08a: Neurons

Question 1

Characteristic nuclear morphology.

Answer 1

Large, spherical, euchromatic; prominent nucleolus

Question 2

“Clumps” in neuron cytoplasm are (X), formally termed (Y).

Answer 2

X = rER 
Y = Nissl bodies

Question 3

In Golgi stain, (X)% of neurons are stained.

Answer 3

X = 1-5

Question 4

Dendrites contain which intracellular structure(s)?

Answer 4

Mitochonria, ribosomes, and sometimes rER

Question 5

(Axons/dendrites) are tapered.

Answer 5

Dendrites

Question 6

Axons contain which intracellular structure(s)?

Answer 6

Mitochondria, cytoskeleton

Question 7

(Axons/dendrites) don’t stain with basic dyes because:

Answer 7

Axons; no rER or free ribosomes

Question 8

What’s the difference in morphology of the pre- and post-synaptic membranes?

Answer 8

Post-synaptic membrane contains many folds (to increase surface area), unlike pre-synaptic membrane

Question 9

The “supporting cells” of the CNS.

Answer 9

1. Oligodendrocyte
2. Astrocyte
3. Microglia

Question 10

Nuclear morphology of oligodendrocytes.

Answer 10

Small, heterochromatic

Question 11

Astrocyte function:

Answer 11

1. Maintain stable microenvironment around neurons

2. Physical support

Question 12

Nuclear morphology of astrocytes.

Answer 12

Small, heterochromatic

Question 13

Microglial cells function:

Answer 13

Defense/immune

Question 14

In CNS, (X) is responsible for myelin synthesis.

Answer 14

X = oligodendrocyte

Question 15

In CNS, (X) are part of the mononuclear phagocyte system, along with (Y).

Answer 15

X = microglial
Y = osteoclasts, macrophages

Question 16

T/F: All CNS cells born/develop in CNS.

Answer 16

False - microglia born in marrow and migrate to CNS

Question 17

In CNS, (X) picks up excess NT.

Answer 17

X = astrocytes

Question 18

Astrocytes contain (X), which are responsible for giving CNS structure.

Answer 18

X = Glial Fibrillary Acidic Protein (bundles of intermediate filaments)

Question 19

What are some characteristics of microglia morphology?

Answer 19

Small size; cytoplasmic inclusions

Question 20

In CNS, (X) covers most free surfaces.

Answer 20

X = astrocytes

Question 21

In PNS, (X) is responsible for myelin synthesis.

Answer 21

X = Schwann cell

Question 22

One Schwann cell myelinates (X) number of internode(s).

Answer 22

X = one

Question 23

In PNS, each internode is myelinated by (X) number of (Y).

Answer 23

X = one
Y = Schwann cell

Question 24

In PNS, each (myelinated/unmyelinated) axon is enclosed by (X). For what?

Answer 24

Both;
X = Schwann cell
Physical support

Question 25

The Endoneurium is:

Answer 25

the CT found within nerve fascicle (in PNS)

Question 26

Endoneurium is comprised of:

Answer 26

Type 3 collagen fibrils

Question 27

Endoneurium runs (perpendicular/parallel) to nerve fibers.

Answer 27

Encircles and runs parallel

Question 28

Endoneurium is bound to (X) of (Y) cells.

Answer 28

``` X = external lamina Y = Schwann ```

Question 29

Perineurium is:

Answer 29

CT that encircles and groups each fascicle (in PNS)

Question 30

Perineurium is comprised of:

Answer 30

1-5 layers of squamous cells, separated by collagen fibrils

Question 31

Epineurium is:

Answer 31

CT that binds fascicles together, into bundle

Question 32

Epineurium is comprised of:

Answer 32

Dense CT and some adipose

Question 33

Epineurium is bound to (X) surrounding tissue.

Answer 33

None; no coherent boundary with surrounding tissue

Question 34

Satellite cells in (CNS/PNS) are a subclass of (X). Where are they located? What's their function?

Answer 34

PNS; X = Schwann cells Surround neuronal cell bodies and control microenvironment

Question 35

Maintaining stable microenvironment in PNS involves (X) transport by (Y) cells.

Answer 35

``` X = active Y = perineurial ```

Question 36

In PNS, which intercellular junctions are important for maintaining stable microenvironment? Why?

Answer 36

Tight junctions; separate endoneurial tissue fluid from fluid surrounding nerve fascicle

Question 37

The tight junctions in PNS are formed by (X) cells.

Answer 37

X = perineurial

Question 38

List the cells that reside in a nerve fascicle.

Answer 38

1. Schwann 2. Fibroblasts 3. Macrophages 4. Mast cells

Question 39

Most, (X)%, of cells in nerve fascicle are (Y).

Answer 39

``` X = 90 Y = Schwann ```

Question 40

In PNS, (X) is responsible for defense/immune function.

Answer 40

X = the immune system

Question 41

T/F: Both CNS and PNS are unique in that CT isn't responsible for providing structure/support.

Answer 41

False - physical support of PNS relies on CT

Question 42

In peripheral nerve injury, retrograde reaction involves (X) part of neuron and anterograde reaction involves (Y) part of neuron.

Answer 42

``` X = (proximal) axon Y = (distal) axon ```

Question 43

Axonal disintegration occurs (X) hours after injury.

Answer 43

X = less than 24

Question 44

Describe steps in anterograde degeneration of neuron.

Answer 44

1. Myelin pinched off from Schwann cell 2. BBB disrupted along entire nerve 3. Influx of additional macrophages

Question 45

Describe nuclear morphological changes in retrograde degeneration of neuron.

Answer 45

1. Peripheral movement of nucleus 2. Dissolution of Nissl bodies 3. Stripping of synapses from dendrites/soma

Question 46

In peripheral nerve injury, division of (X), forming (Y), begins the regeneration of the axon. This occurs in (proximal/distal) neuron.

Answer 46

``` X = Schwann cells Y = Schwann/endoneurial tubes ``` Distal

Question 47

In peripheral nerve regeneration, how do the two severed ends find each other?

Answer 47

1. Schwann/endoneurial tube secretes growth factors that attract proximal axon sprouts 2. Neuritic sprout tips love laminin (major glycoprotein in external lamina)

Question 48

Traumatic neuroma occurs when:

Answer 48

Sprouting axon cannot reach Schwann cell tubes

Question 49

List some reasons why nerve regeneration in CNS is (more/less) favorable than in PNS.

Answer 49

Less - extremely rare 1. External lamina doesn't exist to guide axon sprouts 2. CNS myelin inhibitor of axonal growth (unlike Schwann cells) 3. Astrocytes fill spaces, forming barrier (gliotic scar)