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11/5/2014
1
Prof. Dr. Fawzy Elnady
Introducing
Vet. Neuroanatomy
Function of the nervous system
1. The nervous system coordinates and controls body activity.
2. Receive information (from ext./int. environment)
3. Analyze and integrate that information.
4. Bring the appropriate response.
Copyright © 2006 Thomson Delmar Learning
The Structures of the Nervous System
There are two major divisions of the nervous system:
The central nervous system (CNS) consists of the brain and spinal cord
The peripheral nervous system (PNS) consists of the cranial and spinal nerves, autonomic nervous system, and ganglia
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NervousSystem
Topographically
CNS
BrainSpinalcord
PNS
Cr. Nn Sp. NnIntramuralPlexuses
AutonomicNn & theirganglia
Functionally
Typeofinfo
Somatic Visceral
Sympathetic Parasymphathetic
Direction of fibers
Afferent Efferent
The building blocksof the Nervous system
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• Dendrites:transmit information toward the cell body
• Axons:transmit information away from the cell body
Somatic motor neuron
Neurons by function
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A neuron may synapse on another neuron’s dendrites, cell body, or synaptic ending.
The building blocks of the Nervous system
Supporting cells
Neuroglia or glial cells:
are the supportive cells of the nervous system
Copyright © 2006 Thomson Delmar Learning
• Glial cells (glue) consist of– astrocytes
– microglia
– ependymal cells
– oligodendrocytes
– Schwann cells
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The Gap = synapse
The space between two neurons or between a neuron and receptor is the synapseChemical substances calledneuro‐transmitters are released into the space to allow information to be relayed
Copyright © 2006 Thomson Delmar Learning
A neuron may synapse on another neuron’s dendrites, cell body, or synaptic ending.
Cells that produce the myelin sheath
Schwann cells
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Gaps in the myelin sheath that allow the passage of oxygen and nutrients
Nodes of Ranvier
The part of the neuron that contain the nucleus
Cell body
The membrane surrounding the nerve cell
Neurilemma
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Dense connective tissue holding nerve fibers together
Neuroglia
Group of cell bodies found in the PNS
Ganglia
The space between two neurons
Synapse
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The space between a neuron and a muscle fiber
Neuromuscular junction
The chemical that allows the transmission of a nervous impulse
neurotransmitter
Short projections that receive impulses
Dendrite
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Long projections that transmit impulses
Axons
Nerve Regeneration
Bony protection of CNS
SKULL
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Bony protection of CNS
Vertebral column
The Discs (intervertebral discs)
The vertebrae are protected from each other by IVD
IVD are layers of fibrocartilage that form pads separating and cushioning the vertebrae from each other
The Discs (intervertebral discs)
Outer Annulus fibrosus
Central Nucleus pulposus
no innervation or possible that outer disc innervated
Avascular
Thicker in neck and lumbar regions
Thickest in coccygeal
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Severe compression of spinal cord by extradural malignantlymphoma. Cat.
Lumbar spinal cord after removal of vertebral laminae. dorsal view.
The Spinal Meninges
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Pia mater
Arachnoid
Dura mater
Meninges = membranes
3 membranes surround CNS
The spinal and cranial (cerebral) meninges are continues at the foramen magnum.
Denticulate ligaments
The pia mater is bilaterally thickened along the lateral surfaceof the spinal cord, Midway between successive spinal roots .
Extensions of the pia mater traverse the subarachnoid space,arachnoid mater and attach to the dura mater between thedorsal and ventral roots of spinal nerves.
Thus the denticulate ligaments suspend the SC laterally in theCSF within the subarachnoid space.
Arachnoid mater
Def.
Thin transparent Avascularmembrane between dura and pia
maters.
Shape: Spider‐web like appearance due to has numerous trabeculae & filaments.
It is pressed against the dura by CSF pressure.
Separated from pia by SubArachnoid Space (SAS), which is filled with (CSF).
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Which layer of the meninges is present in the spinal cord but not in the brain?
Epidural space
Which one of the following statements concerning the meninges of the brain and spinal cord is true?
The arachnoid membrane is the finest, most delicate layer, reminiscent یذكرنا بشبكة العنكبوت of a spiderweb, that immediately surrounds the surface of the brain and spinal cord.
The cerebrospinal fluid (CSF) is contained in the subdural space of both the brain and spinal cord.
The superficial‐to‐deep sequence of the meninges on the brain is inverse to that of the spinal cord.
The meninges consist of three layers, which from superficial to deep are the dura mater, arachnoid membrane, and pia mater
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Cauda Equina …. How it is formed?
in the Adult horse:
the cauda equina starts @ the lumbosacral junction.
the conus medullarisextends to S1
the filum terminaleextends to S4
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Structures forming the Cauda Equina:
1‐ Conus medullaris
2‐ Filum terminale
3‐ Spinal nerves (that flank 1 and 2)
Lumbosacral portion of spinal cord
Median section
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Which one of the following statements regardingthe spinal cord is true?
It contains nerve cell bodies within its white matter and axonal processes within its grey matter.
It extends the length of the vertebral canal.
It possesses neurons associated with the parasympathetic nervous system in the region of the intermediate horn.
It receives sensory neurons through the dorsal horn.
Early SPINAL CORD Development
Regions of Developing Neural Tube
Alar Plate
Basal Plate
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Cs spinal cord
Arrangement of gray and white matter in the spinal cord:
(1) Dorsal gray column
(2) Lateral gray column (intermediate gray matter)
(3) Ventral gray column
(4) Dorsal funiculus
(5) Lateral funiculus
(6) Ventral funiculus.
The Mature Spinal Cord
Gray matter
Cervical enlargement ‐ C5 ‐ T2
Lumbar enlargement ‐ L4 – S2
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Model of sympathetic innervation. Preganglionic cells can synapse (A) on postganglioniccells a few segments cranial in the sympathetic trunk; (B) on a postganglionic cell at the segmentwhere the postganglionic fiber emerges; (C) on a postganglionic cell caudal in the sympathetictrunk; (D) the preganglionic cell can bypass the sympathetic trunk ganglia and synapse in the prevertebralganglia.
(1) Preganglionic cell body; (2) Spinal nerve; (3) Ramus communicans; (4) Postganglionic cell body;
(5) Sympathetic trunk ganglion; (6) Sympathetic trunk.
Roots and branches of a spinal nerve
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The Mature Spinal Cord ‐ 3
White matter
Dorsal funiculus
Lateral funiculus
Ventral funiculus
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THE AUTONOMIC NERVOUS SYSTEM
‘NO ONE TELLS ME WHAT TO DO!’’
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Summary of major PNS subdivisions