Spinal Cord I: Overview

Question 1

Division of spinal segments

Answer 1

31
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal

Question 2

Division of Vertebrae

Answer 2

33
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 4 coccygeal

Question 3

Foramen Magnum

Answer 3

the space that the spinal cord passes through to connect to the brainstem

Question 4

Passing order of vertebrae & spinal segments

Answer 4

• first 7 cervical pass above respective vertebrae, 8th pass above first thoracic vertebra (below 7th)
• remaining nerves pass below vertebrae
• 4 coccygeal vertebrae fused; passes below first coccygeal vertebra
• sacral segments also fused

Question 5

Dermatomes

Answer 5

areas of skin whose sensory info project via certain spinal nerves

Question 6

Dermatomes and Segmental Organization

Answer 6

• spinal cord segments send and receive info on certain parts of the body
• cervical segments > arms and head
• thoracic segments > trunks
• lumbar, sacral, coccygeal segments > legs

Question 7

vertebral body

Answer 7

most ventral aspect of vertebrae

Question 8

spinous process

Answer 8

most dorsal aspect of the vertebrae

Question 9

vertebral foramen

Answer 9

space through which the spinal cord projects

Question 10

superior and inferior articular process

Answer 10

help connect vertebrae to one another via facet joint

Question 11

intervertebral foramen

Answer 11

space that spinal nerves pass through the vertebrae

Question 12

intervertebral disk and facet joint

Answer 12

cartilaginous joints that (1) allow for minor movements of the spine and vertebrae, (2) act as ligaments to hold the vertebrae together, (3) act as shock absorbers

Question 13

Longitudinal arterties

Answer 13

• anterior spinal artery provides blood supply to the anterior aspect of the spinal cord
• 2 posterior spinal arteries provide blood supply to the posterior aspect of the spinal cord

Question 14

segmental arteries

Answer 14

derived from vertebral arteries + others that can then branch off into radicular arteries that run along the dorsal and ventral nerve roots

Question 15

Meninges (3)

Answer 15

• dura mater > outermost and thickest layer
• arachnoid mater > middlemost layer; important for cerebrospinal fluid circulation and blood vessel supply
• pia mater > innermost layer

Question 16

Denticulate ligaments

Answer 16

extensions of the pia mater that anchor the spinal cord to the dura mater (meninge)
- located between spinal nerves

Question 17

Lumbar Cistern (definition)

Answer 17

region from conus medullaris to end of dural sac

Question 18

conus medullaris

Answer 18

tapering end of the spinal cord, located around the first lumbar vertebra

Question 19

filum terminale

Answer 19

extension of the pia mater that helps anchor the spinal cord to the vertebral canal
- filum terminale internum is pia mater, externum fuses with dura mater

Question 20

Lumbar cistern (important info)

Answer 20

• spinal cord is shorter than the vertebral column
• after spinal cord ends, dura, arachnoid, and pia mater continues
• subarachnoid space is filled with cerebrospinal fluid (ideal for performing lumbar punctures)
• spinal nerves extend down the canal before passing through their respective intervertebral foramen (creates cauda equina)

Question 21

dorsal roots

Answer 21

comprised of sensory axons that enter the spinal cord

Question 22

dorsal root ganglia

Answer 22

contains the cell bodies of sensory neurons
- lie approximately in the intervertebral foramen

Question 23

ventral root

Answer 23

comprised of motor axons that leave the spinal cord

Question 24

spinal nerve

Answer 24

contains both motor and sensory axons leaving and entering the spinal cord

Question 25

ventral ramus

Answer 25

contain motor and sensory axons innervating the ventral portion of the body (spinal segment)

Question 26

dorsal ramus

Answer 26

contain motor and sensory axons innervating dorsal portion of the body (spinal segment)

Question 27

sympathetic ganglia

Answer 27

located near the intervertebral foramen at each spinal segment - contain afferent and efferent nerve cell bodies responsible for the sympathetic nervous system (spinal segment)

Question 28

white mater

Answer 28

exterior portion of the spinal cord that contains mostly axons

Question 29

gray mater

Answer 29

interior portion of the spinal cord that contains mostly cell bodies

Question 30

dorsal horn

Answer 30

contains mainly interneuron cell bodies for sensory integration and pathways

Question 31

ventral horn

Answer 31

contains the cell bodies of motor neurons which drive muscle activity and interneurons

Question 32

Lissauer's tract

Answer 32

ascending and descending small fibers that generally terminate in the SG - fibers convey pain, temperature, and light tough

Question 33

substantia gelatinosa

Answer 33

collection of cells that receive direct input from the dorsal roots

Question 34

nucleus proprius

Answer 34

similar function to the SG but more ventral and medial in position

Question 35

Reasons for Spinal cord enlargements

Answer 35

- quantity of white mater decreases from rostral to caudal segments (axons projecting bw the brain and lower spinal segments must pass thru upper spinal segments first > tapering of white mater from cervical to coccygeal segments) - gray mater is largest in the cervical and lumbar segments ( neurons are needed for the motor and sensory control of limbs)

Question 36

cervical enlargement

Answer 36

responsible for upper limbs

Question 37

lumbar enlargement

Answer 37

responsible for lower limbs

Question 38

stretch reflex

Answer 38

- spinal reflex - activation of stretch receptors in a muscle activates motor neurons of the same muscle - monosynaptic reflex (sensory fiber synapses directly onto motor neuron it controls) - helps increase muscle tension to protect it from being torn

Question 39

reciprocal inhibition

Answer 39

- while some muscles are activated, their antagonists are inhibited - reciprocal pathway of stretch reflex is disynaptic (sensory axon synapses onto single interneuron which inhibits antagonistic motor neurons) - ensures antagonist muscles don't interfere with the driving muscles of reflex

Question 40

flexor reflex

Answer 40

- spinal reflex - activation of pain receptors activates motor neurons of flexor muscles - polysynaptic reflex (sensory fiber synapses onto many interneurons, which then synapse onto many motor neurons) - important for pain avoidance

Question 41

crossed reflex

Answer 41

- during flexor reflex, pain signals from one leg cross to the other leg to activate extensor muscles and anchor the leg - mediated by crossed interneurons - specific crossed reflex ensures that we maintain balance while flexor reflex occurs

Question 42

Autonomic nervous system

Answer 42

- sympathetic neurons located in sympathetic ganglia of the thoracic and lumbar spinal cord (responsible for flight or flight responses) - parasympathetic neurons located inside the brainstem and sacral spinal cord (responsible for rest and digest responses)

Question 43

locomotion

Answer 43

- central pattern generator > collection of interneurons in the spinal cord that are responsible for driving rhythm of locomotion and pattern of motor neuron activity - interneurons modulated by (1) visual system for object recognition and avoidance, (2) vestibular system for balance, (3) proprioceptive and sensory systems for limb positioning and placement ** brain & brainstem initiate locomotion, spinal cord maintains, different systems modulate