Histo Neurohistology 11.26.12

Question 1

what are the two plexuses of the Enteric NS

Answer 1

Meissner’s Plexus

Aurbach’s Plexus

Question 2

What is Messner’s Plexus

Answer 2

lies in submucosal CT and innervates gland cells int eh mucosa and submucosa and the muscularis mucosa

Question 3

Auerbach’s Plexus

Answer 3

regualtes contractility of the outer muscle layers, which are involved in PERISTALSIS

Question 4

What embryonic layer is CNS derived from?

Answer 4

Ectoderm!

Neuroectoder –> nerual plate –> sinks into underly myesoderm –> neural tube –> neural crest cells

Question 5

What does the neuroectoderm (neuroepithelium) differentiate into?

Answer 5

neurons, glia, ependyma that forms brain and spinal cord

Question 6

What neural elemnts does neural crest give rise to?

Answer 6

Sensory neurons
of cranial and spinal sensory ganglia

Postganglionic neurons
of sympathetic and parasympathetic ganglia

Supporting cells of the PNS (shwann cells and satellite cells of ganglia)

Question 7

What non-neural elemetns does neural crest give rise to?

Answer 7

Cells of the PIA MATER and ARACHNOID MATER

some BRANCHIAL CARTILAGE and some cranial mesenchyme

Pigment producing cells of skin and subcutaneous tissues (MELANOCYTES)

Chromaffin tissue (secretory cells of adrenal medulla)

Question 8

What elements does CNS have that are derived from neural crest

Answer 8

central axons of DRG cells that enter the spinal cord

Question 9

What elemnts does PNS contain that are derived from neuroepithelium

Answer 9

axons of motorneurons that enter spinal nerves

Question 10

What are two impt consequences of CNS Epithelial Origin?

Answer 10

1. CNS contains NO CT (except fo hat ocntributed to invaginating blood vessels)
2. CNS is surrounded by basal laminsa

Question 11

Differnece between CNS and PNS hisologically

Answer 11

PNS has CT
CNS has NO CT

incoming nerves have CT, white matter in spinal cord does not

Look for TRICHOME stain

Question 12

What two types of cell commprise CNS

Answer 12

Neurons and GLia

Question 13

Neurons

Answer 13

irritability and conductivity

erive form presence of an excitable membrane

Question 14

What is dynamic polarization of neurons

Answer 14

specialization of differnt parts of the cell into receptive sites, integrating sites, and impulse-initianting site, and impulse-conducting sites

Question 15

Neuronal Cell Body

Answer 15

gnerally contains large and oviod or spehrical nuclues with euchormati chormatin; Barr bodies may be seen

Perinuclear cytoplasm has many ribosomes, esp within stacks of RER

Question 16

Nissl bodies

Answer 16

seen in soma,
stacks of RER
very basophilic, diffusely

Question 17

Does the axon hillock have Nissl substances?

Answer 17

no

Question 18

What are prominent in nerons?

Answer 18

Golgi complex,

since Nueroanl cell bodies manufacture material (vesicles) for release by axon terminal

contain lysosomes;

Question 19

Lipfuscin granules

Answer 19

insoluble resides of lysosomal activity may accumulate to form Liofuscin ganuesl

esp visible in neurons of sympatheric and dorsal root ganglia

Question 20

Wher eare Melanin grandules found?

Answer 20

within the brain in a region called SUbSTANTIA NIGRA

Question 21

Neurofbirillary Stains

Answer 21

contain silver

turn structures of Cytoskelelal elemnts (MT and NF) ,
revveal shape of cell and its processess

Question 22

What is a dendrite?

Answer 22

generally similar in fine structure to soma

most synaptic input onto nueron occurs onto its dendritic arbor

Dendrites may contain some Nisl substances (RER)

many NF and MT are present, running longitudinally

ORE VISIBLE IN SILVER_STAINED PREPS than by H&E

Question 23

What are axons?

Answer 23

emerge from axon hillock of the soma

most of voluem f neuron is contained within axon `

Question 24

how can you tell the difference betweeen axon and dendrites

Answer 24

Axons have NO ribosomes, b/c no protein synethesis

Axons cylinder is same diameter throughout its entire lenbht

Dendiites are thicker as they emerge form somae and get slowly narorwer

Neuron will NEVER have more than oaxon

Question 25

What are the two PNS supporting cells

Answer 25

Schwann cells ensheath the axons of the peripheral nerve fibers Satellite cells encheath the cell bodies of neurons located in algnia

Question 26

How do all sensory information flowing in from body (Somatic and Visceral) flow in

