Central Nervous System Central Nervous System

Dr. Mohammad AlzoghiabiDr. Mohammad Alzoghiabi

Organization of the Nervous SystemOrganization of the Nervous System

Central nervous systemCentral nervous system

1.1. Brain Brain

2.2. Spinal cordSpinal cord

Peripheral nervous systemPeripheral nervous system

1.1. Sensory receptors Sensory receptors

2.2. Sensory nervesSensory nerves

3.3. Ganglia Ganglia

Central Nervous SystemCentral Nervous System

Functions:Functions: Has information about environmentHas information about environment Organizes reflexes Organizes reflexes Plans & execute voluntary movement Plans & execute voluntary movement Memories, thinking & learningMemories, thinking & learning

Central Nervous SystemCentral Nervous System

Types of nerves Types of nerves

1.1. Sensory or afferent division Sensory or afferent division

2.2. Motor or efferent division Motor or efferent division

Spinal cord Spinal cord

The most caudal portion of CNS The most caudal portion of CNS From the base of the skull to 1From the base of the skull to 1stst lumbar lumbar

vertebra vertebra Contain 31 pairs of spinal nerves Contain 31 pairs of spinal nerves

Spinal cord and nervesSpinal cord and nerves

Sensory verves:Sensory verves:

carry information to spinal cord from different carry information to spinal cord from different organs via dorsal root and cranial nerve ganglia organs via dorsal root and cranial nerve ganglia

Motor nerves:Motor nerves:

carry information from spinal cord to periphery, carry information from spinal cord to periphery, include both:include both:

Somatic Somatic Autonomic Autonomic

Brain Stem Brain Stem MedullaMedulla

breathing, blood pressure, swallowing, coughing breathing, blood pressure, swallowing, coughing and vomiting reflexes and vomiting reflexes

PonsPons

participates with medulla in regulating breathing participates with medulla in regulating breathing

gets information from cerebral hemispheres to gets information from cerebral hemispheres to cerebellumcerebellum

MidbrainMidbrain

Controls eye movementsControls eye movements

contains neucli of auditory and visual system contains neucli of auditory and visual system

CerebellumCerebellum

Functions:Functions:

i.i. Coordination of movementsCoordination of movements

ii.ii. Planning and execution of movementsPlanning and execution of movements

iii.iii. Maintenance of posture Maintenance of posture

iv.iv. Coordination of head and eye movements Coordination of head and eye movements

Thalamus and Hypothalamus Thalamus and Hypothalamus

ThalamusThalamusprocesses all sensory and motor informationsprocesses all sensory and motor informations

HypothalamusHypothalamuscontains centers to regulatecontains centers to regulate

1.1. Body tempBody temp2.2. Water balance Water balance 3.3. Pituitary glandPituitary gland4.4. ADH and oxytocinADH and oxytocin Known as Known as DiencephalonDiencephalon “between brain” “between brain”

Motor CortexMotor Cortex

Anterior to the central cortical sulcusAnterior to the central cortical sulcus

divided into:divided into:1- primary motor cortex1- primary motor cortex2- premotor area2- premotor area3- supplementary motor area3- supplementary motor area

Primary Motor Area (MI)Primary Motor Area (MI)

Right front of the central sulcusRight front of the central sulcus Laterally in the sylvian fissureLaterally in the sylvian fissure Superiorly to the top of the brainSuperiorly to the top of the brain Inferiorly to the longitudinal fissureInferiorly to the longitudinal fissure Topographical representations of the body Topographical representations of the body

areas in an inverted mannerareas in an inverted manner

Primary Motor Area (MI)Primary Motor Area (MI)

Main origin of the pyramidal tractMain origin of the pyramidal tract More than half of motor area concerned with More than half of motor area concerned with

the hands and muscle of speechthe hands and muscle of speech Excitation of a single motor neuron causes Excitation of a single motor neuron causes

the excitation of a specific pattern of the excitation of a specific pattern of movement movement but not a single musclebut not a single muscle

