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Histology Final > Nervous > Flashcards

Nervous Flashcards

1
Q

Nervous tissue is composed of:

A

Neurons/ nerve cells –> have cytoplasmic processes

Glial cells: support neurons

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2
Q

Neurulation

A
  • 3rd to 4th week
  • neuroectoderm develops
  • Neural tube –> neuroblasts and spongioblasts –> Neurons and glia of CNS
  • Neural crista –> Neurons and glia of PNS
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3
Q

Properties of neurons

A
  • Excitable: Respons to changes in Environment (changes in electrical potential)
  • Propagation: Action potentian travels
  • Secretory: Neurotransmitter (Synapse) and neurohormones (by neurosecretory Hormones in Hypothalamus)
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4
Q

Morphological types of neurons

A

UNIPOLAR: embryonic, only one single axon

BIPOLAR: retina and olfactory organ, one single dendrite and one axon

PSEUDO-UNIPOLAR: sensory Neurons of spinal cranial nerve ganglia, dendrite and axon come from common stem

MULTIPOLAR: motor and intermediate, many processes

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5
Q

Functional types of neurons

A
  • Sensory, afferent: accept Stimuli, convey info to CNS
  • Motor, efferent: Signals from brain to effector organsvia spinal cord
  • Intermediate: in between motor and sensory
  • Neurosecretory Neurons: in Hypothalamus, secrete neurohormones
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6
Q

Cell Body of neuron

A
  • large
  • central nucleus
  • Golgi, mitochondria, ER pigemtn inclusions (Melanin)
  • SPECIAL ORGANELLES: nissl substance, neurofilaments
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7
Q

Nissl substance

A
  • also called trigroid
  • cytoplasm of cell Body –> rER and ribosomes
  • in Body and dendrites and NOT IN THE AXON
  • Neurotransmitter are synthesized here
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8
Q

Cytoskeleton of a neuron

A
  • Microtubules
  • Intermediate Filaments –> neurofilaments
  • Microfilaments

–> supporting anf transporting function

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9
Q

Dendrites

A
  • have dendritic spines: for synaptic contact and increases Surface
  • sER, Golgi, cytoskeleton
  • short and unmyleinated (except of pseudo-unipolar)
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10
Q

Functions of dendrites

A
  • receive Stimuli and transmit Impulse to cell body
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11
Q

Axon

A
  • arising from axon hillock
  • turns into initial Segment
  • cytoskeleton, mitochondria, vesicles
  • terminal boutons
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12
Q

Axonal transport

A

–> movement of cellular substances

  • along micortubules
  • KINESIN and DYNEIN are motor proteins

anterograde Transport: from Body to terminal, by kinesin, towards positive end
retrograde Transport: from terminal to Body, by dynein, towards negative end

slow Transport: anterograde
fast Transport: anterograde and retrograde

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13
Q

Functions of neuroglial cells (7)

A
  • support
  • protection
  • insulation
  • metabolic Exchange
  • repair
  • clearance of neurotransmitters from cleft
  • Regulation of intercellular fluid
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14
Q

Classification of glial cells

A

PNS

  • Schwann cells
  • Satellite cells

CNS

  • Microglia
  • Ependymal cells
  • Astrocytes
  • Oligodendrocytes
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15
Q

Schwann cells (PNS)

A
  • surround all axons and dendrites in PNS
  • form either myleinated OR unmyleinated fibers
  • support, protection, regeneration
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16
Q

Satellite cells (PNS)

A
  • small, round or cuboidal
  • surround BODIES of Neurons in ganglia
  • support and protection
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17
Q

Microglia (CNS) /hortega cells

A
  • small and elongated with processes
  • mesenchymal origin
  • tissue Damage –> transform into amoeboid cells and belong to MPS
  • defense and immune functions
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18
Q

Ependymal cells (CNS)

A
  • epithelial lining of ventricles in brain and spinal canal
  • cuboidal or low columnar
  • microvilli on apical Surface (Absorption, secretion)
  • TANYCYTES: cells that have Long basal processes –> Transfer of chemical Signals from Liquor to CNS
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19
Q

Blood - cerebrospinal fluid - barrier

A
  • Endothelial cells of fenestrated capillary
  • b.m.
  • Ependymal cells
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20
Q

Astrocytes

A
  • largest
  • Long branched processes
  • two types
    1. Fibrous astrocytes (in White matter), fewer processes
    2. Protoplasmic astrocytes (Grey matter), more process.
  • processes end in “end feet”
  • end feet are on Neurons, nodes of ranvier and synapses and on b.m. of capillaries (BBB)
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21
Q

blood- brain- barrier

A
  • endothelial cells of continuous capillaries
  • b.m.
  • astrocyte perivascular feet

highly selective
>Transports metabolic products
> restricts passage for Bacteria
> protects CNS from fluctuating Levels of electrolytes

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22
Q

Functions of astrocytes

A
  • support
  • protection
  • metabolic Exchange
  • support synaptic activity
  • removing excess of neurotransmitters
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23
Q

