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Cellular Week 4 > Nervous Tissue - Giffin Lecture > Flashcards

Nervous Tissue - Giffin Lecture Flashcards

1
Q

Concept map for principles?

A

…

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2
Q

What does nervous tissue consist of?

A

1) neurons - transmit electrical impulses from one site in the body to another, and receive and process information
2) neuroglia: non-conducting cells that are in intimate physical contact with neurons; support cells

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3
Q

What are neurons?

A

Basic unit of nervous system

Possess electrical excitability, the ability to respond to a stimulus and convert it into an action potential

Provide most of the unique functions of the nervous system, such as sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions

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4
Q

What do neurons consist of?

A

Cell body = soma

Dendrites (1 to many)

Axon (single - nerve fiber)

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5
Q

Cell body is also called….

What do nuclei look like for nerve cells?

A

Perikaryon or soma

Basically a cell nucleus surrounded by cytoplasm

Nuclei of nerve cells are: large, round, euchromatic and have a single prominent nucleolus

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6
Q

Cell body is what you see when you do a histology slide of a neuron… Hard to see dendrites..

Neurons are usually very active cells!

They have chunky purple stuff in the body..

A

…

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7
Q

Cell Body of a neuron is abundantly supplied with…..

A

1) masses of rough endoplasmic reticulum (Nissl substances)
2) numerous golgi bodies
3) lots of SER
4) many mitochondria
5) extensive cytoskeleton elements
6) Nissl substance

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8
Q

The axon has NO nissl substance

Material synthesized in the cell body must be transported to the periphery

A

….

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9
Q

What is the Nissl substance?

A

Rough endoplasmic reticulum

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10
Q

The axon hillock is close to body followed by the initial segment

A

….

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11
Q

What is enriched in the initial segment of the axon?

A

Na+ channels

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12
Q

What is the axon?

A

Specialized for conducting signals from one nerve cell to another or to muscle fiber or gland cell

Long, thin, cylindrical projection that often join the cell body at a cone-shaped elevation called the axon hillock

NO RER!

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13
Q

Axons with myelin are called….

A

Myelinated axons

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14
Q

Myelin is formed by what?

A

Support cells

Schwann cells in the PNS

Oligodendroglia in the CNS

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15
Q

Cytoplasm for axon?

Plasma membrane for axon?

A

Axoplasm

Axolemma

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16
Q

Virtually all protein synthesis occurs in the cell body (some in the dendrites)

Need to be transported to distal parts - do this with microtubules and antegrade and retrograde transport

A

….

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17
Q

Anterograde transport can be what?

A

Fast - synaptic vesicles, mitochondria - KINESISNS!

Slow B - actin, spectrin

Slow A - tubular, intermediate filaments

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18
Q

Retrograde transport is what?

A

Fast! - synaptic vesicles, mitochondria

By dyneins

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19
Q

What are dendrites?

A

Short, tapering and highly branched

Receptor processes that receive stimuli from other neurons or from the external environment

Information is transmitted to the cell body

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20
Q

Dendrites are…

A

Unmyelinated!

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21
Q

Dendrites have extensive arborizations to do what?

A

Increase SA!

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22
Q

Contents of cell body cytoplasm (with exception of golgi) and the cytoplasm of what are similar?

A

Dendrites!

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23
Q

Axon terminals- presynatpic endings

A

Usually there is only one unbranched axon per neuron

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24
Q

What are axon ends called?

A

Axon collaterals
Telodendria
Axonal terminal
Synaptic knobs

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25
Q

Axon terminals generate and transmit action potentials….

They secrete neurotransmitters from the axonal terminals

A

…

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26
Q

There are lots of mitochondria and synaptic vesicles at axonal terminals!

A

…

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27
Q

A nerve is made up of many nerve cell fibers that are bound together by connective tissue… it has three parts…

A

1) epineurium
2) perineurium
3) endoneurium

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28
Q

Epineurium

A

A sheath of dense collagenous CT with elastic fibers that surrounds the nerve.. Blood vessels of various sizes can be seen.

Allows nerves to be stretched

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29
Q

Perineurium

A

Composed of CT with a lamellar arrangement consisting of several concentric layers. Surrounds bundles of nerve fibers and forms the BLOOD-NERVE BARRIER which isolates the neural environment from humoral facts and cells from the circulation

Fascicles/bundles are organized by this

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30
Q

Endoneurium

A

Consists of thin layer of loose CT which surrounds the individual nerve fibers

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31
Q

Tight junctions between what cells form the isolating barrier in nerves?

A

Perineurium cells!

32
Q

Conduction velocity in the axon is enhanced by …?

A

Myelination

33
Q

Axons in the CNS are myelinated by….

A

Oligodendrocytes

34
Q

Axons in the PNS are myelinated by….

A

Schwann cells!

35
Q

Neural crest cells form what PNS support cells?

A

Schwann cells

Satellite cells

36
Q

Myelination is a dynamic process, which involves the ensheathment of the axon by the glial cell and subsequently the extrusion of cytoplasm from parts of the glial cell. Adhesive proteins on the cytoplasm and extracellular side of the PM contribute to a tight opposition of the lipid bilayers… CONCENTRIC CIRCLES!

A

…

37
Q

The increased lipid content of the myelin sheath provides electrical insulation for the underlying axon

A

…

38
Q

What are nodes of ranvier?

A

Areas of the myelinated axon that are not covered by myelin sheath

39
Q

Each schwann cell myelinated what?

A

A SINGLE internode!

The internode can be up to 1.5 mm in largest nerve fibers

40
Q

What is concentrated at the nodes of ranvier?

