1. Introduction to Health Science Special Senses

2. Cranial Nerves

3. Description of the Special Senses Smell Smell – Occurs when specialized cells in the nose (chemoreceptors) detect chemicals – Results in nerve impulses being sent to the brain for interpretation

4. Nose In the upper part of the nasal cavity are specialized nerve cells called olfactory receptor cells In the upper part of the nasal cavity are specialized nerve cells called olfactory receptor cells These receptor cells contain hair called cilia to which the dissolved chemicals attach These receptor cells contain hair called cilia to which the dissolved chemicals attach Transmitted from the olfactory receptors cells  olfactory bulb  olfactory nerve  brain Transmitted from the olfactory receptors cells  olfactory bulb  olfactory nerve  brain Sense of smell is interpreted then sent back to nasal cavity Sense of smell is interpreted then sent back to nasal cavity Basic smells include Basic smells include Putrid (rotting food) Putrid (rotting food) Pungent (spicy) Pungent (spicy) Floral (flowers) Floral (flowers) Ethereal (medicine smell) Ethereal (medicine smell) Mint Mint

6. Taste Occurs when specialized cells on the tongue (chemoreceptors) detect chemicals Occurs when specialized cells on the tongue (chemoreceptors) detect chemicals – Results in nerve impulses being sent to the brain for interpretation

7. Mouth and Tongue The sense organs that detect dissolved chemicals for the sense of taste are the taste buds The sense organs that detect dissolved chemicals for the sense of taste are the taste buds – Located in the tongue and throughout the mouth When the taste buds are stimulated by chemicals, they generate nerve impulses which are sent to the brain for interpretation When the taste buds are stimulated by chemicals, they generate nerve impulses which are sent to the brain for interpretation There are five basic tastes, although they are not limited to specific parts of the tongue: There are five basic tastes, although they are not limited to specific parts of the tongue: – Sweet (sugars and carbohydrates) – Sour (acids) – Salt (salt) – Bitter (caffeine) – Umami (protein and amino acids)

11. Vision The sense organs that respond to light are the eyes The sense organs that respond to light are the eyes – The light waves travel through the eyes until they reach the back of the eye called the retina – Nerve impulses are generated by specialized cells that are sensitive to light (photoreceptors) – Nerve impulses travel to the brain – Interpreted as visual images – Provide much information about the external world – If there is no light, there is no sight!

13. Eye Eyelid Eyelid – Structures composed of skin, muscles, and lashes – Protect the eye from foreign objects by the blink reflex – Moves tears along the surface of the eyeball to keep the eyeball moist Conjunctiva Conjunctiva – Membrane lining the insides of the eyelids and eyeball – Reduces friction during blinking

16. Eye Sclera Sclera – The white part of the eye – Provides protection and shape to the eye Cornea Cornea – The clear window of the front part of the eye – Allows light waves to enter the eye – Helps to bend the light waves on to the back of the eye (retina)

17. Eye Iris Iris – The colored portion of the eye which contains two sets of muscles – Regulates the size of the pupil to control the amount of light entering the eye Pupil Pupil – An opening in the center of the iris – Passage for light Lens Lens – Transparent disc shaped structure located behind the iris and pupil – Focuses light waves on to the retina

18. Eye Retina Retina – Most inner layer of the eyeball – Located under the sclera – Contains the photoreceptors that when stimulated by light generate nerve impulses which are then sent to the brain for interpretation Optic Nerve Optic Nerve – Nerve that sends and receives impulses to and from the brain

20. Hearing Involves the movement of sound vibrations through the ear Involves the movement of sound vibrations through the ear – When they reach a specialized region in the inner ear nerve impulses are generated by cells that detect movement (mechanoreceptors) – Nerve impulses travel to the brain where they are interpreted as sound

22. Outer Ear Auricle Auricle – The visible portion of the ear on the side of the head – Composed of cartilage – Captures sound waves from environment – Directs them toward the auditory canal Auditory Canal Auditory Canal – Tube lined with hair and wax – Assists in the passage of sound waves to the middle ear – Provides protection for the ear as particles, debris and dust are trapped by the hair and wax

