Nervous system Peripheral Nervous System

Spinal Cord

Lecturer – professor Boronikhina Tatiana Vladimirovna

Nervous system functionsregulation, coordination, and integration of the organ functions and organ system activityaccumulation, processing, and reproduction of received information

Nervous system morphological subdivisionCNS

the brain the spinal cord

PNS the nerve ganglia the nerves the peripheral nerve endings – receptors and effectors

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

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

CNS embryonic origins

Neural tube neuronsmacroglial cells

Mesenchyme microglial cellsmeningesblood vessels

Neurulation – the neural tube formation

PNS embryonic origins

Neural crest cells neuronsmacroglial cells

Mesenchymenerve sheathsganglion capsules and stromablood vessels

Neural crest cell migration

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

Nerves are classified

Anatomically spinal nervescranial nervesautonomic branches

Functionallysensory nervesmotor nervesmixed nerves

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

Nerve histologic composition

a nerve cut across and longitudinally

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

Sensory dorsal root ganglia

are associated with the spinal cord dorsal roots

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

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

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

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

Intramural autonomic ganglia

in the esophageal muscularis externa

in the gastric submucosa

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

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

Postganglionic fibers are unmielynated

form gray autonomic branches

Autonomic system is slower than somatic system

protective corneal reflex

Intramural metasympathetic gangliaare located in the tube-like organ walls

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

Spinal cordis cord-like organ about 43 cm in lengthis located in the vertebral canalis connected with the brain

Spinal cord anatomy

Spinal cord roots and nerves

31 pairs of the mixed spinal nerves

Spinal cord segmentation

Spinal cord functionslocalization of primitive reflex archesintegration of skeletal muscle actions

(flexors and extensors)connection with the brain

Spinal cord organization

Gray matter posterior horns anterior horns lateral horns

(CVIII – LII )

gray commissure central canal

White matter posterior columnsanterior columnslateral columns

Spinal cord gray matter composition

neuron cell bodies neuron processes (mostly dendrites)glial cells:

protoplasmic astrocytesoligodendrocytesependymal cells microglial cells

blood vessels

Spinal cord neuronsare multipolar

somatic motorassociativeautonomic associative

neurons are arranged in nuclei

Spinal cord motor somatic neuronsForm nuclei in the anterior hornsAxons

leave the spinal cord through the ventral root (motor root)

Spinal cord associative neuronsForm nuclei in the posterior horns the intermediate zones

Axons terminate in the gray matterenter the white matter to form tracts

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

Spinal cord white matter compositionmyelinated nerve fibers primary arranged vertically glial cells

fibrous astrocytesoligodenrocytesmicroglial cells

blood vessels

White matter fibers form the spinal cord tracts

PropriospinalAfferent ascendingEfferent descending

Propriospinal tracts

connect the spinal cord segmentscontain axons of associative neurons surround the gray matter

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

Ascending afferent tracts

tr. spinothalamicus(pain, temperature, touch, and pressure sensitivity)

tr. bulbothalamicus (proprioceptive sensitivity)

Spinal cord efferent descending tracts conduct impulses from the braincontainaxons of the brain neurons pass in both the anterior and lateral columns

Pyramidal tract

pyramidal cortical neurons

Spinal cord vesselsblood vessels supply both white and gray matterlymphatic vessels are absent

spinal cord central canal contain cerebrospinal fluid

Meninges protect and supply the spinal cord

dura mater arachnoid pia mater

Subdural and subarachnoid spaces contain cerebrospinal fluid

Reflex arch is a functional unit of the nervous system…neuron chain conducting impulses from receptors to effectors

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)

Somatic reflex arch may consists of two neurons

the knee and elbow reflexes

Reflex arches and the spinal cord tracts

reflex arch may be longer for account of spinal tracts brain neurons

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)

Efferent link of the autonomic reflex arch is bi-neuronal

Efferent link consists of associative neuron motor neuron

Localization of autonomic associative neuronssympathetic – in spinal cord lateral horns (CVIII – LII )

parasympathetic- in spinal cord intermediate zone (SII - SIV )

- in brain stem

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

Thank you for attention!