Senses

How do we get sensory information? Sensory Receptors- sensitive to specific environmental change

Types of Receptors Chemoreceptors- sensitive to chemical concentrations Pain Receptors- sensitive to tissue damage Thermoreceptors- sensitive to temperature Mechanoreceptors- changes in pressure or movement Photoreceptors- light energy

Special Senses Special senses are those whose sensory receptors are within large sensory organs of the head

OrganSense Olfactory Organs (nose etc.)Smell Taste Buds (mouth)Taste EarsHearing Organs of Equilibrium (Ear)Static and Dynamic Equilibrium EyesSight

Sense of Smell Olfactory receptors are chemoreceptors Olfactory bulbs: concentration of neurons

Sense of Taste 4 Taste Sensations 1) Sweet (ex. Sugar) 2) Sour (ex. Lemon) 3) Salty (ex. Table salt) 4) Bitter (ex. Caffeine) Taste Buds: found on tongue (papillae), roof of mouth, and pharynx Taste cells (gustatory cells) are receptors

Vision Notes

EYE Eye – Parts a) Eyelid b) Conjunctiva- membrane that lines inner surface c) Lacrimal gland- secretes tears d) Cornea- transparent, focuses light e) Sclera- white part f) Choroid coat- has blood vessels, has pigment to absorb extra light

Sense of Sight Eye – Parts a)Eyelid and eye lashes- protects eye, keeps moist

Eye- parts cont. b) Conjunctiva- membrane that lines inner surface of the eye lid and the white part of the eye (sclera)

Conjunctivitis (pink eye) - the infection and inflammation of the conjunctiva; caused by virus, bacteria, fungus or even allergies. Conjunctivitis is highly contagious, and the spread should be prevented by washing hands regularly and not touching the eyes.

Eye parts cont. c) Lacrimal gland- secretes tears, lubricates, cleans, moisturizes d) Cornea- transparent, focuses light

Anatomy of the Eyeball The eyeball is made up of 3 layers (tunics). outer layer - sclera middle layer – choroid innermost layer - retina.

Parts of the eye e) Sclera- white part, tough connective tissue f) Choroid - has blood vessels, has pigment to absorb extra light, forms the ciliary body and iris g) Retina- contains visual receptor cells (photoreceptors) 1) Rods- light/dark receptors 2) Cones- color receptors

Fun Fact: The cornea is the only part of the body that can be transplanted from a donor without the chance of the body rejecting it, there are no blood vessels in the cornea.

Colorblindness There are 3 types of cones: cones that detect blue light cones that detect green light cones that detect both green and red light If one of these cones is missing, it is difficult to distinguish between colors. Colorblindness does not mean the person sees in black and white. A more appropriate term is color deficiency.

Eye Parts- cont. h) Ciliary body and suspensory ligaments- holds lens in place i) Lens- focus image on retina J ) Iris- colored part of eye K) Pupil- circular opening in iris, allows light to pass through

Eye parts- cont L) Fovea centralis- region of retina with sharpest vision m)Optic disk- nerve fibers leave eye (blind spot) n)Optic nerve- delivers impulses to brain o)Eye fluids- hold shape of eye 1)Aqueous humor 2)Vitrious humor

With normal vision, the light enters the eye, and the lens focuses the light on the retina. This is called emmetropia.

Optic Disk The Optic Disk is the part of the retina where the nerve fibers leave the eye and join the optic nerve. This gives you the “blind spot” in the vision tests.

Fovea Centralis In the central region of the retina is a yellowish spot called the macula lutea. A depression in its center, called the fovea centralis, is the region of the retina that produces the sharpest images.

Fluids of the Eye The aqueous humor is a watery fluid that fills the space between the cornea and the lens, gives them nourishment, and maintains the shape of the eye. The vitreous humor is a transparent, jelly-like substance which supports the internal parts of the eye and helps maintain its shape.

Changes in Vision

Myopia Myopia (near-sightedness) - the eye is too long and the image lands in front of the retina, making it blurry. People with myopia see near objects well, but have difficulty seeing distant objects.

Hyperopia Hyperopia (far-sightedness) - the eye is too short and the image focuses behind the retina, making the image blurry. People with hyperopia have difficulty seeing close objects, but can see distant objects clearly.

Astigmatism Astigmatism is caused by an irregular curvature of the cornea (it is curved more in one direction than another). Vision is distorted because the lens can’t focus light to a point.

Visual Acuity (Optometry) The Snellen chart is used to measure visual acuity. “Normal” vision is 20/20. This means that you can see at 20 feet what a person with normal vision sees at 20 feet. 20/40 vision means that you can see at 20 feet what a person with “normal” vision can see at 40 feet.

Levels of Vision (you don’t have to copy this) 20/20: Normal vision. Fighter pilot minimum. Required to read the stock quotes in the newspaper or numbers in the telephone book. 20/40: Able to pass the Driver's License Test in all 50 states. Most printed material is at this level. 20/80: Able to read alarm clock at 10 feet. News headlines are this size. 20/200: Legal blindness. Able to see STOP sign letters. (You are only considered to be legally blind if your vision can not be corrected to better than 20/200)

Remember: The lens is the structure at the front of the eye that focuses light on the retina. The lens is made up of water and protein, and is the consistency of hardened jelly.

Presbyopia As we get older, the lens hardens and can’t focus as easily. This makes it difficult to focus on objects close up. (It is often called age-related farsightedness.)

Cataracts As people get older, the proteins in the lens can start to clump, making them cloudy. This isn’t a film over the lens, but rather the lens itself is cloudy. Cataracts can be treated by replacing the lens with an artificial lens.

Fluids in the eye The lens divides the eye into two segments. - Vitreous humor - a jelly like substance that fills the posterior section of the eye; helps maintain the shape of the eyeball. - Aqueous humor - a watery fluid that fills the anterior section of the eye; helps maintain pressure in the eye as well as provides nutrients for the lens and cornea.

Glaucoma Aqueous humor flows out of the eye. If it is not able to drain from the eye, pressure builds up, compressing the retina and optic nerve, resulting in glaucoma and possibly blindness.

Sense of Hearing How do sound waves travel through the parts of the ear?

Sense of Hearing and the Ear Parts of Ear 1) External Ear: collects sound waves a). Auricle (pinna)-funnel shape b). External auditory meatus- S- shaped tube

Middle ear 2) Middle Ear (transmits sound waves) a) Tympanic cavity –air filled space in bone b) Tympanic membrane (eardrum)- semitransparent membrane covered by skin on outside and mucous membrane on inside; cone shaped

Middle ear c) Auditory Ossicles (malleus, incus, stapes)- bones, amplify the force of vibrations 1. Malleus- attaches to eardrum and vibrates 2. Incus vibrates 3. Vibration passes to stapes d) Oval window- opening that leads to inner ear

Inner ear Inner Ear- Complex systems of tubes called labyrinth a)Semicircular canals (three of these)- provide sense of equilibrium (not part of hearing pathway) b)Eustachian tube/ auditory tube- maintains ear pressure, connects to throat Parts of Labyrinth- contains fluid called endolymph 1) Cochlea- Hearing organ a) Round Window- opening in inner ear b) Organ of Corti - contains hearing receptors (hair cells) in fluid that stimulate tectorial membrane