copy right- hongqi zhang-department of anatomy-fudan university systematic...

Copy Right- Hongqi ZHANG-Department of Anatomy-Fudan University

Copy Right- Hongqi ZHANG-Department of Anatomy-Fudan University1

Dr.Hongqi Zhang (张红旗)Email: [email protected]

Systematic Anatomy

Nervous system

The conducting pathway



Concept

Nervours pathway are the routes formed by chains of neurons,through which sensory awareness reaches the cerebral cortex and a motor response is initiated.

Category of nervous pathways:

The ascending (afferent or sensory) pathways

The descending (efferent or motor) pathways

Pyramidal system

Extrapyramidal system.

Each nervous pathway consists of a chain of tracts and associated nuclei.

General introduction about the nervous pathways



Ascending (afferent or sensory) pathwayDifferent types of receptors receive different types of stimuli from the external and internal environment and generate corresponding nervous impulse.which are conducted upward to the cerebral cortex centers to be processed to give rise to corresponding sensations.

Superficial sensation : touch,pain.temperature & two-point discrimination.Deep sensations : proprioception,and vibration sense Visceral sensations: hunger.nausea and visceral pain.Special sensations: smelling,sight,hearing.taste.



A chain of three long neurons and a number of interneurons conduct the nerve impulses generated in response to stimuli from an individual receptor to the somatosensory cortex

Generally,there are three grades neuron implicatedIn ascending pathway

First-order neuron: the cell bodies lie in a dorsal root ganglion or somatic afferent ganglia of cranial nn.

Second-order neurons: the cell bodies lie within the spinal cord or brain stem. such as dorsal column nuclei(sensation of trunk & limbs) or sensory nucleus of trigerminal nerve, their axons usually decussate, ending in the thalamus.

Third-order neurons: the cell bodies lie in the thalamus. project to the sensory cortex (center).



Proprioceptive (deep) sensations pathway Pathway of pain.T,touch & pressure sensation (Sup. sensation) Visual pathwayPupillary light reflex Acoustic pathwayEquilibratory pathwayVisceral sensory pathway:

Sensory pathway

General visceral pathwaySpecial visceral pathway

Motor pathw

ay

Pyramidal system

Extrapyramidal system

Cortionuclear tractCortospinal tract

Cortico-neostriatum-dorsalthalamus –cortex circuitNeostriatum-substantia nigra circuitCorticoponto-cerebellar–cortex circuit

Trunk and limbsHead and face

Sensory and motor pathways lists

Trunk and limbsHead and face

Conscious proprioceptiveand fine touch pathwayof trunk and limbs

Spinal ganglion1st neuron body

Fasciculus gracilis

Fasciculus cuneatus

Gracile and cuneate nuclei2nd neuron body

Decussation of medial lemniscus

Medial lemniscus

VPL3rd neuron body

Central thalamicradiation

T4

VPL-ventral posterolateral nucleus

Fasciculus gracilis Fasciculus cuneatus

Fasciculus gracilis

Fasciculus cuneatus

Spinal ganglion

Cell body position of 1st order neuron Spinal ganglion

Cell body position of 2nd order neuron Gracile and cuneate nuclei in medullaablongata

Cell body position of 3rd order neuron Ventral posterolateral nucleus (VPL) in thalamus

Position of decussation Upper portion of medulla ablongataPosition of fiber tract in spinal cord Post.funiculus of spinal cordName of fiber tract in brain stem Medial lemniscusPosition in internal capsule Posterior limb Projection area in cortex Upper 2/3 of postcentral gyrus and

ant.part of paracentral lobulaThe feature:(A)Fasciculus gracils – conduct sensory impulse above T 4;Fasciculus cuneatus-– conduct sensory impulse below T 5;(B)Fiber arrangement in post funiculus are fiber from sacral,lumbar,thoracic and cervical part from medial to lateral

Features of Conscious proprioceptive and fine touch pathway of trunk & limbs

Spinal ganglia1st neuron body

LaminaⅠ,Ⅳ~Ⅶ2nd neuron body Lat. spinothalamic tract

Ant.spinothalamic tract

Spinal lemniscus

VPL3rd neuron body


Pain, temperature and crude touch pathway of trunk and limbs

VPL-ventral posterolateral nucleus

Spinothalamus tract

Spinal ganglion

Cell body position of 1st order neuron Spinal ganglion

Cell body position of 2nd order neuron Nucleus proprius of post.horn(LaminaⅠ,Ⅳ~Ⅶ) of spinal cord

Cell body position of 3rd order neuron Ventral posterolateral nucleus (VPL) in thalamus

Position of decussation Different spinal segment of spinal cordPosition of fiber tract in spinal cord Ant.& lat.funiculus of spinal cordName of fiber tract in brain stem spinal lemniscusPosition in internal capsule Posterior limbProjection area in cortex Upper 2/3 of postcentral gyrus and

post.part of paracentral lobulaThe other feature:(A) After central process of spinal ganglion enter the spinal cord,ascend 1-2 spinal segments then decussate to contralateral spinal cord.(B) The decussation in spinal cord is not at the same level,rather than at different segments.

