General sensation Composed of sensory receptors throughout the body. General senses Touch, pressure, pain, heat, cold, stretch, vibration. Special senses Vision, hearing, equilibrium, olfaction, taste. Relative to the source of the stimuli. Exteroceptors Interoceptors Propioceptors (sketetal muscle). Conscious. General structure (histology, activity 1) Modified dendrites. Free nerve endings Merkel discs in epidermis Hair follicle receptors Meissner corpuscles: light touch Ruffini corpuscles: deep pressure and stretching. Pacinian corpuscles: pressure recptor. Muscle spindles Golgi tendon organs Receptor physiology Act as signal transducers. Direct relationship between importance and number of clustering of the receptors; punctuate distribution.

Special Senses Vision Olfaction Taste Hearing and equilibrium

1. Vision Organ: Eye ball Accessory structures Activity 1 Lacrimal apparatus. Lacrimal gland: secretes tears; solution of salts and lyzozyme. Lacrimal canals Nasolacrimal canal Eyelids (papebrae) Medial and lateral canthus Caruncle Conjunctiva. Mucus membrane that lines inner surface of eyelids. Stratified squamous and stratified cilindrical epithelium. Eyelashes Ciliary glands: lubricate eyeball Tarsal glands: lubricate eyeball 6 extrinsic eye muscles Activity 1

The eye and associated accessory structures Site where conjunctiva merges with cornea Eyebrow Eyelid Eyelashes Pupil Palpebral fissure Lacrimal caruncle Medial commissure (canthus) Lateral commissure (canthus) Sclera (covered by conjunctiva) Iris Eyelid (a)

The lacrimal apparatus gland Lacrimal sac Excretory ducts of lacrimal gland Lacrimal punctum Lacrimal canaliculus Nasolacrimal duct Inferior meatus of nasal cavity Nostril

The eye and associated accessory structures Levator palpebrae superioris muscle Orbicularis oculi muscle Eyebrow Tarsal plate Palpebral conjunctiva Tarsal glands Cornea Palpebral fissure Eyelashes Bulbar conjunctiva Conjunctival sac Orbicularis oculi muscle (b)

Controlling cranial nerve Extrinsic eye muscles Trochlea Superior oblique muscle Superior oblique tendon Superior rectus muscle Axis at center of eye Lateral rectus muscle Conjunctiva Inferior rectus muscle Medial rectus muscle Lateral rectus muscle Optic nerve Inferior rectus muscle Inferior oblique muscle Annular ring (a) (b) Controlling cranial nerve Name Action Lateral rectus Moves eye laterally VI (abducens) Medial rectus Moves eye medially III (oculomotor) Superior rectus Elevates eye and turns it medially III (oculomotor) Inferior rectus Depresses eye and turns it medially III (oculomotor) Inferior oblique Elevates eye and turns it laterally III (oculomotor) Superior oblique Depresses eye and turns it laterally IV (trochlear) (c)

Internal structure of the eye Composed of 3 layers or tunics External Cornea (transparent) and Sclera (white). Middle Anterior Iris: radial smooth muscle (III ocoulomotor) Uvea: vasculariazed. Cilliar body(muscles) : control the curvature of the lens (cristaline). Cilliary processes: secrete aqueous humor. Posterior Choroid: dark pigment. Inner Retina: sensory region Additional internal structures Humor vitreous Macula lutea (yellow spot): high cone density Fovea centralis: area of maximum (very high amount of cones) sight acuity. Sclera venous sins( Schlemm canal) Ciliary zonule Activity 2 (eye dissection next class)

Internal structure of the eye (sagittal section) Ora serrata Sclera Ciliary body Choroid Ciliary zonule (suspensory ligament) Retina Macula lutea Cornea Fovea centralis Iris Pupil Posterior pole Anterior pole Optic nerve Anterior segment (cavity) Lens Scleral venous sinus (Canal of Schlemm) Central artery and vein of the retina Posterior segment (cavity) (contains vitreous humor) Optic disc (blind spot) (a)

