Introduction to Medical Careers SENSORY SYSTEM

Learning Objectives Define at least 10 terms relating to the sensory system. Describe the function of the sensory system. Identify at least 10 sensory system structures and the function of each. Describe at least five disorders of the sensory system.

Key Terms Accommodation Auditory Cutaneous Equilibrium Gustatory Intraocular Olfactory Receptor Refraction Stimulus Vision

What are the senses? Hearing Smell Nose Taste Ears Sight Touch Eyes Tongue Skin

Structure and Function Sensory system consists of receptors in specialized cells and organs that perceive changes in the internal and external environment The stimuli cause nerve impulses that are sent to the brain for interpretation Environmental stimuli are perceived with the senses of vision, hearing, touch, taste, position, and balance

Considered the most important sensory organ Eye Considered the most important sensory organ 60-90% of all information to the brain is via the eyes 20% of the structure is exposed Structure - 3 parts External Eye Ball Internal

External Skeletal cavity Eye lid & lashes Mucous membrane

Eye ball (i) Sclera- white part, supports and gives structure (e) Cornea- focuses images (outer) (b) Iris- colored part, dilates and contracts to let light in (d) Pupil- black dot, allows light in (f) Lens- focuses images (inner) (k) Optic nerve- transmits info to the brain Optic N. Iris Pupil Cornea Lens

Internal Rods 100 million, sensitive to dim light Cones 7 million, see bright light and color (red, green, blue) (m) Retina back part of the eye that contains the rods/cones Retina

Vision When we see something, light refracts from object -> cornea, where the rays are bent (and turned upside down), to the lens where the rays are focused onto the retina. The retina then turns the image into nerve impulses and sends to the brain via the optic nerve

Figure 20-2 Eye Functions Like A Camera

Ear Hearing Used for hearing Maintains equilibrium Structure external middle inner

How Hearing Works Outer Ear (Pinna) Collects sound, channels to the middle ear. The sound at this point is mechanical sound waves

How Hearing Works Middle Ear Contains the Tympanic Membrane (ear drum) Moves according to the type of sound waves that vibrate it, transmits sounds to the inner ear. Can also protect the inner ear from sounds which may damage it. Pressure is equalized between the ear and the mouth with the Eustachian Tube.

How Hearing Works At this point, the sound waves are vibrating the ear drum, and these waves have to be passed through the ossicles Malleus Incus Stapes

How Hearing Works Inner Ear Cochlea Organ of Corti Contains fluid which transmits sound vibrations to the hairs in the organ of Corti. Organ of Corti Hairs collect sound and send it to the Cochlear nerves, which carry the sound vibrations to the brain.

Equilibrium Semicircular Canals Contain fluid that moves around when we move, telling our brain where we are positioned.

Tongue Taste taste is perceived by specialized cells called taste buds (papillae) Over 10,000 of these, each with 50-150 receptor cells

Nose Smell smell originates in receptors in the nose and travels to the brain via nerves sense of smell is 10,000x more sensitive than taste 5,000 different smells can be perceived 30 primary “pure” odors (peppermint, floral, etc)

Skin Touch 5 specialized cells in the skin sensitive to: touch pressure temp pain Also sensitive to knowing where you are in space.

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Assessment Techniques Sight Ophthalmoscope examines inner structure of the eye Visual acuity with Snellen Test

Assessment Techniques (Continued) Hearing Otoscope is used to view the structures of ear Impedance testing measures flexibility of the tympanic membrane

Disorders of the Sensory System Achromatism Called color blindness, is a common inherited defect Amblyopia Also called “lazy eye,” is poor vision in one eye often resulting from better vision in the other eye during infancy or early childhood

Disorders of the Sensory System (Continued) Astigmatism A congenital defect causing imperfect curvature of the cornea resulting in blurred vision Cataract Clouding of the lens that causes blurred or partial vision Conjunctivitis Also called pink eye, is a bacterial or viral inflammation of the eyelid

Disorders of the Sensory System (Continued) Diplopia Or double vision, results from muscle imbalance or paralysis of an extraocular muscle Epistaxis Nosebleed resulting from disease, trauma, or other conditions such as hypertension, leukemia, or rheumatic fever

Disorders of the Sensory System (Continued) Glaucoma An increase in the pressure inside the eye, caused by trauma or hereditary factors Hyperopia Farsightedness resulting from a congenital deformity in the eye Macular degeneration A slow or sudden painless loss of central vision

Disorders of the Sensory System (Continued) Myopia Nearsightedness resulting from a congenital deformity in the eye Night blindness Poor vision in dim light that results from a deficiency in the rods of the retina

Disorders of the Sensory System (Continued) Otitis media A middle ear bacterial or viral infection common in young children

Disorders of the Sensory System (Continued) Rhinitis Inflammation of the lining of the nose caused by allergic reaction, viral infection, sinusitis, or chemical irritants Ruptured eardrum Results from infection, an explosion, a blow to the head, or a sharp object inserted into the ear

Disorders of the Sensory System (Continued) Sinusitis A chronic or acute inflammation of the cranium Stye Bacterial infection of the sebaceous glands of the eyelid

http://brainden.com/color-illusions.htm#

http://brainden.com/color-illusions.htm# https://www.washingtonpost.com/news/wonk/wp/2015/02/27/12-fascinating-optical-illusions-show-how-color-can-trick-the-eye/?utm_term=.99c39f9a3dc7