Nervous tissue Flashcards
(151 cards)
1
Q
What is the nervous tissue specialized to do?
A
receive information from external & internal stimuli
integrating & analysing it
producing proper stimulus
2
Q
what cells does the nervous tissue consist of?
A
nerve cells (neurons)
glial cells (neuroglial cells)
3
Q
Reception of stimuli is the function of what component?
A
sensory component of PNS
4
Q
process of integration is the function of what component?
A
CNS
5
Q
transmission of response to the effector organ is carried by which component?
A
motor component of PNS
6
Q
What is the structural and functional unit of nervous system?
A
Neurons
7
Q
What does neurons consist of?
A
2 parts: cell body & the processes
8
Q
Size of Cell body
A
4μm as in granular cells in cerebellar cortex to 100μm motor neurons in spinal cord
9
Q
What does the shape of Perikaryon depend on?
A
number of cell processes
10
Q
Shape of unipolar No. of process
A
globular
11
Q
Shape of bipolar No. of process
A
fusiform
12
Q
Shape of multipolar No. of processes
A
stellate, pyramidal, pyriform
13
Q
Shape of nucleus in cell body
A
large, spherical, euchromatic w/prominent nucleolus
14
Q
What does cytoplasm of cell body contain
A
- Highly developed RER & numerous polyribosomes
- Golgi complex around nucleus
- Mitochondria surrounding cytoplasm
- Neurofilaments that bundle together to form neurofibrils
5.Microtubules - Centrioles
7.Inclusions
15
Q
Suggest why the cells may indicate that they are protein synthesizing cells?
A
As it contains Highly developed RER & numerous polyribosomes suggesting that these cells synthesize both structural proteins and proteins for transport
16
Q
What is Nissl bodies?
A
It is rER, free ribosomes & polysomes stained & appeared as basophilic granular areas
17
Q
How does the neurofilaments bundle together?
A
By the action of fixatives
18
Q
What is the function of neurofibril?
A
provide structural support
19
Q
what are neurofibrils stained with?
A
Ag
20
Q
What are the functions of microtubules?
A
involved in axonal transport of neurotransmitter substances, enzymes and other cellular constituents
21
Q
Why are centrioles not seen?
A
as neurons cannot divide
22
Q
What are the inclusions found in the cytoplasm of Perikaryon?
A
- Lipofuscin:(golden brown) residue of undigested materials by lysosomes
- Melanin: dark brown OR black
- Lipid droplets: products of abnormal metabolism or as energy reserve
23
Q
Where is melanin found in neurons?
A
Sunstantia Nigra of the mid brain
24
Q
What are the processes found in the neurons
A
- Dendrite: multiple processes receive stimulus and carry it to the cell body
- Axon: single process that conveys info away from cell body
25
What cell constituents does both axon and dendrite have in cytoplasm?
Mitochodria
neurofibrils
microtubules
26
How does Axon differ from dendrites?
6 differences found at page 135
27
how are neurons classified?
According to:
1. number of processes
2. function
3. Length of axon
28
Where is unipolar neuron found?
1.Spinal ganglia
2.mesencephalic nucleus of trigeminal nerve
29
Where is bipolar neuron found?
1. Cochlear & vestibular ganglia in ear
2. retina in eye
3. Olfactory mucosa in nose
30
Where does multipolar neuron stellate in shape?
1. AHC in spinal cord
2. Sympathetic ganglion
31
Where does multipolar neuron Pyramidal in shape?
pyramidal cells in cerebral cortex
32
Where does multipolar neuron pyriform in shape?
Purkinje cells in cerebellar cortex
33
How is neuron classified according to function
Sensory(afferent): receive stimuli as cells of dorsal root ganglion
motor( efferent): control effector organ as AHC in spinal cord
Interneurons: connect neurons
34
Difference btw Golgi type 1 and 2?
Golgi type 1: long axon, leaves grey matter, enters white matter. Ex: motor neurons in spinal cord, pyramidal cells in cerebral cortex and purkinje cells in cerebellar cortex
Golgi type 2: short axon, does not leave grey matter. Ex: interneurons
35
What is the main function of synapse?
transmit impulse from presynaptic to postsynaptic cell
36
What are the methods in transmission in synapse?
chemical (neurotransmitter) or electrical (gap junctions allowing movement of ions)
37
What are the three site of contacts with the axon?
