Spinal Cord and PNS

CNS

Brain & Spinal Cord

PNS

Sensory

Somatic Motor

Autonomic NS

Length of Spinal Cord Varies with

Age

Spinal cord length in Fetus

end of vertebral Column

Spinal Cord length in Child

L3

Spinal Cord length in Adult

L1/L2

Cervical and LumboSacral enlargements at spinal cord are at

C4-T1

T11-L1

What is the Conus Medullaris

Terminal end of spinal cord

(L1)

What is Filum Terminale

continuation of Pia mater

What is Cauda Equina

Nerves hanging free

(spinal n.n. L2-S5)

Which meninge ends in S2 and is continuous with the epineurium

Dura

The dura mater includes the ________

Epidural Space

THe Epidural space is used for

Epidural anesthesia

(childbirth)

Which Meninge is Delicate and Avascular as well as impermeable

Arachnoid Mater

Arachnoid mater holds the _________

Subarachnoid space

The subarachnoid space is used for

Lumbar Puncture (CSF)

Spinal Block

Which meninge is thin, delicate and adhered tot surface of cord

Pia mater

The pia mater contains the _________

Denticulate Ligaments

Function of the denticulate ligaments

Anchor spinal cord to the dura mater

What does the Pia mater continue as

Filum Terminale

What is the function of the filum terminale

Anchors spinal cord to sacrum

Where is grey matter in the spinal cord

Inner

Butterfly/H shaped

What does gray matter in the spinal cord contain

Unmyelinated axons, cell bodies, dendrites

Synapses=processing

Where is white matter in the spinal cord

Outer

What does white matter in the cord contain

myelinated axons

In the spinal cord where do the changes for white vs gray matter happen

medulla

What is spina bifida

When the meninges and spinal nerves are outside vs inside

Gray matter horns

Dorsal

Ventral

Lateral

The dorsal horn controls what

termination sensory fibers

integration, relay, reflex

The ventral horns control

Cell bodies, lower motor fibers

medial and lateral columns

Lateral horns control

Preganglionic sympathetic cell bodies

cord levvels T1-L3

What Gray matter horn is part of the ANS

Lateral horn

White matter columns

Dorsal

Ventral

Lateral

Which white matter column is all sensory

Dorsal

In the white matter columns are subdivied into what

tracts

Where is there more Gray matter

At the Enlargements b/c of sensory from limbs

Which three longitudinal arteries supply the cord

Anterior spinal a.

2 posterior spinal a.a.

The veins that supply the spinal cord

3 anterior/3 posterior spinal veins

Internal/external vertebral venous plexuses

What are the Peripheral Nerves

Bundles of axons outside the CNS

Mostt peripheral nerves are

myelinated

What myelinates the Peripheral nerves

Schwann cells

Layering of the tissue covering for nerves (outer to inner)

1. epineurium (around whole nerve/ conttinuous w/ dura)
2. Perineurium ( Around each fascicle)
3. Endoneurium (Around each axon)

Where is the Synapse

Between motor neuron and cell

Cervical Spinal Nerves

C1-C8 one more than vertebrae

Thoracic spinal Nerves

T1-T12

mattch the thoracic vertebrae

Lumbar spinal nerves

L1-L5

match the lumbar vertebrae

Sacral Spinal nerves

S1-S5

Match the sacral vertebrae

Coccygeal Spinal Nerves

Co 1

less than coccyx vertebrae

What creates the Cauda Equina

Spinal Nerves L2-S4

Spinal nerve at C1 exits via

Above C1 (below occipital)

C2-C7 exit

Above same number vertebrae

C8 exits

Between C7 and T1

T1-S5 exit

below the same # vertebrae

Nerve root

emerges from spinal cord inside vertebral column

What are the two parts to the nerve root

Dorsal Root

Ventral Root

Functtion of dorsal root

Sensory input only

FUncttion of venttral root

Motor output only

Each nerve divides into

dorsal ramus

ventral ramus

Dorsal ramus

thin/small no plexuses

Ventral ramus

Large and thick

form plexuses

(except thoracic n.n.)

