NERVOUS TISSUE Flashcards
nervous tissue is formed by
a network of many billion nerve cell or neuron
nerve cells ( neurons ), all assisted by many more supporting cells called
glial cells .
all support from any other organ in other tissue except brain and nervous is called
Connective tissue
glial cells are also
nerve cells
Each neuron has hundreds of interconnections with other neurons, forming
a very complex system for processing information and generating responses
Anatomically, the general organization of the nervous system has two major divisions:
CNS and PNS
CNS is consist of
brain and spinal chord
Peripheral nervous system (PNS) , composed of
the cranial, spinal, and peripheral nerves conducting impulses to and from the CNS (sensory and motor nerves, respectively) and ganglia
that are small groups of nerve cells outside the CNS.
ganglia
enters the CNS
sensory nerve
away from CNS
motor nerve
PNS almost made up completely of
nerve fibers/ axons
axons are synonymous to
nerves
nerve fibers
sensory nerve and motor nerve
the way our body does homeostasis
hormonal and nervous control
how we respond to the action to maintain homeostasis
consciously and unconsciously
Neurons respond to environmental changes ( stimuli ) by
altering the ionic gradient that exists across their plasma membranes
All cells maintain such a gradient, also called an
electrical potential, but cells that can rapidly change this potential in response to stimuli (eg, neurons, muscle cells, some gland cells) are said to be excitable or irritable.
Neurons react promptly to stimuli with a
reversal of the ionic gradient ( membrane depolarization ) that generally spreads from the place that received the stimulus and is propagated across the neuron’s entire plasma membrane. This propagation, called the action potential , the depolarization wave , or the nerve impulse , is capable of traveling long distances along neuronal processes, transmitting such signals to other neurons, muscles, and glands.
action potential
nerve impulse
cell body
pericharia
Neurulation in the early embryo.
- Neural folds and neural groove form
from the neural plate.
2.Neural folds elevate and approach one
another.
- As neural folds prepare to fuse and form
the neural tube and dorsal epidermis,
neural crest cells loosen and become
mesenchymal. - The mass of neural crest cells initially
lies atop the newly formed neural tube.
neural tube will give rise to
CNS
neural crest will give rise to
PNS
Functioning part of both CNS and PNS
Neuron
3 major parts of neurons
Cell body/perikaryon
Dendrites
axon
Contains nucleus and most of cell organelles and serve are synthetic or trophic center for entire neurons
Cell body/perikaryon
most cell bodies can be seen in CNS but sometimes can be seen in PNS as
ganglia
numerous elongated processes extending from perikaryon and specialize to receive stimui from other neurons from site called
Dendrites
synapses
single long process ending at synapses specialize to generate and conduct nerve impulse to other cells
axon
neurons can be classified according to no. of processes extending from cell bodies
miltipolar neuron
unipolar neuron
multipolar neuron
have one axon and 2 or more dendrites
bipolar neuron
1 dendrite 1 axon
unipolar neuron/pseudounipolar neuron
have a single process that bifurcates close to the perikaryon, with the longer branch extending to a peripheral ending and the other toward the CNS.
Anaxonic neurons
, with many dendrites but no true
axon, do not produce action potentials, but regulate
electrical changes of adjacent neurons.
most neurons are
multipolar
Bipolar neurons are found in the
retina
olfactory mucosa the (inner ear)
cochlear and vestibular ganglia,
where they serve the senses of sight, smell, and balance, respectively.
Pseudounipolar neurons are found in
the spinal ganglia (the sensory ganglia found with the spinal nerves) and in most cranial ganglia.
Nervous components can also be subdivided functionally
Sensory neurons
Motor neurons
Somatic motor nerves
autonomic motor nerves
Sensory neurons are
afferent and receive stimuli from the receptors throughout the body
Motor neurons are
efferent, sending impulses to effector organs such as muscle fibers and glands
Somatic motor nerves are under
voluntary control and typically innervate most skeletal muscle;
autonomic motor nerves control the
“involuntary” activities of glands, cardiac muscle, and most smooth muscle.
not all skeletal mucle are under
voluntary control
Interneurons
establish relationships among other neurons, forming complex functional networks or circuits
in CNS, most neuronal perikarya occurs in ___, with axons concentrated in ___
grey matter
white matter
in PNS, cell bodies are found in
ganglia and in some regions like olfactory mucosa
PNS made up of
axons are bundled in nerves
Parkinson disease is
a slowly progressing disorder affecting muscular activity characterized by tremors, reduced activity of the facial muscles, loss of balance, and postural stiffness. It is caused by gradual loss by apoptosis of dopamine-producing neurons whose cell bodies lie within the nuclei of the CNS substantia nigra. Parkinson disease is treated with l-dopa (L-3,4-dihydroxyphenylalanine), a precursor of dopamine which augments the declining production of this neurotransmitter.
