grey horn - ventral grey horn

Question 46

In which sections does the lateral grey horn of the spinal cord exist?

Answer 46

only between T1-L2 and S2-S4

Question 47

What does the ventral grey horn contain?

Answer 47

contains somatic neurones that innervate our muscles

Question 48

Give 4 features of white matter that is on the outside of the spinal cord

Answer 48

- dorsal white column - lateral white column - ventral white column - ventral white commisure

Question 49

What is the function of the ventral white commisure in the spinal cord?

Answer 49

allows communication between the right and left sides of the cord by crossing fibres

Question 50

What is the PNS?

Answer 50

All connections outside the brain and spinal cord

Question 51

What do sensory (afferent) fibres do?

Answer 51

send info to the CNS

Question 52

what do motor (efferent) fibres do?

Answer 52

send info away from the CNS

Question 53

How is the spinal cord connected to the PNS?

Answer 53

Via spinal nerve rootlets

Question 54

Where do ventral rootlets or dorsal rootlets leave the spinal cord?

Answer 54

ventral spinal nerve rootlets - leave the anterior lateral sulcus dorsal spinal nerve rootlets - leave the posterior lateral sulcus

Question 55

Explain a simple reflex arc: 1. touch hot object ...

Answer 55

2. sensory neurones travel towards the CNS using the spinal nerve and dorsal aspect of the nerve, with their axons in the dorsal root ganglion, to enter the dorsal horn of the spinal cord 3. in the dorsal horn, fibres synapse with an interneuron 4. interneuron relays the information from the afferent fibres to the efferent fibres 5. efferent neurone leaves the ventral horn and uses the ventral root of the spinal nerve to go to the periphery 6. muscle contracts to withdraw finger away from painful stimulus

Question 56

What happens to the amount of white matter as we ascend the cord?

Answer 56

it increases - so the cervical cord has the most white matter

Question 57

Why is the ventral horn enlarged in the cervical and lumbosacral regions?

Answer 57

- this is where motor fibres to limbs arise - called cervical and lumbosacral enlargements - because there is more cell bodies of neurones in these regions to innervate the limbs

Question 58

What is the difference in the column above and below T6?

Answer 58

Above T6 - there are two dorsal columns on either side of midline: gracile fascicle medially and cuneate fascicle laterally Below T6 - just gracile fascicle

Question 59

How is grey matter organised?

Answer 59

- divided into regions (Rexed's Laminae) | - based on the cellular composition at these levels and relates with function

Question 60

What is proprioception?

Answer 60

joint position sense i.e where our limbs are in space | e.g if your eyes are closed and you raise your arm above your head and you know where it is

Question 61

What are dorsal columns responsible for?

Answer 61

fine touch vibration pressure proprioception

Question 62

What is the lateral corticospinal tract responsible for?

Answer 62

voluntary control of our muscles

Question 63

What is the ventral corticospinal tract responsible for?

Answer 63

voluntary movement

Question 64

What is the spinothalamic tract responsible for?

Answer 64

crude touch temperature pain