Circulation of aqueous humor Posterior segment containing vitreous humor Cornea Lens Iris Lens epithelium Cornea Lens Corneal epithelium ANTERIOR Corneal endothelium Aqueous humor Anterior chamber Ciliary zonule (suspensory ligament) Anterior segment Posterior chamber Scleral venous sinus Ciliary processes Limbus (corneal- scleral junction) Ciliary body Ciliary muscle Anterior ciliary vein Bulbar conjunctiva Sclera

Focusing for distant and close vision Sympathetic + Nearly parallel rays from distant object Lens Ciliary zonule Ciliary muscle Inverted image Ciliary muscle Lens (a) Lens is flattened for distant vision Ciliary zonule (suspensory ligaments) Parasympathetic + Divergent rays from close object Inverted image (c) Anterior segment viewed from behind (b) Lens bulges for close vision

Histology of the retina Sensory tunic Outer pigmented epithelial layer Inner neural layer. Photoreceptors: cones or rods. Bipolar neurons Ganglion Axons of ganglions Activity 3

Photoreceptors of the retina Process of bipolar cell Light Light Light Synaptic terminals Inner fibers Rod cell body Rod cell body Nuclei Cone cell body Mitochondria Outer fiber Retinal (b) Opsin Inner segment Connecting cilia Apical microvillus Outer segment Discs being phagocytized Pigmented layer Discs containing visual pigments Pigment cell nucleus Melanin granules Basal lamina (border with choroid) (a)

(contralateral) fiber Lateral geniculate body of thalamus Visual fields of the eyes and visual pathway to the brain, inferior view Fixation point Right eye Left eye Optic nerve Supra- chiasmatic nucleus Pretectal nucleus Optic chiasma Optic tract Lateral geniculate body Superior colliculus (sectioned) Uncrossed (ipsilateral) fiber Crossed (contralateral) fiber Lateral geniculate body of thalamus Optic radiation Superior colliculus Occipital lobe (visual cortex) Corpus callosum (a) (b)

2. Olfaction Sensory structure: Activity 1 Olfactory epithelium. Chemoreceptor. Olfactory receptor cell: bipolar neuron (I) Support cells: pseudo stratified ciliated epithelium. Basal cells. Activity 1

Olfactory Frontal lobe epithelium of cerebrum Olfactory tract Olfactory receptors Olfactory epithelium Frontal lobe of cerebrum Olfactory tract Mitral cell Olfactory tract Olfactory bulb Glomeruli Nasal conchae Cribriform plate of ethmoid bone Filaments of olfactory nerve Lamina propria connective tissue Route of inhaled air Olfactory gland Axon Basal cell Olfactory receptor cell Olfactory epithelium Supporting cell Dendrite Mucus Olfactory cilia Route of inhaled air containing odor molecules

Green:Bowman’s gland cell Red: support cell Blue:bipolar neuron Green:basal cell Green:Bowman’s gland cell

3. Taste Sensory structure Activity 2 Taste bud. Chemoreceptor. Mechanoreceptor. Thermo receptor. Basic tastes: sweet, sour, salt, bitter. Types (location in figure) Fungiform papillae (mushrooms) Circunvallate papilla (globes) Filiform papilla Cell types Gustatory (taste) cells: bipolar neurons. Support cells Activity 2

Fg: fungiform papillae Fl: filliform papillae Weather’s Fucntional Histology

Location and structure of taste buds on the tongue Taste fibers of cranial nerve Gustatory hair Epiglottis Taste pore Palatine tonsil Lingual tonsil Basal cell Foliate papillae Circumvallate papilla Connective tissue Gustatory receptor cells Stratified squamous epithelium of tongue (c) Gustatory (taste) cells Taste pore Connective tissue Basal cells (b) Taste bud Fungiform papillae (a) (d)

