k2 - histology of nervous system
DESCRIPTION
HistologiTRANSCRIPT
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Histology of Nervous System
IKA MURTI
HISTOLOGY DEPT.
FK UNSOED
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ReferencesJunqueira, LC, Carneiro,J & Kelly RO. Basic Histology. Appleton & Lange.
Young, B & Heath JW. Wheather’s Functional Histology: a text and colour atlas.
Gartner, LP & Hiatt, JL. Color Textbook of Histology, 2nd Edition. WB. Saunders Company
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Introduction The most complex system in the body histologically and physiologically Formed by a network of many billion nerve cells (neurons) All assisted by many more supporting glial cells Each neuron has hundreds of interconnections with other neurons → forming a very complex system for processing information and generating responses
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Outline
Central nervous system (CNS) Peripheral nervous system (PNS) Classification of receptors
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Structural divisions of the nervous systemOrganization Components General description
Central nervous system (CNS)
Brain and spinal cord Overall "command center," processing and integrating information
Peripheral nervous system (PNS)
Nerves and ganglia Receives and projects information to and from the CNS; mediates some reflexes
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Nervous System
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Organization of the Nervous System
Central Nervous System (CNS)Consists of the brain and spinal cord
- Nucleus = a collection of nerve cell bodies in the CNS- Tracts = bundle of nerve fibers within the CNS
integrating, processing, and coordinating
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Peripheral Nervous System (PNS)
Consists of ganglia, cranial nerves, spinal nerves and peripheral receptorsGanglia = a collection of nerve cell bodies in the PNSNerve = bundle of nerve fibers in the PNS
Provides sensory information to the CNSCarries motor commands to peripheral tissues
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Functional divisions of the nervous systemOrganization Components General description
Sensory nervous system
Some CNS and PNS components
Includes all axons that transmit impulses from a peripheral structure to the CNS
Somatic sensory Transmits input from skin, fascia, joints, and skeletal muscles
Visceral sensory Transmits input from stomach and intestines (viscera)
Motor nervous system
Some CNS and PNS components
Includes all axons that transmit nerve impulses from the CNS to a muscle or gland
Somatic motor (somatic nervous system) Voluntary control of skeletal muscle
Autonomic motor (autonomic nervous system)
Involuntary control of smooth muscle, cardiac muscle, and glands
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Cerebrum Grey matter
◦ Outer part cerebral & cerebellar cortex◦ Gyri & sulci◦ Soma, dendrite, initial segment of axon◦ Non-myelinating glial cell◦ Learning, memory, sensory integration, information analysis,
initiation of motor response
White matter ◦ Inner part◦ Myelinated axon & some unmyelinated axon◦ Oligodendrocyte >>
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Cerebral cortex
Molecular layer/plexiform layer ◦ Horizontal cell (of Cajal), neuroglia
Outer granular layer◦ Stellate/granule cell, pyramidal cell,
neuroglia Outer pyramidal layer
◦ Pyramidal cell (small) >>, neuroglia Inner granular layer
◦ Stellate cell, pyramidal cell, neuroglia
Inner pyramidal layer◦ Large pyramidal cell >>, stelate cells,
neuroglia Multiform layer
◦ Martinotti cells◦ Fusiform cells
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Important neurons of the cerebrum are pyramidal neurons
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The largest motor neurons in the cerebral cortex are those found in the fifth stratum of the cortex
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Cerebellum
Coordination & Balance Grey matter
◦ Cerebellar cortex◦ Folding cortex folia◦ Neuronal cell bodies & Glial cell
White matter◦ Medulla ◦ Bundles of myelinated axon
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PURKINJE cell
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Cerebellar cortex
Molecular layer◦ Dendrite of Purkinje cell◦ Unmyelinated axon◦ Stellate cell◦ Basket cell
(Purkinje cell layer)◦ Inhibitory output (GABA NT)◦ Basket cell
Granular layer◦ Small granule cell :
Golgi cell tipe II◦ Glomeruli (cerebellar islands)
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Cerebellar cortex
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Purkinje cell
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Purkinje cell
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Spinal cord
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Unlike the cerebrum and cerebellum, in the spinal cord the gray matter is internal, forming a roughly H-shaped structure that consists
of two posterior (P) horns (sensory) and two anterior (A) (motor) horns all joined by the gray commissure around the central canal