Answer 26

All sensory information flowing in form teh body (somatic and visceral) , with the exception of special senses, is carried by fibers of PSEUDOUNIPOLAR neurosn and enters teh spinal cord via the dorsal roots

Question 27

Dorsal Root Ganglia

Answer 27

and sensory ganglia of some cranial nerves have pseudounipolar neurons NEuorns are heterogeneous in size

Question 28

What size oare DRG and Snesory ganglia

Answer 28

heterogeneous in size size of soma is roughly proportional to axon diamter, and this can vary widely, from very small unmeylinated to large myelinated DRG neurons ahve NO dendirtes, and DRG contains no synapses

Question 29

What is the soma of EACH DRG neuron surrounded by>

Answer 29

single layer of small, flattneed cuboidal cells, the SATELLITE CELLS each surrounded neuon is itslef surrounded by basal lamina and loos CT and whole ganglion is surrounded by a CT capsule that is continous with PERINEURIUM and EPINEURIUm of ass. nerve.

Question 30

does DRG contain lipofuscin granules

Answer 30

YES! OFten!

Question 31

Where are autonomic sympathetic ganglia located?

Answer 31

as swellings along the sympathetic chain.

Question 32

Where are autonomic PS ganglia present?

Answer 32

near, or wihtin teh walls of organs innervated by ANS

Question 33

what kind of neurons in ANS

Answer 33

more homogenous in size than DRGs (all sensory somatic or visceral) unlike DRG, sympathetic ganglia are integrating centers with many synapses

Question 34

In dgestive system, where are enteric ganglia found?

Answer 34

in submucosa --> MEISSNER"S PLEXUS and at eh interace b/w the tinner and outer layers of muscularis exerna (AUERBACH's PLEXUS)

Question 35

Where is Meissner's plexus found?

Answer 35

in submucosa

Question 36

wher eis Auerbach's plexus found

Answer 36

at the interace b/w the inner and outer layers of hte uscularis externa

Question 37

What is a nerve?

Answer 37

cylindrical, flexible struture that contains axons, glia, ans ome fibroblasts

Question 38

Whwat are glia

Answer 38

Schwann cells tey surround each axon whether it is myelinated or not Schwann cells and gibroblasts both manufacure the CT that surrounds each axon

Question 39

Does every axon have a Schwann cell sheath in PNS?

Answer 39

yes!

Question 40

Difference between myeline covering in PNS and CNS

Answer 40

in PNS- one Schwann cell covers one internodal segment on oen axon CNS- one oligodendrocyte covers one internodal segment of many (10-50 axons)

Question 41

What is the general structure of ALL PNS sheaths, meyelinated or unmyelinated?

Answer 41

``` axon (innermost) sheath (myelin or Schwann cell process) Basal Lamina CT layer 1 (Endoneurium (around each axon) CT layer 2 (Perineurium) CT 3 (Epineurium- outermost) ```

Question 42

What is endoneurium

Answer 42

lies arodn each individual myelinated axon or unmyelinated gouprs of axons

Question 43

Perineruium

Answer 43

lies around each budnle of axons and also surrounds the entire nerve

Question 44

Epineurium

Answer 44

loost CT fascia outisde the external perineurial sheath Surrounds entire nerve and blnds in to surrounidng CT All thes CT layers are formed by gibroblass n various latery

Question 45

Descirbe unmeylinated periehral axons

Answer 45

one Schwann cell wrpas a group of aoxons one Schwann cell may invest as mnay as 20 unmyelinated axons Sheath of unmeylinated aoxn does not have nodes of Ranvier, as does a myelin sheath Basal lamina surrounds the whole axon+ sheath complex

Question 46

What does PNSaxon look in H&E staining

Answer 46

dissovled lipid of myelin leaving only ppt netowrk of protein (called neurokeratin, but nrelated to keratins) Nerves look moth-eaten and ragged

Question 47

Osmium

Answer 47

myelin lipid is retained and stains very darkly, while aoxon itself is unstained;

Question 48

Silver stains the cytoskelton, so axon cylinder is vivisle while myelin is not

Answer 48

yep

Question 49

Are peripheral nerves mixed nerves?

Answer 49

yes! contain many diff sizes nad degrees of myelination

Question 50

Fiber group A- heavily myelinated

Answer 50

high velocity, acute pina, temp, touch pressure prorprioception (fine touch fast)

Question 51

TYpe B fibers

Answer 51

less heavily myelinated | Moderate-volecity fibers, visceral fferents, pre-galncilinc autonimcis

Question 52

Type C fibers

Answer 52

slow velocity fibers postgaglionic autonomic, chronic pain

Question 53

Neurovascular budnle

Answer 53

nerves accompany artery, vein, and lymphatic fvessel as they run through CT of body