Gustatory cortex (in insula) Thalamic nucleus (ventral posterior The gustatory pathway Gustatory cortex (in insula) Thalamic nucleus (ventral posterior medial nucleus) Pons Solitary nucleus in medulla oblongata Facial nerve (VII) Vagus (nerve X) Glosso- pharyngeal nerve (IX)

4. Hearing and balance Organ: Ear (sensory receptor for hearing and equilibrium). Outer ear. Hearing Auricle External acoustic meatus Tympanic membrane Ceruminous glands Middle ear. Hearing Tympanic cavity Osicles Malleus (hammer) Incus (anvil) Staples (stirrup). Connects with the oval window. Pharingotimpanic tube. Pressure equalization of middle ear and environment. Inner ear Bony and membranous labyrinth Cochlea: hearing Vestible: equilibrium 3 perpendicular semicircular canals: equilibrium

Internal (inner) ear (labryinth) Structure of the ear Internal (inner) ear (labryinth) External (outer) ear Middle ear Auricle (pinna) Helix External acoustic meatus Lobule Pharyngotympanic (auditory) tube Tympanic membrane (a)

Middle ear Middle ear. Hearing Tympanic cavity Osicles Malleus (hammer) Incus (anvil) Staples (stirrup). Connects with the oval window. Pharingotimpanic tube. Pressure equalization of middle ear and environment.

Structure of the middle ear Entrance to mastoid antrum in the epitympanic recess Auditory ossicles Malleus (hammer) Semicircular canals Incus (anvil) Vestibule Stapes (stirrup) Vestibular nerve External acoustic meatus Cochlear nerve Cochlea Tympanic membrane Oval window (deep to stapes) Pharyngotympanic (auditory) tube Internal jugular vein Round window (b)

The three auditory ossicles in the right middle ear Malleus Incus Epitympanic recess Superior Anterior Pharyngotym- panic tube Tensor tympani muscle Tympanic membrane (medial view) Stapes Stapedius muscle

Inner ear Inner ear Bony labyrinth Membranous labyrinth Contains perilymph; similar composition to CSF since it is connected to the arachnoid space. Membranous labyrinth Suspended in perilymph, contains endolymph. Divisions: Cochlea: organ of Corti, hearing VIII. Vestible: utricle and sacule. Macula; vertcial acceleration (equilibrium). 3 perpendicular semicircular canals Semicircular duct. Ampula; angular acceleration (equilibrium).

Membranous labyrinth of the internal ear Temporal bone Semicircular ducts in semicircular canals: Facial nerve Vestibular nerve • Anterior Superior vestibular ganglion • Posterior Inferior vestibular ganglion • Lateral Cochlear nerve Cristae ampullares in the ampullae Maculae Spiral organ (of Corti) Utricle in vestibule Saccule in vestibule Cochlear duct in cochlea Stapes in oval window Round window

Modiolus Cochlear nerve, division of the vestibulocochlear Anatomy of the cochlea Modiolus Cochlear nerve, division of the vestibulocochlear nerve (VIII) Oval window Spiral ganglion Osseous spiral lamina Vestibular membrane (a) Round window Cochlear duct (scala media) Helicotrema

Tectorial membrane Vestibular membrane Cochlear duct (scala media) Anatomy of the cochlea Tectorial membrane Vestibular membrane Cochlear duct (scala media) Scala vestibuli Spiral ganglion Stria vascularis Spiral organ (of Corti) Osseous spiral lamina Scala tympani Basilar membrane (b)

Tectorial membrane Inner hair cell Afferent nerve fibers Anatomy of the cochlea Tectorial membrane Inner hair cell Afferent nerve fibers Hairs (stereocilia) Outer hair cells Supporting cells Fibers of cochlear nerve Basilar membrane (c)

Hearing physiology Sound waves travel from the outer ear (timpanic membrane) middle ear (Malleus,Incus, staples, oval window) inner ear (scala tympani)/scala vestibuli stimulates the stereocillia of the organ of corti VIII The round window serves as a pressure relief valve.

