17/18. Spinal Cord & Nerves

Question 1

Overview of spinal cord

Answer 1

Part of CNS, communicates with body by spinal (peripheral) nerves
Link between brain and body through white matter tracks
Major center for reflexes in gray matter
Divided into segments based on associated vertebrae
Ends at the level of L1

Question 2

Spinal cord protected by

Answer 2

Vertebral column (occupies vertebral canal)
Meninges (dura mater, arachnoid mater, pia mater)
Cerebrospinal fluid that flows in subarachnoid space

Question 3

General features of spinal cord

Answer 3

Spinal nerves leave spinal cord through intervertebral foramina to travel to targets
Spinal cord does not extend the full length of vertebral canal
Cauda equina present
Filum terminale also present

Question 4

Conus medullaris

Answer 4

Cone-shaped end of spinal cord

Question 5

Cauda equina

Answer 5

Continuation of nerve roots in vertebral canal

Question 6

Fillum terminale

Answer 6

Continuation of pia mater beyond conus medullaris
Anchors to coccyx and tethers spinal cord

Question 7

Development of spinal cord

Answer 7

After 3 months of development, spinal cord grows more slowly than vertebral column
At birth, ends at L3
Adulthood, ends a L1

Question 8

Lumbar puncture

Answer 8

Clinical correlate performed below L1 where spinal cord does not extend

Question 9

Regions of spinal cord

Answer 9

Spinal cord segments are sections of spinal cord with a pair of spinal nerves attached
Segments: cervical (8), thoracic (12), lumbar (5), sacral (5)
Cervical and lumbar regions are enlarged for innervation for upper and lower extremities, respectively

Question 10

Naming for spinal cord segments

Answer 10

Named for spinal nerve that emerges
Cervical - nerve # corresponds with vertebra below
Thoracic and lower - nerve # corresponds with vertebra above

Question 11

Features of cross-section of spinal cord

Answer 11

Gray matter, white matter, and central canal

Question 12

Characteristics of gray matter of spinal cord

Answer 12

Mostly cell bodies
Interior, looks like butterfly
Posterior wings = dorsal horn
Anterior wings = ventral horn

Question 13

Characteristics of white matter of spinal cord

Answer 13

Mostly myelinated axons
Located on outside
Communication between different parts of cord and brain

Question 14

Characteristics of central canal in spinal cord

Answer 14

Contains CSF

Question 15

Neurons of spinal cord

Answer 15

In the back, out the front (dorsal root for sensory input and ventral root for motor output)
Neurons include sensory neurons, interneurons, and motor neurons
Spinal nerves join ventral and dorsal roots and contain both sensory and motor neurons

Question 16

Characteristics of sensory neurons of spinal cord

Answer 16

Unipolar
Dorsal root ganglion (DRG) is a cluster of cell bodies
Attaches at dorsal root

Question 17

Characteristics of interneurons of spinal cord

Answer 17

Multipolar
Cell bodies in dorsal horn

Question 18

Characteristics of motor neurons of spinal cord

Answer 18

Multipolar
Cell bodies in ventral horn

Question 19

Characteristics of spinal nerves (extremity vs axial)

Answer 19

Spinal nerves connect spinal cord to targets of the body
Named and numbered for the vertebral region they emerge (8 cervical spinal nerves but 7 cervical vertebrae)
Nerves to the extremities form nerve plexuses
Nerves to thorax and abdomen follow simple segmented pattern

Question 20

Spinal nerve components

Answer 20

Carries both motor and sensory neurons
Sensory neurons enter spinal cord through dorsal root to dorsal horn (cell bodies in DRG)
Motor neurons leave spinal cord through ventral root to join spinal nerve (cell bodies in ventral horn)
Dorsal rami supply deep back and neck
Ventral rami supply rest of body wall and extremities

Question 21

Motor and sensory functions of dorsal rami

Answer 21

Motor - muscles of deep back and neck
Sensory - skin over vertebral column

Question 22

Motor and sensory functions of ventral rami

Answer 22

Motor- all other skeletal muscles in body wall and extremities
Sensory- rest of skin covering neck, thorax, abdomen, and extremities

Question 23

MS and location of intercostal nerves

Answer 23

Travel between ribs
Motor to intercostal muscles
Sensation from segmented regions of thoracic wall

