SPECIAL SENSES “Bad men live that they may eat and drink, whereas good men eat and drink that they may live.” Socrates CHAPTER 11

Sensory Receptors Distribution of sense receptors Special senses in sense organ Vision Hearing Equilibrium Taste Smell General senses throughout body Pressure, temperature, pain, touch Sense of position Sensory receptors Chemoreceptors-respond to chemicals Photoreceptors-respond to light Thermoreceptors-respond to heat Mechanoreceptors-respond to movement

EYE PROTECTION STRUCTURES Eye cavity bones Eyelids Eyelashes and eyebrow Conjunctiva Lacrimal glands

ANATOMY OF THE EYE MEDIAL & LATERAL CANTHUS SPHERE OF 1 INCH IN DIAMETER RESTS WITHIN A BONY ORBIT CUSHIONED BY FAT MEDIAL & LATERAL CANTHUS MEIBOMIAN GLAND – OIL TO LUBRICATE EYELASHES LYZOSYMES IN TEARS

The eye. Note the three tunics, the refractive parts of the eye (cornea, aqueous humor, lens, vitreous body), and other structures involved in vision.

Light Pathway Structures Cornea – transparent, clear; avascular; main area of refraction Aqueous humor – watery fluid supporting cornea; gives it a curved look Lens – biconvex; changes shape with eye focusing Vitreous humor – gel like fluid; maintains shape of eyeball; aids in refraction

Structure of the Eyeball Sclera (fibrous) – white of the eye; many nerve sensors for pain reception Choroid (vascular) – dark brown pigmented layer; becomes ciliary body anteriorly Retina (sensory) – light receptors Rods Cones

Function of the Retina Pigmented layer Sensitive to light Rods Function in dim light Shades of gray Blurred images Cones Function in bright light Color sensitive Sharp images Connecting neurons

Structure of the retina Structure of the retina. Rods and cones form a deep layer of the retina, near the choroid. Connecting neurons carry visual impulses toward the optic nerve.

COLORS 3 TYPES OF CONES ABSENSE OF CONES = TOTAL COLOR BLINDNESS RED BLUE GREEN ABSENSE OF CONES = TOTAL COLOR BLINDNESS MOST COMMON IS BLUE OR GREEN X-LINKED TRAIT= SEEN IN MEN MIX ALL THREE LIGHTS = WHITE RED & BLUE = PURPLE

PATHWAY OF LIGHT LIGHT COMES THROUGH PUPIL (cornea) TO LENS WHICH REFRACTS IT. LIGHT HITS PHOTORECEPTORS IN RETINA; RECEPTORS TRANSMIT ELECTRICAL SIGNALS VIA BIPOLAR CELLS TO GANGLION CELLS TO OPTIC NERVE TO VISION CENTER IN OCCIPITAL LOBE PHOTORECPTORS ARE RODS AND CONES

MUSCLES OF THE EYE 6 EXTERNAL/EXTRINSIC MUSCLES Used for convergence RECTUS MUSCLES SUPERIOR MEDIAL LATERAL INFERIOR OBLIQUE MUSCLES

Extrinsic muscles of the eye. The medial rectus is not shown. • What characteristics are used in naming the extrinsic eye muscles?

Intrinsic Muscles Used for accomodation Iris – 2 muscles around pupil Circular muscle contracts = constriction Radial muscle contracts = dilation Ciliary Muscle – holds the lens suspends by suspensory ligaments

The ciliary muscle and lens (posterior view) The ciliary muscle and lens (posterior view). Contraction of the ciliary muscle relaxes tension on the suspensory ligaments, allowing the lens to become more round for near vision.  • What structures hold the lens in place?

TERMS OPTIC DISC – BLIND SPOT FOVEA CENTRALIS – ONLY CONES LENS – BICONVEX CRYSTAL-LIKE AQUEOUS HUMOR VITREOUS HUMOR SCLERAL VENOUS SINUS (CANAL OF SCHLEMM) BLIND SPOT – WHERE THE OPTIC NERVE ENTERS THE BRAIN THERE ARE NO PHOTORECEPTORS FOVEA CENTRALIS – AREA OF GREATEST VISUAL ACUITY; LATERAL TO EACH BLIND SPOT. SCHLEMM – CORNER OF CORNEA AND SCLERA

IMBALANCES CATARACTS – LENS BECOMES HARDER AND OPAQUE GLAUCOMA – INCREASED PRESSURE IN FRONT OF LENS CAUSES PRESSURE TO INCREASE AGAINST RETINA AND NERVE LEADING TO BLINDNESS GLAUCOMA – GIVE MIOTIC TO INCREASE DRAINAGE FROM EYE

VISUAL FIELDS & PATHWAYS OPTIC NERVE ENTERS BRAIN FROM EACH EYE MEET AT OPTIC CHIASMA MEDIAL FIBERS CROSS TO OPPOSITE PATHWAYS WHICH BECOME THE OPTIC TRACT SYNAPSE AT HYPOTHALMUS TO FORM OPTIC RADIATION TO VISION CENTER

Nerve Supply to the Eye Optic nerve (cranial nerve II) Ophthalmic branch of trigeminal nerve (cranial nerve V) Oculomotor nerve (cranial nerve III) Trochlear (cranial nerve IV) Abducens (cranial nerve VI)

Nerves of the eye.  • Which of the nerves shown moves the eye?

