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Histology 2018 > Lecture 15 > Flashcards

Lecture 15 Flashcards

1
Q

What are astrocytes, oligodendrocytes, Schwann cells, microglial cells, and ependymal cells?

A

Glial cells

non neuronal cells that support the CNS and also the PNS to a lesser extent

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2
Q

There are 2 different types of astrocytes, Fibrous astrocytes and protoplasmic astrocyes. Explain the differences between them

A

Fibrous A: have long processes with branches and are found in the white matter

Protoplasmic A: have shorter processes with many short branches and are found predominantly in the gray matter

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3
Q

What are the 2 types of glial cells that myelinate axons?

A

oligodendrocytes and Schwann cells

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4
Q

describe the differences between oligodendrocytes and Schwann cells.

A

Oligodendrocytes myelinate several axons in the CNS

Schwann Cells myelinate a section of a single axon PNS

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5
Q

Where is only place that the intraperiod line protein called “Major protein zero” is found?

A

the PNS

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6
Q

What kind of channels and signals is the cell body (Soma) of motor neurons associated with?

A

Associated with ligand gated channels and local potentials

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7
Q

What kind of channels and signals is the denrites of motor neurons associated with?

A

Associated with ligand gated channels and local potentials

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8
Q

What kind of channels and signals is the axon of motor neurons associated with?

A

associated with voltage gated cation channels and action potentials

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9
Q

What is the axon hillock portion of a motor protein? what is it associated with?

A

the site for the origin of the axon that is devoid of Nissle substance

it is associated with action potential generation

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10
Q

What portion of a motor protein contains the following:

the nucleus and Nissle bodies (RER and free ribosomes)

an Extensive RER, abundant mitochondria, abundant microtubules

A

the cell body

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11
Q

Dendrites contain the same cytoplasmic components as the cell body EXCEPT what?

A

the golgi body

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12
Q

What portion of a motor neuron contains the following:

mitochondria and microtubules but lacks RER, ribosomes, and golgi apparatus

A

the axon

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13
Q

describe axons and dendrites in terms of their physical presentation and how that can be used to distinguish them from one another.

A

Axons have a constant diameter until it terminates at the telodenrites (may be myelinated)(contain synaptic vesicles and related proteins)

Dendrites Tend to taper distally and may branch (may have dendritic spines)

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14
Q

distinguish the difference between a nerve and a tract

A

they are both “a bundle of axons”

nerve = PNS

tracts = CNS

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15
Q

distinguish the difference between a ganglion and a nucleus

A

they are both “an aggregation of cell bodies and dendrites”

ganglion = PNS

Nucleus = CNS

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16
Q

Distinguish between the epineurium, perineurium, and endoneurium of a typical peripheral nerve

A

Epineurium: thick fibrous coat that covers the entire nerve

Perineurium: dense CT that covers bundles of axons (fascicles) within a nerve

Endoneurium: A thin layer of reticular CT, composed of Type III collagen, that surrounds individual fibers and Schwann Cells

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17
Q

What is perineurium composed of?

A

Has neuroepithelial fibroblasts on the inner surface that are joined by tight junctions (Zonulae occludens that provide a permeablity barrier) to form the “blood-nerve barrier”

Theses tight junctions must be repaired via microsurgery when reattaching a limb

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18
Q

Describe the differences between Golgi I and Golgi II neurons.

A

Golgi I neurons: neurons with long axons which leave the grey matter of which they are a part

Golgi II neurons: Neurons with short axons which ramify through the gray matter

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19
Q

Which direction does anterograde transport occur in a nerve cell? describe the different speeds at which this transport can occur

A

Anterograde transport: cell body toward the axon and utilizes kinesin

Slow (1-6 mm per day)

Intermediate (50-100 mm per day)

Fast (400 mm per day)

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20
Q

Which direction does retrograde transport occur in a nerve cell? describe the different speed at which this transport occurs

A

axon toward the cell body and utilizes cytoplasmic dynein

100-300 mm per day

(Carries endocytosed materials and recycled proteins)

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21
Q

name some of the functions of astrocytes (probably dont need to know all of these)

A

mediates the exchange of nutrients and metabolite between blood and neurons

Development of the cerebral cortex (radial glial cells extensions form through the developing brain to provide

Potassium sink (take in excess K+ from the environment

Secretion of neuron trophic factors

Uptake/metabolism of neurotransmitters (Ach is a good example of this)

Help form noncollagenous scar tissue after injury to the CNS

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22
Q

List 3 of the main functions of microglial cells

A

Phagocytic in the CNS

Recruit leukocytes across the BBB

Modulate initiation and progression of immune responses along with astrocytes

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23
Q

Describe ependymal cells in terms of their physical cell type, where they are found, and what they do.