1. Axosomatic: cell body
2. Axodendritic: dendrite
3. Axoaxonic: axon
38
What is synapse formed of?
1.Presynaptic side:
. Many mitochondria
. separate of zones of dense cytoplasm
2.Synaptic cleft:
. 20-30 nm width
. shows delicate fibers and granules
3.postsynaptic side:
. has receptors
.Continuous zone of dense cytoplasm associated with synaptic web which is formed by interlinked proteins
39
What does the interlinked protein in continuous zone of dense cytoplams in postsynaptic side do?
1. fix neurotransmitter recepters to CM
2. Translate neurotransmitter-receptor interaction into intercellular signal
40
Where does the axon arise from?
Axon hillock
41
What does sheath of Schwann (neurilemmal sheath) consist of?
1.Flat cell w/ flat nucleus
2. form thin chain around myelin of a nerve fiber
42
Function of Schwann cells?
1. formation of myelin sheath in peripheral nerves
2. Electric insulation
3. Regeneration where axon grows from the proximal stump along the path
43
LM of myelin sheath
After routine fixation lipoprotein dissolves
Stained black with osmic acid
44
Myelin sheath is stained black with which stain
Osmic acid
45
What is the function of node of Ranvier and internodal segment?
Enhances the speed of nerve impulse
46
Number of Nissl bodies varies according to what?
Neuronal type & functional state
47
how is myelin sheath formed in PNS?
By schwann cell. Each schwann cell wraps around 1 segment of a single axon
48
How is myelin sheath formed in CNS?
By oligodendroglia processes. Each oligodendroglia cell wraps around 1 or more segments of many axons.
49
What is myelin sheath made of?
made of many layers of modified cell membrane w/ higher proportion of lipids
50
E/M of myelin sheath
Fused spiral laminae of plasmalemma
51
Describe the stages of myelination.
Text book page 139
Summary:
1- Axon invagination
2- Single turn of CM
3- Many turns
4- Cytoplasm pushed to cell body --> compaction
5- fusion of CM
52
What does PNS consist of?
Nerves
Ganglia
Nerve endings
53
What is peripheral nerve covered by?
Dense connective tissue (Epineurium)
54
Nerve bundles are surrounded by...
Perineurium
55
perineurium is formed of flattened epithelium like cells joined by ---- junction
Tight
56
Function of perineurium
forms a barrier to protect the nerve fibers
57
Inside the bundle the nerve fibers are connected by
endoneurium
58
what does sheath of Henle consist of?
Reticular fibers formed by schwann cells
59
what does sheath of Henle consist of?
Reticular fibers formed by schwann cells
60
How does H&E stain Nerve fiber?
lipid component of myelin have been dissolved during dehydration
61
How does osmic acid stain fiber?
black ring around the site of the axon
62
Define Ganglia
Collection of nerve cells and glail cells outside CNS supported by connective tissue
63
Types of Ganglia
Craniospinal
Autonomic
64
Difference btw spinal and sympathetic ganglia
10 differences
65
In a wounded nerve fiber, what are the 2 distinct types of changes?
Retrograde degeneration & Wallerian degeneration
66
Where does Retrograde degeneration occur in the nerve?
In nerve cell and proximal part of nerve fiber
67
What happens in retrograde degeneration?
1. Chromatolysis: disappearance of Nissl bodies w/ dec. in basophilia
2. Inc. Volume of perikaryon w/ loss of dendrites so becomes globular
3. Migration of nucleus to peripheral position
4. Disappearance of golgi body and mitochondria
5. fragmentation of neurofibrils
6. lysosomes increase
68
What happens in Wallerian degeneration?
1. Axon: Neurofibrils appear beaded, segmented, granular and finally disappears.
2. Myelin sheath shows widening of nodes of Ranvier. Internodal segments are now called fermentation chambers as fat split to fatty acids
3. Schwann cell proliferate giving rise to cellular columns that act as a guide for the growing axons during regeneration
69
What are the stains used to show degeneration?
1. Ag: Golgi body & neurofibrils
2. Osmic acid: myelin sheath
3. Basic stain: Nissl bodies
70
When does Regeneration take place?
1. When microphage remove debris and secrete interleukin 1, stimulating Shwann cells to secrete substances that promote nerve growth
2. Growth of axon in proximal part in direction of the columns of Schwann cells
71
When there is an extensive gap btw distal and proximal segments or when distal segment disappears what does the newly grown nerve fiber may form?
