L11 Spinal Cord

1INNERVATION Brain Spinal CordPeripheral nerves

Locations of nerve tissue

Anatomical Divisions of the Nervous System: Central Nervous System (CNS)

brain and spinal cordcontained within bone (skull, vertebral column)

Peripheral Nervous System (PNS) all nerve tissue outside CNSsensory & motor divisions

Every skeletal muscle fiber is supplied (INNERVATED) by a motor neuron

Skeletal Muscle is voluntaryfibers will not contract unless a neuron tells them to

(all movements are initiated by the nervous system)

junction Neuromuscular

Muscle

Neuromuscular Junction

fibers

muscle

neurons (2)

BIO223: Human Anatomy L11: Spinal Cord and Innervation UNC-Asheville, f2011

2Muscle contraction is a biochemical rxn each fiber always contracts with the maximum force it can.Strength of contraction of an entire muscle (ex. Deltoid) is determined by % of fibers within the muscle firing at the same time.

How do muscles control force?Nerves and Neurons a nerve is an organ

a neuron is a cell of nerve tissue

Neuron

neuroglia

NERVE

200x

NERVE TISSUE

NeuronsNeurons

Neurons: impulse-conducting nerve cells Neuroglia: supporting cells

NeurogliaNeuroglia

Direction

Axon HillockTrigger Zone

AXON

Axon (only 1, but branches) conducts impulse release neurotransmitters into synapse (junction bet. cells) NT alters the activity of cells

[excitatory / inhibitory]

Neuron basic structure

Cell Body(soma)

Cell body (soma)Dendrites

Direction of impulse

Synaptic knobs

Schwann cell(neuroglia)

Dendrites

Functional Classification of Neurons1. Sensory (input) PNS 2. Motor (output) PNS 3. Interneurons (processing) CNS

sensory

motor

interneurons

motor (= efferent) neurons produce effects on body structures (ex. muscle; glands) travel from CNS motor organ

sensory (= afferent) neurons provide info about intl & extl conditions travel from sensory organ CNS

Motor & Sensory Innervation

interneurons Connect neuronneuron Involved with thought, processing, memory, etc.


3Sensory Neuron(unipolar)

axon

Interneurons(multipolar)

dendrites

Motor Neuron(multipolar)

axon

dendrite

cell body

axonaxon axon

muscle

nervegross structure of PNS containing the axons of

several neurons

Axon

Spinal Cord

Vertebrae

NERVE 100s+ of axons wrapped together supporting cells (neuroglia) blood supply connective tissue

NeuronVertebrae

IntervertebralForamen

Spinal Nerve

Neuroglia

axons

RRadial Nerve

TricepsTriceps

Nerves are distinct gross anatomical structures(ultimately originate from brain or spinal cord)

TricepsTriceps

TricepsTriceps

Nerves can be entirely sensory, entirely motor, or mixedA neuron can only be sensory (afferent) or motor (efferent)

Spinal cord

Afferent neuron(ex. from skin)

Efferent neuron(to muscle)

Nerve Sensory neurons Motor neurons

Nerve


4StimulusSensory neuron

Sensory and motor neurons often travel within the same nerve.

Effector response

Processing Motor neuron

SPINAL NERVE

formed in the intervertebral foramen from branches off

spinal cord

Originate between each pair of vertebrae

spinal cord

spinal cord

spinal nerve

cord cord

Posterior view

Spinal Nerves (PNS)Spinal Cord (CNS)

SPINAL NERVESemerge along vertebral column

Spinal nerves are named by the vertebrae they emerge

between.

Spinal nerves organs of PNS exit between each pair of vertebrae (intervertebral foramina) carry both sensory & motor fibers

SKULLbrain

C1

C2

C3

C4

C1

C2

C3

C4

C5

Spinal CordSpinal Nerves(emerge at each vertebral level)

Segmentation of spinal cord; numbering of spinal nerves

C5

C6

C7

T1

T3

T2

C5

C6

C7

C8

T2

T1

T3

Formed in intervertebral foramen by junction of dorsal and ventral roots

from spinal cord.

SPINAL NERVE

Denticulate Ligament (pia)Separates dorsal/ventral roots

Ventral RootDorsal Root

Form a spinal nerve here(on other side of dura)


5Spinal cord cross sections

Anterior median fissure Ventral (anterior)gray horns

Ventral root

Spinal nerve

Orientation of spinal cord cross-section

Dorsal (posterior)gray horns

Dorsal Root

Dorsal root ganglion

Fibers of Dorsal Root are entirely sensoryFibers of Ventral Root are entirely motor

cross-section

Ventral root only contains axons of motor neurons(cell bodies in anterior gray horn of spinal cord)

Dorsal root ganglionContains cell bodies of sensory neurons

Ventral Ramus(mixed sensory + motor)

to limbs & anterior body wall

Each Spinal Nerve branches into dorsal and ventral ramus

Spinal Nerve

Ventral Root(motor only)

Dorsal Ramus(mixed sensory + motor)

to intrinsic back muscles[ex. erector spinae]

Dorsal Root ganglion

Dorsal Root(sensory only)


6Dorsal RootVentral Root

Dorsal Root Ganglion

Spinal Nerve

Dorsal Ramus

Ventral Ramus

Ventral Ramus supplies muscles anterior to spinal cord, including all muscles of limbs

Dorsal Ramus supplies intrinsic back muscles(erector spinae is only muscle we will dissect)

All other back muscles are actually muscles of the limbs, which are supplied by ventral rami

Muscles supplied by Ventral ramus

Muscles supplied by Dorsal ramus

Anterior median fissure Anterior

median fissure

GRAY MATTER contains unmyelinated nerve tissue (ex. cell bodies) WHITE MATTER contains myelinated axons

Somatic motor

Gray versus White Matter

White matterGray matter White matter

Gray matter

Visceral motorVisceral sensorySomatic sensory

One neuron can be in both gray and white matter.

Dendrites

Cell Body(soma)

Nodes of Ranvier

Myelin is produced by neuroglia: PNS = Schwann cells CNS = oligodendrocytes

Fatty substance that wraps around & insulates axonsincreases speed impulse travels:

without myelin ~2 mphw/ myelin ~300 mph

MYELIN

Direction of impulse

Schwann cells

Ranvier

Myelin sheathaxon

Schwann cell


/ColorImageDict > /JPEG2000ColorACSImageDict > /JPEG2000ColorImageDict > /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict > /GrayImageDict > /JPEG2000GrayACSImageDict > /JPEG2000GrayImageDict > /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict > /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False

/Description > /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ > /FormElements false /GenerateStructure true /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles true /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /NA /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /LeaveUntagged /UseDocumentBleed false >> ]>> setdistillerparams> setpagedevice

Documents

L11 Spinal Cord