Spinal Cord

Question 1

What is the conus medullaris?

Answer 1

Terminal point of the spinal cord @ ~L1-L2

Question 2

What are the meningeal coverings of the SC

Answer 2

Brown - dura mater

Green = arachnoid mater

Red = pia mater

Question 3

Describe the spaces in the SC

Answer 3

Red = epidural space (fat and venous plexus)

Yellow = subarachnoid space (CSF and spinal blood vessels)

Question 4

What are denticulate ligaments

Answer 4

Thickening of pia and glial elements that form ribbons along lateral surface of SC

Question 5

What is the filum terminalae

Answer 5

Extension of pia and supporting cells that connects the conus medullaris to the coccyx bone

Question 6

Label the following

Answer 6

Posterior (posterolateral sulcus) – where sensory info enters

Posterior median fissure

Anterolateral sulcus – where motor info exits

Anterior median fissure

Question 7

Differences between SC sections at cervical, thoracic and lumbar segments?

Answer 7

• Cervical and lumbar have the most grey matter because they innervate the limbs
• Cervical white matter > thoracic > lumbar because motor information from all spinal segments is carried at the most caudal sections

Question 8

Two sources of spinal cord blood supply

Answer 8

1. Vertebral basilar system
   * PICAs and vertebral arteries join to form the posterior spinal artery and anterior spinal artery
2. Segmental arteries

• Posterior brances of intercostal arteries give rise to segmental spinal arteries
• Segmental spinal arteries branch to form either (a) radicular arteries that supply roots at each level of SC or (b) segmental medullary arteries which supply either the PSA or the ASA
• Segmental p

Question 9

Where do segmental spinal arteries originate

Answer 9

Anterior intercostal arteries

Question 10

What originates from segmental spinal arteries

Answer 10

1) Radicular arteries (supplies roots)
2) Segmental medullary arteries (supply the ASA or the PSA)

Question 11

Describe the blood supply from the ASA and PSA to the SC

Answer 11

• The ASA supplies the anterior 2 thirds of the SC, including the base of the posterior horns
• The PSAs supply the posterior 1/3 of the SC

Question 12

What is the composition of a spinal nerve

Answer 12

1) Sensory root (afferent) to posterolateral sulcus
2) Motor root (efferent) exiting from anterolateral sulcus

Question 13

Number of cervical vertebrae and nerves

Answer 13

CI - CVII (7 vertebrae)

C1-C8 (8 nerves)

Question 14

Number of thoracic nerves and vertebrae

Answer 14

TI - TXII (12 vertebrae)

T1-T12 (12 nerves)

Question 15

Number of lumbar nerves and vertebrae

Answer 15

LI-LV (5 vertebrae)

L1-L5 (5 nerves)

Question 16

Number of Sacral nerves and vertebrae

Answer 16

5 vertebrae fused as sacrum

5 nerves (S1-S5)

Question 17

Number of Coccygeal nerves and vertebrae

Answer 17

1-4 coccygeal vertebrae (fused as coccyx)

1 nerve (C0)

Question 18

Where are the sympathetic nervous system efferents in the SC?

Answer 18

T1-L2 segments; cell bodies are in LATERAL HORNS in thoracic cross-sections

Question 19

Where are the parasympathetic visceral efferents in the SC?

Answer 19

S2-S4

Question 20

Where are the SC enlargements?

Answer 20

1. Cervical: C4/5 - T1
2. Lumbosaral: L2-S3

Question 21

What is visible in a SC cross-section from T1-L2/3?

Answer 21

Lateral horn (intermediolateral cell column)

-contain preganglionic sympathetic cell bodies

Question 22

What is visible in a SC cross-section at S2-S4

Answer 22

Lateral horn

Preganglioic parasympathetic cell bodies

Question 23

What type of information is carried by General Somatic Afferents (GSAs)

Answer 23

• Discriminative Touch
• Proprioception
• Somatic pain and temperature

Question 24

What type of information is carried by General Visceral Afferents?

Answer 24

• Sensation from the viscera

Question 25

What type of information is carried by General Somatic Efferents?

Answer 25

* motor to skeletal muscles

Question 26

What type of info is carried by General Visceral efferents

Answer 26

Motor to viscera * Originates in lateral horns, exits via the anterolateral sulcus, travels through motor roots to spinal nerve

Question 27

Interomediolateral nucleus

Answer 27

Cell bodies of visceral motor efferents found only in T1-L2 (SYMPATHETIC) and S2-S4 (parasympathetic efferents)

Question 29

Where are parasympathetic motor (efferent) nerves found?

Answer 29

1. Cranial nerves 9-12 2. S2-S4 of spinal cord

Question 30

Which laminae are present in the dorsal (posterior) horns?

Answer 30

Rexed laminae I - VI: I = Posterior (dorsal) root fibers mediating pain, temperature, and touch; posteromarglnal nucleus II: Subatantla gelatinosa neurons mediating pain transmission III and IV: Proper sensory nucleus receiving Inputs from substantla gelatinosa and contributing to anterolateral system V: Neurons receiving afferent Input from vlscera, skin, and muscle VI: (only in cervical): afferents from muscle spindles

Question 31

Which nuclei are present in dorsal horns?

Answer 31

1) substantia gelatinosa 2) nucleus propius 3) dorsal nucleus of clarke

Question 32

Function of Lissauer tract (posterolateral fasciculus)

Answer 32

Sensory fibers carrying pain and temperature will ascend or descend several spinal cord levels here before synapsing In the dorasal horn.

Question 33

Path of sensory fibres containing discriminative touch and proprioceptive info

Answer 33

1) Enter through posterior horn (posterolateral sulcus) 2) Ascend in ipsilateral (same side) dorsal/posterior columns (e.g., fasciculus gracilis, fasciculus cuneatus)

Question 34

Path of sensory fibres containing PAIN information

Answer 34

* Enter dorsal horn * travel up/down 1-2 segments in Lissauer tract * Modulation in substantia gelatinosa/Rexed laminae 2 * synapse in nucleus proprius * Decussate via anterior commissure and travel in the **contralateral spinothalamic tract**

Question 35

Path of alpha motor neurons

Answer 35

Exit anterior (ventral) horn and travel to muscles

Question 36

Path of Ia, Ib, and II fibres carrying proprioceptive information (destination = cerebellum)

Answer 36

* Enter via dorsal horn * Synapse at Dorsal nucleus of **Clark if L3-C8** * Travel in ipsilateral spinocerebellar column * If below L3, travel in fasciculus gracilis then synapse in **Clarke Nucleus** * If above C8, travel in fasciculus cuneatus and synapse in the accessory cuneate nucleus * Then travel in cuneocerebellar track to cerebellum

Question 37

What travels in the anterior corticospinal tract

Answer 37

* UMNs concerned with **proximal trunk musculature** (ipsilateral) * Cross over in appropriate level of spinal cord

Question 38

What travels in lateral corticospinal tract

Answer 38

UMNs to ipsilateral (same side) anterior horn Mostly for limb musculature Somatotopic (cervical musculature is most medial, sacral most lateral)