Features of pain, temperature and crude touch pathway of trunk and limbs of trunk & limbs

Unconscious proprioceptivepathway of trunk and limbs

Spinal ganglion

Post. spinocerebellar tract

Ant. Spinocerebellartract

Lamina Ⅴ-Ⅶ

Inf. cerebellar peduncle

Sup. cerebellar peduncle

Nucleus thoracicus

In this conducting tract,only two-order neurons are involved.

1st neuron body 2nd neuron body

Learn it by yourself

Trigeminal ganglionGeniculate ganglion of facial n.Sup. ganglions of glossopharangeal n. and vagus n.1°neuron

Pontine nucleus of V2nd neuron body

Spinal nucleus of V1st neuron body

Trigeminal lemniscus Trigeminothalamic tract

Spinal tract of trigeminal n.

VPM 3rd neuron body


Pain,temperature and crude touch pathway of head and face

Cell body position of 1st order neuron Trigerminal ganglion in cranium

Cell body position of 2nd order neuron Potine nucleus and spinal nucleus and trigerminal nerve.

Cell body position of 3rd order neuron Ventral posteromedial nucleus (VPM) in thalamus

Position of decussation Pons and medulla oblongataName of fiber tract in brain stem Trigerminal lemniscusPosition in internal capsule Posterior limbProjection area in cortex Lower 1/3 of postcentral gyrusThe other feature:(A) Potine nucleus of trigerminal n. related to tonch,pression sensation of head

and face.spinal nucleus of trigerminal n. related to pain,temperature

sensation of head and face.

(B) Decussation is not at one level.

Features of pain,temperature and crude touch pathway of head and face



Review of the structure related to eye

Rod cellCone cell

Bipolarcell

Ganglioncell

Pigmented cells



The neurons and its visual impulse conduction of the retina

Optic nerve

Optic chiasma

Optic tract

Lateral geniculate body

Optic radiation

Visual area

Visual pathway

Visual pathway

Optic nerve

Optic chiasma

Optic radiation

Lateral geniculate body

Visual area

Optic tract



A Ipsilateral complete blindness

B bitemporal hemianopia

CEF Contralateral homonymous hemianopia of both visual fields

D ipsilateral nasal hemianopia

D

A B

C

DE

F

Projection of optic nerve in occipital lobe cortex


Pathway for papillary light reflex ?

Pathway for pupillary light reflex

Pretectal area

Accessory oculomotor nuclei

Occculomotor n.

Ciliary ganglia

Sphincter pupilCiliary muscle

Cell body position of 1st order neuron Bipolar neuron in retina

Cell body position of 2nd order neuron Ganglion cell in retina

Cell body position of 3rd order neuron Sup.cuniculus in midbrain

Cell body position of 4th order neuron Lateral geniculate body in diencephalon

Position of decussation Optic chiasma in diencephalonPosition in internal capsule Posterior limb (optic radiation)Projection area in cortex Upper and lower close to calcarine

sulcus in occipital lobe (Broadmen:area 17)

The other feature:(A) Four grade neurons are involved in optic pathway .(B) Decussation feature: fiber from nasal half retina decussate only(C) the fiber from upper half retina project to cortex above calcarine sulcus

the fiber from lower half retina project to cortex below calcarine sulcus(D)One eye visual impulse project to double cortex of occipital lobe

Features of optic pathway

Pretectal area

Accessory oculomotor nuclei

Occculomotor n.

Ciliary ganglia

Sphincter pupilCiliary muscle

Pathway for pupillary light reflex

Cell body position of 1st order neuron Bipolar neuron in retina

Cell body position of 2nd order

neuron

Ganglion cell in retina

Cell body position of 3rd order

neuron

Pretectal nuclear

Cell body position of 4th order neuron Both side accessory nuclear of

oculomotor nerve.