Errors of Refraction and Other Eye Disorders Hyperopia Myopia Astigmatism Strabismus Convergent Divergent Amblyopia Infections Conjunctivitis Inclusion conjunctivitis Ophthalmia neonatorum Injuries Cataract Glaucoma Disorders involving the retina Diabetic retinopathy Macular degeneration

The ear. Structures in the outer, middle, and inner divisions are shown.

HEARING AND BALANCE OUTER EAR PINNA/ AURICLE EXTERNAL AUDITORY MEATUS CERUMINOUS GLANDS TYMPANIC MEMBRANE (EARDRUM)

MIDDLE EAR TYMPANIC CAVITY FROM EARDRUM LATERALLY TO OVAL WINDOW AND ROUND WINDOW MEDIALLY PHARYNGOTYMPANIC TUBE ( ALSO KNOWN AS EUSTACHIAN TUBE) 3 BONES – OSSICLES MALLEUS INCUS STAPES EAR INFECTIONS PREVENT THE MOTION OF THE OSSICLES WHICH LEADS TO DECREASED HEARING.

IMBALANCES OTITIS MEDIA – MIDDLE EAR INFECTION RESULTING FROM BACTERIA IN SORE THROAT TRAVELING UP THE CANAL MYRINGOTOMY – PLACING TUBES IN TYMPANIC MEMBRANE TO EQUALIZE THE PRESSURES BETWEEN MIDDLE AND OUTER EAR

INNER EAR OSSEOUS LABYRINTH MEMBRANOUS LABYRINTH VESTIBULE COCHLEA SEMICIRCULAR CANALS PERILYMPH FILLS THE BONY LABYRINTHS MEMBRANOUS LABYRINTH ENDOLYMPH FLUID

The inner ear. The vestibule, semicircular canals, and cochlea are made of a bony shell (labyrinth) with an interior membranous labyrinth. Endolymph fills the membranous labyrinth and perilymph is around it in the bony labyrinth.

STATIC EQUILIBRIUM MACULAE ARE SENSORY HAIRS EMBEDDED IN A BONY MEMBRANE WITHIN THE VESTIBULE AS YOUR HEAD MOVES, THE OTOLITHS ROLL WITH GRAVITY, BENDING THE HAIRS HAIR CELLS SEND AN IMPULSE DOWN THE NERVE TO BRAIN RELATING YOUR POSITION IN THE SPACE AROUND YOU

Action of the receptors (maculae) for static equilibrium Action of the receptors (maculae) for static equilibrium. As the head moves, the thick fluid above the receptor cells, weighted with otoliths, pulls on the cilia of the cells, generating a nerve impulse. What happens to the cilia on the receptor cells when the fluid around them moves?

DYNAMIC EQUILIBRIUM RECEPTORS IN SEMICIRCULAR CANALS THAT RESPOND TO ROTATIONAL OR ANGLED MOVES 3 D PLANES IN SPACE RECEPTOR REGION IS CRISTAE AMPULLARIS (HAIR CELLS IN A GEL LIKE CUPOLA {CAP}) BALANCE OCCURS ALONG WITH SIGHT & PROPRIOCEPTORS OF MUSCLES CONSTANT RATE, STOPS SENDING MESSAGES UNTIL YOU STOP THEN TELLS YOU ABOUT IT.

Action of the receptors (cristae) for dynamic equilibrium Action of the receptors (cristae) for dynamic equilibrium. As the body spins or moves in different directions, the cilia bend as the head changes position, generating nerve impulses.

Cochlea and the organ of Corti. The arrows show the direction of sound waves in the cochlea.

HEARING COCHLEAR DUCT IS FILLED WITH AN ENDOLYMPH- CONTAINING MEMBRANOUS LABYRINTH WHERE THE ORGANS OF CORTI ARE FOUND ORGAN OF CORTI CONTAINS A BASILAR MEMBRANE WHERE THE HAIR CELLS (HEARING RECEPTORS) ARE POSITIONED

FOLLOW THE SOUND WAVE!!! SOUND WAVE ENTERS THE EAR CANAL THE WAVE VIBRATES THE TYMPANIC MEMBRANE (EAR DRUM) VIBRATION MOVES THE OSSICLES IN A LEVER FASHION, TRANSMITTING THE SOUND WAVE TO THE OVAL WINDOW AGITATION OF THE WINDOW SETS FLUID IN INNER EAR INTO MOTION CAUSES A PRESSURE WAVE ACROSS BASILAR MEMBRANE BENDING HAIRS

