Module 5 Nervous tissue Part 1 Flashcards
True or false
All the nerve tissues found in the body
belong to the Nervous System
True
Nervous system three major functions
- Sensory
- Integration
- Motor
Monitors internal & external
environment through presence of
receptors
Sensory
Interpretation of sensory
information
Integration
Response to information processed
through stimulation of
effectors
Motor
Two Anatomical Divisions of Nervous system
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
Central nervous system (CNS) consist of
Brain and spinal cord
Brain and spinal cord contains of
nerve cells-neuron
Supporting cells- neuroglia
Peripheral nervous system (PNS) consists of
All the neural tissue outside of the CNS
Transmit impulse from PNS to CNS
Afferent division (sensory input)
Transmit impulse from CNS out to PNS
Efferent division (motor output)
2 types of efferent division
- Somatic nervous system
- Autonomic nervous system
Small group of nerves outside the CNS
Ganglia
Two types of nerve cells in nervous system
- Neurons or nerve cell
- Neuroglia or glial cell
Two types of nerve cells in nervous system
- Neurons or nerve cell
- Neuroglia or glial cell
Processing, transfer, and storage of information
Neurons or Nerve cell
Support, regulation & protection of neurons
Neuroglia or Glial cell
Neuron structure
- Dendrite
- Cell body or perikaryon
- Axon
- Synaptic terminal
Are the elongated processes extending from
perikaryon
Dendrite
Specialized to receive stimuli from other neurons
synapse
Dendrite
Consists of nucleus and most of cell organelles
except cell processes
Cell body or perikaryon
Serve as trophic center for all the neurons
Cell body or perikaryon
With large euchromatic nucleus with well developed nucleolus.
Cell body or perikaryon
contains Nissl substance or Nissl bodies which are
large masses of polysomes and Rough endoplasmic reticulum indicative of high rate protein synthesis
Cell body or perikaryon
Are large masses of polysomes and Rough endoplasmic reticulum indicative of high rate protein synthesis
Nissl substance or Nissl bodies
A single long process ending at synapses
Axon
Specialized to generate and conduct nerve impulses to other cells
Axon
Covered with myelin sheath
Axon
Axon End has many small branches called
telodendria
end is knob like structure that forms part of
synapse connection with other neuron
Axon
Unique sites in the neuron that send stimuli
Synaptic terminal/synapse
Axons surrounded by
myelin sheath
Myelinated axons
presence of myelin speeds
up the transmission of
action potentials along the
axon
Myelin sheath
unmyelinated gaps left when
myelin laid down in segments
(internodes) along the axon
Nodes of ranvier
area where neuron communicates
with another cell ( muscle cell, another
neuron attached or close to it)
Synapse
At the synapse there are
- Pre-synaptic cell
- Post- synaptic cell
- Synaptic cleft
- Synaptic knob
It is the neuron that sends
message
Pre-synaptic cell
It is the cell that receives
message
Post-synaptic cell
small gap that separates pre- synaptic membrane
and post-synaptic membrane
Synaptic cleft
expanded portion of axon of presynaptic
neuron
Synaptic knob
contain vesicles of neurotransmitters
Synaptic knob
chemical messengers released at presynaptic
membrane
Neurotransmitters
bind to receptors of postsynaptic membrane are
broken down by enzymes are reassembled at
synaptic knob for use in case of another impulse
Neurotransmitters
Classifications of neurons
- Structural classification
- Functional classification
based on number of processes
coming off of the cell body
Structural classification
4 structural classification
- Anaxonic neurons
- Unipolar (pseudounipolar) neuron
- Bipolar neuron
- Multipolar neuron
no anatomical clues to
determine axons from
dendrites
Anaxonic neurons
Anaxonic neurons functions are
unknown
single process coming off
cell body
Unipolar
(pseudounipolar) neuron
giving rise to dendrites (at one end) & axon (making up rest of process)
Unipolar
(pseudounipolar) neuron
two processes coming off cell
body – one dendrite & one axon
Bipolar
only found in eye, ear & nose
Bipolar
Example of where bipolar can be found
cells of retina,
vestibular & cochlear
ganglia
multiple dendrites & single
axon
Multipolar
it is the most common type neuron
Multipolar
Example of multipolar neuron
motor nerve cells of
ventral gray matter of
spinal cord & brain stem
based on type of information & direction of info
transmission
Functional classification
3 Functional classification
- Sensory (afferent) neurons
- Motor (efferent) neurons
- Association (interneurons)
transmit information from receptors of PNS
to CNS
Sensory (afferent) neurons
most sensory neurons are unipolar, few are bipolar
Sensory (afferent) neurons
transmit motor information from CNS to effectors
(muscles/glands/adipose tissue) in periphery of body
