NERVOUS TISSUE Flashcards
1
Q
Tissue composed of neurons (nerve cells) and associated gliocytes (supporting cells)
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Nervous Tissue
2
Q
Nervous Tissue is derived from
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Neural ectoderm
3
Q
It makes up the structural and functional components of the nervous system.
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3
Q
It makes up the structural and functional components of the nervous system.
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Neural ectoderm
4
Q
Amorphous ground substance – minimal
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Intercellular substance
5
Q
Intercellular substance fiber?
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very fine collagen
6
Q
FLUID
Cerebrospinal fluid produced by ependymal cells of the
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choroid plexus
7
Q
Is a mass of villi that originate from the tela choroidea and form a fuzzy tuft of epithelium that extends into the brain vesicles.
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choroid plexus
8
Q
Cells
Major component of nervous tissue
Classified as
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Neuron and gliocyte
9
Q
Basic functional unit of the nervous system.
Specifically designed to receive stimuli from the environment, conducts electrical impulses throughout the body, and process information.
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Neuron or Nerve Cell
10
Q
Cell membrane is called ?
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neurolemma
11
Q
Cytoplasm is called ?
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neuroplasm
12
Q
Neurons are highly secretory and they have lots of RER (Nissl substance or chromophilic substance in neurons)
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13
Q
Is visible as a clump of basophilic materials in the perikaryon except in the axon hillock and axon.
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The chromophilic substance
14
Q
Presents neurofibrils and neurofilaments that corresponds to the
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myofibrils and myofilaments, respectively of myocytes.
15
Q
Unlike other cells, neuron it is composed of two major parts:
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cell body and processes.
16
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Stimulate by environmental changes or the activities of other cells
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dendrites
17
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contain the nucleus and mitochondria, ribosomes and other organelles and inclusion.
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cell body
18
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conducts nerve impulse (action potential) toward synaptic terminas.
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axon
19
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Affect another neuron or affector organ (muscle or gland)
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Synaptic terminals
20
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Nerve cell
i. Expanded part of the neuron
Contains relatively large, centrally located euchromatic, round nucleus with nucleolus, and the main part of the neuroplasm.
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Cell Body
21
Q
Nerve cell
ii. Cytoplasmic extensions that arise from the soma
There are two processes
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processes
22
Q
There are two processes:
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Axon and Dendrites
23
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That transmits impulses
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Axon
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That receives impulses.
Dendrite
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All neuron have only one axon, which is usually the longer of the two processes
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The junction where a neuron communicates with another neuron or an effector cell (e.g. muscle fiber) is called
synapse.
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A single long process that arise from the bulging portion of the cell body
Axon hillock
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Has a uniform diameter throughout its length and is generally straight except at its end where it gives of terminal branches collectively called the
telodendron
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The terminal part of the axon releases a chemical called
Which acts on the membrane of the other cells.
neurotransmitter
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i. An axon enveloped by one fold of plasma membrane of neurolemmal cells (schwann cells)
Has a smaller diameter than the myelinated nerve fiber Conducts impulses more slowly
Unmyelinated nerve fiber
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An axon enveloped by plasma membrane of oligodendrocyte (in CNS) or neurolemmocyte (in PNS) that wraps spirally around it several time to form the lipid-rich ?
Myelin sheath
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Starts at the point where the axon emerges from the axon hillock.
Myelination
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The myelin sheath is discontinuous at intervals called
myelin node (nodes of Ranvier)
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Is a bulb-like junction between two adjacent neurolemmal cells (the node is located between one schwann cell and the next)
myelin node
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Is constricted because myelin is not formed in it.
Node
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The areas of the axon covered by myelin sheath are called
which are sites of impulse propagation and saltatory conduction (impulse “jumps from node to node”)
internodes
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is the cytoplasmic region of myelin between the internode and the node of Ranvier
Paranode
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In H and E stained sections the axon cut longitudinally appears as a tiny elongated rod supported on either side by wavy streaks of myelin sheath (neurokeratin).
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In silver or ossium stained sections the axon cut longitudinally appears as a tiny elongated rod supported by a transparent tube-like myelin sheath.
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The myelin sheath is also interrupted by tiny diagonally oriented lines
Which represent an area of loosening of the myelin sheath.
Schmidt-Lanterman incisures,
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In transverse section:
With LM the myelinated axon appears as a central dot surrounded by
skeleton of myelin sheath
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With TEM the myelinated axon appears as circular profile surrounded bY
a layered ring of myelin sheath
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are numerous in the axon, providing the power to run the sodium potassium pump that keeps the transmembrane potential at normal levels
Mitochondria
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The small circular profiles in the axoplasm are ?
That that maintain normal axonal shape, and guide neurotransmitter molecules synthesized in the soma to their destination in the terminus of the axon
neutotubules
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A short process radiating from the soma
Varies in number from zero to many
Dendrites
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Many branch and rebranch like branches of a tree and gradually tapers at its end.
Dendrites
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Many branch and rebranch like branches of a tree and gradually tapers at its end.
Dendrites
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Classification of Neuron
Based on the number of cell processes
Unipolar neuron
Pseudounipolar neuron
Bipolar neuron
Multipolar neuron
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Classification of Neuron
Based on the number of cell processes
Unipolar neuron
Pseudounipolar neuron
Bipolar neuron
Multipolar neuron
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Based on function
Transmission or conducting neurons
Secretory neurons
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Has only one process, the axon.
Present only in the developing (embryonic) nervous system.
Unipolar neuron
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Cell of the cranial and spinal ganglia
Soma is very large (100-150 µ in diameter) with a large, round centrally located nucleus
Has two processes (one axon and one dendrite) that fuse close to the cell body but separate at some distance from it.
