Special Sense - Everything but Vision

General senses

• Thermoreceptors → temp

• Nocireceptors → pain

• Baroreceptors → pressure

• Proprioreceptors → position of body in space

Special senses

• Chemoreceptors → taste & smell

• Mechanoreceptors → hearing & equilibrium

• Photoreceptors → vision

Taste

• Anterior 2/3 of tongue → facial nerve (CN Vll / 7)

• Posterior 1/3 of tongue → glossopharyngeal nerve (CN lX / 9)

• Tongue have Papillae that house chemoreceptors

Special sense (taste) vs. General sense of tongue

• Anterior 1/3 of tongue:

  • Special sense (taste): facial nerve (CN Vll)

  • General sense: mandibular branch of trigeminal nerve (CN V₃)

• Posterior 1/3 of tongue:

  • Special sense (taste): glossopharyngeal nerve (CN lX)

  • General sense: glossopharyngeal nerve (CN lX)

Extrinsic muscles of the tongue

• Innervated by: Hypoglossal nerve (CN Xll)

• 3 muscles:

  • Genioglossus muscle → protracts tongue

    • (Genio = chin)

  • Styloglossus muscle → elevates & retracts tongue

    • (Attached to styloid process)

  • Hypoglossus muscle → depresses tongue

    • (Attached to hyoid bone)

Smell

• CN 1 - Olfactory nerve

  • Is the chemoreceptor that brings smell to the Primary Olfactory Cortex

Pathway for smell

• Primary Olfactory Cortex:

  • Located mostly at the medial aspect of the temporal lobe; conscious awareness of odors

Anatomy of ear

External, middle, & internal ear

Structures of external ear

• Auricle (funnels sound)

• External auditory canal (sound travels through)

• Tympanic membrane (vibate)

Structures of middle ear

• Auditory ossicles (3) → MIS

  • Malleus (pressed against tympanic membrane)

  • Incus

  • Stapes (pressed against oval window)

• Pharyngotympanic tube

  • Pressure equilization

Auditory ossicles

• Malleus - “hammer”

• Incus - “anvil”

• Stapes - “stirrup”

Structures of internal ear

Mechanoreceptors:

• Semicircular canals - equilibrium

• Cochlea - hearing

Others:

• Oval window - vibrations in

• Round window - vibrations out

Internal ear - other view

• CN Vlll (vestibulocochlear nerve) goes through internal acoustic meatus

• Temporal bone

• Auditory cortex of temporal lobe of cerebrum

Vestibulocochlear nerve

• CN Vlll

• Joins cochlear nerve from cochlea & vesitbular nerve from vestibule

• Goes through internal acoustic meatus to pons & medulla

Summary

• Olfactory tract → primary olfactory cortex (medial temporal lobe)

• Primary auditory cortex (lateral temporal lobe)

• Primary visual cortex (occipital lobe)

• Suppliers: middle cerebral & posterior cerebral artery