Study Guide for Senses

 

Hearing (Elizabeth)

 

Hearing—composed by loud, soft, high pitch, and low pitch. Hearing distinguishes: sound intensity, pitch and location

 

Lets say someone is talking, you get the sound waves, which then go in your ear. They go through small part of the ear. It then gets to the cochlea, which is composed of small little hair things. When the hearing vibration enters, the small like hair starts moving, due to the vibration, which makes the channel open and the calcium ions come out. Eventually the hearing vibration get turned in to a nerve that goes to the brain.  The signals consist of information about pitch and intensity and which ear the signal is coming from.  The brain processes these signals to determine exactly what we are listening to and where it is coming from.

 

Some examples may be we could put loud and soft music to see how the people respond to it. Another would be to put a nice melody and then hard rock.  Or, as we saw in the perception lab (available on the course web page) we can close our eyes and have someone clap their hands around our head and we can point to where the sound is coming from.  Likewise, we could have them make sounds of different pitches (as with the guitar demo) and determine which pitch is higher or lower.  Same thing with loud and soft.  Finally, we can close our eyes and using sound alone can identify who is talking (sound recognition).

 

Lets say you put very loud music close to your ear, then when you put soft music your ear will still be vibrating from the loud music and will not really tell the difference. Another to trick your hearing is when you are next to a speaker and then you go home, you will still feel kind of like the music is in your ears. 

 

 

Vision         (Vesna and Dennise)

 

What constitutes vision?

 

• Color
• Motion
• Form
• Depth
• Contrast/brightness

 

Explain Physiology and Process of sense?

           

Light enters the eye by first passing through the cornea, a clear layer of tissue that begins focusing the image. Behind the cornea a substance like thickened water, called aqueous humor, keeps the front of the eye firm and slightly curved. Light travels through this fluid to reach the iris. The iris is a beautiful colored texture ring-shaped muscle that gives our eye its color. The hole in the center of the iris, called the pupil dilates and constricts to control the amount of light entering the eye. By contracting or relaxing, the iris can change the size of the pupil to compensate for changing lightning conditions. Once the light passes through the pupil it is further focused by a bit of clear, stiff, jelly-like tissue called the lens. The lens can squeeze tight in to a ball or be stretched flat, allowing us to shift our focus between near or far objects. Behind the lens, another clear liquid, called the vitreous humor, fills most of the eyeball, and light passes through this liquid to finally come to a focus (upside down) on the very back of the eye on a sheet of issue called retina.  The retina is composed of millions rods and cones which distinguish colors and light levels.  By sending signals of different types to the brain depending on the wavelength and number of photons they receive.  There is an area of the retina where the signals are sent through called the optic nerve.  No rods or cones sit in this region and hence we cannot sense any light that falls there.  That is why this region is called the “blind spot.” 

 

The information passed to the brain by the eye consists only of “images” made of color and intensity information mapped out according to where the image was on the retina and which eye it came from.  The brain processes the signals to extract information about depth and motion and is responsible for determining what we are looking at. Signals from the left and right eye are processed to give depth perception.  This is the purpose of binocular vision.

 

 

Find some demos of how it works?

 

            Looking at a color and at a shape you can see both but it is easier to interpret a form and its motion than a color because the brain processes the info about motion and form at a an earlier stage.  This makes sense from a survival viewpoint because it is important to escape danger (in the form of a predator, say) QUICKLY, and danger recognition depends more on figuring out the form and motion of an object than its color. Or if you look at a mountain far away and a car right beside you the car looks bigger. Also all kinds of shadings tell you the depth in the object.  (With the added help of binocular vision).  We can distinguish many different colors as evidenced in the senses lab (available on the course web page) where we sorted color samples from blue to red.  We can perform a similar feat with shades of gray using our ability to distinguish light intensity.

 

Find some examples of how it doesn’t work?

 

            Everyone has a blind spot. A blind spot is a part of your eye that has no light receptors cells because of this if you want to see something that hits right on your blind spot you cant detect color, nor motion, nor depth, nor form.  Mr. Waugh presented us with an example of how the blind spot distorts our perception in the perception lab available on line.  We also considered optical illusions and “persistence of convention” in the lab, which are further examples of how we can misperceive things with our vision.  (The video we saw as a class showed someone who had blindsight, and we described a video we watched in which someone was unable to recognize faces because they were “face blind”  (Their brain was able to recognize other objects, but not faces, even though their eyes functioned well.)

 

Extra Facts

 

·        Pure form is easier to interpret than color.

·        1/3 of the brain processes what we see.

·        After we detect motion our brain first processes it in black and white.

·        We see things that are closer bigger then things that are far away because of perspective.

·        Shading gives you information about depth (as does binocularity).

·        Vision is the monopolist of the senses.

 

Smell (Helmuth, Gary, Ricardo P. and Ricardo A.)

 

·       The sense of smell is one of the oldest senses.

·       The sense of smell is one of the chemical senses.

·       Since it is one of the oldest senses, it was believed that the information went into the brain very easily. But odors are processed by a complex network of neuronal connection.

·       The odor molecules are determined by their size and shape.

·       The brain identifies them by their shape

·       The odor molecules have to be small enough so they can evaporate, reach the nose and then dissolve in the mucus.

