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Histology > Nervous tissue > Flashcards

Nervous tissue Flashcards

1
Q

Nervous tissue embryological origin

A

The nervous tissue is ectodermal in origin and develops from the nerual tube and neural crest

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2
Q

Anatomical divisions of the nervous system

A

Central Nervous System

Peripheral Nervous System

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3
Q

Centeral nervous system components

A

Brain inside the cranial cavity

Spinal cord inside the vertebral column

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4
Q

Peropheral nervous system components

A

Cranial nerves and spinal nerves
Nerve ganglia
Nerve endings

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5
Q

Structural divisions of nervous tissue

A 
Nerve cells (Neurons)
Glial cells (Neuroglia)
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6
Q

Neuron

A

The structural and functional unit of the nervous tissue

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7
Q

Functions of the neuron

A
  • Reception, transmission and processing of stimuli
  • Triggering certain cell activities (contraction of muscles)
  • Release of neurotansmitters and other informational molecules
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8
Q

Neuron consists of:

A

Perikaryon (Cell body)
Dendrites
Axon

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9
Q

Neurons can be classified according to ….. and ……

A
  • According to the number of cell processes arising from the cell body
  • According to function
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10
Q

Classification according to the number of cell processes arising from the cell body of neuron

A
  • Pseudo-unipolar nerve cell
  • Bipolar nerve cell
  • Multipolar nerve cell
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11
Q

Classification according to function of neuron

A 
Afferent Neurons (Sensory neurons)
Effrent Neurons (Motor neurons)
Inter-neurons (Relay neurons)
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12
Q

Pseudo-unipolar nerve cells

Characteristics and sites

A

The cell body has one process that soon divides into 2 branches (the dentrite and axon)
Neurons of spinal ganglia

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13
Q

Bipolar nerve cell

Characteristics and sites

A

The cell body has 2 processes arising from 2 poles.

Bipolar neurons of retina and olfactory mucosa

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14
Q

Multipolar Nerve cells

Characteristics and classifications

A 
The cell has many short dendrites and a single long axon
It can be subclassified into:
Polygonal nerve cells
Pyriform nerve cells
Pyrimidal nerve cells
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15
Q

Polygonal nerve cells sites

A

Most common type and found in nerve cells of sympathetic ganglia and spinal cord

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16
Q

Pyriform nerve cells sites

A

The cell body is pear-shapped

Purkinke cells in the cerebellum

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17
Q

Pyrimidal nerve cells sites

A

The cell body is pyrimidal in shape

Cells of the cerebral cortex

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18
Q

Sensory neurones description

A

Recieve sensory stimuli from the environment and from within te body and carry them to the CNS

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19
Q

Motor neurones description

A

Carry motor impulses from the CNS to the effector organs as muscles and glands

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20
Q

Inter-neurons description

A

They are associative neurons that establish relationships among other neurons

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21
Q

Perikaryon

Definition, site, size, shape and structure

A
  • It is the part of the neuron that contains the cytoplasm and nucleus, exclusive of the cell processes
  • Perikaryons are present only in the gray matter of the CNS and ganglia of the PNS and some sensory regions (Olfactory mucosa and retina)
  • Pyrimidal cells of the cerebral cortex reach 150 um in diameter while cell bodies of granule cells of the cerebellum are only 4-5 um
  • the cell body may be round, oval or angular
  • The perikaryon is surrounded by a very thin cell membrane
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22
Q

Nucleus of perikaryon

A

It is single, large, spherical and central with fine disspersed euchromatin and prominent nucleolus

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23
Q

Cytoplasm of perikaryon

A

Mildly basophilic

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24
Q

Nissl’s bodies/granules

LM, EM and fuction

A

LM: The cytoplasm contains large basophilic granules
EM: They consist of highly developed rER arranged in parallel cisternae with free ribosomes and polyribosomes inbetween
Function: Synthesis of both structural proteins and proteins for secretion
After exhaustion or injury, they disapper as they are broken down (chromatolysis)
Extend to the dendrits but not in the axon

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25
Q

Cytoplasmic organelles of nerve cell body

A

Nissl’s granules
Golgi complex (peri-nucleus)
Mitochondria (abundant at axon terminal)
Lysosomes (primary, secondary and lipofusin pigment)
Microtubules (supportive and share in transmission of impulses)
Intermediate filaments (Neurofilaments)
No centrosome

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26
Q

Cytoplasmic inclusions of the nerve cell body

A

-Stored food as lipid and glycogen granules
-Lipofusin pigments in old nerve cells
-Melanin pigment in nerve cells of the substantia nigra of the midbrain
(Absence of melanin leads to parkinson’s)

