BY 115 Spinal Cord, Cranial Nerves, Spinal Nerves, Autonomic Nervous System

Spinal cord

Located within vertebral canal; runs length of body from foramen magnum to L1 vertebra; divided into gray matter and white matter

Five parts of spinal cord

Named for nerves that attach to them; superior to inferior: cervical, thoracic, lumbar, sacral, coccygeal

Cervical enlargement

Neurons that innervate upper limb

Lumbosacral enlargement

Neurons that innervate lower limb

Conus medullaris

Tapering inferior end of spinal cord; official “end” of spinal cord

Cauda equina

Inferiorly, groups of axons

Filum terminale

Within cauda equina; thin strand of pia mater

Meninges of spinal cord

Continuous with cranial meninges; three layers (superficial to deep): dura mater, arachnoid mater, pia mater

Spinal epidural space

Between vertebral canal and dura mater

Central canal of spinal cord

Lined with ependymal cells; contains CSF

Gray matter of spinal cord

Located centrally within spinal cord; contains neuron cell bodies, dendrites, and unmyelinated processes; organized into horns and the gray commissure

Anterior gray horns

Contains cell bodies of somatic motor neurons; innervates skeletal muscle

Lateral gray horns

Contains cell bodies of autonomic motor neurons; prominent in the T1-L2 regions of spinal cord; associated with sympathetic motor output

Posterior gray horns

Receive sensory information; contain sensory neuron axon terminals and interneurons

Gray commissure

Unmyelinated axons crossing from side-to-side; contains central canal

White matter of spinal cord

External to gray matter; contains bundles of primarily myelinated axons; organized into three regions called funiculi

Anterior funiculus

On anterior side of cord between anterior gray horns and anterior median fissure

Lateral funiculus

Lateral side of spinal cord

Posterior funiculus

Between posterior gray horns and posterior median sulcus

Spinal cord tracts

Bundles of axons that run in white matter of spinal cord; includes ascending tracts (sensory axons = traveling to brain) and descending tracts (motor neurons = traveling from brain)

Cranial nerves

12 pairs, part of the PNS, numbered I-XII, named primarily for structure or function

CN I

Olfactory nerve; sensory only, responsible for olfaction (smell); olfactory nerve fibers pass through the cribriform plate; synapse in the olfactory bulb

Anosmia

No sense of smell

CN II

Optic nerve; sensory only; responsible for vision; includes optic chiasm (axons from nasal halves of retinas cross to opposite side) and optic tracts (carry information toward brain)

CN III

Oculomotor nerve; somatic motor and parasympathetic motor functions

Oculomotor somatic motor functions

Supplies superior rectus (SR), inferior rectus (IR), medial rectus (MR), inferior oblique (IO), and levator palpebrae superioris

Oculomotor parasympathetic motor functions

Supplies sphincter pupillae (constricts pupil) and ciliary muscle (changes lens shape)

CN IV

Trochlear nerve; somatic motor only; innervates superior oblique; helps depress the eye, particularly when eye is adducted

Anopsia

Lack of vision

Diplopia

Double vision

CN V

Trigeminal nerve; mixed nerve: sensory + somatic motor; motor innervation to muscles of mastication

Trigeminal nerve sensory distribution

Sensory innervation from much of the face and anterior scalp, nasal and oral cavities, and teeth; distributed across ophthalmic branch (V1), maxillary branch (V2), and mandibular branch (V3)

CN VI

Abducens nerve; somatic motor; innervates lateral rectus; abducts eye (moves it laterally)

ID 1

Cervical plexus

ID 2

Cervical enlargement

ID 3

Brachial plexus

ID 4

Lumbosacral enlargement

ID 6

Conus medullaris

ID 7

Lumbar plexus

ID 8

Sacral plexus

ID 9

Filum terminale

ID 10

Atlas

ID 11

Cervical part

ID 13

Thoracic part

ID 14

Lumbar part

ID 15

Sacral part

ID 16

Cauda equina

ID 17

C1

ID 18

C2

ID 19

C3

ID 20

C4

ID 21

C5

ID 22

C6

ID 23

C7

ID 24

C8

What nerve is between C8 and T2?

T1

ID 25

T2

ID 26

T3

ID 27

T4

ID 28

T5

ID 29

T6

ID 30

T7

ID 31

T8

ID 32

T9

ID 33

T10

ID 34

T11

ID 35

T12

What nerve is between T12 and L2?

L1

ID 36

L2

ID 37

L3

ID 38

L4

ID 39

L5

ID 40

S1

ID 41

S2

ID 42

S3

ID 43

S4

ID 44

S5

ID 45

Co1

ID 1

Spinal cord

ID 2

Posterior rootlets

ID 3

Conus medullaris

ID 4

Posterior root

ID 5

Posterior root ganglion

ID 6

Cauda equina

ID 7

Filum terminale

ID 1

Pia mater

ID 2

Arachnoid mater

ID 3

Dura mater

ID 1

Spinous process of thoracic vertebra

ID 2

Epidural space

ID 3

Dura mater

ID 4

Denticulate ligament

ID 5

Spinal nerve

ID 6

Subdural space

ID 7

Intervertebral foramen

ID 8

Arachnoid mater

ID 9

Subarachnoid space

ID 10

Pia mater

ID 11

Spinal cord

ID 12

Body of thoracic vertebra