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Internal anatomy of the spinal cord : The organization of gray matter and white matter
Grey matter◦ Inner part ◦ Butterfly-shaped◦ Central canal ◦ Anterior horn (motor) ◦ Posterior horn (sensory)◦ Neuronal cell bodies◦ Neuroglial cells
White matter◦ Outer part◦ Axons (mostly myelinated)
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A cross section of spinal cord shows the transition between white matter (left) and
gray matter (right)
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Comparison of Various Spinal Cord Segments
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The skull and the vertebral column protect the CNS Between the bone and nervous tissue are membranes of connective tissue called the meninges
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Meninges
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Meninges Duramater
◦ Dense connective tissue◦ Periosteal duramater◦ Meningeal duramater◦ Epidural space◦ Subdural space
Arachnoid◦ Trabecular meshwork◦ Subarachnoid space- CSF◦ Arachnoid villi
Piamater◦ Thin layer of loose
connective tissue◦ Close to brain tissue but not
contact◦ Fibroblast
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Meninges
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Meninges in spinal cord
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Meninges in spinal cord
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CLINICAL CORRELATIONS
• Meningiomas : slow growing tumors of the meninges, usually benign, produce clinical effects by compressing the brain and increasing intracranial pressure
• Meningitis : an inflammation of the meninges resulting from bacterial or viral infection in the CSF
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BLOOD-BRAIN BARRIER : a system of tight junctions in the endothelial cells of brain capillaries that form a
semi-permeable membrane, allowing only certain substances to
enter the brain
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Neuroglia
Blood-Brain Barrier (BBB) is formed by:
1. Astrocyte end feet
2. Basal membran
2. Endothelial cells (of brain capillary)
Most capillaries in the body
Brain capillaries
(BBB)
Astrocyte
Neuron
Oligodendro cyte
Ependyma
Microglia
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Blood brain barrier
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Choroid plexus
The choroid plexus consists of highly specialized regions of CNS tissue containing ependyma cells and vascularized piamater
that project from specific walls of the ventricles
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Choroid plexus
• Section of the bilateral choroid plexus (CP) projecting into the fourth ventricle (V) near the cerebrum and cerebellum
• It is elaborately folded with many finger-like villi
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Choroid plexus
each villus is seen to be well-vascularized with capillaries (C) and covered by a continuous layer of ependymal cells (arrow)
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The choroid plexus is specialized for transport of water and ions across the capillary endothelium and ependymal
layer and the elaboration of these as CSF
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MEDICAL APPLICATION
• A decrease in the absorption of CSF or a blockage of outflow from the ventricles during fetal or postnatal development → hydrocephalus
• Enlargement of the head followed by mental impairment
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Peripheral nervous system
Ganglia◦ Cluster of soma◦ Satellite cell
Nerve fiber◦ Bundles of myelinated & unmyelinated axon◦ Supported with connective tissue◦ Motor & sensory nerve fibers
Nerve endings◦ Receptors
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Peripheral nervous system
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Ganglia Ganglia are typically ovoid structures containing neuronal cell bodies and glial cells supported by connective tissue
A. Dorsal root ganglia/sensory ganglia/spinal ganglia B. Autonomic ganglia
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Sensory ganglia
Unipolar cell bodiesreceive afferent impulses that go to the CNS associated with both cranial nerves (cranial ganglia) and the dorsal root of the spinal nerves (spinal ganglia) The large neuronal cell bodies of ganglia are associated with thin, sheet-like extensions of small glial cells called satellite cells
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Autonomic ganglia
◦ Sympathetic ganglia◦ Multipolar cell bodies◦ Nuclei eccentric + lipofuchsin granule◦ Less satelite cells
◦ Parasympathetic ganglia◦ Near effector organ
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GANGLION CELL
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A sensory ganglion (G) has a distinct connective tissue capsule (C) and internal framework continuous with the epineurium and other components of peripheral nerves,
except that no perineurium is present and there is no blood-nerve barrier function. Fascicles of nerve fibers (F) enter and leave these ganglia. X56. Luxol fast blue.