Oligodendrocytes (CNS)

A
  • small
  • numerous cytoplasmic processes
  • predominant in White matter
  • myelination of axons in CNS
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24
Q

Myelinated nerve fibers

A
  • Schwann cells in PNS
  • Oligodendrocytes in CNS
  • White
  • large Diameter
  • abundant in somatic nervous System
  • 120m/ sec –> FAST
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25
Q

Non-myelinated nerve fibers

A
  • axons lie loose in schwann cells (PNS)
  • Grey
  • small Diameter
  • in autonomic nervous System
  • 1-2 m/sec –> SLOW
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26
Q

Formation of non-myelinated nerve Fiber (in PNS)

A
  • Axons invaginate in clefts of Schwann cells
  • MESAXON: Zone of Apposition of schwann cell
  • continuous sheath –> no nodes of ranvier
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27
Q

Structure of non-myelinated nerve Fiber (in PNS)

A
  1. Axon (one or more)

2. Neurilemma (cytoplasm and organelles of schwann cell)

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28
Q

Formation of myelinated nerve Fiber (in PNS)

A
  • ONE axon invaginates into Schwann cell

- MESAXON rotates around cell, enveloping axon

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29
Q

Structure of myelinated nerve Fiber (in PNS)

A
  1. Axon
  2. Myelin (layers of schwann cell Plasma membrane)
  3. Neurilemma (extruded cytoplasm of schwann cell)

Fiber is surrounded by b.m. and endoneurium

30
Q

Nodes of Ranvier

A
  • gapds between Schwann cells along the myelinated axon
  • not covered by Myelin sheath
  • Neurilemma is still present
  • ion channels present here
31
Q

Internodal segment

A
  • between two nodes
  • one schwann cell myelinates one Segment
  • electrical insulation by Lipid Content
  • allows for saltatory conductance –> increases speed
32
Q

Myelination process in the CNS

A
  • by oligodendrocytes
  • cytoplasmic processes rotate around axon
  • one oligodendrocyte can contribute to myelination to up to 50 axons
33
Q

Specialties in myelination of CNS

A
  • astrocytes cover nodes
  • internodal Segments are Shorter
  • chemical differences between PNS and CNS Myelin
  • no b.m and no endoneurium!!!!!
  • fibers cannot Regenerate!!!!
34
Q

Regeneration of PNS fibers

A
  • distal part of Fiber degenerates
  • Fragmentation
  • phagocytosed by macrophages
  • Body swells, nucleus moves peripherally, nissl substance disappears
  • Schwann cells divide and form the cord - axon follows
  • 1-3 mm a day
35
Q

Functional organization of the nervous system

A
  • somatic
  • autonomic
    > Sympathetic
    > Parasympathetic
36
Q

Principles of CNS organization

A

Gray matter:

  • neuronal cell bodies
  • non-myleinated axons, dendrites, glail cells
  • bodies arranged in nuclei or multiple layers
  • neuronal processes and glial cells: NEUROPIL

White matter:

  • myelinated axons and glial cells
  • TRACT / FASCICLE: bundle of axons
37
Q

Spinal cord

A
  • Deep ventral median fissure and shallow dorsal median Sulcus
  • dorsolateral Sulcus on each side –> entry of sorsal nerve roots
  • Ventrolateral Sulcus: Exit of ventral nerve roots
38
Q

Grey matter of spinal cord

A
  • ventral Horns: bodies of large somatic motor Neurons
  • dorsal Horns: bodies of intermediate Neurons
  • small lateral Horns: bodies of autonomic (sympathetic) efferent Neurons (in T and L)
  • central canal: lined by ebendymal cells and contains CSF
39
Q

White matter of spinal cord

A
  • ascedning tracts of sensory fibers and descending motor tracts
40
Q

Cerebellum

A
  • for smooth, coordinated movements, posture, Equilibrium

- folds form the arbor vitae which increase size

41
Q

Cerebellar cortex

A

three layers

  1. Outer molecular layer:
    - non myelinated fibers
    - glial cells: stellate and Basket cells
  2. Purkinje cells
  3. Inner granular layer: granulae cells and golgi cells
42
Q

Purkinje cells

A
  • large bodies
  • extensively branched dendritic System into molecular layer
  • axon extends down though granular layer into White matter
  • receive excitatory Inputs from afferent fibers and inhibitory Inputs from molecular layer
43
Q

Stellate cell (in cerebellum)

A
  • star shaped
  • in molecular layer
  • dendritic System
  • axon synapses with dendrites or bodies of purkinje
44
Q

Basket cells (in Cerebellum)

A
  • irregular Body
  • in molecular layer
  • dendritic System
  • axon is Long, goes perpendicular to the foldm synapses with Body of purkinje
45
Q

Cerebellar basket

A

complex of inhibitory synapses surrounding the Body of purkinje cell

  • axons of Basket and stellate cells and axons of purkinje cells
46
Q

Granular cell (Cerebellum)

A
  • in granular layer
  • small Body
  • Short, branched dendrites
  • axon gies up to molecular layer to Synapse with purkinje, stellate, Basket and Golgi
47
Q