Neuroma (Swelling) that can be source of spontaneous pain
72
What happens in a demyelinating disease?
damage to myelin sheath w/ loss of ability to transmit electrical impulses
73
All tumours in nervous system are originating from glial ot nerve cells?
Glial cells as it can divide unlike adult neuron
74
What is the largest glial cell?
Astrocytes (macroglia)
75
Shape of Astrocyte
Star shaped w/ multiple long processes
76
Shape of Astrocyte's nucleus
have the largest and pale nucleus
77
Can astrocytes divide? Explain why
Yes as it has centrioles
78
How does Astrocyte can keep their shape?
as it show bundles of intermediate filaments made of GFAP
79
What is the origin of Astrocyte?
Ectodermal
80
Where are astrocytes present?
Grey and white matter
81
Give out the functions of astrocytes
1-control metabolic exchange btw nerve cell and blood
2- Blood Brain Barrier
3- Structural support
4- Repair process by formation of scar tissue
82
What are the 2 types of astrocytes?
Cytoplasmic and Fibrous astrocytes
83
Compare btw the two types of astrocyte
1.Cytoplasmic: in grey matter, cytoplasm is granular, has many shorter processes
2. Fibrous: in white matter, cytoplasm is fibrillary, fewer long processes
84
What glial cell is the most numerous in white matter?
Oligodendrocyte
85
What are the two types of Oligodendrocyte?
Satellite and interfasicular
86
Compare between the two types of Oligodendrocyte
page 146
87
What is the smallest and rarest glial cells w/ many short branches?
Microglia (mesoglia)
88
What is the origin of Microglia?
Mesoderm
89
Describe the structure of Mesoglia
Nucleus: Dark, oval
Cytoplasm: Scanty
Centrioles: not present
90
Which neuroglial cell is considered a phagocytic cell?
Microglia
91
Function of Microglia?
Phagocytic activity
92
Function of Satellite cells.
Structural and metabolic support for neuronal cell bodies
93
Type of epithelium in ependymal cell
Simple cubical ciliated
94
Where is the ependymal cell at?
Lines the ventricles of the brain and central canal of spinal cord
95
Functions of Ependymal cell
production and movement of CSF
96
What does receptors do?
Convert internal and external stimuli into nerve impulses
97
What are receptors classified into?
Exteroceptors: receive external stimuli
Prorioceptor: receive stimuli in muscle
Interceptors: receive internal stimuli
98
What does effectors do?
bring efferent nerve impulses to effectors
99
What type from receptors classification are found in Epithelium?
Exteroceptor
100
Give out Receptors in epithelium
1-Free nerve endings
2-Merkel endings
3-Peritrichial nerve endings
4-Neuroepithelium endings
101
Where is free nerve endings found?
Epidermis of the skin and cornea of the eye
102
What are the free nerve endings responsible for?
Mechanoreceptor for
pain
touch
temperature
103
Is the free nerve ending covered with myelin sheath
No, it loses its myelin below the basement membrane and passes in between the epithelial cell
104
Is the free nerve ending capsulated?
No
105
Where is merkel ending present?
Epidermis of hairless skin
106
What is merkel ending mechanoreceptor for?
touch
107
is merkel ending capsulated?
No
108
Does Merkel ending have myelin sheath?
No, It loses its sheath and forms a disc like expansion under merkel cell
109
Peritrichial nerve ending is present in...
hairy skin around hair follicles
110
Peritrichial nerve ending is mechanoreceptor for...
Touch and movement of hair
111
Is Peritrichial nerve ending encapsulated?
No
112
Where is neuroepithelium found?
1-Taste buds for taste
2- Organ of Corti for hearing
3- Macula utriculi, Macula sacculi, Crista ampullaris for equilibrium
113
Is there effectors in coonective tissue?
No, all are receptors
114
Free nerve endings in CT are present in
Dermis of the skin and stroma of the stroma of the cornea
115
Meissner's corpuscle is found in
Dermal papillae of the skin especially in palm and sole
116
Is the Meissner;s corpuscle encapsulated?
Yes, oval in shape
117
Meissner's corpuscle is mechanoreceptor for
touch
118
How is the Meissner's corpuscle formed?
