LAB2 QUIZ1

Central Nervous System (CNS)

Brain & Spinal Cord only

Peripheral Nervous System (PNS)

– 12 pair of Cranial Nerves (exit base of brain)

– 31 pair of Peripheral Nerves (exit spinal cord)

12 pair of Cranial Nerves

exit base of brain

31 pair of Peripheral Nerves

exit spinal cord

• Information travels to and from the CNS from

Somatic regions (skin, skeletal muscle, joints, bone ) or

Visceral regions

Somatic regions

(skin, skeletal muscle, joints, bone )

Visceral regions

(organs, cardiac/smooth muscle, glands)

Visceral PNS regions include two branches of the

Autonomic Nervous System (ANS):

o SNS  sympathetic NS

o PSNS  parasympathetic NS

Cytoskeleton made of

microtubules and bundles of actin called

nissil bodies

Now called

Chromatophilic substance =

rough ER

Trigger zone =

Initial segment + Axon hillock

Organelles of the soma

(neurosoma, cell body)

Nucleolus, Mitochondria, vesicles,

lysosomes, Golgi, numerous

inclusions like pigment, lipid

droplets, etc. NO centrioles.

Dendrites

taper to a point distally.

Axons do not

stain in any myelinated regions so you

may only see the proximal part of an axon (trigger zone)

Nervous tissue =

Neurons + Neuroglia

Estimated the nervous

system is made up of a

trillion (1012)

neurons

Neuroglia (glial or

accessory cells)

• 10 times as many neuroglia as neurons

• “Helper cells” for neurons

• Each type has specific function

• Names and functions differ in CNS vs. PNS

Schwann cells make myelin in the

PNS

myelin is an

insulating coating on axons that speeds signal movement

Two neuroglia of the PNS include:

Schwann cells and satellite cells that support PNS neurons

CNS has four specialize neuroglia (glia, accessory) cells:

Ependymal cells, astrocytes, microglia, and oligodendrocytes

Neurons can have one to thousands of

dendrites

dendrites

which receive incoming signals from other cells.

Neurons (except anaxonic) have only one

axon

axon

which carry signal away from soma toward the next cell it communicates with

Cylinder of nerve tissue within the vertebral canal (thick as little

finger) average:

1.8 cm X 45 cm

vertebral column grows faster so, in an adult, the spinal cord

only extends to the

L1 vertebrate than branches.

Branches to 31 pairs of spinal nerves which exit either side from

between

cervical, thoracic, lumbar & sacral vertebrate

Plexus

are nerves that form branches with other nerves along spinal

cord: There are cervical, brachial, lumbar, & sacral regions

Cervical & brachial plexus go to

head and neck

Thoracic nerves branch to muscle of

body wall and ribs

Lumbar and sacral plexus go to

pelvis & legs

Cauda equina is

L2 to S5 nerve root bundles/branches

(resemble horse’s tail) to pelvis and legs

Medullary cone is

inferior tapered tip of spinal cord

Columns now called

“funiculus”

Gray matter =

-neuron cell bodies with little/ no myelin

-soma and dendrites (never myelinated)

White matter =

myelinated axons

(lipid in myelin gives it a whitish

appearance).

(Gray Matter) Right and left dorsal (posterior) horns

Incoming unipolar sensory neuron somas & fibers enter spinal cord

(Gray Matter) Right and left ventral (anterior) horns

Outgoing multipolar motor neuron fiber; soma in SC

(Gray Matter) Connected by gray commissure punctured by a central canal

Canal continuous with 4th ventricle; lined with ependymal cells & CSF;

collapsed in most adults

White funiculi =>

tracts are bundles of myelinated axons that carry

signals up & down spinal cord to and from the brain called fasciculi (used

to be called “columns”)

CNS: tracts =

named fibers filled with axons with a similar origin,

function, & destination (same as “nerves” in PNS

Rootlets

spread nerve roots along

surface of SC so signals enter/exit all

along surface of spinal cord

Most PNS nerves are mixed

carry both sensory and motor

axons running in opposite directions

Any one axon within fiber only

carries signal one way

axons of motor neuron

exit

ventral horn

Soma of sensory neuron

Axons of sensory neuron

enter

dorsal horn

Root =

short extension at spinal cord divide into rootlets at

surface of spinal cord

Ramus =

first branches of spinal nerve

4 rami branch from each spinal nerve:

meningeal (back to meninges), communicating (to ANS),

ventral & dorsal (to somatic regions anterior & posterior body wall)

Fascicle =

bundles of axon

Nerve =

many fascicles

bound together

Gyri =

upward folds

Sulcus =

shallow grooves

Fissure =

deep grooves

The hollow regions within the brain (ventricles) and spinal cord

(central canal) are the remnants of

the original neural tube

which expanded at proximal end to form ventricles and distal

end to form central canal

Nerve (in PNS) =

cord-like bundle of axons bound by CT containing

both sensory and motor neurons to and from the spinal cord

Epineurium

is CT covering on each nerve

Perineurium

surrounds each fascicle including blood vessels

Endoneurium

on each axon (basal lamina + fibrous CT sleeve

external to the neurolemma) separates individual axon fibers

Protective Coverings on Brain and Spinal Cord are

called

Meninges (Meninx)

On spinal cord Arachnoid mater

layer of simple squamous epithelium lining dura mater and

deeper loose mesh of fibers filled with CSF (creates

subarachnoid space)

On spinal cord Pia mater

delicate membrane adherent to spinal cord anchored by

• Terminal filum anchor end of cone to coccyx region

• denticulate ligaments along sides limit side to side motion

On spinal cord Dura mater (dural sheath)

tough collagenous membrane surrounded by epidural space

filled with fat and blood vessels

• Epidural anesthesia utilized during childbirth

• Layer of fatty cushion superficial to dura (in epidural sp