HA spinal cord & spinal nerves

The brain and the rest of the body

The spinal cord provides a vital link between…

Sensory and motor impulses

The spinal cord is a pathway for…

Reflexes

The spinal cord is responsible for ___, which are the quickest reactions to a stimulus

16-18 inches

Length of spinal cord

Roughly cylindrical, slightly flattened posteriorly and anteriorly

Gross anatomy of the spinal cord

• Posterior median sulcus

• Anterior median fissure

2 longitudinal depressions:

• on posterior surface

• on anterior surface

Cervical

1. Cervical enlargement (soma) innervates the upper limbs

2. Thoracic

3. Lumbar

5. Coccygeal

Other parts of the spinal cord

Sacral

4. Lumbosacral enlargement innervates the lower limbs

Shorter

The spinal cord is ___ than the vertebral canal

Conus medullaris

“End” of the spinal cord proper (L1)

Caudate equina (pony/horse tail)

Groups of axons

Film terminale

• within the cauda equina: ___ ___

  • Pia mater that anchors the conus medullaris to the coccyx

31

How many pairs on spinal nerves that connect the CNS to muscles, receptors and glands

• 8

• 12

• 5

• 5

• 1

Each side of the spinal cord contains:

• cervical nerves (C1-C8)

  • Start above C1

  • All other start below each vert

• Thoracic nerves (T1-T12)

• Lumbar nerves (L1-L5)

• Sacral nerves (S1-S5)

• Coccygeal nerve (Co1)

Spinal cord meninges

• protects and encapsulates the spinal cord

• Continuous with the cranial meninges

Epidural space

• houses blood vessel

• Epidurals (anesthetic) given here

Dura mater

Not doubled layered like in the brain

Spinal cord meninges

• narrow subdural space a potential space

• Arachnoid mater

• Subarachnoid space filled with CSF

Pia mater

Adheres directly to the spinal cord

denticulate ligaments

• supports blood vessels supplying the spinal cord

• Creates extensions: ___ ___

  • Suspend and anchor the spinal cord laterally to dura mater

Inner / outer

The spinal cord is partitioned into an ___ gray matter region and an ___ white matter region

Gray matter

Dendrites, soma, unmyelinated axons

White matter

Myelinated axons (Oligodendrocytes)

Schwann cells

There are no ___ ___ in CNS

Column

Funiculus means

Gray matter

Central, butterfly shape

• anterior horns

• Lateral horns

• Posterior horns

• Gray commissure

Gray matter is distributed into:

Gray matter

• Soma of somatic motor neurons

  • Motor nuclei

• Skeletal muscle

anterior horns

(motor sensations)

Lateral horns:

• T1-L2 only

  • Soma of autonomic motor neurons (SNS)

    • Autonomic motor nuclei

  • Cardiac & smooth muscle, & glands

Posterior horns:

(Sensory signals)

• Inter neuron soma

  • Sensory (visceral and somatic) nuclei

  • Sensory neurons axons

Gray commissure:

• unmyelinated axons

• Communication route between R & L (desecration- crossing bodies’ midline)

• Houses central canal (lined by epidermal cells)

External

White matter is ___ to the gray matter

Funiculus (column)

• posterior funiculus

• Lateral funiculus

• Anterior funiculus

  • Interconnected by the white commissure

White matter is partitioned into 3 regions, each called a ___

Bundle of axons in CNS

Ascending and descending tracts =

Tracts

The axons within each funiculus are organized into ___

Ascending tract

Send sensory information to brain

Descending tracts

Motor information away from the brain

Spinal nerves

• 31 pairs

• Made up of motor and sensory axons

• Contain connective tissue wrappings called endonerurium, perinerium, and epineurium

Motor axons

Anterior and lateral horns

• anterior root

  • ___ ___ emerge from the spinal cord

• Soma are located in…

Posterior root

• contain sensory axons only

• Soma in the posterior root ganglion, attached to posterior root

Spinal nerve in the intervertebral foramen

Anterior root + posterior root =

Both motor & sensory axons

Spinal nerve contains…

Rami (arm)

From intervertebral foramen(hole that forms when vertebrae are stacked together), spinal nerves splits into ___

Posterior ramus

• smaller

• Deep muscles and skin of the back

Anterior ramus

• larger

• Anterior and lateral portions of the trunk and upper/lower limbs

Dermatome

• Segment of skin supplied by a single spinal nerve

• All except C1 innervate skin

• the dermatome map

  • Clinical uses

Nerve plexus

Network of interweaving anterior rami

• split into multiple named nerves that innervate body structures

Cervical, brachial, lumbar, and sacral

What are the principle plexuses?

Intercostal nerves

• no thoracic plexus

• ___ ___: anterior rami of spinal nerves T2-T11

Cervical plexus

• anterior rami of C1-C5

• Anterior neck muscles and skin of neck, head and shoulders

Phrenic nerve

• ___ ___:“C3-5 keep you alive”

  • Innervate the diaphragm

Brachial plexuses

• ___ ___: supply the upper limbs

• C5-T1

• Innervates the pectoral girdle and the entire upper limb of one side

Rami

Trunks

Divisions

Cords

R ealy

T ired

D rink

C offee

5

How many major terminal branches emerge from the 3 cords

1. Axillary nerve

Shoulder

2. Median nerve

Anterior forearm and most of hand

3. Musculocutaneous nerve

Anterior arm muscles

4. Radial nerve

Posterior arm and forearm

5. Ulnar nerve

Anterior/medial forearm

Obturator nerve

• ___ ___: main nerve of the anterior division

  • Medial thigh

Femoral nerve

• ___ ___: main nerve of the posterior division

  • Anterior thigh

Sciatic nerve

• ___ ___: largest and longest nerve

  • Posterior thigh

Lumbar plexuses

L1-L4

Sacral plexuses

L4-S4

2

How many divisions wrapped in a common sheath?

1. The tibial division

Posterior leg

2. The common fibular division → deep fibular and superficial fibular

• common fibular: anterior leg

• Superficial fibular: lateral leg

Reflexes

Rapid, automatic, involuntary reactions of muscles or glands to a stimulus

Stimulus

Required to initiate a response

Rapid response

Requires that few neurons

• minimal delay

Automatic response

Occurs the same way every time

Involuntary response

Requires no internet of reflex activity

Reflex arc

Neural wiring of a single reflex

PNS

Reflexes always begins at a receptor in the ___

CNS

Reflexes communicates with the ___

Ends

Reflexes ___ at a peripheral effector

Stimulus

Reflex response requires ___

Ipsilateral or contralateral

A reflex arc may be:

Ipsilateral

Receptor and effector on same side

Contralateral

Sensory and receptor on the opposite side

Gray

Interneuron crossing ___ commissure

Monosynaptic or polysynaptic

Reflexes may be:

Monosynaptic

Sensory axons synapse directly on motor neurons

Polysynaptic

Exhibit a number of synapses involving interneurons within the reflex arc