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Spinal Ganglion
Higher magnification shows the small, rounded nuclei of glia cells called satellite cells (S) which produce thin, sheet-like cytoplasmic extensions that completely envelope each large neuronal perikaryon, some containing lipofuscin (L). X400. H&E
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Sympathetic Ganglion
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Immunostained satellite cells form thin sheets (S) surrounding neuronal cell bodies (N). Like the effect of Schwann cells on axons, satellite glial cells insulate, nourish, and regulate the microenvironment of the neuronal cell bodies. X1000. Rhodamine red-labeled antibody against glutamine synthetase
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Parasympathetic Ganglion
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Parasympathetic Ganglion
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Nerve fiber & supporting tissue
Nerve fiber◦ Bundles of myelinated & unmyelinated axon
Supporting tissue◦ Epineurium
◦ outer sheath of fibrocollageneous tissue
◦ Perineurium◦ surrounds groups of axons and endoneurium to form a small
bundles (fascicles)
◦ Endoneurium◦ surrounds individual axons and their associated Schwann cells as
well as capillary blood vessels
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• Groups of fibers are bound together into bundles (fascicles) by a perineurium
• All the fascicles of a nerve are enclosed by a epineurium
• Each axon is surrounded by an endoneurium
Nerve Sheath
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Nerve fibers
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Nerve fibers
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Nerve fibers
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Classification of receptors
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Classification of receptors
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Classification of receptors
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Structure and location of sensory receptors in the skin and subcutaneous layer
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Receptors
MEISSNER’S CORPUSCLE
Mechanoreceptor Capsule (+) Lamellae of fibroblast & Schwann cell
Dermal papilla
MERKEL’S CORPUSCLE
Mechanoreceptor Capsule (-) Merkel cell & Merkel disks Epidermis
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Receptors
PACCINIAN’S CORPUSCLE Mechanoreceptor : pressure
Capsule (+) Lamellae of fibroblast + schwann cell
Hipodermis, dermis, periosteum, joints capsule, visceral organs
FREE NERVE ENDINGS
Nociceptor Capsule (-) Branches of unmyelinated nerve fiber
Dermis
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Receptors
RUFFINIAN’S CORPUSCLE
Mechanoreceptor Capsule (-) Branches of unmyelinated nerve fiber
Dermis, hipodermis, joints capsule
KRAUSE’S ENDBULB
Mechanoreceptor Capsule (+) Bulb formed by intracapsular fluid
Genitals, conjunctiva, oral cavity, nasal cavity, peritoneum
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Receptor
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Pacinian corpuscles
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Krausse endbulb
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Two types of proprioceptors : a muscle spindle and a tendon
organ
In muscle spindles, which monitor changes in skeletal muscle length, sensory nerve endings wrap around the central portion of intrafusal muscle fibers
In tendon organs, which monitor the force of muscle contraction, sensory nerve endings are activated by increasing tension on a tendon
The Golgi tendon organs = neurotendinous organs
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Muscle spindle
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Free nerve endings
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Golgi Tendon Organ
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Golgi Tendon Organ
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THE SPECIAL SENSES
Sensory organs have special receptors that allow us to smell, taste, see, hear, and maintain equilibrium or balance
Information conveyed from these receptors to the central nervous system is used to help maintain homeostasis
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Thank you…………