General Sensory Pathways of the Face Area, Taste Pathways and Hearing Pathways

General Sensory Pathways of the Face Area, Taste Pathways and Hearing Pathways

Lecture Objectives Describe pathways for general sensations (pain, temperature, touch and proprioception) from the face area. Describe taste pathways. Describe hearing pathways.

Sensory Innervation of Head Most of the sensory innervation of the head region is supplied by some cranial nerves Trigeminal, facial, glossopharyngeal & vagus Spinal nerves (C1 C3) participate in the sensory innervation of the head

Cranial Nerves Innervating Head Sensory Innervation: Modalities and Territories

GSA Trigeminal ganglion Skin of face and head Mucus membrane Nasal cavity Oral cavity Paranasal sinuses Eye External ear Dura matter TMJ Teeth Trigeminal nerve (V)

Geniculate ganglion GSA External ear & mastoid SVA Taste from tongue (anterior ⅔) GVA Soft palate Floor of the mouth Pharynx Facial Nerve (VII)

Glossopharyngeal Nerve (IX) GSA External ear Superior ganglion SVA Taste from tongue (posterior ⅓) Inferior ganglion GVA Tongue (posterior ⅓) Fauces Pharynx Middle ear Carotid sinus baroreceptors Carotid body chemoreceptors Inferior ganglion

GSA External ear Superior jagular ganglion SVA Taste (epiglottis & base of tongue) Inferior nodose ganglion GVA Pharynx Larynx Other viscera Inferior nodose ganglion Vagus Nerve (X)

Sensory Innervation of Head Summary Trigeminal nerve GSA Skin of face and head Mucus membrane Facial nerve GSA external ear & mastoid SVA taste from tongue (anterior ⅔) GVA soft palate, floor of the mouth, pharynx Glossopharyngeal nerve GSA external ear SVA taste from tongue (posterior ⅓) GVA tongue (posterior ⅓), fauces, pharynx, middle ear Vagus nerve GSA external ear SVA taste (epiglottis & base of tongue) GVA pharynx, larynx, other viscera Spinal nerves (C2 C3) GSA scalp & dura mater

Sensory Innervation of Head Summary 1 st order neurons Trigeminal nerve Trigeminal ganglion (V) GSA Facial nerve Geniculate ganglion (VII) GSA, GVA, SVA Glossopharyngeal nerve Superior ganglion (IX) GSA Inferior ganglion (IX) SVA, GVA Vagus nerve Superior jugular ganglion (V) GSA Inferior nodose ganglion (V) GVA, SVA Spinal nerves Dorsal root ganglion (C1 C3)

Cranial Nerve Innervating Head Central Sensory Component

Brainstem Sensory Nuclei Nucleus of tractus solitarius (GVA, SVA) Trigeminal sensory complex (GSA) Spinal nucleus Main sensory nucleus Mesencephalic nucleus

Nucleus of Tractus Solitarius GVA, SVA Sensory nucleus for Facial nerve Glossopharyngeal nerve Vagus nerve Contains 2 nd order neurons Axons cross midline 3 rd order neuron PVM of thalamus Axons internal capsule corona radiata cortex (postcentral gyrus)

Facial Nerve

Glossopharyngeal Nerve

Vagus Nerve

Trigeminal System Most of the sensory information from head are carried by the trigeminal nerve Face, oral & nasal cavities, cornea, meninges and cranial blood vessels Small sensory components (GSA) of cranial nerve VII, IX, X All GSA information is processed by trigeminal nuclei

Trigeminal Nerve Sensory Nuclei Mesencephalic nucleus (GSA) Unconscious proprioception Location, Extension Main sensory nucleus (GSA) Touch & pressure Spinal nucleus* (GSA) Pain & temperature Extensions Medulla C2 Somatotopic organisation Ophthalmic most caudal Mandibular most rostral *receive GSA from V, IX, X

Trigeminal Nerve Sensory Nuclei Spinal nucleus parts Pars caudalis Below pyramidal decussation Pain & temperature Receive fibers from: C1 C3, GSA from IIV, IX, V, cerebral blood vessels Pars interpolaris Below rostral third of the inferior olivary nucleus Pain sensation from teeth Light touch Pars oralis Light touch Discriminative touch Main sensory nucleus Light touch Discriminative touch

Trigeminal Nerve Sensory Nuclei 1 st order neurons Trigeminal ganglion 2 nd order neurons Trigeminal nerve sensory nuclei Except mesencephalic nucleus Contains 1 st order neurons Central axons cross midline Form trigeminal lemniscus 3 rd order neurons VPM nucleus of thalamus Internal capsule

Trigemino cervical Complex Upper cervical afferents converge to the pars caudalis of spinal trigeminal nucleus Cervical headache (cervicogenic headache) Pain referred from cervical origin to the head structures

Trigemino vascular system Cerebral vessels and meningeal vessels are innervated by trigeminal nerve Pain afferents converge to the spinal trigeminal nucleus Migraine

Vestibulocochlear Nerve (VIII) Formerly called the acoustic or auditory nerve Brainstem (between pons & medulla) Internal acoustic meatus Mainly a sensory nerve Consists of two branches: Cochlear branch Associated with hearing Receptors in the spiral organ in the cochlea The cell bodies in the spiral ganglion Axons travel to nuclei in the medulla if damaged deafness or tinnitus (ringing) is produced

Auditory Nuclei/Pathway 1 st order neuron spiral ganglion 2 nd order neurons Cochlear nuclei Anterior & posterior Location Relations inferior cerebellar peduncles Axons cross and uncross midline 3 rd order neurons Posterior nucleus of trapezoid body & superior olivary nucleus Axons lateral lemniscus 4 th order neurons Inferior colliculus Medial geniculate body (5 th ) internal capsule auditory cortex (superior temporal gyrus)

Vestibulocochlear Nerve (VIII) Vestibular branch Associated with equilibrium Receptors in the semicircular canals, saccule, and utricle The cell bodies in vestibular ganglion Axons travel to nuclei in the thalamus; some fibers also travel to the cerebellum Lesion results in disequilibrium, vertigo, nystagmus, ataxia

The Vestibular Nuclei/Pathway Location 4 th ventricle Vestibular nuclei (2 nd order neurons) Lateral vistibulospinal tract Superior Medial Inferior Inputs from cerebellum Axons To spinal cord To eye muscles nerves (III, IV, VI) To thalamus (VP) vestibular area in cerebral cortex (postcentral gyrus)