·       Smells are detected in the nose by the specialized receptor cells of the olfactory epithelium. These are called olfactory receptor neurons.

 

How does the smell sense work?

·       Once the odor molecules reach the nose, they travel through it and reach the mucus.

·       In the mucus part, the molecules are plugged into the cilia where the receptors receive the information. There are 5,000,000 different receptors

·       The cilia outgrow of neurons and then collect and transmit information to the brain olfactory valve.

·       In the olfactory valve, The glomeruli nerve cells tell you what odor is the most important

·       The information passes directly to the limbic system. Odors entering the nostril are processed on the same side of the brain.

 

Smell and Memory

·       Smell is closely related to memory.

·       Humans identify most of the odors by memory.

·       Humans can differentiate between 10,000 different smells

·       The damages that can occur when you have a stroke are not mainly affected to the sense of smell but to the memory

·       You can still smell but your memory doesn’t recognize the smells.

·       As you get older, your smell sense begins to decrease.

 

Example of its correct function

·       In the senses lab (on the course web page) we could not distinguish cucumber from onion when our noses were plugged (taste alone didn’t do it, nor for that matter, would touch or sight since the sample were blended up and colored to look the same), but could easily do it with smell.

 

Example of fooling it

·       If two chemicals are similar in shape they can fool the cilia receptors in your nose and cause a detection signal to be sent so the brain thinks the chemical is present when it is not.  Likewise, one can have such an intense memory recollection that one thinks the smell associated with it is present when it is not.  This is analogous to a hallucination of hearing or seeing (which also occur).

 

Touch (Debbie, Orit, Jhonny, Ale)

1.Touch- Texture, pressure, temperature, smoothness, if something is sharp,etc.  We have touch receptors for hot, cold, pain and pressure.  Our brain can process these signals to distinguish textures, temperatures, force and damage to and orientation of our bodies (see proprioception)

2.The skin is made of sensory neurons, when you touch something the sensory neurons respond in a way that travels through your body through the spinal cord and then the message is sent to the brain, and what the brain does is that it tells you what you feel and the reflexes you have for example if you touch something very hot your brain tells your that it is very hot and that you are hurting yourself so you immediately know that you have to remove your hand from  the fire. The thalamus is a very important part of the brain. This part is the first part where we receive the message that the sensory neurons send.  The brain stem is very important because that is what makes our reflexes work. The brain stem lies below the thalamus and the hypothalamus.

3.Our sense can be very important for us, for example if we touch something very hot our sense tells us that its hot and forces us to remove our hand because that way you stop the hurt of getting burned, other example is if you are touching a soft teddy bear your brain tells you that the feeling is good and soft and you enjoy how it feels.

4. Our senses can also be fooled for example, if we place your hand in really cold water and then you put it in really boiling water you won’t feel boiling water you will just feel that it’s warm. But if you start moving around your hand after a while you will start to feel that the water is really getting very hot. another way we can fool our senses is if our hand goes numb, you can’t feel your hand very well so if you try to touch your hand or you try to add pressure to your hand you won’t feel pain you will just feel tickles.

Taste (Laura, Tatiana, Veronica, Steven)

 

 

The taste buds on our tongues can distinguish the flavors: salty, sweet, bitter and sour

There are four different types of buds that are tuned in to each of these flavors and they reside in different parts of the mouth (e.g. we taste sweet on the tips of our tongues and bitter at the back).  Each taste has evolved for a different purpose.  So, for example, the sweet detectors at the front tell us that a food is good, while the bitter detectors tell us if we have a potential poison.  The signal form the tongue is sent to the brain where it either responds with an all clear (go ahead and eat it) or a spit is out response.  In a food safe environment it is advantageous to have little taste discernment since you can eat almost everything safely and food is necessary for survival.  In an environment with a significant threat from poisons being a “picky eater” is safer and more beneficial for survival.  The letter type of taster is known as a “super taster.”

We saw in the cafeteria how we could distinguish the four basic tastes in different parts of the tongue.  We also saw how some tastes can confuse our ability to taste (brushing your teeth makes orange juice taste more sour and bitter than it really is).  We also saw in the senses lab (see web page if you forget it) that without smell we have very limited taste differentiation (see smell study guide above).  We were unable to distinguish cucumber from onion by taste alone. 

 Proprioception

Our sense of proprioception tells us the location and state of our various body parts and our body as a whole.

The same nerves that work in touch (see above) exist throughout our bodies (e.g. at joints and in muscles) and send signals regarding pressure and pain.  These signals are sent to our brains where they are turned into a mental image of how our bodies are configured.  The inner ear tells us the orientation of our bodies relative to up and down.

We can see the good functioning of proprioception by closing our eyes and having someone move our arm to any location.  We can tell where our arms are without looking.  Likewise, we can tell if we are standing up or lying down without looking.  In the senses lab we shut our eyes and many of us were still able to touch our finger tips together.

We can fool this sense, for example, by spinning around so that we get dizzy.  This is confusing our inner ear so we no longer can tell where down is.  Phantom limb syndrome is another way in which proprioception is fooled.  Our brain “feels” a part of our body that is no longer there.  We watched a video about this as a class.  The transcript of the video is available through the PBS site linked to on our course web page.