Golgi cell (Cerebellum)

A
  • in granular layer (superficial part)
  • irregular Body
  • dendrites in both granular and molecular layers
  • axon synapses with dendrites of Granular cells
48
Q

Afferent fibers in cerebellum

A

MOSSY AFFERENT
pontine nuclei - granular cells - purkinje dendrites

CLIMBING AFFERENT
olive nuclei - directly with purkinje dendirtes

49
Q

Cerebellar glomerulus

A

synapses surrounding the end oof mossy fibers

  1. mossy afferent Fiber –> Center of Glomerulus
  2. Dendrites of granular cells
  3. Axon of golgi –> send inhibitory imp. to granular cells
50
Q

Efferent Neurons and fibers in cerebellum

A
  • Purkinje cells: only efferent cells
  • Purkinje axons: only efferent fibers

purkinje cells send inhibitory projections to deeper cerebellar nuclei

51
Q

Glia of cerebellar cortex

A

Lopogliocytes: modified astrocytes

  • in Purkinje cell layer
  • processes form glial limiting membrane
52
Q

Cerebral cortex

A

6 layers: neocortex
less than 6: allocortex

  1. Molecular layer
  2. Outer granular layer
  3. Outer pyramidal layer
  4. Inner Granular layer
  5. Inner pyramidal layer
  6. Multiform cell layer
53
Q

Molecular layer of cerebral cortex

A
  • few Neurons

- non myeliated fibers

54
Q

Outer granular layer of cerebral cortex

A
  • small pyramidal cells

- stellate cells

55
Q

Outer pyramidal layer of cerebral cortex

A
  • Pyramidal cells of medium size

- Martinotti cells

56
Q

Inner granular layer of cortex

A
  • mainly stellate cells
57
Q

Inner pyramidal layer of cortex

A
  • large and huge pyramidal cells in motor cortex

- axons in motor Cortex travel tospinal cord : pyramidal tract

58
Q

Multiform cell layer of cortex

A
  • wide Variety of cells

- contains fusiform cells: Body and processes oriented at righ angle to surface

59
Q

Types of cerebral cortex

A

granular type:
- granular layers are predominant in SENSORY ZONE

agranular type
- pyramidal layers are predominant in MOTOR ZONE

60
Q

Functional types of cerebral Cortex neurons

A
  • medium, large and huge pyramidal cells are efferent

- all others are intermediate

61
Q

Orientation of cerebral fibers

A
  • tangential (horizontal) fibers: layers 1, 2, 4,5
  • radial fibers:
    >afferent fibers synapsing with dendrites of efferent and inermediate in superficial layers
    >efferent fibersfrom purkinje Neurons in layers 3 and 5
62
Q

Cortical column

A
  • Morphofunctional unit of cerebral Cortex
  • vertical column thriugh cortical layers of brain
  • cells of column have same receptive field
63
Q

Principles of PNS organization

A

Ganglia: aggregations of Neuron cell bodies

Peripheral nerves: combination of afferent and efferent nerve fibers

64
Q

Peripheral nerve

A
  • one or more bundles of afferent and efferent fibesr
65
Q

Organization of a nerve

A

ENDONEURIUM surrounds nerve Fiber (loose CT)
PERINEURIUM surrounds fascicle (loose CT)
EPINEURIUM surrounds more fascicles (dense irregular)

66
Q

Ganglia (2 types)

A
  • Sensory: spinal root and cranial ganglia

- Autonomic: sympathetic and parasympathetic

67
Q

Spinal (dorsal root) ganglion

A
  • contain sensory Neuron cell bodies
  • Neurons are pseudo-unipolar
  • bodies of Neurons are peripheral, fibers are in the Center
  • each nucleus surrounded by satellite cells and capsule of loose CT
68
Q

Sympathetic glangion

A
  • either paravertebral or prevertebral
  • neuronal cells are motor and multipolar
  • nucleo of neuronal cells are eccentrally located
69
Q

Parasympathetic ganglion

A
  • intramural –> lie close to effector organ
  • bodies of mulipolar Neurons are clumped together scattered in tissue of organ
  • Neurons are surrounded by satellite cells
  • large nuclei
70
Q

Reflex arch

A

monosynaptic: only two Neurons
polysynaptic: one or more interneurons involved –> allows processing or inhibition

71
Q

Somatic Reflex arch

A
  1. receptor in Skin
  2. Body of sensory Neuron in spinal Ganglion
  3. Body of intermediate in dorsal horn
  4. Body of motor Neuron in ventral horn
  5. Effector ending in skeletal muscle
72
Q

Autonomic (parasympathetic) Reflex arch

A
  1. Receptor in inner organ, vessel
  2. Body of sensory Neuron in spinal Ganglion
  3. Efferent part is made of two Neuron chain, 1st Neuron in laterl horn
  4. 2nd Neuron in autonomic Ganglion
  5. Effecotr in smooth muscle, gland

Histology Final (18 decks)

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