A

Na+ voltage-gated channels

41
Q

Where are potassium channels located in nerves?

A

Internodes

42
Q

Nerve conduction is propagated/generated at nodes of ranvier

A

….

43
Q

What is the conduction called in myelinated nerves?

A

Saltatory conduction

44
Q

Schwann cells proliferate and remyelinate areas where it has been demyelinated… each lost myelin internode is replaced by….

Consequences?

A

Several shorter internodes with smaller diameter….

Consequently there are more internodes and the thickness is decreased - slower conduction

Have to make more jumps!

45
Q

One schwann cell can ensheath….? Axons

But can myelinated…. ? ….axons

A

One schwann cell can ensheath multiple axons, but myelinated only ONE axon….

Sheathing is NOT myelination! It is just holding it into position!

46
Q

Small diameter nerve fibers are ….

A

Non-myelinated! - just ensheathed?

47
Q

Multipolar neurons

A

Most abundant in CNS - big for motor neurons

Many processes extend from the cell body; all are dendrites except for a single axon!

48
Q

Bipolar neuron

A

Two processes extend from the cell body: one is a fused dendrite, the other is an axon

Rare

Found in some special sensory organs (olfactory mucosa, eye, ear).

49
Q

Unipolar (pseudounipolar)

A

One process extends from the cell body and forms central and peripheral processes; which together comprise an axon

Found mainly in PNS - Common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves

50
Q

Unipolar neurons have a little neck

Cell body live together in sensory ganglia

A

…

51
Q

Two types of sensory ganglia?

A

Spinal (dorsal root) and cranial ganglia

Associated with spinal and cranial nerves respectively

52
Q

What do the sensory ganglia contain?

A

Contain large sensory neurons and abundant small glial cells, called satellite cells

53
Q

Sensory neurons are what type of neuron?

A

Pseudounipolar

One process extends from the cell body and forms central and peripheral processes, which together comprise an axon

Has a little neck for the cell body

54
Q

Satellite cells

  • where they derived from?
  • control over what?
  • supply what to what?
  • act as….?
A

Neural crest cell derived

Control over the microenvironment of ganglia

Supply nutrients to the surrounding neurons

Act as protective, cushioning cells

55
Q

Look at slides of satellite cells!

A

…

56
Q

Neuroglia or “glia”

A

Do not generate or propagate AP

Forms half of the CNS

Acts as “glue” that hold nervous system together

Smaller than neurons and more numerous

57
Q

What can glial do that neurons cant?

A

Can divide and multiply in mature CNS

Can form cancers!

58
Q

What are the four main functions of glial cells?

A

1) to surround neurons and hold them into place
2) to supply nutrients and o2 to neurons
3) to insulate one neuron from another
4) to destroy and remove the carcasses of dead neurons

59
Q

What does the oligodendrocyte to/responsible for?

A

Responsible for forming and maintaining myelin sheath in CNS

Forms concentric circles

60
Q

How many oligodendrocytes per axon?

A

One oligodendrocyte may myelinated one axon or several!

61
Q

What do oligodendrocytes look like under a microscope?

A

Fried egg!

62
Q

What are astrocytes?

A

Largest of the neuroglia

Play a role in inducing the blood-brain barrier phenotype in the brain capillaries

Provides physical and metabolic support for nerve cells

Help maintain the appropriate chemical environment for the generation of action potentials

Undergo the process of glosis - scar formation

63
Q

See slides of astrocytes

A

…

64
Q

What can astrocytes be stained for?

A

Glial fibrillation acidic protein (GFAP)

65
Q

Astrocytes foot processes surround brain capillaries and during development induce what?

A

Endothelial cells to form tight junctions!!

This is the basis for blood-brain barrier - a system of controlled transcapillary transport which maintains homeostasis in the CNS

66
Q

When neurons are lost and brain tissue is damaged, what happens?

What is this process called?

A

Astrocytes proliferate, fill the gaps, and restore CSF-brain and blood-brain barriers

This process is called astrogliosis

Is for the CNS what scarring is for extraneural tissues

67
Q

What are microglia?

Where do they originate?

A

Smallest of the glial cells

Originate in the yolk sac and populate the brain mesenchyme

Are the primary immune cells of the CNS and are similar to peripheral macrophages

68
Q

Microglial nodule

A

Cluster of microglial cells and lymphocytes surrounding a virus-infected neuron

69
Q

What are ependymal cells?

A

Cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia

They line the ventricles of the brain and central canal of the spinal cord

70
Q

Look at slide of ependymal cells that have cilia that project into the ventricle

A

….

71
Q

What is the growth cone of an axon (or dendrite) composed of?

A

Flat, fanlike membranes called the lamellipodia

72
Q

What protrudes from the lamellipodia?

A

Fine tubes called fillapodia

73
Q

The filipodia extend and retract constantly and explore their surroundings. When a Filipino, instead of retracting, attaches itself to a substrate, it makes…?

A

A growth cone that advances in that direction!

74
Q

What projects into the filipodia of the growth cone?

A

Actin filaments!! (Growing axons)

75
Q

Near the periphery of the growing axon, the actin filaments elongate by polymerization of the actin proteins… what happens in the middle by contrast?

A

In the central part of the lamellipodia, actin filaments are broken down.

At the center of the axon, the neurite that elongates behind the advancing growth cone, a cytoskeleton made of TUBULIN forms!

Vesicles travel along these microtubules and fuse with the growth cone’s membrane to let it expand

76
Q

What happens to a neuron if it is cut in the PNS?

A

Regeneration!

Schwann cells degenerate and then reproliferate

Cellular Week 4 (11 decks)

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