Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves HEAD/NECK : Cranial Nerves Special Sense Nerves –I,II,VIII Somatic Motor Nerves –Eye—III,IV,VI –Tongue--XII “Rest of body” nerves –IX,X,XI Face and jaws –VII, V

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves Nerve “targets” in head SENSORY SpecialGeneral Smellskin Visionteeth Hearingeye tongue oral cavity nasal cavity middle ear throat meninges MOTOR MusclesGlands eyessalivary extrinsicsweat intrinsiclacrimal jawsmucous facial expression larynx tongue throat ear

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves Base of the skull—cranial nerves out Ethmoid (olfactory) I. Olfactory Sphenoid (optic) II. Optic III. Oculomotor IV. Trochlear VI. Abducens Temporal (otic) VII. Acoustic/Auditory/ Vestibulocochlear Face/Jaws V. Trigeminal VII. Facial Throat (rest of body) IX Glossopharyngeal X. Vagus XI. Spinal Accessory XII. Hypoglosal

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves Special Sense Nerves Internal auditory meatus (temporal) Inner earVIII. Auditory Optic canal (sphenoid) RetinaII. Optic Cribiform plate (ethmoid) Olfactory epithelium I. Olfactory EXIT FROM CRANIAL CAVITY TARGETNERVE

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves

Somatic Motor Nerves (eye muscles and tongue) EXIT CR. CAVITYTARGETNERVE Hypoglossal canal (occipital) Intrinsic, extrinsic mm. of tongue XII. Hypoglossal “Sup.,med.,inf.rectus Inferior Oblique Levator palpebrae superioris III. Oculomotor (Also parasympathetic to ciliary mm, constrictor pupillae) “Lateral rectusVI. Abducens Sup. Orbital fissure (sphenoid) Superior oblique m. (with trochlea) IV. Trochlear

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves

“Rest of body” nerves (all exit from jugular foramen)

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves

Cranial Nerves Twelve pairs: –2 attach to forebrain (Telen- & Diencephalon) –10 attach to brainstem (Mes-, Met- and Myelencephalon) Names relate to appearance or function Classification ?

Olfactory Nerve (= CN or N I) 1º function? Origin? Destination? _____________(By way of cribiform plate of ethmoid) Only CN directly attached to Cerebrum

Visual System Eye Accessory structures –Eyebrows, eyelids, eyelashes, tear glands –Protect eyes from sunlight and damaging particles Optic nerve (II) –Tracts –Pathways Eyes respond to light and initiate afferent action potentials

Optic Nerve (N II) 1º fu? ori? dest? - by way of optic foramen of sphenoid to Diencephalon (optic chiasma) and to occipital lobe

Oculomotor (N III) C: Motor O: Mesencephalon D: Somatic motor to superior, inferior, medial recti and inferior oblique; visceral motor to intrinsic eye muscles by way of superior orbital fissure

Trochlear (N IV) C: Motor O: Mesencephalon D: superior oblique by way of superior orbital fissure

Trigeminal (N V) C: Mixed three major branches 1. ophthalmic (sensory) 2. Maxillary (sensory) 3. Mandibular (mixed) O: face / nuclei of pons D: sensory nuclei in pons / muscles of mastication

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves V: Trigeminal (3 nerves in 1!) V1. Ophthalmic –Exits with eye muscle group (superior orbital fissure, through orbit to superior orbital notch/foramina) –Sensory to forehead, nasal cavity V2. Maxillary –Exits foramen rotundum through wall of maxillary sinus to inferior orbital foramina) –Sensory to cheek, upper lip, teeth, nasal cavity V3. Mandibular –Exits foramen ovale to mandibular foramen to mental foramen –Motor to jaw muscles--Masseter, temporalis, pterygoids, digastric –Sensory to chin –Sensory to tongue

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves

Abducens (CN VI) C: Motor O: Pons D: Runs lateral rectus eye muscle

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves VII: Facial Nerve (exits cranial cavity with VIII--internal auditory meatus) Facial muscles (five branches fan out over face from stylomastoid foramen) –Temporal –Zygomatic –Buccal –Mandibular –Cervical “chorda tympani” (crosses interior ear drum to join V 3 ) –Taste to anterior 2/3 of tongue –Submandibular, sublingual salivary glands Lacrimal glands

Facial (N VII) C: Mixed O: sensory from taste receptors of anterior 2/3 of tongue / motor from pons D: Sensory to sensory nuclei of pons / motor muscles of facial expression, visceral motor to tear gland.

Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves

Vestibulocochlear (N VIII) C O ? D

Glossopharyngeal (CN IX) C: mixed O: sensory from posterior 1/3 of tongue / motor from medulla oblongata D: medulla / muscles for swallowing, parotid gland

Vagus (N X) C: Mixed O: Sensation from pharyngeal area and outer ear / motor from medulla D: Sensory to medulla / visceral motor to thoracic and abdominal cavities and their organs. Major motor pathway for ANS

Accessory (N XI) and C: Motor O: Motor nuclei of medulla and spinal cord D: Swallowing, trapezius & scm muscles Hypoglossal (N XII) C: Motor O: Motor nuclei of medulla D: Tongue musculature

Mnemonic Out On Our Table Top Are Fruits, Very Green Vegetables And Hamburgers

Extrinsic Eye Muscles

Anatomy of the Eye Three coats or tunics –Fibrous: Consists of sclera and cornea –Vascular: Consists of choroid, ciliary body, iris –Nervous: Consists of retina

Anatomy of the Eye Fibrous tunic: Outer –Sclera: White outer layer, maintains shape, protects internal structures, provides muscle attachment point, continuous with cornea –Cornea: Avascular, transparent, allows light to enter eye and bends and refracts light Vascular tunic: Middle –Iris: Controls light entering pupil; smooth muscle –Ciliary muscles: Control lens shape; smooth muscle Retina: Inner –Contains neurons sensitive to light –Macula lutea or fovea centralis: Area of greatest visual acuity –Optic disc: Blind spot Compartments –Anterior: Aqueous humor –Posterior: Vitreous humor –helps maintain ocular pressure –keeps eye inflated –largely responsible for shape of eye Lens –Held by suspensory ligaments attached to ciliary muscles –Transparent, biconvex

Functions of the Complete Eye Eye functions like a camera Iris allows light into eye Lens, cornea, humors focus light onto retina Light striking retina is converted into action potentials relayed to brain

The Retina Provides black backdrop for increasing visual acuity Sensory retina and pigmented retina Photoreceptors –Rods: Noncolor vision Rhodopsin reduction: Light adaptation Rhodopsin production: Dark adaptation –Cones: Color vision

Sensory Receptor Cells

Rods and Cones Photoreceptors are depolarized in the dark, continuously releasing neurotransmitter. When hyperpolarized by light-->decrease amount of neurotransmitter. Rods- activated below starlight. Scotopic vision, no color, poor acuity. Cones- activated with brighter light. Photopic vision. Color vision.

Rods and Cones Most of what we think of as seeing is mediated by cones. Individual loses cone vision, legally blind. Individual loses rod vision, experience difficulties at low levels of illumination (night blindness). Cones are only receptors in fovea.

Other visual pathways Ganglion cells--> pretectum. Between thalamus and midbrain. Coordinates the pupillary reflex. Suprachiasmatic nucleus of the hypothalamus. Involved in day/night cycle and biological rhythms. Superior colliculus in midbrain. Coordinates head and eye movements.