Theoretical background to the

study of the sense organs and

pathways of the central nervous

system. Ascending projection

pathways of the brain and spinal

cord. Descending projection

pathways (pyramidal and

extrapyramidal).

Composed by

Natalia Leonidovna Svintsitskaya,

Associate professor

of the Chair of Human Anatomy,

Candidate of Medicine

environment

animal

organismNervous system

sensory

neuron

stimulus reaction

effectorInter-

neuronreceptor

Motor

neuron

Nervous System stimulus and reaction

Sensory System

Modality of Sensation

Receptor

Sensory Tract

Primary Neuron

Secondary Neuron

Tertiary Neuron

Termination

Modality of Sensation

General Sensation, Special Sensation

vision, hearing, equilibrium, smell, taste

Exteroception, Interoception, Proprioception

conscious vs. unconscious proprioception

position sensation, kinesthesia

Touch, Pain, Temperature Sensation

discriminative vs. light touch sensation

fast vs. slow pain

Receptors

Peripheral Nerve Ending

Receptor Neuron

Olfactory Neuron of Olfactory Epithelium

Specialized Receptor Cell

Merkel cell of Epdermis

Taste (Gustatory, Clear) Cell of Taste Bud

Photoreceptor cells of Retina

Hair cells of Inner Ear

Receptor: Peripheral Nerve Endings

Receptor Neurons of Craniospinal Ganglion

Pseudounipolar neurons of dorsal root ganglia

Trigeminal (semilunar, Gasserian ganglion),

geniculate (VII), superior IX, superior X ganglia (GSA)

Geniculate (VII), inferior IX, inferior X ganglia (VA)

Morphological Classification

Free nerve endings

Expanded tip endings

Encapsulated endings ----- CT envestment

Receptors

Free Nerve Endings

- Nerve endings without special structural

organization

- pain and temperature receptor

Expanded Tip Endings

- Merkel’s Touch Corpuscle

Merkel cells in basal layer of epidermis

- Type I Hair cells of Vestibular Labyrinth

Pathways for General Sensation

Touch & Proprioception from body

Posterior White Colum-Medial Lemniscal Pathway

Pain & Temperature from body

Spinothalamic Tract

cf. Spinoreticular or Spinoreticulothalamic Tract

General Sensation from Face

Trigeminothalamic Tracts

Sensory System General Sensation

Pain Pathway

Spinothalamic Tract

Anteromedial System

Modality: Pain & Temperature Sensation,

Light Touch from body

Receptor: Free Nerve Ending

1st Neuron: Dorsal Root Ganglion

2nd Neuron: Dorsal Horn

Anterior White Commissure

Spinothalamic Tract (Spinal Lemniscus)

3rd Neuron: Thalamus

Internal Capsule ----- Corona Radiata

Termination: Primary Somesthetic Area (S I)

Spinothalamic Tract

Spinothalamic Tract

Modality: Pain & Temperature Sensation,

Light Touch from body

Receptor: Free Nerve Ending

1st Neuron: Dorsal Root Ganglion

2nd Neuron: Dorsal Horn

Anterior White Commissure

Spinothalamic Tract (Spinal Lemniscus)

3rd Neuron: Reticular Formation

4rd Neuron: Thalamus

Internal Capsule ----- Corona Radiata

Termination: Diffuse Cerebral Cotex

Spinoreticulothalamic Tract (Paleospinothalamic Tract)

Spinothalamic Tract

spinothalamic

tract

anterior white

commissure

posterior root

decussation

- contralateral loss of pain and temperature

sensation below the level of lesion

Modality: General Sensation from face

Receptor: Most receptors in the face

1st Neuron: Trigeminal (Semilunar) Ganglia

2nd Neuron: Trigeminal Sensory Nucleus

pain & temperature ---- pars caudalis of

spinal tract nucleus of V

Ventral and Dorsal Trigeminothalamic Tract

3rd Neuron: Thalamus

Internal Capsule ----- Corona Radiata

Termination: Primary Somesthetic Area (S I)

Trigeminothalamic Tract

Trigeminothalamic

Tract

A. trigeminal ganglion

B. trigeminal sensory

nucleus

C. thalamus

D. cerebral cortex

1. spinal tract of

trigeminal nerve

2. ventral

trigeminothalamic tract

3. dorsal

trigeminothalamic tract

4. corona radiata

V. trigeminal nerve

Spinocerebellar Tract

Posterior SCbllT

Inferior

cerebellar

peduncle

Post. SCbllT and

cuneocerebellar

tract

posterior

white column

posterior root

Anterior SCbllT

superior

cerebellar

peduncle

anterior

spinocerebellar

tract

anterior white

commissure

posterior root

Predominant Sensory Syndromes

• Herpes Zoster- inflammatory reactions of dorsal root ganglion

- severe pain on the dermatomes of affected ganglion

followed by rashes and vesicle

• Tabes Dorsalis

- common variety of neurosyphilis

- posterior colum and spinal posterior root lesion

- loss of discriminative touch sensation and consciousproprioception below the level of lesion

- posterior column ataxia

- lancinating pain

- loss of deep tendon reflex (DTR)

Herpes Zoster (Shingles)

• varicella-zoster virus

reactivation from the dorsal root ganglia

• unilateral vesicular

eruption within

a dermatome

• T3 to L3 dermatome

lesions are frequent

• zoster ophtahalmicus

(ophthalmic division

of trigeminal n., V1)

• Ramsey-Hunt syndrome

(sensory br. of VII)

• acyclovir, antiviral agent

Herpes Zoster

(Shingles) Zoster ophthalmicus

Tabes Dorsalis (Neurosyphilis)

posterior column lesion - sensory symptoms, posterior column ataxia

Tabes Dorsalis

Subacute Combined

Degeneration

Ataxic Gait and Position:

- Watches the ground

in walking

- Positive Romberg Test

- Stick and Stamp Sign

Posterior Column

Ataxia

Friedreich’s Ataxia

posterior spinocerebellar tract lesion - cerebellar ataxia

Muscle Status - Balance and Posture

alcohol and cerebellar dysfunction

Syringomyelia

initial symptom - bilateral loss of pain and temperature sensation

Syringomyelia

initial symptom - bilateral loss of pain and temperature sensation

Trigeminal Neuralgia

(tic douloureux)

- excruciating episodic pain

in the area supplied by

trigeminal nerve, especially

second and third division

- trigger point

- intense pain makes the

patient grimace (tic)

- antiepileptic drug (phenytoin,

carbamazepine) is effective

- surgical treatment