Objective: Describe and observe how taste and

smell are related to one another Describe different sensory receptors

found in the body Journal: What are the different types

of taste receptors found on your tongue?

Ability to sense changes in the environment is necessary for maintaining homeostasis Initiates protective reflexes▪ Internal changes trigger responses such as

pain or high temperatures

All sense organs must be able to detect a stimulus in the environment

Depending on the stimulus, a different receptor will be activated

Signal is transmitted over a nervous system “pathway” to brain

Photoreceptors – stimulated by light, in eye

Chemoreceptors – stimulated by chemicals, in tongue and nose

Pain receptors – stimulated by physical damage

Thermoreceptors – stimulated by change in temperature

Mechanoreceptors – stimulated by change in position

Taste and smell:Receptors are chemoreceptors

Associated with food intake, influence flow of digestive juices, and affect appetite

Chemoreceptors in taste buds in mouth and throat

Taste bud consists of Taste pore▪ Opening through which fluids in mouth come

into contact with surface of receptor cells Taste receptor cells▪ Modified epithelial cells with surface folds

called microvilli that contain chemical receptors

Located on papillae (bumps on your tongue and throat)

Two Types: Fungiform papillae▪ Small, all over the top

and sides of the tongue

Circumvallate Papillae ▪ Large, on the back of

the tongue

Taste buds consist of: ~50 receptor cells

surrounded by supporting cells

Basal cells develop into supporting cells then receptor cells

▪ Gustatory hairs project through the taste pore

Four kinds of tastes caused by different chemical stimuli: Sweet, Sour, Bitter, and Salty

Chemoreceptors that allow for smell are called olfactory receptors

Located in the nasal cavity

Olfactory neurons Located in the olfactory epithelium and

sense changes in smell through the olfactory hairs

Connect to olfactory nerve filaments that carry the sensory information to the neurons of the olfactory tract in the olfactory bulb

Supporting Cells Metabolic and physical support cells for the

olfactory neurons

The physical stimuli are chemical substances carried in the air that are dissolved in the mucus in the nose.

Pathway: Olfactory Hairs Olfactory Neurons

Olfactory Nerve in the Brain Neurons connect directly into the brain

from the nasal epithelium through the cribriform plate

Holding your nose can help take away unpleasant taste of food.

Journal: Explain why ice cream tastes different than a lemon.

Two functions: Hearing and Equilibrium

Physical forces from sound and movements stimulate the mechanoreceptors

Three parts of the ear: External ear, Middle ear, Inner ear

Made up of: Auricle (aka Pinna) – appendage on side of head External auditory canal – curving tube, about 1 in

long▪ Ends at ear drum (aka Tympanic membrane)▪Separates external and middle ear

▪ Auditory canal lined with hair and contains ceruminous glands▪Produces cerumen (ear wax) to protect inner ear

▪ Sound waves travel thru canal, strike the tympanic membrane and cause it to vibrate

Tiny cavity hollowed out of temporal bone Also connects to the throat by

Pharyngotympanic tube Sore throat could spread to ear, causes middle

ear infection Contains three small bones called ossicles

Names describe shape:▪ Malleus (hammer), Incus (anvil), Stapes (stirrup)

Malleus attached to tympanic membrane and incus

Incus attached to stapes Stapes presses against a

membrane that covers the oval window (small opening in inner ear)

Sounds cause tympanic membrane to vibrate, which is then transmitted and amplified by ossicles Causes movement of fluid in

inner ear

Mechanoreceptors found in fluid-filled chambers known as the membranous labyrinth Endolymph – thick fluid

Bony labyrinth covers membrane labyrinth to provide protection Perilymph – watery fluid between bony and

membranous labyrinth

Bony labyrinth divided into three parts:Cochlea (hearing)– snail-like shape, contains

organ of Corti which is covered in hairs Surrounded by endolymph, sound waves causes

liquid to move, which moves hairs ▪ Nerve impulse stimulated when hairs are bent

Semicircular Canal (balance) – 3 half-circle canals Endolymph surrounds receptors (crista

ampullaris) which are covered in hair ▪ Nerve impulse stimulated by rotation of head