Direct light reflex Shined side pupil shrink

Indirect light reflex unshined side pupil shrink

One side optic nerve injury Direct light reflex disappear

indirect light reflex exist

One side oculomotor nerve injury Direct , indirect light reflex disappear

Features of pupillary light pathway



Vestibulocochlearapparatus


Acoustic pathway

Spinal organ

Bipolar neuron of cochlear ganglion

Cochlear nerve

Cochlear nuclei

Trapezoid body

Lateral lemniscus

Medial geniculate body Acoustic radiation

Transverse temporal gyrus

Inferior coliculus3rd neuron body

1st neuron body

2nd neuron body

4th neuron body


Cell body position of 1st order neuron Spiral ganglioni

Cell body position of 2nd order neuron Cochlear nuclei in pons

Cell body position of 3rd order neuron Lower colicullus

Cell body position of 4th order neuron Medial geniculate bodyPosition of decussation Pons Position in internal capsule Posterior limb (acoustic radiation)Projection area in cortex Transverse temporary gyrus

(Broadmen:areas 41,42)

The other feature:

(A) One cerebral hearing center receive both hearing impulse. if one side

hearing cortex injury,no apparent effect to hearing sensation.

(B) The fiber from cochlear nucleus:about 1/3 ascending at same side.about

2/3 fibers firstly decussate to contralateral side then ascend.

Features of acoustic pathway



Descending (efferent or motor ) pathway

Pyramidal system and extrapyramidal systemGenerally,in pyramidal system,two order neurons are involved.The first-order neuron, the cell bodies lie in the motor area of cerebral cortex.The second-order neuron, the cell bodies lie in the somatic motor nuclei in the brain stem and somatic motor nuclei in the ant.horn of spinal cord. their axons innervate the skeletal muscle of the head,the trunk and the limbs.But in extrapyramidal system involved more than 2 neurons (3-6) are needed.


Copy Right- Hongqi ZHANG-Department of Anatomy-Fudan UniversityThe equilibratory pathway




Descending (motor) conducting pathway

Pyramidal systemExtrapyramidal system

Corticospinal tract

Corticospinal tract

Decussation of pyramid

Lat. corticospinal tract

Ant. corticospinal tract

upper motor neuron

Motor neuron of ant.hornLower motor neuron

pyramidUncrossed fiber(2%)Decussation of

pyramidLat. corticospinal tract (90%)


Cortex motor area

Uncrossed fiber (8%)

Cell body position of 1st order neuron Cortex in upper 2/3 of precentral gyrus and ant,part of paracentral lobula

Cell body position of 2nd order neuron Motor neurons of ant. horn in spinal cord

Position passing internal capsule Posterior limb

Position of tract in brain stem Midbrain: cerebral pudenclePons: deep surface of basilar partMedulla: pyramid

Position of decussation Pyramidal decussation:in medulla

Name & position of tracts in spinal

cord

Ant,corticospinal tract (ant.funiculus)Lat.corticospinal tract (lat.funiculus)

Projection area in cortex Upper & lower cortex close to calcarinesulcus in occipital lobe (Broadmen:area 17)

The other feature:

(A) Lat.cordticospinal tract innervate same side skeletal mm. of limbs

(B) Ant.cordticospinal tract innervate both side skeletal mm. of trunk

Features of corticospinal tract



pyramidUncrossed fiber (2%)

Decussation ofpyramid

Lat. corticospinal tract ( 90%decussated fiber)


Lateral corticospinal tract of one sideInnervate the skeletal muscle of same side upper and lower limbsAnterior corticospinal tract of one sideInnervate the trunk skeletal muscle of both left and right sides

Uncrossed fiber (8%)

Lat.corticospinaltract

Limbs muscles

Trunk musclesAnt.white

commissure Ant.corticospinaltract

Mimor component of ant.corticospinal tract (ipsilateral)

Trunk muscles(ipsilateral)

Ant.corticospinal tract: innervate both side trunk skeletal musclesLat.corticospinal tract: innervate same side skeletal mm.of limbs



Nucleus of oculomotor n.

Nucleus of trochlear n.

Motor nucleus oftrigeminal n. Nucleus of abducent n.

nucleus of facial n.

Nucleus ambiguus

Nucleus of accessory n.

Nucleus of hypoglossal n.

Precentralgyrus

Corticornuclear tract



Motor nucleus oftrigeminal n. Nucleus of abducent n.

nucleus of facial n.

Nucleus ambiguus

Nucleus of accessory n.


Precentralgyrus

Corticornuclear tract

Corticonucleartract




trigeminal Motor nucleus

Facia nucleus (upper).

