Spinal cord

BY,

DAWN V TOMY M.PHARM.,ASST. PROFESSOR,

DEPT. OF PHARMACOLOGY,

ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

Wednesday, December 17,

2014ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

1



2

INTRODUCTION• The central nervous system (CNS) consists of the brain and spinal

cord.

• The brainstem connects the brain to the spinal cord. Brain

communicate with the peripheral nervous system (PNS) through the

spinal cord.

• The spinal cord is continuous with the brain and lies caudally to the

brain, protected by the vertebra and spinal meninges .

• The spinal cord starts from the base of the skull, starting below

the foramen magnum and terminates at the first or second lumbar

vertebra.

STRUCTURE AND FUNCTION OF

SPINAL CORD.



3

Spinal Cord



4

• Slender column of nervous tissue

continuous with brain and brainstem.

• Extends downward through vertebral

canal protected by the spinal meninges.

• Begins at the foramen magnum and

terminates at the first and second lumbar

vertebrae (L1/L2) interspace.

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus

medullarisCauda equina

Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement



5

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus


Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement

The spinal cord and spinal nerves serve

two functions:

Pathway for sensory and motor

impulses.

Responsible for reflexes

(functional independence).

Structure of the Spinal Cord:



6

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus


Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement

External anatomy:

Spinal cord is situated inside the vertebral canal

protected by the spinal meninges. Typical adult

spinal cord length - ranges between 42 and 45 cm

(16 to 18 inches) and diameter - 2 cm.

Spinal cord starts from medulla oblongata and runs

to the lower of 1st lumbar or superior of the 2nd

lumbar vertebra (in New born till 3-4 lumbar,

grows 4-5 years stops but vertebral canal grows till

adulthood). The spinal cord is shorter than the

vertebral canal that houses it.



7

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus


Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement

Two enlargements in the spinal cord at:

• Cervical C4 to T1- nerves to upper limbs,

• Lumbar T9-T12 – lower limbs

Conus medullaris: It is the tapered inferior end

(conical) of the spinal cord below lumbar

enlargement between the 1st and 2nd lumbar

vertebrae, which marks the official “end” of the

spinal cord.

Cauda equina (horse tail): They are inferior to

conus medularis, which forms collection of nerve

roots (lumbar, sacral, coccyx-groups of axons) that

project and leave inferiorly from the spinal cord.



8

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus


Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement

Filum terminale: They are structures within the

cauda equine consists of thin strands of pia mater,

which helps to anchor the conus medullaris to the

coccyx.



9

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus


Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement

The spinal cord is associated with 31 pairs

of spinal nerves, which connect the CNS

to:

• Receptors.

• Effectors (muscle and glands).

Each side of the spinal cord contains:

• 8 cervical nerves (called C1–C8)

• 12 thoracic nerves (T1–T12)

• 5 lumbar nerves (L1–L5)

• 5 sacral nerves (S1–S5)

• 1 coccygeal nerve (Co1).



1

0

Brainstem

Spinal cord

(a) (b)

Foramen

magnum

Cervical

enlargement

Vertebral

canal

Lumbar

enlargementConus


Filum terminale

Conus

medullaris

Lumbar

enlargement

Cervical

enlargement

In cross section:

– Roughly cylindrical elongated lower part

of CNS.

– Slightly flattened both posteriorly and

anteriorly.

– External surface has two longitudinal

depressions:

• The posterior (dorsal) median sulcus.

• The anterior (ventral) median fissure.

Structure of the Spinal Cord



11

White matter

Gray matter

Lateral funiculus

Posterior funiculus

Gray commissure

Central canal

(a)

Posterior horn

Dorsal root

of spinal nerve

Dorsal root

ganglion

Ventral root

of spinal nerve

Anterior

horn

Anterior

median

fissure

Portion of

spinal nerve

Anterior

funiculus

Posterior median

sulcus



12

Internal anatomy:

1. Grooves

• White matter divide into right and left.

• Anterior median fissure – deep wide groove.

• Posterior median sulcus – shallow narrow.

2. Roots

• Bundle of axon connect nerve to spinal nuclei.

• Posterior root – sensory.

• Anterior root – motor.

• Posterior root ganglion-swelling at the posterior nerve.

o Root lets - connecting to spinal cord.




13

White matter

Gray matter

Lateral funiculus

Posterior funiculus

Gray commissure

Central canal

(a)

Posterior horn

Dorsal root

of spinal nerve

Dorsal root

ganglion

Ventral root

of spinal nerve

Anterior

horn

Anterior

median

fissure

Portion of

spinal nerve

Anterior

funiculus

Posterior median

sulcus



14

Location and Distribution of Gray Matter:

In the spinal cord, it is centrally located

• Its shape resembles a letter H or a butterfly.

• Surrounded by white matter, dendrites, cell bodies, unmyelinated axons and neuroglia.

• Central canal filled with CSF.

• The gray matter may be subdivided into the following components:

o Anterior horns.

o Lateral horns.

o Posterior horns.

o The gray commissure - cross bar which connects 2 halves horns.

o Nuclei - clusters of cell bodies form functional groups.

Sensory and motor nuclei.

