*Cranial Nerves & Pathways

*Objectives

* Compare and Contrast cranial nerves to spinal nerves

* Know which cranial nerves are central and which are peripheral

* Know the 4 functions of all cranial nerves together

* Draw, interpret, and analyze the corticobrainstem tracts

* Explain the process of olfaction (receptors, CN I, cortical areas)

* Explain taste (receptors, CN VII & IX, solitary n.)

* Explain vision (visual field, anatomy & receptors, CN II, visual pathway)

* Explain coordination of eye movements (III, IV, VI efferents)

* Explain hearing (anatomy & receptors, CN VIII, auditory pathway)

* Explain sensory and motor control of face (CN V & VII)

* Explain swallowing & speaking (CN V, VII, IX, X efferents)

* Explain head control (CN XII efferents)

* Explain parasympathetic control of viscera (CN X)

* Describe or draw the auditory, visual, and pupillary pathways

Special SensesMotor (and somatosensory)Autonomic

*Venn Diagram

• Somatosensory

• Somatomotor• Ganglia for

afferents outside of CNS

• Reflexes • Sympathetic

components

• Special senses

• Vary in components (S, M, B)

• From specialized nuclei in BS

• Parasympathetic component

• All have both (B)

• From gray laminae in SC

Cranial Nerves

Spinal Nerves

*Cranial Nerve Overview

*What are cranial nerves?

*4 functions

*Motor innervation to muscles of face, eyes, lips, tongue, jaw, and throat

*Somatosensory information from face and jaw (touch, vibration, proprioception, pain, etc)

*Special senses – vision, hearing, taste, smell, vestibular

*Parasympathetic regulation

*Corticobrainstem tracts

*Draw the corticobrainstem tracts!!

*Refer to this drawing during the rest of the cranial nerves lectures!

*Corticobrainstem = corticonuclear = corticobulbar

*Smell (Olfaction)

*Key Structures:

*Chemoreceptors

*Cranial Nerve I (Olfactory bulb and tract)

*Olfactory Cortex

*Key Points:

*

*

*

*Dysfunctions called

–osmia (ex: anosmia)

*Taste (Gustation)

*Key Structures:

*Chemoreceptors

*CN VII & IX (facial & glossopharyngeal)

*Solitary Nucleus

*VPM, Gustatory Cortex

*Key Points:

*

*

*

*Vision – Visual Field

*Peripheral vision is only one eye

*Blind spot is location of

optic nerve in retina

*Image is flipped – peripheral vision is located in medial retina

*Test your peripheral vision!

*Find the edge of vision on your R, first with your R eye, then only with your left.

*Find your blind spot!

*Close your L eye. Find your R blind spot with a finger.

*Vision - Anatomy

*Photoreceptors

*Located in the retina

*Rods – black and white

*Cones – 3 pigmented types to detect colors

*Cornea Lens Retina Optic n.

*Fovea:

*

*Refraction of light

*Visual and Pupillary

Pathways

*Visual

*Carries information from retina

*Goes to LGB

*Then to hypothalamus, midbrain, primary visual cortex

*Pupillary

*Using visual information in midbrain…

*Goes to EW, through oculomotor nerve to constrictor muscles

*Eye movements

*CN III, IV, VI

*Nuclei in midbrain & pons

*Medial Longitudinal Fasciculus

*

*

*4 Rectus muscles, 2 Oblique muscles, 1 eyelid muscle

*Movements are normally coordinated

*Hearing

*Sound wave tympanic membrane 3 ear bones (malleus, incus, stapes) cochlea hair cells (mechanoreceptors) spiral ganglia cochlear nerve

*http://www.healthline.com/vpvideo/hearing-animation

*Motor control of face musculature

*CN VII (facial)

*2 halves of facial nucleus

*Upper

*Lower

*CN V

*muscles of mastication

*Sensory Information from

Face

*CN V (trigeminal)

*Ophthalmic (V1) S

*Maxillary (V2) S

*Mandibular (V3) B

*Trigeminal nuclei

*Mesencephalic

*Sensory, Motor

*Spinal

*Swallowing

*Salivation CN IX, parotid gland

*Somatosensation of posterior tongue & throat

*CN IX Solitary n.

*Swallowing

*Nucleus Ambiguus, Solitary, Dorsal Motor of X combination of CNs IX, X, XII

*Speaking

*Motor control of larynx & soft palate

*Corticonuclear tract Nucleus Ambiguus CN X

*Motor control of tongue

*Corticonuclear tract Hypoglossal nucleus CN XII

*Motor control of jaws

*Corticonuclear tract Trigeminal motor nucleus CN V

*Motor control of lips

*Corticonuclear tract Facial nucleus CN VII

*Parasympathetic control

*CN Reflexes & Testing

1. Smell: use smelling salts or other substances to test sense of smell (A-1)

2. Pupillary reflex: direct & consensual responses (A-2, E-3)

3. Eye coordination: test for eye position & nystagmus (E-3,4,6)

5. Sensation of face: Touch, pain, temp (A-5)

7. Blink reflex: Test blinking (A-5, E-7)

Face muscles: Check facial expressions (E-7)

8. Test balance & hearing

9. Gag reflex: (A-9, E-10)

11. MMT trapezius & SCM (E-11)

12. Tongue: check for atrophy (E-12)

Pages 351-353 LE