Nucleus ambiguusNucleus of accessory n.


Nucleus of abducent n.


Morter cortex

Facia nucleus (lower)

One side corticornuclear tract

Nuclear of hypoglossal nReceive fiber of contralateral corticonuclear tract only

Lower part of facial nucleusReceive the fiber of contralateral corticonuclear tract only



Nuclear of hypoglossal nReceive the fiber of contralateral

corticonuclear tract only

Lower part of facial nucleusReceive the fiber of contralateral corticonuclear tract only

Upper part of facial nucleusReceive the fiber of corticonuclear tract of both left and right side

Facial nuclear

corticonuclear tract

Facial nuclear

hypoglossal nuclear

Corticonuclear tract



Corticonucleartract

Facial n.

Supranuclear paralysis.

Infranuclear paralysis.

Facial nerveSupranuclear paralysisInfranuclear paralysis



Corticonucleartract

Hypoglassol n.

Supranuclear paralysis.

Infranuclear paralysis.

Hypoglassol nerveSupranuclear paralysisInfranuclear paralysis

Cell body position of 1st order neuron

Cortex in upper 1/3 of precentral gyrus

Cell body position of 2nd order neuron

Somatic motor nuclei in brain stem

Position passing internal capsule GenuPosition of tract in brain stem Corticonuclear tract give rise to motor

nuclei at different level.Position of decussation Pyramidal decussation:in medullaName & position of tracts in spinal cord

Ant,corticospinal tract (ant.funiculus)Lat.corticospinal tract (lat.funiculus)

The other feature:(A) One side corticonuclear innervate both sides: oculomotor n,trochear n,motor

nuclear of trigerminal nerve,abducent nuclear,upper part of facial

nuclear,nuclear ambiguus,accessory nuclear .

(B) Lower part of facial nuclear and hypoglassol nuclear receive only the fiber of

contralateral corticonuclear tract.

Features of cortinuclear tract

The following contents

Learn by yourself



Descending pathway-Extrapyramidal system

It is the descending nervous pathway which influence and control the movement of body except the pyramidal system.

The system includes the corpus striatum.together with the subthalamic mucleus.substantia nigra.red nucleus and reticular formatin of brain stem. the main functions of the extrapyramidal system in man are to regrlate the tonicity of the muscles,maintain the normal body posture and produce habitual and rhythmic movements.



Concept: is a common name for the descending pathways besides the pyramidal system.

Function is to regulate the toniety of the muscles, coordinate the muscular activities,mainitain the normal body posture and produce habitual and rhythmic movements.

For example:…

The extrapyramidal system mainly include:

The Cortico-neostriatum-dorsal thalamus-cortex circuit.

The corticoponto-cerebellar-cortex circuit.

The neostriatum-substantia nigra circuit.

The globus palidus-subthalamus circuit.

Nervous pathway- Extrapyramidal system


Copy Right- Hongqi ZHANG-Department of Anatomy-Fudan UniversityCorticoponto-cerebellar-cortex circuit

Six orders neuronsRelay.Three decussation



Summary of nervous pathwaysAscending pathway consists of three order neurons

Descending pathway consists of two order neurons

General speaking,during their conducting course of both

ascending & descending pathways.There is a

decussation,that is,one side hemisphere receive

sensory impulse of contralateral half of the body.and

innervate the movement of contralateral half of the body.

One side visual area and auditory area receive visual

impulse and auditory impulse of both sides

Babinski reflex - an UMN sign Adult response - plantar flexion of the big toe and adduction of

the smaller toes Pathological (Infant) response - dorsoflexion (extension) of

the big toe and fanning of the other toes Indicative of upper motor neuron(UMN) damage



Clinical features of upper & lower motor neurons lesion

Upper motor neuron Lower motor neuronCell body location Cerebral cortex & their

axon (motor tract)Motor nuclei of cranial nerve. Motor neuron of Ant.horn of spinal cord

Muscle tone increased decreased

Deep reflex hyperactive Decreased or absent

Superficial reflex Decreased or absent absent

Pathological reflex

Existed (babinski sign) absent

Muscle size Slight atrophy Pronounced atrophy

Classical description

Spastic paralysis Flaccid paralysis



Corticospinal tract

Lat.corticospinal tract


Copy Right- Hongqi ZHANG-Department of Anatomy-Fudan UniversityParalysis of facial muscle


Copy Right- Hongqi ZHANG-Department of Anatomy-Fudan UniversityParalysis of tongue muscle

copy right- hongqi zhang-department of anatomy-fudan university systematic...

Documents