Pseudounipolar neuron
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Both processes appear structurally as axons but functionally, the processes are afferent and efferent
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Pseudounipolar neuron
Synapses with a sensory receptor or soma from another ganglion; brings signals to the soma in the cranianiospinal ganglion.
Afferent process
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arises from the craniospinal and extends to the dorsal horn of the gray matter of the spinal cord where it synapses with an interconnector neuron; carries the signal from the soma to the interconnector neuron.
Efferent process
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Has two processes (one axon and one dendrite) that originate at opposite poles of the soma.
Bipolar neuron
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EXAMPLES OF BIPOLAR
Photoreceptor cells of the eye retina
Olfactory hair cells of the olfactory epithelium
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Has many processes (one axon and several dendrites) that arise from an oval, pyramidal or stellate soma.
Occurs in motor nuclei in the gray matter of the brain and spinal cord
Multipolar neuron
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The axon arises from the conical axon hillock
The cell body in silver stained tissue section has an angular outline.
Multipolar neuron
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Neuron Classification Based on Function
-Multipolar neurons that comprise the majority of neurons in the body. Ex. Golgi type I and Golgi type II neurons in the brain and spinal cord.
Transmission or Conducting Neurons
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Multipolar neurons specialized to secrete hormones.
Ex. Secretory neurons of the hypothalamus that secrete oxytocin and antidiuretic hormone (ADH) into the neurohypophysis of pituitary gland.
Secretory neurons
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Neuroglial
= nerve glue
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how many times the number of neurons in the body
10-50 times
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Connective tissue cell of the nervous system
Protects, support and supply nourishment to the nervous tissue.
Non-conducting cells that are in intimate physical contact with neurons
Gliocyte or Glial Cell or Neuroglial Cell
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Provide physical support and electrical insulation to nervous tissue, and metabolic exchange between the nervous tissue and the vascular system
Contain organelles and inclusions like those in a typical cell.
Smaller than neuron but also presents cytoplasmic processses
Gliocyte or Glial Cell or Neuroglial Cell
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Gliocyte or Glial Cell or Neuroglial Cell classified as ?
gliocyte of the central nervous system (CNS) and gliocyte of the peripheral nervous system (PNS)
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Gliocytes of the CNS is Derived from ectoderm of the neural tube except for the .
microgliocytes
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Gliocytes of the CNS They are classified as ?
macrogliocytes and microgliocytes
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Macrogliocytes / Large Gliocytes
Astrocytes or Spider cells
Ependymal cells
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Microgliocytes / Small Gliocytes
classified as ?
Oligodendrocytes
Microglial cells or microgliocytes
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The most numerous gliocytes in the CNS, even more than neurons
Termed “star cells” because of their stellate shape with numerous foot (cytoplasmic) processes (or pedicles) and a large, pale ovoid nucleus
Astrocytes or Spider Cells
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These processes are pressed up against the soma of a neuron and against the blood vessel.
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Provide structural support to the CNS, store glycogen and release glucose
Astrocytes or Spider Cells
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Can undergo mitosis to form scar tissue
Phagocytize harmful substances and have antigenic properties
Astrocytes or Spider Cells
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Two Types of Astrocytes or Spider Cells
Fibrous Astrocytes
Protoplasmic astrocytes
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Have a long, thin, sparsely branched processes
Located in the white matter.
Fibrous Astrocytes
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Have numerous short, thick, highly branched processes
Located in the gray matter.
Protoplasmic astrocytes
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Tall and epitheloid in nature – look like epithelium but not possess a basement membrane
Ependymal Cells
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cells that line the brain ventricles and central canal of spinal cord.
Kinociliated cells
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In brain ventricles, the ependymal cells come in contact with the pia mater to form the
tela choroidea
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Closely associated with neurons and blood vessels in the brain and spinal cord
Oligodendrocytes
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produce myelin sheath of myelinated nerve fibers of the CNS.
Peripheral nervous system
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Have metabolic role
Small clear cells with small, round, heterochromatic, centrally located
nucleus
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short thin cytoplasmic processes, and dense cytoplasm rich in organelles especially
mitochondria, RER and microtubules
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Small thin cells with short, branched cytoplasmic processes
Scattered in the central nervous system
Microglial Cells or Microgliocytes
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Resident phagocytes in response to minor injuries
protect neurons by engulfing potentially harmful materials
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Relatively rare in normal CNS tissue
Derived from
mesoderm
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Derived from ectoderm of the neural crest
Gliocytes of the PNS
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Classified as
Amphicyte and Schwann cell.
90
Oval or spindle-shaped cells with scanty cytoplasm and round nucleus located at the expanded middle part of the cells
Amphicytes or Satellite Cells or Capsule Cells
91
Several amphicytes form a rosary-like capsule around individual cell bodies of neurons located
cranial and spinal ganglia.
92
Enclose both the unmyelinated and myelinated axons in the peripheral nervous system
A single neurolemmocyte can invest one to several nerve fibers
Produce myelin sheath of myelinated nerve fibers in the PNS.
Neurolemmocytes (Schwann cells or Shwann sheaths or Neurolemmal sheats)
93
Neurons that lose the organ they innervate also undergo degeneration and are replaced by
astrocytes
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Nerve fibers that temporarily lose their function when pressure is applied on them for a short period
recover their function after removal of pressure.
(first degree injury),
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Nerve fibers that are pressed severely for a prolonged period of time
or transected from their proximal portions will die.
second degree injury
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In case of amputation or posterior digital neurectomy (in horse), the neurites and band fibers may form a large painful nodule
neuroma