24. Middle Ear Tympanic Membrane Tympanic Membrane – Known as the eardrum, it is the first structure of the middle ear – It vibrates with the sound waves and passes the vibrations to the middle ear bones Auditory Ossicles Auditory Ossicles – Three tiny bones in the middle ear that continue the passage of sound vibrations – They also amplify the vibrations twenty times Eustachian Tube (auditory tube) Eustachian Tube (auditory tube) – Small tube extending from the middle ear into the throat – Helps to equalize pressure inside the ear

26. Inner Ear Cochlea Cochlea – Snail shaped structure – Membrane-lined fluid-filled canals that continue to pass along the sound vibrations – Reach a specialized structure of the inner ear called the Organ of Corti where nerve impulses are generated – The impulses are transmitted to the brain where they are interpreted Vestibulocochlear Nerve Vestibulocochlear Nerve

28. Touch Detection of various amounts of pressure by the skin Detection of various amounts of pressure by the skin Nerve impulses are generated by cells that are sensitive to movement (mechanoreceptors) and sent to the brain for interpretation Nerve impulses are generated by cells that are sensitive to movement (mechanoreceptors) and sent to the brain for interpretation

29. Skin The skin contains several different types of nerve receptors The skin contains several different types of nerve receptors – Sensitive to deep pressure like poking or light touch All regions of the skin are sensitive to touch All regions of the skin are sensitive to touch – The greatest number of touch receptors are found in the fingers, toes, and face Once the nerve impulses for touch are generated, they are sent to the brain for interpretation Once the nerve impulses for touch are generated, they are sent to the brain for interpretation

31. Learning Log Learning Log – What problems could we have with our senses? – What would cause those problems?

32. Disorders of the Special Senses Conjunctivitis Conjunctivitis – Conjunctivitis is the inflammation of the conjunctiva – Can be caused by viruses, bacteria, fungi, and allergies – The most common cause is viral – ”Pinkeye” is the common term for conjunctivitis

33. Middle Ear Infection (Otitis Media) Causes include anything that causes the Eustachian (auditory) tubes to become blocked, inflamed or irritated Causes include anything that causes the Eustachian (auditory) tubes to become blocked, inflamed or irritated – Examples include colds, sinus infections, allergies, tobacco smoke – Babies who spend a lot of time drinking in the supine position Most common symptom is earache Most common symptom is earache Treatment includes Treatment includes – Antibiotics for bacterial infections – Use of warm cloths and analgesics to relieve pain – Possible surgery if ear infections recur frequently

34. Deafness Complete or partial loss of hearing in one or both ears May be caused by a blockage of the sound waves through the middle ear – – Wax build up, foreign objects, tumors or other matter – – Generally improves once the blockage is removed May also result from damage to the nerves or to the Organ of Corti – – Usually irreversible and may progressively get worse Treatment may include removal of the blockage, hearing aids, or cochlear implants www.kidshealth.org

35. Myopia Nearsightedness Nearsightedness – When a person sees near objects clearly and distant objects are blurred Physical length of the eye is greater than the optical length Physical length of the eye is greater than the optical length Symptoms include blurred vision of distant objects, squinting, eyestrain, and sometimes headaches Symptoms include blurred vision of distant objects, squinting, eyestrain, and sometimes headaches Treated with concave lenses or LASIK surgery Treated with concave lenses or LASIK surgery

36. Hyperopia Farsightedness Farsightedness – A person sees far objects clearly and near objects are blurred Physical length of the eyeball is too small or the focusing power of the lens is too weak Physical length of the eyeball is too small or the focusing power of the lens is too weak Symptoms include blurred vision of close objects, eye strain, aching eyes, and headaches while reading Symptoms include blurred vision of close objects, eye strain, aching eyes, and headaches while reading Treated with convex lenses Treated with convex lenses Surgical options also available Surgical options also available

37. Presbyopia Normal loss of power of the eye which occurs as a consequence of aging Lens becomes less flexible and less able to bulge or accommodate for near vision Symptoms are similar to those of farsightedness and include: – – blurring of close objects – – eye strain – – holding objects further from the face to focus – – headaches or fatigue from focusing on close objects Treatments may include the use of reading glasses or bifocals