Sound: source and propagation Area of compressed molecules Area of rarefaction Wavelength Crest Air pressure Trough (a) (b) Time Amplitude (c)

Route of sound waves through the ear External ear Middle ear Internal ear Air External acoustic meatus Malleus, incus, stapes (ossicles) Oval window Fluids in cochlear canals Tympanic membrane Pinna Upper and middle Lower Pressure Time Spiral organ (of Corti) stimulated One vibration Amplitude Amplification in middle ear

Hz 20,000 (High notes) Hz 1500 Hz 500 Hz 20 (Low notes) Resonance of the basilar membrane and activation of the cochlear hair cells Stapes Scala vestibuli Cochlear nerve Oval window Perilymph Round window Scala tympani Basilar membrane Cochlear duct (a) Base Apex Basilar membrane 500 Hz Relative lengths of basilar fibers within different regions membrane 4000 Hz Hz 20,000 (High notes) Hz 1500 Hz 500 Hz 20 (Low notes) 24,000 Hz (b) (c)

cortex in temporal lobe Simplified diagram of the auditory pathway to the auditory cortex of the brain Medial geniculate body of thalamus Primary auditory cortex in temporal lobe Inferior colliculus Lateral lemniscus Superior olivary nucleus (pons- medulla junction) Midbrain Cochlear nuclei Vibrations Medulla Vestibulocochlear nerve Vibrations Spiral ganglion of cochlear nerve Bipolar cell Spiral organ (of Corti)

Equilibrium physiology Located in the vestibular apparatus Vestible Utricle and saccule (sacs) within vesitble. Receptor: Macculae (static equilibrium) Hair cells (stereocillia) are embedded in the otholitic membrane which contain CaCO3 (otoliths). Respond to vertical acceleration. Membranous semicircular ducts Ampulla (located at the base of each perpendicular duct). Mechism of dynamic equilibrium (angular acceleration). Receptor: Crista ampullaris. Stereocilia covered by a gelatinous cupula. Endolymph stimulates the recptor.

Macula of saccule Macula of utricle Kinocilium Otolithic Stereocilia Structure of a macula Macula of saccule Macula of utricle Kinocilium Stereocilia Otoliths Otolithic membrane Hair bundle Hair cells Supporting cells Vestibular nerve fibers

Otolithic membrane Kinocilium Ster eocilia Depolarization The effect of gravitational pull on a macula receptor cell in the utricle Otolithic membrane Kinocilium Ster eocilia Depolarization Hyperpolarization Receptor potential (Hairs bent towar kinocilium) d (Hairs bent away from kinocilium) Nerve impulses generated in vestibular fiber Increased impulse frequency Decreased impulse frequency Excitation Inhibition

Macula within the utriculus (otolith chamber) (Bouins, H&E, Bar = 36 Macula within the utriculus (otolith chamber) (Bouins, H&E, Bar = 36.4 µm). 1. ciliated sensory cells; 2. sustenticular cells; 3. connective tissue; 4. cupula (gelatinous matrix); 5. globular sensory epithelium; 6. collagenous connective tissue; 7. otolith chamber; 8. cranium.

Location and sturcture of a crista ampullaris Flow of endolymph (a) Crista ampullaris Fibers of vestibular nerve Cupula (b) Turning motion Ampulla of left ear Ampulla of right ear Cupula Cupula at rest Position of cupula during turn Position of cupula during turn Fluid motion in ducts Increased firing Horizontal ducts Decreased firing (c) (d) Afferent fibers of vestibular nerve

Pathways of the balance and orientation system Vestibular receptors Visual receptors Somatic receptors Input Vestibular nuclear complex Reticular nuclei Cerebellum Central nervous system processing Oculomotor control (cranial nerve nuclei III, IV, VI) (eye movements) Spinal motor control (cranial nerve nuclei XI and vestibulospinal tracts) (neck movements) Output