Contains upper motorneurons which project Contains upper motorneurons which project directly to spinal cord directly to spinal cord

Lesion in MI leads to flaccid paralysisLesion in MI leads to flaccid paralysis

Premotor AreaPremotor Area

Anterior to the primary motor cortexAnterior to the primary motor cortex Superiorly to the longitudinal fissure Superiorly to the longitudinal fissure Inferiorly to the sylvian fissureInferiorly to the sylvian fissure Same topographical organization as the Same topographical organization as the

motor cortexmotor cortex Responsible for more complex patterns of Responsible for more complex patterns of

movement movement

Supplementary Motor AreaSupplementary Motor Area

Has another topographic organizationHas another topographic organization Contraction often bilateralContraction often bilateral

- bilateral grasping movements (climbing)- bilateral grasping movements (climbing)- attitudinal movements- attitudinal movements- fixation movements- fixation movements- positional movements of head and eyes- positional movements of head and eyes

Other Motor RegionsOther Motor Regions

Bronca’s Area: responsible for vocalizationBronca’s Area: responsible for vocalization Voluntary eye movement field:Voluntary eye movement field:

controls the eye movement to certain controls the eye movement to certain objects and blinkingobjects and blinking

Head rotation area Head rotation area Area of hand skillsArea of hand skills

destruction destruction motor apraxia motor apraxia

White Matter of Spinal CordWhite Matter of Spinal Cord

Posterior faniculusPosterior faniculus Anterior faniculusAnterior faniculus Lateral faniculusLateral faniculus

Tract: Tract: Composed of nerve fibers sharing a Composed of nerve fibers sharing a common origin, destination and functionscommon origin, destination and functions

Posterior funiculusPosterior funiculus

Contains one ascending fibers concerned with two Contains one ascending fibers concerned with two modalitiesmodalities- kinesthesia- kinesthesia- discriminative touch- discriminative touch

Lesion of this area causes loss of:Lesion of this area causes loss of:- vibration sense- vibration sense- position- position- two point discrimination- two point discrimination- fine touch (tested by piece of cotton)- fine touch (tested by piece of cotton)- weight perception- weight perception

Lateral & Anterior funiculiLateral & Anterior funiculi

Ascending Tracts:Ascending Tracts: Dorsal spinocerebral tractDorsal spinocerebral tract Ventral spinocerebellar tractVentral spinocerebellar tract Spinocervical thalamic tractSpinocervical thalamic tract Lateral spionothalamic tractLateral spionothalamic tract Anterior spinothalamic tractAnterior spinothalamic tract

Lateral & Anterior funiculiLateral & Anterior funiculi

Desending TractsDesending Tracts Corticospinal tractCorticospinal tract Rubrospinal tractRubrospinal tract Lateral vestibulospinal tractLateral vestibulospinal tract Medial vestibularspinal tractMedial vestibularspinal tract Reticulospinal tractReticulospinal tract Descending autonomic pathwayDescending autonomic pathway

Ascending TractsAscending Tracts

Dorsal spinocerebellar tract:Dorsal spinocerebellar tract:

conveys impulses from muscle spindle, golgi conveys impulses from muscle spindle, golgi organ via (DRG) to cerebellumorgan via (DRG) to cerebellum

Ventral spinocerebellar tract:Ventral spinocerebellar tract:

conveys impulses to cerebellum from golgi conveys impulses to cerebellum from golgi organorgan

Ascending TractsAscending Tracts

Spinocervical thalamic tract:Spinocervical thalamic tract:

conveys impulses to thalamus; carries the conveys impulses to thalamus; carries the kinesthesia & discriminative touchkinesthesia & discriminative touch

Laeral spinothalamic tract:Laeral spinothalamic tract:

transmits pain & temperature sensations transmits pain & temperature sensations to thalamus to thalamus

