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BLOCK 2 - Histology (Grace) > Nervous Tissue > Flashcards

Nervous Tissue Flashcards

1
Q

2 principal types of cells in nervous system?

A
  • neurons
  • supporting cells
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2
Q

Supporting cells in CNS?

A

Ependymal cells

Neuroglial cells:

  • Astrocyte
  • Oligodendrocyte
  • Microglia
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3
Q

Supporting cells in PNS?

A 
Schwann cells (surround nerve processes)
Satellite cells (surround nerve cell bodies in ganglia)
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4
Q

Neuron cell body

  • is also called?
  • has what type of nucleus?
  • contains…?
A
  • called “perikaryon”

- euchromatic nucleus (very active)

- contains: nissel bodies (stacks of rough ER), ## mitochondria, large perinuclear golgi

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5
Q

Where are Nissl bodies & free ribosomes found in neurons?

A
  • extend into dendrites but not into the axon

- NOT in axon hillock

- dependence on cell body for maintenance

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6
Q

Dendrites:

A
  • Carry information towards the cell body
  • Greater diameter than axons
  • Unmyelinated
  • Arborizations = dendritic trees
  • greatly increase receptor surface of neuron
  • Contain organelles characteristic of cell body
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7
Q

Axons:

A
  • Carry information away from cell body
  • 1 axon for each neuron
  • Origin = AXON HILLOCK
  • NO Nissl and Golgi
  • Terminal arborizations (axon terminals)
  • Contains: Microtubules, neurofilaments, mitochondria &vesicles
  • Plasma membrane =** Axolemma**
  • Contents = Axoplasm
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8
Q

Golgi Type 1 Neuron:

A
  • Motor nuclei of CNS
  • pyramidal cells = long axons (1 meter+)
  • leave gray matter of CNS, traverse white matter, terminate in the periphery
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9
Q

**Golgi Type 2 **Neuron:

A
  • Golgi cells in cerebellum
  • stellate neurons = short axon
  • Axon branched near target organ
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10
Q

sensory neurons

A

receptors TO cns

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11
Q

motor neurons

A

cns/ganglia TO effector cells

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12
Q

interneurons

A

make up 99.9% of neurons

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13
Q

MULTIPOLAR NEURONS

A

1 axon + 2 or more dendrites

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14
Q

BIPOLAR NEURONS

A

1 axon + 1 dendrite

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15
Q

PSEUDOUNIPOLAR NEURONS

A

1 process (axon) that divides close to cell body into 1 processes

(develop as bipolar but processes fuse, then branch)

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16
Q

ANTEROGRADE transport

A

AWAY from cell body TO periphery
- Kinesin

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17
Q

RETROGRADE transport

A

RETURN from axon terminal & dendrites TO cell body
- Dynein

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18
Q

synapses occur between…

A

neuron –> neuron

neuron –> effector cell (muscle, gland)

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19
Q

Types of SYNAPSES

A

axosomatic/axodendritic

(axon bouton –> dendrite)

axoaxonic

(axon bouton –> axon)

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20
Q

ELECTRICAL SYNAPSES

A

gap junctions (ion movement b/t cells)

  • smooth muscle (nexus)
  • cardiac muscle

NOT skeletal muscle

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21
Q

CHEMICAL SYNAPSES

A

presynaptic bouton –> synaptic cleft –> postsynaptic membrane

  • cleft = 20-30nm
  • synaptic vesicles release neurotransmitters
    ex. neuromuscular junction
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22
Q

Schwann Cells

A

- mylenation in PNS

  • originate from neural crest cells
  • create myelin sheath aroudn axon
  • sheath = Schwann cells or neurilemma (Schw.cell cytoplasm)
  • neurilemma = nucleus + most organelles

NO MYELINE = axon hillock + axon terminal

  • Nodes of Ranvier b/t schwann cells in sheath
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23
Q

Where is cytoplams located in the myelin sheath?

