Nervous system
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Transcript of Nervous system
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Nervous system Peripheral Nervous System
Spinal Cord
Lecturer – professor Boronikhina Tatiana Vladimirovna
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Nervous system functionsregulation, coordination, and integration of the organ functions and organ system activityaccumulation, processing, and reproduction of received information
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Nervous system morphological subdivisionCNS
the brain the spinal cord
PNS the nerve ganglia the nerves the peripheral nerve endings – receptors and effectors
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Nervous system functional subdivision
Sensory (afferent) part includes the sensory neurons, receptors, and sensory tracts generates impulses and conducts them to the CNS
Motor (efferent) partincludes the motor neurons, effectors, and motor tractstransmits impulses from the CNS to muscles and glands
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Nervous system motor part subdivision
Somatic NSis voluntary innervates the skeletal musclesmotor neurons are in the CNS
Autonomic NSis involuntaryinnervates the smooth muscles, cardiac muscles, and glandsmotor neurons are in the PNS
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CNS embryonic origins
Neural tube neuronsmacroglial cells
Mesenchyme microglial cellsmeningesblood vessels
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Neurulation – the neural tube formation
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PNS embryonic origins
Neural crest cells neuronsmacroglial cells
Mesenchymenerve sheathsganglion capsules and stromablood vessels
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Neural crest cell migration
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Nervous system organ histologic composition
Nervous tissue cellsneuronsglial cells
Minimal connective tissueBlood vesselsCerebral-spinal fluid (CSF)
in the spinal cord canalin the brain ventriclesbetween the meninges
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Nerves are classified
Anatomically spinal nervescranial nervesautonomic branches
Functionallysensory nervesmotor nervesmixed nerves
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Nerves are nerve fiber bundles invested by connective tissue sheaths
Endoneurium - surrounds each nerve fiber
Perineurium - surrounds nerve fiber bundles
Epineurium - surrounds the entire nerve
spinal nerve
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Nerve histologic composition
a nerve cut across and longitudinally
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Nerve ganglia contain the PNS neurons
Sensory gangliacontain sensory neuronsbelong to both the somatic and autonomic nerve systemare associated with the spinal cord dorsal roots and
some cranial nerves
Motor (autonomic) gangliacontain motor neurons of the autonomic nerve systembelong to the autonomic nerve systemare associated with the autonomic branches
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Sensory dorsal root ganglia
are associated with the spinal cord dorsal roots
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Histologic composition of the dorsal root ganglion
pseudounipolar sensory neuron cell bodies initial parts of their processesoligodendrocytes:
satellites surround the neuron cell bodies lemmocytes surround the neuron processes
connective tissue capsule and stroma
Sensory ganglia lack synapses
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Processes of the dorsal root ganglion neurons
Dendrites in the spinal nerve (afferent innervation)
Axons in the spinal cord dorsal root (sensory root)
(!!) All processes are mielynated
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Axons of pseudounipolar sensory neurons
Enter the spinal cord synapse with the spinal cord neuronsform the sensory ascending tract in the white matter posterior columns
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Motor ganglia are the autonomic ganglia
Extramural gangliaParavertebral ganglia
form the sympathetic trunks are sympathetic
Prevertebral ganglia form the nerve plexuses are either sympathetic or parasympathetic
Intramural gangliaare located in the organ thickness are parasympathetic
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Intramural autonomic ganglia
in the esophageal muscularis externa
in the gastric submucosa
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Histologic composition of the autonomic gangliathe multipolar motor neuron cell bodies neuron processesoligodendrocytes:
sattelites surround the neuron cell bodieslemmocytes surround the neuron processes
connective tissue capsule and stroma
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Processes of the autonomic ganglion motor neurons
Dendrites branch within the ganglion
Axons (postganglionic fibers) leave the ganglionterminate in effectors on
smooth musclescardiac musclesglands
Preganglionic fibers synapse with the ganglion motor neurons
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Postganglionic fibers are unmielynated
form gray autonomic branches
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Autonomic system is slower than somatic system
protective corneal reflex
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Intramural metasympathetic gangliaare located in the tube-like organ walls
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Neuron composition of the metasympathetic ganglia
contain three types of multipolar neurons sensoryassociativemotor
