1. Introduction to Medical Careers
SENSORY SYSTEM

2. 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.

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

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

5. 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

6. 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

7. External
Skeletal cavity
Eye lid & lashes
Mucous membrane

8. 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

10. 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

11. 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

12. Figure 20-2 Eye Functions Like A Camera

13. Ear Hearing Used for hearing Maintains equilibrium Structure external
middle
inner

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

15. 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.

16. 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

17. 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.

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

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

21. 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)

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

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

39. 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

40. 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

41. 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

42. 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

43. 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

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

45. 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

46. 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