A

inner collar of cytoplasm

  • b/t axon + myelin

Schmidt-Lantermann clefts

  • small ilands w/i lamellae of myelin

perinodal cytoplasm

  • @ node of ranvier

outer collar fo perinuclear cytoplasm

  • around myelin
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24
Q

Unmyelinated nerves (PNS)

A
  • enveloped by Schwann cell cytoplasm
  • Single axon or group of axons:

*may be enclosed in a single invagination of Schwann cell surface

* axon rests in a cleft in the cytoplasm of a Schwann cell, with a single mesoaxon

25
Q

Which type of axon conducts impulses faster?

what is the action of an impulse “jumping” form node to node called?

The speed of transmition is directly related to…

A

MYELINATED = FASTER

  • “Saltatory Conduction”
  • speed directly related to myelin thickness + axon thickness
26
Q

Satellite Cells

A
  • Surround ganglionic neuronal cell bodies
  • Cuboidal: complete layer around cell body (only nuclei visible)
  • Originate from neural crest cells
  • Analogous to Schwann cell
    *insulation
    *nutrition
27
Q

Neuroglia

A
  • “GLIAL” cells in CNS
  • More numerous than neurons
  • Most brain tumors = glial in origin
28
Q

3 types of neuroglia:

A

oligodendrocytes

  • form myeline in CNS
  • 1 cell can myelinate multiple neurons

astrocytes

  • physical + metabolic support for CNS neurons
  • found attached to blood vessels

microglia

  • phagocytic cells of CNS
29
Q

ASTROCYTES

A
  • Largest of glial cells
  • 2 kinds:
  • *PROTOPLASMIC** = prevalent in gray matter
  • *FIBROUS =** more common in white matter
  • have elaborate processes
  • extend b/t vessels and neurons
30
Q

When there is damage to the CNS, which cells form scar tissue?

A

ASTROCYTES

(fibrous connective tissue)

31
Q

Which neuroglial cells might have a role in regulating tight junctions of Blood-Brain Barrier?

A

ASTROCYTES

32
Q

BLOOD BRAIN BARRIER

A
  • functional barrier w. tight/occluding junctions sealing capilary endothelium
  • controls passage of substances fr blood into CNS tissue

= protects neuronal microenvironment

  • perivascular feet of astrocytes on basal lamina capillaries helps regulate

= stable composition and constant balance of ions in the interstitial fluid

= Protects neurons + glial cells from potential toxins + infectious agents

NOT in Choroid plexus and posterior pituitary, etc.

33
Q

OLIGODENDROCYTES

A
  • CNS myelin formed by:
    *concentric layers of oligocyte plasma membrane
  • Aligned in rows between axons
  • gives off several tongue-like processes –> wraps around an axon

= internodal segment

- oligodendrocyte forms myelin sheaths for several (3—50) nerve fibers

34
Q

Microglia

A
  • Part of mononuclear phagocytic system
  • Present in small numbers

** (proliferate during injury/disease)**

  • Secrete immunoregulatory cytokines = dispose of unwanted cellular debris
35
Q

Ependyma

A
  • Lines fluid-filled cavities of CNS
  • Cuboidal to columnar (fluid-transporting characteristics)
  • several locations = specialized to:

produce cerebrospinal fluid

36
Q

CHOROID PLEXUS

A

- Modified ependyma (simple cuboidal - produces CSF)

- dialated fenestrated capillaries

- invaginated fold of pia mater (villi)

  • lateral, 3rd, 4th ventricles in brain
  • removes water from blood + release it as CSF
37
Q

What are the 3 layers/categories of connective tissue sheaths?

A

endoneurium

perineurium

epineurium

38
Q

ENDONEURIUM

A
  • thin layer of reticular fibers produced by the Schwann cells
  • surrounds individual nerve fibers
39
Q

PERINEURIUM

A
  • Surrounds bundles of nerve fibers
  • sheath of unique connective tissue cells
  • Cells joined by tight junctions
  • Form a barrier to passage of most macromolecules
  • Protects nerve from aggression
  • numerous actin microfilaments = contractile cells
40
Q

EPINEURIUM

A
  • outermost tissue of peripheral nerve
  • typical dense connective tissue:

(binds fascicles together)

  • adipose tissue often seen in larger nerve sheaths
  • carry blood vessels supplying nerves:

(vessels branch + penetrate perineurium)