CONTINUED THE HAIR CELLS IN ORGAN OF CORTI MOVE WITH THE WAVE WHICH CAUSES STIMULATION/ IMPULSE UP TO THE COCHLEAR NERVE THEN TO AUDITORY CENTER IN TEMPORAL LOBE LENGTH OF HAIR CELLS DETERMINES FREQUENCY HEARD SHORT = HIGH & LONG = LOW

ADAPTIONS CONTINUED INPUT LEADS TO “TUNING OUT” ****** HEARING IS THE LAST SENSE TO LEAVE OUR AWARENESS WHEN WE FALL ASLEEP, RECEIVE ANESTHESIA OR DIE****** BE CAREFUL WHAT YOU SAY!!!!

DEFICITS DEAFNESS – HEARING LOSS OF ANY DEGREE CONDUCTION- CONDUCTON IS BLOCKED/ INTERUPTED SENSORINEURAL – DAMAGE TO RECEPTORS, NERVE OR AUDITORY CORTEX MENIERE’S DISEASE CONDUCTION CAN USE A HEARING AID THAT WORKS ON BONE CONDUCTION PRINCIPLES SENSORINEURAL – HEARING AIDS DON’T WORK WELL. COCHLEAR TRANSPLANTS ARE BEING DONE IF PROBLEM NOT IN THE AUDITORY CENTER MENIERE – DEGENERATIVE LOSS – VERTIGO SEEN AS WELL AS LOSS OF HEARING

TASTE 10,000+ TASTE BUDS (RECEPTORS) IN ORAL CAVITY- MOST ON TONGUE CHEMICALS DISSOLVE IN SALIVA BATHE THE PAPILLAE WHERE THE GUSTATORY CELLS/ HAIRS ARE FOUND TRANSMIT IMPULSE TO BRAIN

Sense of Taste Taste receptors (buds) on tongue Stimulated by substance in solution Basic tastes Sweet Salty Sour Bitter Other tastes Water Alkaline Metallic Umami Cranial nerves Facial (VII) Glossopharyngeal (IX)

Special senses that respond to chemicals. UMAMI Special senses that respond to chemicals. (A) Organs of taste (gustation) and smell (olfaction). (B) A taste map of the tongue.

5 TYPES OF TASTE SWEET – RESPONDS TO OH- GROUPS SOUR – RESPONDS TO H+ BITTER – ALKALOIDS SALTY – METALS UMAMI - GLUTAMATES EAT SUGAR AND SALT TO GIVE CARBS AND MINERALS SOURS GIVE VITAMIN C UMAMI – BODYS CRAVE FOR MEAT BITTER ARE USUALLY POISONOUS OR SPOILED – PROTECTIVE TO NOT LIKE THESE

Sense of Smell Smell receptors in nasal cavity Stimulated by substances in solution in nasal fluids Smells stimulate appetite and flow of digestive juices Olfactory nerve (cranial nerve I)

OLFACTORY OLFACTORY RECEPTORS IN ROOF OF NOSE CHEMICALS DISSOLVED IN THE FLUID/ MUCUS STIMULATE THE OLFACTORY HAIRS AND THEN OLFACTORY RECEPTOR CELLS (NEURONS) SEND IMPULSE UP OLFACTORY NERVE TO CORTEX IN BRAIN RECOGNITION OF SMELLS IS LINKED TO LIMBIC SYSTEM & EMOTIONS WHICH IS WHY THERE ARE CERTAIN SMELL THAT “REMIND US” OF WARM HAPPY TIMES, AWFUL TIMES ETC.

ADAPTIONS FREQUENT INPUT OF AROMA CAUSES “TUNING OUT” ANOSMIAS – LOSS OF SMELL OLFACTORY AURAS HAVING A COLD, A HEAD INJURY OR AGING CAN CAUSE A LOSS IN SMELL ABILITY = DANGEROUS BECAUSE CAN’T TELL IF FOOD IS BAD, SMELL SMOKE, BURNT TOAST, ETC OLFACTORY AURAS – SENSATION OF SMELLING SOMETHING BEFORE A SEIZURE OCCURS. Electrical activity before a seizure triggers a remembered smell.

FACTORS AFFECTING TASTE SMELL AND TASTE CLOSELY RELATED TEMPERATURE TEXTURE ODOR SPICINESS APPEARANCE

SENSORY IMBALANCES STRABISMUS PRESBYOPIA PRESBYCUSIS STRABISMUS – CROSSED EYES; 20/20 VISION AROUND 7 PRESBYOPIA – FAR SIGHTED NESS OF AGING PRESBYCUSIS –HEARING LOSS IN SIXTIES DUE TO OTOSCLEROSIS

Sense of Position Proprioceptors (position receptors) Are located in muscles, tendons, joints Relay impulses of body parts in relation to each other Send impulses to the cerebellum for coordination Help maintain equilibrium

Questions, anyone?