Special Senses Lecture 1 PDF

Introduction to the Special Senses  Five Special Senses  Olfaction  Equilibrium THE SPECI...

Introduction to the Special Senses  Five Special Senses  Olfaction  Equilibrium THE SPECIAL SENSES  Gustation  Hearing  Vision Dr. Gregory Karapetian Lecture 1 1 2 Olfaction: Smell Olfaction: Smell  Olfactory Organs  Layers of olfactory organs  Provide sense of smell  Olfactory epithelium: ◼ Olfactory receptors  Located in nasal cavity on ◼ Supporting cells either side of nasal septum ◼ Basal (stem) cells  Made up of two layers:  Lamina propria: ◼ Olfactory epithelium ◼ Areolar tissue ◼ Lamina propria ◼ Blood vessels Olfactory Organs – located within ◼ Nerves ◼ Olfactory glands 3 4 The Olfactory Organs Olfaction: Smell  Olfactory Glands  Secretions coat surfaces of olfactory organs  Olfactory Receptors  Specialized neurons involved in olfactory reception – detecting dissolved chemicals interacting with odorant-binding proteins 5 6 1  Olfaction: Smell Olfaction: Smell  Olfactory pathways follow the axons leaving  Olfactory Pathways the olfactory epithelium  Arriving information reaches information centers  Collect into 20+ bundles without always first synapsing in thalamus  Penetrate cribriform plate of ethmoid  Reach olfactory bulbs of cerebrum – where the first synapse occurs Cribriform Plate  Axons leaving olfactory bulb travel along olfactory tract to reach olfactory cortex, hypothalamus, and portions of limbic system 7 8 Olfaction: Smell Gustation: Taste  Olfactory Discrimination  Gustation provides information about the foods  We can distinguish thousands of chemical stimuli and liquids we consume  CNS interprets smells by the pattern of receptor activity  Taste receptors (gustatory receptors) are  There is a considerable turnover of the olfactory distributed on tongue and portions of pharynx receptor population and larynx  Number of olfactory receptors declines with age  Clustered into taste buds 9 10 Gustation: Taste Gustatory Receptors  Taste buds contain  Basal (stem) cells  Gustatory cells ◼ Extend taste hairs  Taste buds are integrated with lingual through taste pore papillae (projections) ◼ Survive about 10 days on the surface of the Taste buds tongue before replacement  Filiform papillae  Fungiform papillae  Circumvallate papillae 11 12 2  Gustatory Discrimination Gustation: Taste  Dissolved chemicals contact taste hairs  Gustatory Discrimination  Bind to receptor proteins of gustatory cell  Activate chemically gated ion channels  Taste Sensitivity  Stimulation produces depolarization of cell  Exhibits significant individual differences  Release of neurotransmitters  Some conditions are inherited  Neurotransmitters generate action potentials ◼ Ex: phenylthiocarbamide (PTC): ◼ 70% of people taste it, but 30% do not AP  Number of taste buds ◼ Begins declining rapidly by age 50 13 14 Vision: The Eye Structures of the Eye (1 of 3)  Accessory Structures of the Eye  Palpebrae (Eyelids)  Provide protection, lubrication, and support  Continuation of skin  Include:  Blinking keeps surface 1. Palpebrae (eyelids) of eye lubricated, free of 2. Superficial epithelium of eye dust and debris 3. Lacrimal apparatus  Palpebral fissure ◼ Gap that separates free margins of upper and lower The superficial eye eyelids 15 16 Structures of the Eye (2 of 3) Structures of the Eye (2 of 3)  Superficial Epithelium of Eye  Superficial Epithelium of Eye  Lacrimal caruncle is a mass of soft tissue that contains  Conjunctiva glands producing thick secretions ◼ Epithelium covering outer surface ◼ Generates “sand-like” deposits after sleeping at night of eye – ocular conjunctiva ◼ Epithelium covering inner surfaces of eyelids – palpebral conjunctiva Viral conjunctivitis 17 18 3  Structures of the Eye (3 of 3) Sectional Anatomy of the Eye  Lacrimal Apparatus  Produces, distributes, and drains tears  Lacrimal gland is the “tear gland” ◼ Secretions contain lysozyme – an antibacterial enzyme 19 20 The Eye The Eye: Fibrous Tunic (1 of 3)  Three Layers of the Eye  Sclera – white of the eye 1. Outer fibrous tunic Fibrous  Cornea – initial structure to “bend” entering light 2. Middle vascular tunic Neural  The limbus is the border between the cornea and sclera 3. Inner neural tunic  Eyeball Sclera  Hollow Vascular  Divided into two cavities: Cornea ◼ Large posterior segment ◼ Smaller anterior segment 21 22 The Eye: Vascular Tunic (2 of 3) The Eye: Vascular Tunic (2 of 3)  The Choroid (also: the Uvea)  The location of the iris and ciliary muscle  The iris contains both  Vascular layer between fibrous pupillary dilator and and neural tunics constrictor muscles  Blood vessels here deliver ◼ Change the diameter of oxygen and nutrients to retina pupil, thereby regulating  Secretes and reabsorbs amount of light entering eye aqueous humor that circulates  Ciliary Muscle within chambers of eye ◼ Controls shape of lens, which is essential to focusing 23 24 4  The Pupillary Dilator and Constrictor Muscles The Eye: Neural Tunic (3 of 3)  The Retina  Outer layer called: Pigmented part  Inner Neural part ◼ Contains visual receptors and associated neurons ◼ Rods and cones are types of photoreceptors: ◼ Rods ◼ Do not discriminate light colors ◼ Highly sensitive to light ◼ Cones ◼ Provide color vision ◼ Densely clustered in fovea, at center of macula lutea 25 26 The Retina in Diagrammatic Sagittal Section The Eye: Neural Tunic (3 of 3)  Fovea is the region just lateral to the optic disc  Optic Disc is the origin of optic nerve – blind spot Photograph of the retina as seen through the pupil 27 28 Glaucoma Age-Related Macular Degeneration  Over time the optic nerve becomes damaged,  Deterioration of the macula (location of fovea) usually due to high intraocular pressure Macula Optic disc Fovea “Dry” ARMD accounts for ~90% Poor flow of “Wet” Macular “Dry” Macular aqueous humor Degeneration Degeneration Results in loss of central vision 29 30 5  Demonstration of the Presence of a Blind Spot The Eye  Ciliary body and lens divide eye  Small anterior segment ◼ Anterior chamber: ◼ Extends from cornea to iris ◼ Posterior chamber: ◼ Extends from iris to lens  Large posterior segment ◼ Extends from lens to the posterior of the eye ◼ Vitreous humor – gelatinous mass stabilizes shape, supports retina 31 32 The Eye The Circulation of Aqueous Humor  Smaller anterior segment  Aqueous humor ◼ Fluid circulates within anterior eye ◼ Diffuses through walls of anterior chamber into Canal of Schlemm ◼ Re-enters circulation  Intraocular pressure ◼ Fluid pressure in aqueous humor ◼ Helps retain eye shape 33 34 The Eye Factors Affecting Focal Distance  The lens is the main structure involved in:  Light refraction ◼ Bending of light by cornea and lens Intraocular Lens (IOL) used in cataract surgery  Focal point ◼ Specific point of intersection on retina  Focal distance  Accommodation ◼ Distance between center of lens and focal point  Shape of lens changes to focus image on retina 35 36 6  Accommodation Visual Abnormalities 37 38 Visual Abnormalities The Eye  Astigmatism  Curvature of cornea is oblong, so light passing through is not refracted properly  Visual image is distorted  Visual acuity  Clarity of vision  “Normal” rating is 20/20 39 40 Image Formation Visual Physiology: Photoreceptors  Rods  Respond to almost any photon (they do not discriminate light colors), regardless of energy content  Cones  Color vision is the integration of information from red, green, and blue cones  Color blindness – the inability to detect certain colors 41 42 7  Standard Test for Color Vision Visual Physiology  Central Processing of Visual Information  Axons from ganglion cells converge on optic disc ◼ Ganglion cells: M cells monitor rods, P cells monitor cones  Axons penetrate wall of eye and proceed as the two optic nerves (one for each eye) to reach diencephalon Cranial Nerve II the Optic Nerve at the optic chiasm 43 44 Visual Physiology Visual Physiology  Visual data from a combined field  The Field of Vision of vision arrives at the visual  Experiencing depth perception occurs by comparing cortex of the occipital lobes relative positions of objects between left-eye and  Lateral (retinal) information stays right-eye images within its respective hemisphere, while medial (retinal) info crosses  The Brain Stem and Visual Processing to opposite hemisphere  Circadian rhythms  Optic radiation ◼ Related to the day-night cycle  Bundle of projection fibers linking Cranial Nerve II the Optic Nerve ◼ Affects other metabolic processes within the body lateral geniculate with visual cortex 45 46  The visual pathway must also consider the field of vision 47 8