41
Q

SENSORY GANGLIA

A
  • Craniospinal (DRG, cochlear)
  • Pseudounipolar neurons:
    *larger
    *close together
  • Thick fascicles
42
Q

AUTONOMIC GANGLIA

A
  • Sympathetic and Parasympathetic
  • Multipolar neurons
    *smaller
    *far apart
  • Diffuse nerve fibers
43
Q

Autonomic Nwevous System (ANS)

conducts impulses to:

A
  • smooth muscle
  • cardiac muscle
  • glandular epithelium
44
Q

THORACO-LUMBAR OUTFLOW

A

Sympathetic

  • norepinepherine
  • postganglionic fibers
45
Q

CRANIO-SACRAL OUTFLOW

A

Parasympathetic

  • acetylcholine
  • preganglionic + postganglionic fibers
46
Q

Enteric Nervous System

A
  • Confined w/i wall of gut
  • 2 sets of Plexus
  • *Myenteric (Auerbach)**
  • *Submucous(Meissner)**
  • unmyelinated nerve fibers intermingled w neuronal cell bodies
  • maintain peristaltic movements + secretory function of the gut
47
Q

Spinal Cord & Spinal Nerves

A
  • Directly continuous with brain
  • 31 segments:
    8 cervical
    12 thoracic
    5 lumbar
    5 sacral
    1 coccygeal
  • Each segment = pair of spinal nerves
  • Each spinal nerve is joined to its segment of cord by roots or rootlets
    (grouped as posterior (dorsal) or anterior (ventral) roots)
48
Q

Grey Matter in spinal cord:

A
  • Anterior Grey Horn
  • Posterior Grey Horn
  • Lateral Grey Horn
  • Grey commissure
  • surrounds the central canal

has neuron cell bodies, dendrites, axons & glia

49
Q

White matter in spinal cord:

A

pheripheral

  • contains mainly myelinated fibers
  • Arranged in three pairs of funiculus = Anterior, Lateral &Posterior
  • Functionally related bundles of axons called TRACTS
50
Q

CORTEX of brain

A

**gray matter **

  • contains cell bodies, axons, dendrites, and glial cells, synapses
51
Q

NUCLEI of brain

A

Islands of gray matter

  • found in deep portions of cerebrum and cerebellum
52
Q

WHITE MATTER of brain

A

contains mainly:

  • myelinated axons of nerve cells
  • glial cells
  • vessels
53
Q

Cerebrum

A

Cerebral cortex + white matter
- Cerebral cortex = 6 layers

  • PYRAMIDAL CELLS of cerebral cortex:
  • *found in layers III, V**
  • *small, medium, large pyramidal cells**
54
Q

PURKINJE CELLS

A

IN CEREBELLAR CORTEX

  • located between outer molecular layer + inner granular layer

apical numerous dendrites (arborize in molecular layer)

  • have a single axon (not visible in H&E)
  • *extends into granular layer**
  • *beginning of outflow from cerebellum**
55
Q

3 layers of CNS connective tissue:

MENINGES

A

COVER BRAIN & SPINAL CORD

Dura Mater:

  • outermost

Arachnoid:

  • beneath dura

Pia Mater:

  • innermost layer; rests directly on brain/spinal cord
  • delicate layer
56
Q

Some parts of CNS have no Blood Brain Barrier:

A
  • Neurohypophysis
  • Substantia nigra
  • Locus ceruleus
57
Q

Response to Injury in Nervous Systems:

“Wallerian degeneration”

A

anterograde

  • degeneration of axon distal to site of injury
  • *PNS degeneration takes a few days**
  • *CNS degeneration takes several weeks**

*Some retrograde degeneration also occurs
(only extends for several internodal segments)

58
Q

Response to Injury in Nervous Systems:

“Chromatolysis”

A
  • loss of Nissl substance from cell body:
  • *1-2 days after injury**
  • Changes in cell body are proportionate to:
    amount of axoplasm lost from injury
    (large amount =CELL DEATH)
59
Q

Response to Injury:
“Motor fiber cut”

A

muscles atrophy

BLOCK 2 - Histology (Grace) (10 decks)

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