Unit 8:  The Senses

The Senses DB Explain why the smell of a doctor�s office or the smell of turkey cooking on Thanksgiving can easily generate an emotional response. Hint: there is a concept called sense memory that should be referenced here. OR The ear is important in not only hearing, but balance. Explain how the ear functions, and how it can be easily damaged by loud noises, and result in hearing loss. OR How do we perceive color? Why does the color wash out when we look at a bright light, or are out in the sun?

Responsibilites for the week Work on APT project. Writing paper!!  Lesson 1: Sense Organs Lesson 2: The Eye Lesson 3: The Ear The Senses: Quick Wrap-Up Unit 8 Practice Quiz Discussion Seminar The Senses Module Exam

LEARNING OUTCOMES HS120-U8-1    Classify sense organs as special or general.     HS120-U8-2    Describe the general sense organs and their functions.     HS120-U8-3    Identify the structures and functions of the eye.     HS120-U8-4    Identify the structures functions of the ear. HS120-U8-5    Discuss the physiology of hearing.

Classify sense organs as special or general Eye Taste buds Ear Nose General: Microscopic receptors Pacinian corpuscles Meissner’s corpuscles Muscle spindles

. What is the difference between special and general sense organs?

The differences Special = they have large and complex organs or localized groupings of specialized receptors like taste buds on tongue. These are the senses that you typically think of; except for perhaps touch!

A very special sense

The differences General = made of microscopic receptors widely distributed throughout the body. Pacinian corpuscles = pressure and high frequency Meissner’s corpuscles = fine touch and low frequency Muscle spindles = propriocetors (muscle length and location)

Sense organ functions Vision Hearing Smell Taste Balance

How is a stimulus converted into a sensation? Stimulus detected [sound] Stimulus converted to electrical signal or nerve impulse= [middle ear] Signal transmitted over nervous system “pathway” = [VIII cranial nerve] Sensation perceived in brain = [music]

music Sound is: A pressure disturbance (alternating areas of high and low pressure) originating from a vibrating object

Eye anatomy Sclera = white of the eye (cornea) Choroid = contains a dark pigment to prevent scattering of light rays Retina = innermost layer of eyeball (rods and comes) Iris = circular colored part of eye Conjunctiva = mucous membrane that lines eyelids and covers the sclera Lacrimal gland = tear duct Pupil = black center of iris; a hole Lens = ciliary muscles contract the lens for focusing

Posterior wall of Rods only right eye Pg 563 Less cones cones Disc Macula Lutea Mostly Cones Fovea Centralis ONLY Cones Detailed color vision Optic Disc Lateral to ML. Radiates Blood V.

The Retina: Photoreceptors Rods: Respond to dim light Are used for peripheral vision Ex. Best to see moonlit evening when you don’t look directly at object. Recognize best when they move. Peripheral. Cones: Respond to bright light Have high-acuity color vision Are found in the macula lutea Are concentrated in the fovea centralis

The Retina: Ganglion Cells and the Optic Disc

Focusing Light on the Retina; Pathway of light entering the eye: Light is Refracted cornea Refracted again aqueous humor Lens vitreous humor the neural layer of the retina to the photoreceptors

Major visual disorders Refraction disorders Myopia = nearsightedness Astigmatism = irregularity in cornea or lens Conjunctivitis = pink eye Strabismus = convergent Cataracts=? Macular Degeneration=? Glaucoma=?

Eye anatomy Sclera Choroid Retina Iris Conjunctiva Lacrimal gland Pupil Lens Ciliary Muscles

Ear anatomy External ear External auditory canal Tympanic membrane eardrum

Ear anatomy Middle ear Ear bones = ossicles Malleus Incus stapes Auditory or Eustachian tube

Ear anatomy Inner ear Bony labrinth Perilymph Vestibule Semicircular canals Cochlea Crista ampullaris Organ of Corti

PATH: Transmission of Sound to the Inner Ear

Sound and Mechanisms of Hearing Sound vibrations beat against the eardrum The eardrum pushes against the ossicles, which presses fluid in the inner ear against the oval and round windows This movement sets up shearing forces that pull on hair cells Moving hair cells stimulates the cochlear nerve that sends impulses to the brain

Deafness Conduction deafness – something hampers sound conduction to the fluids of the inner ear (e.g., impacted earwax, perforated eardrum, osteosclerosis of the ossicles) Sensorineural deafness – results from damage to the neural structures at any point from the cochlear hair cells to the auditory cortical cells

Hearing impairment Blockage of external auditory canal Otosclerosis = structural irregularities in stapes Tinnitus = ringing in ears (may be symptom of otosclerosis) Otitis = ear infection Meniere’s disease = chronic inner ear disease, resulting in vertigo

areas for taste receptors Sour Bitter POSTERIOR TONGUE salty Sweet -tip ANTERIOR TONGUE

Taste Sensations There are five basic taste sensations Sweet – sugars, saccharin, alcohol, and some amino acids Salt – metal ions Sour – hydrogen ions Bitter – alkaloids such as quinine and nicotine Umami – elicited by the amino acid glutamate

Influence of Other Sensations on Taste Taste is 80% smell Thermoreceptors, mechanoreceptors, nociceptors also influence tastes Temperature and texture enhance or detract from taste

Which one would be the worst to lose?

Have you any questions. Do you have any questions Have you any questions? Do you have any questions? Are there any questions? Can I answer anything? Can I answer anything for anybody? Is anything unclear? Is everything clear? The End…