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27
Q

Dendrites definition

A

Usually multiple and short
Become thinner as they subdivide more
The branches are profuse, tapering and originate at acute angles to the main stem

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28
Q

Dendrites cytoplasm

A 
Contains mitochondria
Nissl's bodies
Neurofilaments
Microtubules
No Golgi
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29
Q

Dendrites Function

A

Increase receptive area of the cell to stimuli

Carry impules to the cell body (centripetal)

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30
Q

Axon definition

A

Always single, long and cylinderical with constant regular diameter
The plasma membrane is called axolemma
The cytoplasm is called the axoplasm
Arise from the perikaryon by a conical area known as axon hillock

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31
Q

Axon branches

A

Only branches terminally by giving terminal arborizations in PNS
May give branches at right angles to their main direction called collaterals in CNS

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32
Q

Axons’ cytoplasm and its contents

A 
-Contains 
Mitochondria
microtubules 
Neurofilaments 
some cisternae of sER
-Devoid of 
rER
Ribosomes 
Nissl's bodies
Golgi apparatus
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33
Q

Axon function

A

The axons carry nerve impulses from the cell bodies to the effector organ (centrifugal)

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34
Q

Nerve fibre

A

A nerve fibre consists of an axon enveloped by a special sheath of ectodermal origin

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35
Q

Two types of sheaths that cover the axon

A
  • The cellular sheath (neurolemmal sheath)

- Myelin sheath

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36
Q

Cellular sheath sites

A

Only in the PNS

37
Q

Cellular sheath description

A

Cellular sheath is formed in the PNS, by schwann’s cells that is surrounded by basal lamina and contains central flattened nucleus

38
Q

Functions of neurolemmal sheath:

A

Formation of myelin sheath
Important for regeneration of nerve fibre after trauma
Phagocytosis of cellular debris and myelin after nerve injuries

39
Q

Myelin sheath description

A

It is an interrupted fatty tube that directly surrounds the axon
It is composed of lipoprotein complex and appears white in the fresh state

40
Q

Myelin sheath formation in the PNS and the CNS

A

It is formed by Schwann’s cells in the PNS and by Oligodendrocytes in the CNS

41
Q

Functions of the myelin sheath

A

Helps in rapid conduction of nerve impulses

Insulation of the nerve impulses

42
Q

Nerve definition

A

It is a group of nerve fibres longitudinally arranged parallel to each other in the PNS

43
Q

Tract definition

A

It is a group of nerve fibres longitudinally arranged parallel to each other in the CNS

44
Q

Types of nerve fibres according to length of fibre

A
  • Golgi type I: They are very long fibres

- Golgi type II: They are short fibres

45
Q

Types of nerve fibres according to their sheaths

A
  • Non-myelinated without neurolemmal sheath: In gray matter of CNS
  • Non-myelinated with neurolemmal sheath: Post-ganglionic sympathetic fibres
  • Myelinated without neurolemmal sheath: White matter of CNS
  • Myelinated with neurolemmal sheath: Peripheral nerve trunks
46
Q

The myelin sheath shows gaps along its path called

A

Nodes of Ranvier

47
Q

The distance between 2 nodes id called …….. and consists of ……. Schwann cell

A

Internode segment …… one

48
Q

Clefts of Schmidt-Lanterman

A

Cone-shapped clear areas in the myelin sheath that represent part of the cytoplasm of the Schwann’s cell within the myelin layer after the winding process
These cleft facilitate the passage of nuitrition from the Schwann’s cell to the myelin

49
Q

Staining features of myelin sheath

A

Myelin sheath dissolves during preperation and staining by H&E
Myelin sheath appears black when stained by osmic acid

50
Q

The myelin sheath in the CNS is formed by ……

A

Oligodendrocytes

51
Q

The myelinated axons of the CNS lack

A

Neurolemmal sheath

52
Q

Longitudinal arrangement of parallel nerve fibres in the PNS is called ….

A

Nerve trunk

53
Q

Nerve trunk has external sheath of dense connective tissue called …..

A

Epineurium

54
Q

Each nerve bundle is surrounded by dense connective tissue coat called ….. that is formed of …….

A

Perineurium ……. flattened epitheliod cells joined at their edges by tight junctions

55
Q

Function of perineurium

A

Forms the blood-nerve barrier

plays a protective role

56
Q

Each nerve fiber with its myelin sheath and Schwann’s cell is enveloped ….. formed of …..