Question 24

Location and MS of nerves of abdominal muscles

Answer 24

Travel between layers of abdominal muscles
Somatic motor to abdominal muscles
Sensation from segmented regions of abdominal wall

Question 25

Characteristics of nerve plexuses

Answer 25

Network of ventral rami from multiple segments Muscles of extremities perform complex functions- need sophisticated innervation from multiple SC segments

Question 26

Types of nerve plexuses

Answer 26

Brachial plexus= motor and sensory to upper extremity Lumbosacral plexus= motor & sensory to lower extremity

Question 27

Nerves of upper extremity

Answer 27

Axillary nerve Musculocutaneous nerve Radial nerve Median nerve Ulnar nerve All coming from brachial plexus

Question 28

Characteristics of brachial plexus

Answer 28

Anterior rami of C5-T1 Sensory- skin of upper extremity Motor- skeletal muscles of upper extremity 5 terminal branches

Question 29

Pathway of extremity nerves

Answer 29

Roots from spinal cord Trunks Divisions Cords Branches

Question 30

Roots and MWS of axillary nerve

Answer 30

Roots- C5 and C6 Motor- Teres minor (rotator cuff) and deltoid Weakness with damage- shoulder abduction and shoulder lateral rotation Sensory- skin over shoulder

Question 31

Roots and MWS of musculocutaneous nerve

Answer 31

Roots- C5, C6, C7 Motor- Coracobrachialis, biceps brachii, brachialis Weakness with damage- flexion at elbow, supination Sensory- skin over lateral forearm

Question 32

Roots and MWS of radial nerve

Answer 32

Roots- C5, C6, C7, C8,T1 Motor- triceps brachii, posterior forearm compartment Weakness with damage- extension at elbow, wrist, & fingers, supination Sensory- skin over posterior arm, forearm, hand

Question 33

Roots and MWS of median nerve

Answer 33

Roots- C6, C7, C8, T1 Motor- anterior forearm compartment Weakness with damage- flexion at wrist & fingers, pronation Sensory- skin over lateral palm, fingertips of digits 1-3

Question 34

Roots and MWS of ulnar nerve

Answer 34

Roots- C8 and T1 Motor- anterior forearm compartment Weakness with damage- finger abduction and adduction Sensory- skin over medial hand

Question 35

Nerves of lower extremity

Answer 35

Femoral nerve, obturator nerve, gluteal nerves, sciatic nerve consisting of tibial nerve & common fibular nerve, superficial fibular nerve, and deep fibular nerve

Question 36

Components of lumbosacral plexus

Answer 36

Lumbar plexus and sacral plexus

Question 37

MWS of femoral nerve

Answer 37

Motor- iliopsoas, quadriceps femoris, sartorius Weakness with damage- flexion at hip, extension of knee Sensory- skin over anterior thigh, medial leg

Question 38

MWS of obturator nerve

Answer 38

Motor- adductor longus, brevis, & magnus, gracilis Weakness with damage- adduction of thigh at hip Sensory- skin over medial thigh

Question 39

MW of gluteal nerves

Answer 39

Motor- gluteus Maximus, medius, minimus, and tensor fascia lata Weakness with damage: extension at the hip

Question 40

Characteristics of sciatic nerve

Answer 40

Consists of tibial nerve and common fibular nerve Joined by connective tissue “Sciatica” = compression of sciatic nerve resulting in pain down back of lower extremity

Question 41

MWS of tibial nerve

Answer 41

Motor- hamstring muscles, posterior compartment soft leg (superficial & deep) Weakness with damage- extension of hip, flexion at knee, plantarflexion at ankle, toe flexion Sensory- skin over sole of foot

Question 42

MW of common fibular nerve

Answer 42

Motor- short head of biceps femoris Weakness in flexion of knee may not be apparent

Question 43

MWS of superficial fibular nerve

Answer 43

Motor- lateral compartment of leg Weakness with damage- eversion of foot Sensory- skin over dorsum of foot (not between first 2 toes)

Question 44

MWS of deep fibular nerve

Answer 44

Motor- anterior compartment of leg Weakness with damage- dorsiflexion of foot, extension of toes, inversion of foot Sensory- skin between first 2 toes