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

• Special:• 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

conesMacula Lutea

Mostly Cones

Fovea CentralisONLY Cones

Detailed color vision

Optic

DiscLateral to ML. Radiates Blood V.

cones

Less cones

Rods only

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• Refracted again• 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 receptorsSour Bitter POSTERIOR

TONGUE

Sour Bitter

Sour Bitter

salty salty

salty salty

salty Sweet -tip

ANTERIOR TONGUE

salty

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? Are there any questions? Can I answer anything? Can I answer anything for anybody? Is anything unclear? Is everything clear?