A

endoneurium ……. thin layer of reticular fibers

57
Q

Nerve ganglion definition

A

collection of nerve cell bodies outside the CNS

58
Q

Nucleus/Center definition

A

Collection of nerve cell bodies inside the CNS

59
Q

Nerve ganglion structure

A

Ovoid structures surrounded by C.T capsules containing neuronlal bodies and glial cells

60
Q

Ganglia types

A

Cranio-spinal ganglia

Autonomic ganglia

61
Q

Cranio-spinal ganglia:

A

Sensory ganglia
Impulses are transmitted from the ganglia to the CNS
Cranial ganglia are present in the path of cranial nerves
Spinal ganglia are present in the path of spinal nerves

62
Q

Autonomic ganglia:

A

The impulses are transmitted from the CNS tothe ganglia
They are motor (visceral in function)
They form the sympathetic and parasympathetic ganglia

63
Q

Cranio-spinal ganglia structure

A 
The capsule is thick and poorly vascular 
Pseudo-unipolar cells
Central pale nucleus 
Few 
Arranged in groups
Complete layer of satellite cells
Thickly myelinated 
No synapses
64
Q

Sympathetic ganglia

A

LOOK BOOK PG 117

65
Q

Synapse definition

A

It is the site of contact between 2 neurons or between neurons and other effector organs

66
Q

Axodendritic

A

Conection between the axon of a neuron and the dendrite of another neuron

67
Q

Axosomatic

A

Connection between the axon of a neuron and the cell body of another neuron

68
Q

Axoaxonic

A

Connection between the axon of a neuron and the axon of another neuron

69
Q

Chemical synapse

A

The type of chemical messenger is responsible for the transmission of the impulse from one neurone to another

70
Q

Synaptic cleft

A

The intercellular space between the pre and post synaptic membranes. It is filled with tissue fluid and traversed by filamentous material

71
Q

Electric synapses

A

There is a direct electrical transmission of impulses from one neuron to another through gap junctions that connect the pre and post synaptic membranes

72
Q

Neuroglial cells stain

A

Stained with silver or gold impregnations

73
Q

Neuroglial cells in the CNS

A

Astrocytes
Oligodendrocytes
Microglial cells
Ependymal cells

74
Q

Neuroglial cells in the PNS

A

The neurolemmal cells (Schwann’s cells)
Satellite cells in nerve ganglia
Muller’s cells in retina

75
Q

Astrocytes embryonic origin

A

Ectoderm

76
Q

Astrocytes structure

A

Star-shapped cells with multiple long processes

Some processes extend to form foot-like expansion on wall of blood capilaries

77
Q

Astrocytes cellular structure

A

The cell contains single, central, rounded, pale nucleus with fine chromatin
The cytoplasm is mildly basophilic, the lysosomes are called gliosomes and bundles of intermediate filaments

78
Q

Types of astrocytes

A

Fibrous astrocyes

Protoplasmic astrocytes

79
Q

Functions of astrocyes

A

Structural support
When damaged, responsible for repain and formation of scar (glial) tissue
Form the blood-brain barrier
Nutrtion

80
Q

Fibrous astrocytes

Site, description and cytoplasm

A

Present in the white matter of CNS
Have long thin and smooth processes
Their cytoplasm contains bundles of filaments

81
Q

Protoplasmic astrocytes

Site, description and cytoplasm

A

Present in the white matter of CNS
Have many short thick branched processes
The cytoplasm is abundant, granular and with little amount of filaments

82
Q

Ependymal cells

Origin, shape and function

A

Ectodermal in origin
Simple columnar epithelial cells linning the choroid plexus, the brain ventricles and the central canal of the spinal cord
Maybe ciliated which facilitate movement of CSF

83
Q

Microglia functions

A

Phagocytic cells
Involved with inflammation and repair in CNS
Act as APC (Antigen-presenting cells)

84
Q

Oligodendrocytes functions

A

Formation of myelin sheath in the CNS

Supportive and nutritive function to the surrounding nerve cells

85
Q

Microglia

origin and shape

A

Mesodermal in origin and derived from blood monocytes
Small elongated cells with branching processes arising from each pole of cell
The cell body and its processes has spines that project from their surfaces

86
Q

Microglia cytoplasmic content

A

Contains a single, central, oval, dense nucleus

The cytoplasm is basophilic contains usual cells inclusions espicially lysosomes

87
Q

Oligodendrocytes

Origin and sites

A

Ectodermal in origin

present in the white and grey matter of CNS

88
Q

Oligodendrocytes function

A

They have few short prcesses that wrap around the axon in the CNS fprming myelin sheath

89
Q

Oligodendrocytes cytoplamic contents

A

Contains a single, central, oval, small nucleus, moderately stained
The cytoplasm is scanty forming a rim around the nucleus and contains mitochndria, ribosomes, Golgi complex and microtubules

Histology (5 decks)

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