Motor (efferent) neurons
all are multipolar
Motor (efferent) neurons
Association (interneurons)
transmit information between neurons within CNS;
analyze inputs, coordinate outputs
Association (interneurons)
most common type of neuron (
20 billion)
Association (interneurons)
4 Neuron Doctrine
- An independent anatomic unit
- Neuron is physiological unit
- Neuron is a genetic or developmental unit
- Nerve cell is a trophic (to nourish) unit
consisting of an axon and dendrites , no physical
continuity
An independent anatomic unit
Only thru neurons are impulse detected
Neuron is physiological unit
A neuroblast gives rise to single nerve cell & its
processes
Neuron is a genetic or developmental unit
once axon is severed, distal portion degenerates
while the proximal part survives & regenerate since its still attached to & nourished by the cell body
Nerve cell is a trophic (to nourish) unit
Axons of Neurons tend to group together into
Organized bundle
Organized bundle
1.Nerves in PNS
2. Tracts/pathways in the CNS
Most axons surrounded by
Myelin sheath
White matter are
Myelinated
Gray matter are
unmyelinated
Cell bodies of neurons are
clustered together
Clustered together
- Ganglia in the PNS
- Nuclei/centers in the CNS
support neuronal survival and
activities
Glial cells
More abundant in the mammalian brain
than neurons
Glial cells
CNS, has very small amount of……..and……….glial cells served as re3placement for the cells of the
connective tissues in some aspects
connective tissue and collagen
4 types of CNS neuroglia
- Astrocytes or Astroglia
- Oligodendrocytes/ Oligodendroglia
- Microglia or Mesoglia
- Ependymal cells
2 types of PNS neuroglia
- Schwann cells (neurolemmocytes)
- Satellite cells
o largest with numerous radiating processes
o Star shaped with central nuclei
o Unique and the most number of glial cells in CNS
Astrocytes/Astroglia
3 types of Astrocytes
- Fibrous astrocytes
- Protoplasmic astrocytes
- Glial fibrillary acid protein
are astrocytes with long
processes and found in the white matter
Fibrous astrocytes
are astrocytes with shorter
processes and mostly found in the gray matter
Protoplasmic astrocytes-
made the bundle of
intermediate filaments and served as unique marker for astrocytes since astrocytes are the most common source of brain tumor
Glial fibrillary acid protein
create supportive framework for neurons
Astrocytes/Astroglia
create “blood-brain barrier” called glial limiting
membrane
Astrocytes/Astroglia
monitor & regulate interstitial fluid surrounding
neurons, movement of nutrients, water and
metabolites between neurons and blood vessels
Astrocytes/Astroglia
o stimulate formation of scar tissue secondary to CNS
injury
Astrocytes/Astroglia
o Guiding and supporting movements and locati9ns of
developing neurons in the CNS
Astrocytes/Astroglia
o With less processes and Shorter than other
neuroglia
Oligodendrocytes/ Oligodendroglia
create
myelin sheath around axons that serve as
insulator of neurons in the CNS
Oligodendrocytes/ Oligodendroglia
Extend sheetlike processes – the myelin sheath,
that surrounds parts of several axons
. Oligodendrocytes/ Oligodendroglia
Most common glial cells in the white matter ( color
is due to the lipid concentrated in the membrane
wrapped sheaths
. Oligodendrocytes/ Oligodendroglia
Microscopically seen as small cells with rounded,
condensed nuclei over unstained cytoplasm
. Oligodendrocytes/ Oligodendroglia
o Small phagocytic type, mesodermal in origin
o Small cells with short processes distributed
evenly in the gray and white mater
o Resembles inactive fibroblast
Microglia/Mesoglia
“brain macrophages”, phagocytize cellular
wastes & pathogens together with neutrophils
. Microglia/Mesoglia
Nuclei of microglial cells can be identified
using Hematoxylin and Eosin stain, observe
their small dense, elongated structure
compared with the lightly stained nuclei of
other glial cells
. Microglia/Mesoglia
o Cuboidal or columnar cells lining the cavities of
CNS
o line ventricles of brain & central canal of spinal
cord
Ependymal cells
Joined apically with junctional complexes like
in Epithelial cells but it has no basal lamina
Ependymal cells
Ependymal cells in
Embryo????
Adult?????
Embryo: ciliated
o Adult: some are ciliated
produce, monitor & help circulate CSF
Ependymal cells
- surround all axons of neurons in PNS creatingneurilemma around them
Schwann cells or neurolemmocytes
Neurilemma allows for potential regeneration
of damaged axons
. Schwann cells or neurolemmocytes
creates myelin sheath around most axons of
PNS- one Schwann cell forms myelin sheath in
one segment of an axon
. Schwann cells or neurolemmocytes
- Serve as covering for
the large neuronal cell
bodies in the ganglia of
PNS
Satellite cells
- support groups of cell
bodies of neurons w/in
ganglia of PNS with
insulation, nutrition and
regulation of their
environment
Satellite cells