Vestibule (sense gravity) – btw cochlea and s. canal

In US – over 6 million people with a hearing deficit

CONDUCTIVE DEAFNESS Conditions in outer or middle ear blocks

vibrations External auditory canal blocked with wax, water Scarring of eardrum

NERVE DEAFNESS Problem in cochlea or auditory pathway to brain Receptors in organ of Corti can’t interpret

sounds Correction - chochlear implant

Nerve impulse doesn’t make it to brain

http://www.youtube.com/watch?v=Go9pONJBffk

Frequency Heard?

8 kHz10 kHz12 kHz14 kHz15 kHz

16 kHz 17 kHz18 kHz19 kHz20 kHz21 kHz22 kHz

Could you hear all the frequencies?What is your hearing threshold?How do dog whistles work?Does the frequency of sound you can

hear change as you age?

Objective: Label and describe the structures of the

eye Explain how the eye allows you to see

Journal: List and explain the difference between

the two types of deafness.

The eye is covered with three layers of tissue: sclera, choroid, retina

SCLERA (aka “whites of the eyes”) Made up of tough, fibrous tissue Front has a transparent portion – Cornea

(“window”)▪ Covers iris – colored portion of eyes

Conjuntiva – mucous membrane keeps eye moist

Lacrimal Gland – produces tears▪ Found in upper lateral portion

CHOROID Middle layer of eyeball Contains dark pigment to prevent scattering

of incoming rays of light Made up of 2 involuntary muscles: Iris and

ciliary▪ Pupil is actually a hole in the center of the

iris muscle▪ 2 kinds of muscles in iris: circular –

constricts pupil, lateral – dilates pupil▪ Ciliary muscle helps to focus on objects▪Relaxed for distance, contracted for close

RETINA Contains microscopic

photorecepotors:▪ Rods – nightime vision, black and

white▪ Cones – daytime vision, color▪3 types detect color – red, green, blue

Macula Lutea – yellowish area near center of retina Surrounds fovea centralis – a

depression that contains the most conesVisual acuity is obtained by focusing

the image on the fovea centralis

Fluid maintains intraocular pressure of eyeball Fluid refracts light rays to focus on retina

Aqueous Humor – fluid in front of lens Vitreous Humor – Jellylike material in the

posterior cavity Lens – directly behind pupil

Held in place by ligament Elastic to allow change of shape

Light is stimulus of vision - photoreceptors

Light enters the eye at the pupil, and is refracted by lens to focused on retina Inner layer of retina contains rods and cones

Nerve impulses created by rods and cones are collected and exit with the optic nerve

No rods cones are present where optic nerve exists Blind spot = optic disc

Image must be focused on retina for clear picture If eyes are elongated:

Image focuses in front of retina, distant objects blurry▪ Known as nearsightedness or Myopia▪ Corrected using a diverging lens

If eyes are shorter: Image focuses behind retina, close objects blurry▪ Known as farsightedness of Hyperopia▪ Corrected using a converging lens

Astigmatism – curvature of cornea or lens abnormal, fails to refract light properly Corrected using glasses or special contacts

CATARACTS Lens of eye no longer transparent, becomes

cloudy Need more light to see If completely opaque, person will be blind CORRECTION – surgery to replace lensGLAUCOMA Aqueous humor not drained properly,

intraocular pressure builds up Distorts soft tissue of the eye and can cause

blindness CORRECTION - surgery to drain fluid, drugs to

increase drainage

Unable to distinguish certain colorsCaused by a recessive gene on the

X chromosome Men (XY) more likely to have▪ 10 % of males are colorblind

Women (XX) not as common▪ Less than 1 % of females are cb

Occurs when cones are nonfunctional

Most common – red cones missing Can’t distinguish red from green