neurons are arranged in a local reflex archprovide peristaltic movementsare relatively independent on the CNS
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Spinal cordis cord-like organ about 43 cm in lengthis located in the vertebral canalis connected with the brain
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Spinal cord anatomy
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Spinal cord roots and nerves
31 pairs of the mixed spinal nerves
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Spinal cord segmentation
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Spinal cord functionslocalization of primitive reflex archesintegration of skeletal muscle actions
(flexors and extensors)connection with the brain
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Spinal cord organization
Gray matter posterior horns anterior horns lateral horns
(CVIII – LII )
gray commissure central canal
White matter posterior columnsanterior columnslateral columns
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Spinal cord gray matter composition
neuron cell bodies neuron processes (mostly dendrites)glial cells:
protoplasmic astrocytesoligodendrocytesependymal cells microglial cells
blood vessels
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Spinal cord neuronsare multipolar
somatic motorassociativeautonomic associative
neurons are arranged in nuclei
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Spinal cord motor somatic neuronsForm nuclei in the anterior hornsAxons
leave the spinal cord through the ventral root (motor root)
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Spinal cord associative neuronsForm nuclei in the posterior horns the intermediate zones
Axons terminate in the gray matterenter the white matter to form tracts
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Spinal cord ANS associative neuronsForm nucleisympathetic in the lateral horns (CVIII – LII )
parasympathetic in the intermediate zone (SII - SIV )
Axons leave the spinal cord through the ventral root
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Spinal cord white matter compositionmyelinated nerve fibers primary arranged vertically glial cells
fibrous astrocytesoligodenrocytesmicroglial cells
blood vessels
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White matter fibers form the spinal cord tracts
PropriospinalAfferent ascendingEfferent descending
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Propriospinal tracts
connect the spinal cord segmentscontain axons of associative neurons surround the gray matter
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Spinal cord afferent ascending tracts conduct impulses towards the brainconsist ofaxons of the ganglion sensory neurons in the posterior columns
axons of associative neurons in both the lateral and anterior columns
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Ascending afferent tracts
tr. spinothalamicus(pain, temperature, touch, and pressure sensitivity)
tr. bulbothalamicus (proprioceptive sensitivity)
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Spinal cord efferent descending tracts conduct impulses from the braincontainaxons of the brain neurons pass in both the anterior and lateral columns
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Pyramidal tract
pyramidal cortical neurons
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Spinal cord vesselsblood vessels supply both white and gray matterlymphatic vessels are absent
spinal cord central canal contain cerebrospinal fluid
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Meninges protect and supply the spinal cord
dura mater arachnoid pia mater
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Subdural and subarachnoid spaces contain cerebrospinal fluid
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Reflex arch is a functional unit of the nervous system…neuron chain conducting impulses from receptors to effectors
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Somatic reflex archSensory (afferent) neuron
in the dorsal root ganglionAssociative neuron
in the spinal cord posterior hornMotor (efferent) neuron
in the spinal cord anterior horn
innervates skeletal muscles (efferent innervation)
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Somatic reflex arch may consists of two neurons
the knee and elbow reflexes
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Reflex arches and the spinal cord tracts
reflex arch may be longer for account of spinal tracts brain neurons
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Autonomic reflex archSensory (afferent) neuron
in the dorsal root ganglionAssociative neuron
in the spinal cord autonomic nuclei Motor (efferent) neuron
in the autonomic ganglion
innervates smooth muscle cells, cardiac musclecells, and glands (efferent innervation)
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Efferent link of the autonomic reflex arch is bi-neuronal
Efferent link consists of associative neuron motor neuron
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Localization of autonomic associative neuronssympathetic – in spinal cord lateral horns (CVIII – LII )
parasympathetic- in spinal cord intermediate zone (SII - SIV )
- in brain stem
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Histological composition of
Dorsal root (sensory root)axons of sensory neurons
Ventral root (motor root)axons of somatic motor neuronsaxons of autonomic associative neurons
Spinal nerve (mixed)dendrites of sensory neuronsaxons of somatic motor neuronsaxons of autonomic associative neurons
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Thank you for attention!