A

ciliated cuboidal cells line the ventricular system of the CNS. (sometimes considered to be a microglial cell)

Function in transport

Secrete cerebrospinal fluid, especially in the choroid plexus

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24
Q

Define satellite glial cells

A

form crescents around cell bodies in the ganglia

Function as support cells

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25
Q

For astrocytes, oligodendrocytes, schwann cells, microglial cells, ependymal cells, and satellite cells, state their origin.

A

Astrocytes: from the neural crest (neuroepithelium) and are found only in the CNS

Oligodendrocytes: derived from the neural crest (neuroepithelium) and are found only in the CNS

Schwann cells: derived from the neural crest (neuroepithelium)

microglial cells: derived from macrophages

ependymal cells: derived from neuroepithelium (not the neural crest)

satellite cells: derived from the neural crest and form crescents around cell bodies in the ganglia

26
Q

Identify where ependymal cells are found.

A

They line the ventricular system of the CNS (also make CSF in the choriod plexus)

27
Q

What are Schmidt-Lanterman clefts (incisures) are a component of the myelin sheath in the PNS. Describe these clefts.

A

residual areas of cytoplasm within the major dense lines

28
Q

Describe the major dense line that forms part of the myelin sheath in the PNS.

A

an electron-dense line created by cytoplasmic space remnant adjacent inner leaflets

29
Q

In the myelin sheath, what are the Internal and external mesaxons?

A

they are the outer and innermost points of fusion between the outer leaflets (extracellular leaflets)

30
Q

in the myelin sheath, what is the Intraperiod line?

A

an electron-dense line created by extracellular space between adjacent outer leaflets

31
Q

In the myelin sheath, what is the role of myelin protein zero (mpz)?

A

myelin protein zero (mpz): a transmembrane protein that forms homodimers that go on to form homotetramers with the opposing homodimers from the major protein zero in the outer leaflet (binds with it’s own cells)

32
Q

in the myelin sheath, what is the role of myelin basic protein?

A

myelin basic protein: found in the major dense line and is a protein that is associated with stabilizing the lipids in the inner leaflets (common in both the CNS and PNS)

33
Q

in the myelin sheath, what is the role of proteolipid protein?

A

proteolipid protein: a protein that basically replaces the role of major protein zero in the CNS, which has 4 homophobic domains that reside in the membrane and 2 extracellular loops

34
Q

In what cell type is connexin 32 found, and where in this cell is it most concentrated?

A

expressed in Schwan cells and is concentrated in the paranodal region and the incisures of Scmidt-Lanterman.

35
Q

List the issues that are associated with mutations in myelin protein zero (mpz), proteolipid protein, and connexin 32

A

myelin protein zero (mpz): mutations in this are related to Charcot-Marie-Tooth diseases

proteolipid protein: Mutations in this protein result in Pelizaeus-Merzbacher disease

connexin 32: mutations in this induce the demyelinating X-linked Charot-Marie-Tooth disease

36
Q

describe the structure of mylein in the PNS

A

myelin from adjacent Schwann Cells interdigitate at the nodes of Ranvier

Their connections in the extracellular space (intraperiod oline) are formed by 2 proteolipid protein molecules, from opposing membranes, interacting with their 2 extracellular loops

37
Q

describe the structure of mylein in the CNS

A

nodes feature an Astrocytic End-foot, which prevents myelin from different oligodendrocytes from touching

Their connections in the extracellular space (intraperiod line) are formed by 2 mpz molecules, from opposing membranes, coming together to form a homotetramer

38
Q

In the CNS, why doesn’t myelin from adjacent oligodendrocytes interdigate at the node of ranvier, like they do in the PNS?