Axon enters corpuscle after losing its sheath
It spirals up between modified flattened Schwann cells arranged transversely till it ends at the upper pole of the corpuscle
119
Krause's end pulp in present
deep in the dermis of the skin of external genetalia
120
Krause's end bulb is mechanoreceptor for
touch
121
Is Krause's end bulb encapsulated?
Yes, ovoid bodies in shape
122
How does the axon enter capsule of kause's end bulb
Axon loses its myelin sheath and branches repeatedly inside
123
Ruffini Corpuscles is present
deep in dermis of the skin, especially in sole
124
Ruffini corpuscle is a mechanoreceptor for
stretch and twisting of the skin
125
Is ruffini corpuscle encapsulated?
Yes, fusiform bodies in shape
126
Axon enter the capsule of ruffini corpuscle how?
losing its myelin sheath before entering and branches between parallel collagen fibres inside
127
Where is Pacinian corpuscle found?
1-Dermis & hypodermis of the skin
2-Periosteum of the bone
3-Joint capsule
4- CT of some organs as pancreas wall of rectum and urinary bladder
128
Pacinian corpuscle is mechanoreceptor for...
Vibration & pressure that responds to displacement of the capsule lamellae
129
Is pacinian corpuscle mechanoreceptor in joint capsule?
No, it is proprioceptor
130
Is pacinian corpuscle encapsulated?
Yes, large ovoid up to 1 mm in length
131
Describe the encapsulation of pacinian corpuscle
-thin connective tissue capsule
-enclosing 20-60 concentric lamellae consisting of very thin flat cells by narrow spaces filled w/gel like material
-towards the center, the lamellae become closely packed
132
Describe the myelinated nerve fiber in pacinian corpuscle
-Myelinated nerve fiber enters the corpuscle at one pole
-Schwann cell becomes continuous w/ the capsule
-Myelin sheath ends inside the corpuscle
- Naked nerve fiber runs parallel to the longitudinal axis and ends in a small expansion
133
True or false: myelin sheath of nerve in pacinian corpuscle ends outside the corpuscle
False: ends inside the corpuscle
134
Where is golgi tendon (tendon spindle) present?
Present in tendons near muscle insertion
135
What is the golgi tendon mechanoreceptor for?
Compression-muscle tension
136
Is golgi tendon one of the proprioceptors?
Yes
137
Describe the encapsulation of golgi tendon.
C.T sheath surrounding large bundles of collagen fibers w/collagen fibers of tendon
138
True or false: sensory nerve on golgi tendon penetrates the capsule to end around the collagen bundles
True
139
Give out the receptors in connective tissue
1-free nerve ending
2-Pacinian corpuscle
3-Ruffini corpuscle
4-kause’s end bulb
5-Meissner’s corpuscle
6-golgi tendon(tendon spindle)
140
Site of muscle spindle
Skeletal muscle and more numerous in muscle involved in fine movements
141
What is muscle spindle mechanoreceptor for?
Stretch-muscle length
142
What is the muscle spindle receptor responsible for?
1- regulation of muscle tone through stretch reflex
2-keeps the CNS informed about the length of the muscle —> indirectly influence the control of voluntary muscle
143
Shape of muscle spindle
Fusiform, lying parallel to muscle fibers
144
Size of muscle spindle
Up to 6 mm long, less than 1 mm in diameter
145
Structure of muscle spindle
-capsule surrounding
-lymph filled space
-contains intrafusal fibers and nerve fibers
146
What is intrafusal fibers
-much smaller than skeletal muscle fibers
-central non-striated area containing the nuclei
147
What are the two types of nuclei that may be found in intrafusal fibers?
Nuclear bag: central nuclear area is dilated
Nuclear chain: no dilatation and the nuclei are in the form of chain
148
Afferent fibers of muscle spindle
Annulospiral: unmyelinated, large, envelope nonstriated central portion of intrafusal
Flower-spray: unmyelinated small located at striated perioheral part of intrafusal muscle fiber
149
What is the effector in muscle tissue
Moto end plate
150
Why does the post synaptic membrane has many deep junctional folds?
More surface area and more acetylcholine receptors
151
Why does the muscle fiber cytoplasm under junctional folds has many mitochondria, rER and free ribosomes
As these organelles are involved in synthesis of specific acetylcholine receptors in the membrane of the cleft as well as acetylcholinesterase