The cell body is the
neuronal region that contains the nucleus and surrounding cytoplasm, exclusive of the cell processes
finely dispresed, reflecting intense synthetic activity
chromatin
cytoplasm of perikaryon
concentrated RER and other polysomes appear as clumps of basophilic material called chromatophilic substance (or Nissl substance, Nissl bodies
purplish
basophilic materials
usually short and devided to 3 branches
dendrites
usually covered with synapses and are the principal signal reception and processing sites on neurons
dendrites
Most neurons have only one axon
, a fine cylindrical process that varies in length and diameter according to the type of neuron. Axons are usually very long processes
Axons originate from a pyramid-
shaped region of the perikaryon called the
axon hillock
The plasma membrane of the axon is often called
the axolemma and its contents are known as axoplasm.
distal end of an axon forms a
terminal arborization
and axons of interneurons and some motor neurons have branches called
COLLATERALS that end at synapses influencing the activity of many other neurons
Each branch ends with a dilation called a
terminal bouton
contacts another neuron or non-nerve cell at a synapse to initiate an impulse in that cell.
terminal bouton
has faster electrical impulse/depolarization
unmyelinated axon
soltatory conductions
nerve impulse jump
only inc
unmyelinated axon mostly found in
SPINAL CORD.
sites where nerve impulse are transmitted from one neuron to another/ from neurons and other effector cells
synapse
structure of synapse is
unidirectional
nervous tissue communicates with our body via
electro chemical signal
electrical signal
neuron to neuron communication
electrical-chemical-electrical
it converts electrical signal 9nerve impulse( from pre synaptic cell into chemical signal that effects the post synaptic cells.
synapse
most synapses release
neurotransmitter
small molecules that bind specific receptor proteins to either open or close ion channels or initiate second messenger cascade.
neurotransmitter
space bet. presynaptic to postsynaptic
synaptic cleft
synaptic vescicle holds ACH.
bababa si synaptic neurons, open calcium channel
the calcium will go inside
it will initiate vescicle to fusse with pre synaptic cleftvia exocytosis=
ACH
ACH will be free floating on
synaptic cleft
ang received by post synaptic cleft (ACH receptors)
Components of synapse
Presynaptic axon (terminal bouton) Postsynaptic axon
Presynaptic axon (terminal bouton)
wheere neurotransmitter is released by exocytosis
Postsynaptic axon
receptor for neurotransmitter and ion channels and other mechanism to initiate nerve impulse
calcium in blood
PTH
released by osteoclast
Calcium in bone
Calcitonin
pag na receive na ni post si neurotransmitter
either excitatory or inhibitory effect of the post synaptic
if an axon forms a synapse with a cell body it is called
axosomatic synapse
axon with a dendrite
axodendritic
axon with another axon for modulation of electrical siignal
axoaxonic
type of connective tissue that supports CNS
glial cells
supports neuronal survival and activities and ten times more abundant in neuron
Glial cells
6 types of Glial cells
Oligodendrocyte Shwann cells (neurolemocyte) satellite cells Epindymal cells Microglia Astrocytes
Oligodendrocyte
produce mylein seath
provide electrical insulation for neurons in CNS
Oligodendrocyte
predominant glial cells in CNS of white matter
Oligodendrocyte
why white matter is white
lipid concentration in the wrapped membrane seath
-axon na may myeline seath
have large number of radiating process and also unique in cns
astrocytes
most numerous glial cells of CNS and diverse structurally and functionally
astrocytes
types of astrocytes
fibrous astrocytes
protoplasmic astrocytes
typical in white matter and have relatively few long processes
fibrous astrocytes
predominant in grey matter and have many shorter branch processes
protoplasmic astrocytes
largest processes of all astrocytes are reinforced with bundles of intermediate filaments called
Glial fibrilary acid proteins/GFAP
serves as unique marker for astrocytes, the most common source of brain tumor
Functions associated with various astrocytes
- Regulates extracellular concentrations around neurons
- Guides and physically supports movement of locations of differentiating neurons in the developing CNS.
- extending processes and expanded perivascular feet that cover endothelial cells and contribute to BBB.
- Serves as a gate sp that it will limit substances from the blood to go to the brain
- Adds extra layer of filtrarion
- Form a barrier layer expanded process called GLIAL LIMITING MEMBRANE
Astrocytes communicate directly via
Gap junctions
glial cells in CNS
Oligo
astro
epindymal
Ependymal cells
columnar/cuboidal cells that lines the ventricles of the brain and centra; canal of spinal chord
in some CNS location apical ends of Ependymal cells have
-cilia
facilitate movement of CSF
-long microvilli
for absorption
Epindymal cells are joint apically by
junctional complexes like of epithelial
Microglial
short cells with small irregular processes evenly distributed throughout grey and white matter
secrete a number of immunoregulatory cytokenes and constituate major mechanism of immune defense in CNS
Microglial cells
macrophages of CNS
Microglia
Microglia came from
blood circulating monocytes
Shwann cells
(neurolemocyte)
glial cells found in PNS
Shwann cells
from neural crest
serve as myelinating cells of PNS and support cells of peripheral neurons
Shwann cells
Satellite cells
SUPPORT GANGLIA
forms and intimate covering layer over the large neuronal cell body in ganglia of PNS
Electrically insulate PNS cell bodies
Satellite cells
regulates nutrients and waste exchange for cell bodies in ganglia
Satellite cells
Major regions of CNS
Cerebrum, cerebellum, spinal chord
covering of CNS
meninges
membrane of Connective tissue located bet. bone and nervous tissue of CNS.
meninges
meninges layers
dura matter -taas
arachnoid -gitna
pia matter
where can we see the blood vessel
subarachnoid space
where subdural hematoma happen
subarachnoid space
tas ng arachnoid
subdural space
A functional barrier that allows much tighter control than that in most tissue.
Blood brain barrier
main structure of BBB
Capiliary endothelium
where cells are tightly sealed together by occluding junction
Choroid plexus
consist of highly specialized tissue with elaborate folds and many villi
Choroid plexus
consist of highly specialized tissue with elaborate folds and many villi
remove water from blood and release it as CSF
Choroid plexus
nerves are also
axons
nerves
bundles of nerve fibers (axon) sorrounded by swann cells and CT.
peripheral nerve
consist of axon from motor neurons
only large myelinated axons have
myeline seaths adn nodes of ranvier
endonerium
sorrounds shwann cells
group of axons sorrounded by
perinurium
sorround perinurium is
epinurium
