5 senses

5 Senses

• Hearing

• Sight

• Smell

• Touch

• Taste

Hearing

Ear is in three parts: Outer, Middle and Inner

Outer Ear

• The outer ear is called the pinna or auricle (say: or-ih-kul). This is the part of the ear that people can see.

Earwax

Earwax has several important jobs. 1. It protects and moisturizes the skin of ear canal,

preventing dry, itchy ears. 2. It contains special chemicals that fight off

infections that could hurt the skin inside the ear canal.

3. It acts as a shield between the outside world and the eardrum. When dust, dirt, and other things enter your ear, the earwax traps them so they can't travel any further.

Middle Ear

After sound waves enter the outer ear, they travel through the ear canal and make their way to the middle ear. The middle ear's main job is to take those sound waves and turn them into vibrations that are delivered to the inner ear. To do this, it needs the eardrum, which is a thin piece of skin stretched tight like a drum.

Middle Ear cont.

The eardrum separates the outer ear from the middle ear and the ossicles (say: ah-sih-kulz).

- malleus (say: mah-lee-us), which is attached to the eardrum and means "hammer" in Latin - incus (say: in-kus), which is attached to the malleus and means "anvil" in Latin - stapes (say: stay-peez), the smallest bone in the body, which is attached to the incus and means "stirrup" in Latin

Inner EarThe inner ear contains two of the most intricate parts of the hearing mechanism: the cochlea and vestibular labyrinth. The fluid-filled, snail-shaped cochlea (KOK-le-uh) — which is no larger than a pea — begins at the oval window. Sound vibrations from the oval window travel into the fluid of the cochlea, where tiny specialized cells convert the vibrations into electrical impulses. The auditory nerve transmits these impulses to your brain.

The vestibular labyrinth consists of three semicircular tubes that connect to one another and control your sense of balance. These canals contain fluid and cells sensitive to fluid movement. The cells track your body's movement so that you're aware of where your head is in relation to the world around you.

http://www.bbc.co.uk/science/humanbody/body/factfiles/hearing/hearing_animation.shtml

Sight

Cornea The clear covering of the eye.

Iris The colored opening in the eye.  The iris' job is to open or close to adjust the amount of light that actually enters the eye.  

Lens The lens is a converging lens so that it can create a real image on the back wall of the eye.  The lens is actually soft in the middle (like a bag of water) so that the muscles around it can adjust its shape and focus.  This allows us to focus on something close to us and far away. Retina The projection screen at the back of the eye.  If the image gets focused here, vision is good. Optic Nerve The nerve that carries the signal from the retina to the brain.  It is also the cause of the blind spot you have in each eye.

Color and LightRods

Rods are nerves that are very good at sensing low levels of light.  They actually become more active in low light situations.  The drawback is that they only sense black and white or shades of gray.

Cones Cones are nerves that are very good at detecting

color but require more light to function.  They become less active in low light situations.  They are located more toward the center of the retina. Cones come in three sub types: Red, Blue, and Green. 

What does 20/20 mean?

"20/20" means the smallest letters you can recognize at a distance of 20 feet are the same size as those a person with normal eyesight can see at the same distance.  You have normal (20/20) eyesight.

If you have 20/40 visual acuity, the smallest letters you can recognize at 20 feet a person with normal eyesight can recognize when they are 40 feet away.  In other words, your visual acuity is only half as clear as that of a person with normal eyesight (20/40 = 50%). 

Smell

Any odor molecules in the air will past by and get stuck to the mucus in your nose. The sensory hairs sense the odor and transmit messages to your brain. Your brain, therefore knows the odor. The smell receptor cell is located high up behind your nose. The receptor is sensitive to chemicals in the mucus in your nose.

Every time we breathe, air flows through the nasal cavity. The turbinates (shelves of bones) makes the air flow down through the back of the mouth into the throat. Some air that flows into your mouth passes the olfactory organs.

Humans have seven primary odors that help them determine objects:

Camphoric Mothballs

Musky Perfume/Aftershave

Roses Floral

Pepperminty Mint Gum

Etheral Dry Cleaning Fluid

Pungent Vinegar

Putrid Rotten Eggs

Touch

Types of Nerves

Response of Nerves

Rapidly-Adapting:

Stop sending the signal quickly.

(example: pressure)

Slowly-Adapting:

Signal is sent for a long time. (example: hot/cold)

Facts

You have more pain nerve endings than any other type.

The least sensitive part of your body is the middle of your back.

The most sensitive areas of your body are your hands, lips, face, neck, tongue, fingertips and feet.

Shivering is a way your body has of trying to get warmer.

There are about 100 touch receptors in each of your fingertips.

Taste

There are four different types of taste buds. You can taste sweets in the front of your tongue and sour taste at both sides of your tongue At the back, you taste bitter things. All over your tongue, you taste salty things.

Taste Buds

You have 10,000 taste buds on your tongue. Your saliva helps move the flavors in your mouth.

http://www.bbc.co.uk/science/humanbody/body/factfiles/taste/taste_animation.shtml