Special Senses Sensory Information Eye Ear

Sensory Information The Sensory-Somatic System uses sensory neurons to provide the CNS with information about the external environment Skin contains numerous different types of sensory receptorssensory receptors Proprioceptors in muscles, tendons, joints and ears respond to limb and body movement Proprioceptors Taste Receptors on the tongue allow us to taste Taste Receptors Olfactory Receptors in nasal cavity allow you to smell Olfactory Receptors Photoreceptors in the eye respond to light Photoreceptors Mechanoreceptors in the ear respond to sound Mechanoreceptors

Sensory Information The combination of multiple sensory receptors allows the brain to determine what a specific stimuli is and how to respond Ie. Taste and smell receptors are closely related Sensory adaptation occurs when a receptor becomes accustomed to a stimulus

Eye The Human Eye Layers and Chambers The Retina Accommodation Defects

Layers and Chambers The human eye contains 3 distinct layers and 3 chambers: Layers 1.External Layer 2.Intermediate Layer 3.Internal Layer Chambers 1.Anterior Chamber 2.Posterior Chamber 3.Vitreous Chamber

Layers and Chambers External Layer Sclera and cornea Intermediate Layer Choroid, iris, and ciliary muscles Internal Layer Retina Anterior Chamber Aqueous Humour Posterior Chamber Lens Vitreous Chamber Vitreous Humour

The Retina The retina contains 4 major layers:major layers 1.Pigmented Epithelium – Prevents light scattering 2.Light Sensitive Cells – Sensory Cells that respond to light 3.Bipolar Cells – Carry nerve impulse to optic nerve cells 4.Optic Nerve Cells – Carry Nerve impulse to CNS

The Retina The Light sensitive cells include: Rods Photoreceptors that respond to low-intensity light Cones Photoreceptors that respond to high-intensity light and color Each cone is responsible for a specific colorspecific color Rods and cones are not evenly distributed throughout the eye Fovea Centralis is in the middle of the retina and contains many densely packed cones Fovea Centralis The blind spot is the area where all ganglion axons converge to form the optic nerve There is no rods and cones causing a blind spot

The Retina Nerve Impulse Generation in a rodGeneration Due to a light-sensitive pigment called rhodopsin 1.Light strikes rhodopsin 2.Rhodopsin splits into a pigment portion and opsin (a protein) 3.This splitting changes the membrane chemistry of a rod and generates a nerve impulse

Accommodation The adjustments made to the lens and pupil for objects near and farlensfar Is due to ciliary muscles and suspensory ligaments Near object Ciliary Muscles Contract, Suspensory Ligaments slacken, Lens becomes more round Far Object Ciliary Muscles Relax, Suspensory Ligaments tighten, Lens becomes more flat Age causes the lens to be less elastic, resulting in a longer time to accommodate

Defects Glaucoma Build-up of aqueous humour as a result of blocked drainage ducts Increased pressure in the eye kills ganglion cells Cataract Lens becomes opaque and prevents light from passing throughopaque Tx – Remove flecks via sound vibrations Astigmatism Irregular shape of cornea or lens prevents light from properly focusing on the retina Tx – Proper Corrective LensesLenses

Defects Myopia (Nearsightedness) Myopia Eyeball is too long or cornea is too round and lens cannot flatten enough to focus image on retina Individual can easily see near objects but has difficulty focusing on far objects Tx – Concave Corrective LensConcave Hyperopia (Farsightedness) Hyperopia Eyeball is too short or cornea is too flat and lens cannot become round enough to focus image on retina Individual can easily see far objects but has difficulty seeing near objects Tx – Biconvex Corrective LensBiconvex Laser Eye Surgery Laser Eye Surgery

Ear The Human Ear Hearing Equilibrium Disorders and Treatments

The Human Ear The Ear is divided into 3 distinct sections: 1.The Outer EarThe Outer Ear Pinna and auditory canal 2.The Middle Ear Tympanic Membrane, ossicles, oval window and Eustachian tube 3.The Inner Ear Vestibule, semi-circular canals, cochlea The ear has 2 main functions: – Hearing – Equilibrium

Hearing It involves a number of steps: 1.The pinna gathers sound waves which are then passed down the auditory canal 2.The sound waves then cause the tympanic membrane to vibrate 3.The vibrations pass through the ossicles onto the smaller oval window (amplification) 4.The vibrations on the oval window triggers the movement of fluid within the cochleacochlea 5.Depending on the sound frequency, the fluid causes vibrations in different areas of the basilar membranefrequency 6.Vibrations in the basilar membrane causes tiny hair cells (stereocilia) in the Organ of Corti to brush against the tectorial membranestereocilia 7.The hair cell movement triggers a nerve impulse

Hearing Nerve impulses generated by the cochlea are processed in the temporal lobe of the brain

Equilibrium Balance had to do with 2 types of equilibrium: 1.Static Equilibrium – Providing information in regards to head position Horizontal or vertical plane 2.Dynamic Equilibrium – Providing information in regards to body movement 3 dimensions

Equilibrium Static Equilibrium The vestibule contains the saccule and utriclevestibuleutricle These provide information to the brain in regards to head position The saccule and utricle use hair-like cilia suspended in gel material and otoliths to generate nerve impulsesimpulses 1.When the head moves in position, the otoliths move by gravity 2.The gelatenous material moves along with the otoliths 3.The cilia then bend accordingly, initiating a nerve impulse

Equilibrium Dynamic Equilibrium The fluid filled semi-circular canals provide the brain with information in regards to movement and rotationsemi-circular canals 1.When an individual moves, fluid within the semi- circular canals moves 2.The fluid movement is detected by a cupula within the ampula of each canalcupulaampula 3.The movement of fluid bends the cupula which subsequently bends cilia 4.The bending of the cilia forward generates nerve impulses, whereas bending backward inhibits nerve impulses

Equilibrium Nerve impulses generated by the vestibule and semi-circular canals are processed in the cerebellum of the brain

Disorders and Treatments Ear Infections A bacterial/viral infection of the ear Results in fluid build-up in Eustachian tube, impacting hearing Tx – Time and anti-biotics/virals Tinnitus Ringing in the ears Caused usually by loud sounds Tx – Time, can be permanent Hearing Loss Multiple causes (genetic, trauma, etc.) Tx – Depends on type of deafness

Disorders and Treatments Conductive deafness Sound waves do not transfer to cochlea Treated by a cochlear implantcochlear implant Sensorineural Hearing Loss Damage to stereocilia results in difficulty hearing Treated by a hearing aidhearing aid