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Functions of the Spinal Cord

• Transmit

• Transmit

• Integrate

Brain Spinal Cord Periphery

Sensory Info

Motor Commands

Ascending tracts

Descending tracts

Fasciculus gracilisDorsalwhitecolumn

Fasciculus cuneatus

Dorsalspinocerebellar tract

Lateralspinothalamic tract Ventral spinothalamictract

Ventral whitecommissure

Lateralcorticospinal tract

Lateralreticulospinal tract

Ventral corticospinaltract

Medialreticulospinal tract

Rubrospinaltract

Vestibulospinal tractTectospinal tract

Ventralspinocerebellartract

Transmitting Information

Receptor

Sensory neuron

Integration center

Motor neuron

Effector

Spinal cord(in cross section)

Interneuron

Stimulus

Skin

1

2

3

4

5

Integration - Reflexes

Spinal Cord Protected by

Bone

Meninges

Cerebrospinal fluid

Bony Protection

Meninges 3 Membranes surrounding the spinal cord

Pia materArachnoid materDura mater

Meninges Basic Arrangement

Spinal Cord

Pia mater

Arachnoid mater

Dura mater

Subarachnoid spaceEpidural space

CSF

Produced from blood by specialized capillaries (choroid plexuses) in the brain

Functions:1. Support2. Protect3. Buffer

Spinal Cord Anatomy

Foramen magnum – L1

CervicalnervesC

1 – C

8

ThoracicnervesT

1 – T

12

LumbarnervesL

1 – L

5

Sacral nervesS

1 – S

5

Coccygeal nerve Co1

31 spinal nerve pairs

31 spinal segments

C2C3

C4

C5T1

T2

T2T3T4T5

C6

C8C7 C7

C6

T6

T7T8T9

T10

T11

T12L1

S2S3

L1

L2

L3

L4

L5

L2

L3

L4

L5

S1

C5

C6

C8

T2

C5

C6

S1

C2

C3

C4C5C6C7C8

C8 C8

C7 C7

T1T2T3T4T5T6T7T8T9

T10

T11T12

L1L2

L3

S1

L5S2

S1

S1

S3

S2 S1S2

S4S5

L5L5

L4L5L5

L4

C6 C6

C5

L4

L3

L2

L1

L4

Dermatomes

Spinal Cord Anatomy

Conus Medullaris & Cauda Equina

Filum Terminale

Spinal Cord – Cross Sectional Anatomy

White Matter – Myelinated axons

Gray Matter – SomataDendritesUnmyelinated axons

Dorsal column

Central canal

Graycommissure Dorsal horn Gray

matterLateral horn

Ventral hornVentral columnLateral column

Whitecolumns

Spinal Cord – Cross Sectional Anatomy

Ascending tracts

Descending tracts

Fasciculus gracilisDorsalwhitecolumn

Fasciculus cuneatus

Dorsalspinocerebellar tract

Lateralspinothalamic tract Ventral spinothalamictract

Ventral whitecommissure

Lateralcorticospinal tract

Lateralreticulospinal tract

Ventral corticospinaltract

Medialreticulospinal tract

Rubrospinaltract

Vestibulospinal tractTectospinal tract

Ventralspinocerebellartract

Spinal Cord – Cross Sectional Anatomy

White Matter – Organized into columns and tracts

Spinal Cord – Cross Sectional AnatomyGray Matter Organization

Somaticsensoryneuron

Dorsal root (sensory)

Dorsal root ganglion

Visceralsensory neuron

Somaticmotor neuron

Spinal nerve

Ventral root(motor)

Ventral horn(motor neurons)

Dorsal horn (interneurons)

Visceralmotorneuron

Interneurons receiving input from somatic sensory neurons

Interneurons receiving input from visceral sensory neurons

Visceral motor (autonomic) neurons

Somatic motor neurons

Fascicle

Epineurium

Perineurium

Endoneurium

AxonMyelin sheath

Basic Structure of a Nerve

Spinal Nerve AnatomyVentral and Dorsal Roots

Ventral and Dorsal Rootlets

Dorsal Root Ganglion

Spinal Rami

Dorsal ramus

Ventralramus

Dorsal ramus

Motor and sensory signals to/from the posterior trunk

Ventral ramus

Motor and sensory signals to/from the anterior trunk and limbs

Ventral ramus

Rami communicantes – carrying autonomic nerve fibers

All ventral rami(Except T2-T12)

Form Interlaced bundles of nerve fibers

Nerve Plexuses

4 major plexuses

Cervical PlexusBrachial PlexusLumbar PlexusSacral Plexus

Primarily serve the limbs

C1

C2

C3

C4

C5

Segmentalbranches

Lesser occipitalnerveGreater auricularnerve

Ansa cervicalis

Phrenic nerve

Supraclavicularnerves

Transversecervical nerve

Ventralrami:

Ventral rami

Cervical PlexusMostly cutaneous nerves

Axillary

Musculo-cutaneous

Radial

Ulnar

C4

C5

C6

C7

C8

T1

Brachial Plexus Supplies the upper limb

Gives rise to several important nerves

Axillary Nerve

Carries sensory info from the shoulder region and motor commands to the deltoid muscle.

Musculocutaneous NerveCarries sensory info from the lateral arm and motor commands to the biceps brachii and brachialis muscles.

Radial Nerve

Carries sensory info from the posterior arm and motor commands to the triceps brachii, wrist extensors and brachioradialis muscles.

Ulnar Nerve

Carries sensory info from the palm and the medial hand/fingers and sends motor commands to the wrist flexors and intrinsic hand muscles.

Obturator

Femoral

Obturator

Femoral

Lumbar Plexus

L1

L2

L3

L4

L5

Supplies much of the lower limb

Part of the lumbosacral plexus

Gives rise to several important nerves

Femoral NerveCarries sensory info from much of the thigh, leg, and foot and sends motor commands to quadriceps femoris muscles.

Obturator NerveCarries sensory info from the thigh and sends motor commands to adductor muscles.

Pudendal

Sciatic

L4

L5

S1

S2

S3

S4

S5

Co1

Superiorgluteal

Inferiorgluteal

Sacral Plexus

Superior gluteal

Inferior gluteal

Pudendal

Sciatic

Supplies much of the pelvis, thigh, and leg

Part of the lumbosacral plexus

Gives rise to several important nerves

Sciatic NerveCarries sensory info from the skin of much of the lower limb and sends motor commands to hamstring muscles as well as other muscles of the lower leg and feet.

Sciatic

Gluteal NervesPrimarily send motor commands to adductor muscles of the thigh and to the gluteus maximus.

Superior gluteal

Inferior gluteal

Pudendal NerveCarries sensory info from the external genitalia and supplies motor commands to the external urethral and anal sphincters.