A

the “end-foot” of an astrocyte contacts the node of ranvier and prevents interdigation of the myelin

39
Q

Compare the structure of presynaptic membranes and postsynaptic membranes.

A

Presynaptic Membranes: voltage-gated calcium channels (used to bring in Ca2+ to bring synaptic vesicles to the surface after the arrival of an action potential)

Postsynaptic Membranes: have neurotransmitter receptors

40
Q

describe the role of SNAPs, vesicle docking proteins, and synapsins to synaptic structure and transmission.

A

SNAPS: receptors that bind synaptic vesicles to presynaptic membrane

Vesicle docking proteins: are SNAP receptors found in presynaptic and synaptic vesicular membranes

Synapsins: filaments in the presynaptic membrane

41
Q

Describe Axosomatic synapses

A

Axosomatic: axon terminal synapses with the neuron cell body

42
Q

Describe Axoaxonic Synapses

A

Axoaxonic: Axon terminal synapses with another axon terminal

43
Q

Describe Axodendritic Synapses

A

Axodendritic: Axon terminal synapses with a dendrite

44
Q

Describe Axospinous Synapses

A

Axospinous: axon terminal synapses with dendritic spine

45
Q

Describe Excitatory Synapses

A

Excitatory: more positive end-plate potential (closer to threshold in synapse)

46
Q

Describe Inhibitory Synapses

A

Inhibitory: more negative end-plate potential (farther from threshold in synapse)

47
Q

List the meninges in order from superficial to deep

A

Bone (not a meninge)

Epidural space (not present around the brain)

Dura mater

Subdural space

Leptomeninx

48
Q

What is the subdural space associated with?

A

Subdural space: associated with venous sinuses (where we drain cerebrospinal fluid)

49
Q

Where is CSF normally found?

A

Subarachnoid space (between the arachnoid matter and the pia matter) and ventricles

Permeates between or through the endothelial cells lining the venous sinus

50
Q

describe the arachnoid-CSF barrier

A

the arachnoid membrane prevents the CSF in the subarachnoid space from coming in contact with the fluid of the extracellular space of the dura mater.

The CSF drains around the cerebral hemispheres to the arachnoid villi (which are placed along the venous sinus)

51
Q

Describe the Blood-CSF barrier

A

In order for the choroid plexus to make CSF, ultrafiltrate plasma from the blood must pass through he fenestrated (“leaky”) endothelium of the blood capillary

52
Q

Describe the Blood Brain Barrier

A

The tight junctions of the brain capillary endothelium are the structural component of the blood-brain barrier.

Some substances can still diffuse across this through the “astrocytic end-feet” that contact the capillary wall

53
Q

The choroid plexus is a highly infolded ____ ____ epithelium that extends into the ____ from the roof plate

A

simple cuboidal

ventricles

54
Q

The choroid epithelium is linked by _____ ______ with apical microvilli, infolding of the ____ _____ membrane, and abundant mitochondria

A

tight junctions

basal plasma

55
Q

what is present in the apical membranes of the choroid plexus that plays a major role in the formation of CSF?

A

Na+, K+, and ATPase pumps

56
Q

list the similarities and differences the ependyma has with the choroid plexus

A

both are simple cuboidal

both feature apical microvilli

ependyma is endothelium while choroid plexus is epithelium

ependyma is linked by zonula adherentes while C.P. uses tight junctions

ependyma has cilia while C.P. does not

57
Q

What are tanycytes in the 3rd ventricle tightly linked to? what is their function?

A

Tanycytes in the third ventricle are tightly linked to the adjacent ependymal cells

they send processes through the glia limitans to form end-foot processes on underlying blood vessels

58
Q

list similarities and differences between sensory and autonomic ganglia

A

both have a CT epineurium capsule

Sensory: clustered pseudounipolar neurons

postganglionic neurons ARE myelinated

satellite cells abundant around the body of each neuron

Autonomic: clustered multipolar neurons

postganglionic neurons ARE NOT myelinated

less satellite cells

59
Q

Where are sensory ganglia (dorsal root ganglia) found?

A

one centrifugal process in the remus of the spinal nerve

another into the spinal cord

60
Q

Where are autonomic ganglia (sympathetic ganglia) found?

A

near presynaptic cells within the CNS

Histology 2018 (20 decks)

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