Dorsal and Ventral ramus =

Mixed

both sensory and motor

Singles - Virus name

Varicella Zoster Virus

Where does the shingles virus live

Dorsal Root Ganglion

Cervical Plexus

C1-C5

Brachial Plexus

C5-T1

Intercostal Nerves

T1-T12

Lumbar Plexus

L1-L4

Sacral Plexus

L5-S4

Sensory Division

Sensory Recepttors→ sensory neuron → Dorsal Root ganglion→ Dorsal Horn

Somatic Motor Division

Skeletal muscle→ Motor neuron→ Ventral horn

ANS Division

Cell→ Postsynaptic neuron → autonomic neuron → presynaptic neuron → Lateral Neuron

2 neuron pathway

Dermatome

A specific area of the skin that receives sensory input from a pair of spinal nerves

What overlaps their edges up to 50%

Dermatomes

Why is it necessary to sever or anesthetize three successive spinal nerves

In order to produce total loss of sensation in one dermatome due to the overlapping in edges

Ascending tracts- White matter Function

Contain sensory tracts into thalamus and then on to cerebrum (awareness) and cerebellum

Ascending tracts are

usually a three neuron pathway

Descending tracts- white matter- Function

Motor output from brain to spinal cord

Usually a 2 neuron pathway

Lateral Spinothalamic tract of spinal cord function

Sensory for pain and temperature

Clinical application for lateral spinothalamic tracts of the spinal cord

lesions in this pathway can cause chronic pain

Dorsal Column tract of the spinal cord

Gracile fasiculus (lower body)

Cuneate fasiculus (upper body)

Dorsal Column tract of the spinal cord- function

ttouch information and conscious proprioception

Dorsal Column tract of the spinal cord - clinical application

Tactile agnosia

unable to recognize objects from touch

Sensation is still in tact but would need visual input to identify object

Lateral Corticospinal tract of the spinal cord - function

Fine motor control (voluntary)

Lateral Corticospinal tract of the spinal cord - clinical application

amyotrophic lateral sclerosis (ALS)

ALS

Degeneration of lateral tract/ loss of motor neurons= muscle atrophy

sensory pathways remain in tact

Spinothalamic pathway

First order neurons end in posterior horn of spinal cord

synapse with second order neurons which crossover to other side of spinal cord and form the ascending spinothalamic tract

Third order neurons continue from there to cerebral cortex

sends signals to contralateral cerebral hemisphere

Gracile Fasciculus

Carries signals from mid thoracic and lower parts of the body

vibration, visceral pain, deep touch, proprioception from lower limbs and lower trunk

Gracile Fasciculus pathway

First order nerve fibers that travel up the ipsilatteral side of spinal cord

Tterminantes at tthe gracile nucleus of the medulla oblongata

Cunate Fasciculus

Originate from T6 and up (upper limb and chest)

Fibers end in the cunate nucleus on the ipsilateral side of medulla oblongatta

Medial lemnisucs- formed the second order neurons of gracile and cunate systems that crossover in the medulla

Third order neurons go from thalamus to cerebral cortex

Corticospinal tracts

two neuron pathway

Paresis

muscle weakness/ partial paralysis

paraplegia

paralysis of legs and part of trunk

quadriplegia

paralysis of all 4 limbs

Hemiplegia

paralysis on one side

loss of motor control ipsilateral

r side stroke- leftt side damage

Two partts of PNS

Sympathetic (SNS)

Parasympathetic (PSNS)

CNS 1 neuron from spinal cord

Somatic motor

lower motor neuron

ANS 2 neurons from spinal cord

preganglionic neuron

postganglionic neuron

Visceral sensory afferents

Conducts pain or reflex sensations from internal organs/ blood vessels to CNS

Motor efferents

signals to CNS to target organs

SNS thoracolumbar Division

Lateral horns

T1-L2-L3