Anterior spinothalamic tract:Anterior spinothalamic tract:

transmits light touch sensations to brain transmits light touch sensations to brain stem & thalamus stem & thalamus

Descending TractsDescending Tracts

1. Corticospinal tract (pyramidal) 1. Corticospinal tract (pyramidal) From motor cortex to medulla as follow: From motor cortex to medulla as follow: 30% from the motor cortex to the muscles30% from the motor cortex to the muscles 30% from the premotor and supplementary 30% from the premotor and supplementary

cortex to the musclescortex to the muscles 40% from somatosensory areas40% from somatosensory areas

divided into:divided into:1.1. Crossed (lateral corticospinal tract)Crossed (lateral corticospinal tract)2.2. Uncrossed fibers (anterior corticospinal tract)Uncrossed fibers (anterior corticospinal tract)

Corticospinal Pathway (pyramidal) Corticospinal Pathway (pyramidal)

From the cortexFrom the cortex internal capsule internal capsule thru thru brain stembrain stem via medulla where majority of via medulla where majority of the fibers cross in the lower medulla the fibers cross in the lower medulla lateral lateral coticospinal tract of the cordcoticospinal tract of the cord interneurons interneurons (few in dorsal horn and very few in anterior (few in dorsal horn and very few in anterior motor neurons)motor neurons)

N.B. also a few of fibers do not cross but N.B. also a few of fibers do not cross but pass ipsilaterally in ventral corticospinal tractpass ipsilaterally in ventral corticospinal tract

Corticospinal tract (pyramidal) Corticospinal tract (pyramidal)

3% of pyramidal fibers with 16 3% of pyramidal fibers with 16 m myelinatedm myelinated Originate from betz cells in the motor areaOriginate from betz cells in the motor area Impulses conveyed are facilitatory to flexor Impulses conveyed are facilitatory to flexor

motor neuronsmotor neurons Terminates in internurons laminae IV-VIITerminates in internurons laminae IV-VII Lesion: Lesion: Homolateral paralysisHomolateral paralysis Contralateral paralysisContralateral paralysis

In addition to: spasticity, hyperactive myotatic In addition to: spasticity, hyperactive myotatic reflexes and clonusreflexes and clonus

Descending TractsDescending Tracts

2. Rubrospinal tract2. Rubrospinal tract Neuronal origin is in red nucleus (midbrain)Neuronal origin is in red nucleus (midbrain) Terminates similarly as pyramidal tractTerminates similarly as pyramidal tract Indirect corticospinal tractIndirect corticospinal tract Facilitates flexor motor neurons Facilitates flexor motor neurons

3. Lateral vestibulospinal tract3. Lateral vestibulospinal tract Neuronal origin lie in pons (lateral vestibular Neuronal origin lie in pons (lateral vestibular

nucleus)nucleus) Terminates at laminae VII & VIII Terminates at laminae VII & VIII Facilitates extensor motor neurons Facilitates extensor motor neurons

Descending TractsDescending Tracts4. Medial vestibularspinal tract:4. Medial vestibularspinal tract: From media vestibular nucleus in ponsFrom media vestibular nucleus in pons Terminates as latera tractTerminates as latera tract Facilitates flexor motor neurons Facilitates flexor motor neurons

5. Reticulospinal tract:5. Reticulospinal tract:a. pontine reticulospinal tracta. pontine reticulospinal tractfrom pons from pons terminates at laminae VII & VIIIterminates at laminae VII & VIIIfacilitates extensor motor neurons facilitates extensor motor neurons b. medullary reticulospinal tract b. medullary reticulospinal tract terminates at VII & IXterminates at VII & IXfacilitates flexor motor neurons facilitates flexor motor neurons

Descending TractsDescending Tracts

6. Descending autonomic pathway:6. Descending autonomic pathway: Neuronal origin at hypothalamus Neuronal origin at hypothalamus Small caliber fibersSmall caliber fibers Project into intermediolateral of column Project into intermediolateral of column