special sense i – vision. visual pathway lesion in optic nerve leads to loss of vision on the same...

Special sense

I – VISION

Visual pathway

• Lesion in optic nerve leads to loss of vision on the same side of lesion

• optic tract: *Left optic tract is responsible for vision in nasal

half of left visual field and temporal half of right visual field

*right optic tract is responsible for vision in nasal half of right visual field and temporal half of left visual field

II- HEARING

Auditory pathway

• External ear: collect sounds & direct it to tympanic membrane

• Middle ear: sounds vibrate the tympanic membrane then transmitted to auditory ossicles

• Types of conduction: 1- ossicular conduction 2- air conduction3- bone conduction• Austachian tube: responsible for equalizing

pressure on either side of tympanic membrane

III- TASTE

• Taste buds situation

Taste pathway

• Taste sensation

IV- SMELL

Smell pathway

Vision Hearing Smell Taste

Receptor Rods & cons Hair cell in organ of corti

Olfactory receptor Taste buds

Site In retina Inner ear Nose Tongue

Nerve Optic nerve Auditory nerve“vestibulocochlear “

Olfactory nerve *Anterior 2/3 of tongue: fibers of facial nerve*Posteior 1/3 of tongue: glossopharyngeal nerve*Vagal fibers from other regions

Relay in thalamus

Relay in thalamus

Relay Not relay in thalamus

Relay

Cerebral cortex

Occipital role Temporal lobe Olfactory cortex includes structures which form apart of limbic system

Parietal lobe