Lateral only in thoracic area autonomic motor.




15

White matter

Gray matter

Lateral funiculus

Posterior funiculus

Gray commissure

Central canal

(a)

Posterior horn

Dorsal root

of spinal nerve

Dorsal root

ganglion

Ventral root

of spinal nerve

Anterior

horn

Anterior

median

fissure

Portion of

spinal nerve

Anterior

funiculus

Posterior median

sulcus



16

Location and Distribution of White Matter:

• The white matter of the spinal cord is external to the gray matter.

• Three regions. Composed of tracts – (bundles of axon).

Ascending sensory tract.

Descending motor tract.

o Posterior (white column) funiculus:

lies between the posterior gray horns and the posterior median sulcus.

o Lateral (white column) funiculus.

o Anterior (white column) funiculus.

Between the anterior gray horns and the anterior median fissure.

• The anterior funiculi are interconnected by the white commissure.




17

White matter

Gray matter

Lateral funiculus

Posterior funiculus

Gray commissure

Central canal

(a)

Posterior horn

Dorsal root

of spinal nerve

Dorsal root

ganglion

Ventral root

of spinal nerve

Anterior

horn

Anterior

median

fissure

Portion of

spinal nerve

Anterior

funiculus

Posterior median

sulcus

Tracts of the Spinal Cord



18

• Ascending tracts conduct sensory impulses to the brain.

• Descending tracts conduct motor impulses from the brain to motor

neurons reaching muscles and glands.

Posterior spinocerebellar tract

Lateral corticospinal tract

Lateral reticulospinal tract

Rubrospinal tract

Anterior spinocerebellar tract

Lateral spinothalamic tract

Anterior reticulospinal tract

Medial reticulospinal tract

Fasciculus cuneatus

Fasciculus gracilisDorsal column

Anterior spinothalamic tractAnterolateral

system

Anterior

corticospinal

tract

Ascending Tracts



19

• Major ascending (sensory) spinal cord

tracts:

• Fasciculus gracilis and fasciculus

cuneatus.

• Spinothalamic tracts.

• Lateral and anterior.

• Spinocerebellar tracts.

• Posterior and anterior.

Midbrain

Pons

Medulla

Thalamus

Sensory

cortex of

cerebrum

Cerebrum

(frontal

section)

Brainstem

(transverse

sections)

Spinal cord

(transverse section)Sensory fibers

cross over

Spinothalamic

tract

Fasciculus

Cuneatus tract

Sensory impulse

from skin

temperature

or pain receptors

Descending Tracts



2

0

• Major descending (motor) spinal cord

tracts:

• Corticospinal tracts.

• Lateral and anterior.

• Reticulospinal tracts.

• Lateral, anterior and medial.

• Rubrospinal tract.

Midbrain

Pons

Brainstem

(transverse

sections)

Spinal cord

(transverse section)

Motor cortex

of cerebrum

Cerebrum

(frontal

section)Corticospinal

tract

Medulla

oblongata

Motor fibers

cross over

Motor impulse to

Skeletal muscle

Nerve Tracts of the Spinal Cord



21

Functions of Spinal Cord



22

• Center for spinal reflexes.

• Conduct pathway for nerve impulses to and from the

brain and brainstem.

Reflex Arcs



23

• Reflexes are automatic, subconscious responses to stimuli within or

outside the body.

• Simple reflex arc (sensory – motor).

• Most common reflex arc (sensory – association – motor).

Receptor

(a)

Sensory or

afferent neuronMotor or

efferent neuronCentral

Nervous

System

Effector

(muscle or gland)

Reflex Arcs



24

General Components of a Spinal Reflex



25

Receptor

Sensory neuron

Motor neuron

White matter

Gray matter

Spinal cord

DorsalInterneuron

4

5

3

2

1

(b)

Cell body

of sensory

neuron

Effector

(muscle

or gland)

Central

canal

Ventral

Reflex Behavior



26

• Example is the knee-jerk reflex.

• Simple monosynaptic reflex.

• Helps maintain an upright posture.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Spinal cord

Patella

Patellar ligamentDirection of impulse

Axon of sensory

neuron

Cell body of

sensory neuron

Cell body of

motor neuron

Axon of motor

neuron

Effector (quadriceps femoris

muscle group)

Receptor associated with

dendrites of sensory neuron

Reflex Behavior



27

• Example is a withdrawal reflex (flexor reflex).• Prevents or limits tissue damage.

Interneuron

Spinal cord

Axon of sensory neuron

Cell body of sensory neuron

Dendrite of

sensory

neuronPain

receptor

in skin

Direction

of impulse

Cell body of

motor neuron

Axon of

motor neuronEffector (flexor

muscle contracts

and withdraws part

being stimulated)

Tack

Reflex Arc



28

• Example crossed extensor reflex.

• Crossing of sensory impulses within the reflex center to produce an

opposite effect.=Stimulation

= Inhibition

Interneuron

Flexor contracts

Sensory neuron

+

++

–

––

Motor

neurons

Extensor

contracts

Flexor

relaxesMotor

neurons

Extensor

relaxes



29



30

Spinal cord

Health & Medicine

Transcript of Spinal cord