Chapter 13

Question 1

The adult spinal cord

Answer 1

ends between vertebrae L1 and L2
1/2 inch (14mm) wide
about18 inches (45cm) long

Question 2

Bilateral Symmetry

Answer 2

• Grooves divide the spinal cord into left & right
• Posterior median sulcus
  – on the posterior side
• Anterior median fissure:
  – deeper groove on anterior side

Question 3

The Distal End (3)

Answer 3

Conus medullaris:
- thin, conical final cord below lumbar enlargement
Filum terminale:
- thin thread of fibrous tissue at the end of conus medullaris
- attaches to coccygeal ligament
Cauda equina:
- nerve roots extending below counts medullaris

Question 4

Naming Spinal Nerves

Answer 4

Cervical nerves:
- are named for inferior vertebra
All other nerves:
- are named for superior vertebra

Question 5

Roots

Answer 5

2 branches of spinal nerves:
ventral root:
- contains axons of motor neurons
dorsal root:
- contains axons of sensory neurons
Dorsal root ganglia:
- contain cell bodies of sensory neurons

Question 6

The Spinal Nerve

Answer 6

Each side of spine
- dorsal and ventral roots join
- to form a spinal nerve

Question 7

The Meninges

Answer 7

• specialized membranes isolate the spinal cord from the surroundings
  Spinal meninges:
• protect the spinal cord
• carry blood supply
• continuous with cranial meninges
  meningitis:
• viral or bacterial infection of the meninges

Question 8

The Meningeal Layers

Answer 8

Dura mater (superficial):
- outer layer of the spinal cord
Arachnoid mater:
- middle meningeal layer
Pia meter(deepest layer) :
- inner meningeal layer

Question 9

The epidural space

Answer 9

• between spinal dura mater and walls of the vertebral canal
• contains loose connective and adipose tissue
• anesthetic injection site

Question 10

Inter-layer spaces

Answer 10

Subdural space:
- between arachnoid mater and dura mater
Subarachnoid space(tiny thin black line):
- between arachnoid mater and Pia mater
- contains collagen/elastin fiber network(arachnoid trabeculae)
- filled with cerebrospinal fluid(CSF)

Question 11

Structures of the Spinal Cord

Answer 11

Paired denticulated ligaments:
- extend from Pia mater to dura mater
- stabilize side-to-side movement
Blood vessels:
- along the surface of the spinal Pia mater
- within subarachnoid space

Question 12

White Matter

Answer 12

• superficial
• contains myelinated and unmyelinated axons

Question 13

Gray Matter

Answer 13

• Surrounds the central canal of the spinal cord
• contains neurons cell bodies, neuroglia, unmyelinated axons
• has projections (gray horns)

Question 14

Nuclei

Answer 14

Nuclei
- functional groups of cell bodies
Sensory nuclei
- dorsal(posterior)
- connect to peripheral receptors
Motor Nuclei:
- ventral (anterior)
- connect to peripheral effectors

Question 15

What’s the organization of white matter?

Answer 15

3 columns (funiculi) on each side of the spinal cord:
- posterior white columns
- anterior white columns
- lateral white columns

Question 16

Tracts

Answer 16

Tracts or fasciculi:
- in white columns
- bundles of axons
- relay same information in same direction
Ascending tracts = sensory tracts
- carry information to brain
Descending tracts = motor tracts
- carry motor commands to spinal cord

Question 17

Organization of spinal nerves

Answer 17

Every spinal cord segment:
- is connected to a pair of spinal nerves
every spinal nerve:
- is surrounded by 3 connective tissue layers
- that is support structures and contain blood vessels

Question 18

3 Connective tissue layers

Answer 18

Epineurium: most superficial, wrap the entire nerve
- outer layer
- dense network of collagen fibers
Perineurium:
- middle layer
- divides nerve into fascicles (axon bundles)
Endoneurium:
- inner layer
- surrounds individual axons

Question 19

Dermatomes

Answer 19

• bilateral region of skin
• monitored by specific pair of spinal nerves
• Map of skin that represents which spinal nerve is responsible for the sensation in what we feel on our skin.

Question 20

Nerve Plexuses

Answer 20

• complex, interwoven networks of nerve fibers
• formed from blended fibers of ventral rami of adjacent spinal nerves
• control skeletal muscles of the neck and limbs

Question 21

What numbers are Cervical plexus and what nerve?

Answer 21

C1 to C5
Phrenic nerve

Question 22

What numbers are Brachial Plexus and what nerve? What does it control?

Answer 22

C5 to T1
Axillary nerve
As a whole innovate control muscle of arm and hand

Question 23

What numbers are Lumbar plexus and what nerve?

Answer 23

T12 to L4
Femoral nerve

Question 24

what numbers are Sacral plexus and what nerve?

Answer 24

L4 to S5
Sciatic nerve which is biggest nerve in body

Question 25

what are T2 to T11?

Answer 25

thoracic nerve strait

Question 26

what are T2 to T11?

Answer 26

thoracic nerve Straight

Question 27

Reflexes

Answer 27

- automatic responses coordinated within spinal cord - through interconnected sensory, motor, and interneurons. - produce simple and complex reflexes

Question 28

Neutral Reflexes

Answer 28

- Rapid, automatic responses to specific stimuli - basic building blocks of neural function - 1 neural reflex proceeds 1 motor response

Question 29

The reflex Arc

Answer 29

- the wiring of a single reflex - beginning at receptors - ending at the peripheral effector

Question 30

Complexity

Answer 30

The complexity of neural circuit: - monosynaptic reflex: -- sensory neuron synapses directly onto motor neuron - polysynaptic reflex: -- at least 1 interneuron between sensory neuron and motor neuron

Question 31

Spinal reflexes range in what?

Answer 31

Range in increasing order of complexity: - monosynaptic reflexes - polysynaptic reflexes - intersegmental reflex arcs

Question 32

Monosynaptic reflexes

Answer 32

Have least delay between sensory input and motor output: - ex. stretch reflex (such as patellar reflex) Completed in 20-40 msec

Question 33

Withdrawal Reflexes

Answer 33

Move body part away from the stimulus (pain or pressure): ex. flexor reflexes - pulls hand away from hot stove Strength and extent of response: - depends on intensity and location of stimulus

Question 34

Reciprocal inhibition

Answer 34

For flexor reflex to work: - the strength reflex of antagonistic (extensor) muscle must be inhibited (reciprocal inhibition) by interneurons in spinal cord

Question 35

Reflex Arcs

Answer 35

Ipsilateral reflex arcs: - occur on the same side of body as stimulus - stretch, tendon, and withdrawal reflexes Crossed extensor reflexes: - involves a contralateral reflex arc - occurs on side opposite stimulus

Question 36

Crossed Extensor Reflexes

Answer 36

Occur simultaneously, coordinated with flexor reflex ex. flexor reflex causes the leg to pull up: - crossed extensor reflex straightens the other leg - to receive body weight - maintained by reverberating circuits

Question 37

Integration and control of spinal reflexes

Answer 37

Though reflex behaviors are automatic: - processing centers in brain can facilitate or inhibit reflex motor patterns based in spinal cord

Question 38

Voluntary movements and reflex motor patterns

Answer 38

- Higher centers of the brain incorporate lower, reflexive motor patterns Automatic reflexes: - can be activated by brain as needed - use few nerve impulses to control complex motor functions - walking, running, jumping