Sensory+Organs

= Sensory Organs =

Sensory receptors respond to a particular modality of stimulus by causing the production of action potentials in a sensory neuron. Sensory receptors can be categorized on the basis of structure or function. 1. Mechanoreceptors- mechanical force 2. Pain receptors- tissue damage 3. Chemoreceptors- dissolved chemicals 4. Photoreceptors- light

Law of specific nerve energies- the sensation characteristic of each sensory neuron is that produced by its normal stimulus

Cutaneous Sensation- There are several different types of sensory receptors in the skin, each of which is specialized to be maximally sensitive to one modality of sensation. A receptor will be activated when a given area of the skin is stimulated, this area is the receptive field of that receptor.

In summary:

 * Large stimulus[[image:http://faculty.stcc.edu/AandP/accessoryimages/arrows/rtblue.gif width="60" height="30" align="right" caption="arrowrtblue.gif (2035 bytes)"]] || large receptor[[image:http://faculty.stcc.edu/AandP/accessoryimages/arrows/rtblue.gif width="60" height="30" align="right" caption="arrowrtblue.gif (2035 bytes)"]] potential || action potential is[[image:http://faculty.stcc.edu/AandP/accessoryimages/arrows/rtblue.gif width="60" height="30" align="right" caption="arrowrtblue.gif (2035 bytes)"]] triggered || action potential runs along axon[[image:http://faculty.stcc.edu/AandP/accessoryimages/arrows/rtblue.gif width="60" height="30" align="right" caption="arrowrtblue.gif (2035 bytes)"]] into CNS || Sensory[[image:http://faculty.stcc.edu/AandP/funimages/exclam.gif width="29" height="64" align="right" caption="exclam.gif (547 bytes)"]] information crosses a synapse to continue in CNS! ||
 * Small stimulus[[image:http://faculty.stcc.edu/AandP/accessoryimages/arrows/rtblue.gif width="60" height="30" align="right" caption="arrowrtblue.gif (2035 bytes)"]] || small receptor[[image:http://faculty.stcc.edu/AandP/accessoryimages/arrows/rtblue.gif width="60" height="30" align="right" caption="arrowrtblue.gif (2035 bytes)"]] potential || no action[[image:http://faculty.stcc.edu/AandP/funimages/X.gif width="47" height="60" align="right" caption="X.gif (826 bytes)"]] potential is triggered ||  //(nothing)// ||  //(nothing)//  ||

http://faculty.stcc.edu/AandP/AP/AP2pages/Units14to17/unit15/sensory.htm

Lateral Inhibition - sharpening of sensation. This is the field that is stimulated most strongly. Chemoreceptors - respond to chemical changes in the internal environment are called interoceptors, and those that respond to external are exteroceptors.

Taste- is evoked by receptors that consist of barrel-shaped taste buds. http://images.google.com/imgres?imgurl=http://static.howstuffworks.com/gif/taste-6.gif&imgrefurl=http://health.howstuffworks.com/tongue2.htm&usg=__aVw0iOZ8hRf_yd5PIhLsikTLY6U=&h=400&w=400&sz=63&hl=en&start=7&sig2=yIODpE-CGr8G3qtorObqVQ&um=1&itbs=1&tbnid=xpxGJ5pkDc0WEM:&tbnh=124&tbnw=124& prev=/images%3Fq%3DTaste%2Bbuds%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26sa%3DN%26rls%3Dorg.mozilla:en-US:official%26tbs%3Disch:1&ei=Cgu6S9n_G4GdlgfUmsGVCg

Your tongue can tell the difference between: salty- sodium though ion channel sour- hydrogen through ion channel sweet- binds to membrane receptor bitter- binds to a membrane receptor



Smell- from olfaction, the sense of smell are located in the olfactory epithelium.__//

//__Vestibular Apparatus and Equilibrium__//
//__The sense of equilibrium is due to the function of the organ called the vestibular apparatus. This is a called the cochlea, which is involved in hearing, form the inner ear within the temporal bones of the skull.

Ears and hearing. The outer ear- sounds are funneled by the auricle into the external auditory meatus. The middle ear is the cavity between the tympanic membrane on the outer side and the cochlea on the inner side. Inner ear- composed of the cochlea and the vestibular apparatus.



http://images.google.com/imgres?imgurl=http:__//__www.arthursclipart.org/medical/senseorgans/anatomy%2520of%2520the%2520ear.gif&imgrefurl=http://www.arthursclipart.org/medical/senseorgans/page_01.htm&usg=__xJtXFkmltf8O8hGKR0qCl_ff7IY=&h=1097&w=1369&sz=449&hl=en&start=5&sig2=92MXMv7sxTcZyFv_hRz6Tg&um=1&itbs=1&tbnid=IhNA6bQwWJuPUM:&tbnh=120&tbnw=150&prev=/images%3Fq%3DAnatomy%2Bof%2Bthe%2Bear%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26hs%3Dm7U%26sa%3DN%26pwst%3D1%26rls%3Dorg.mozilla:en-US:official%26tbs%3Disch:1&ei=PhC6S8jNLoX6lwf12vWVCg

=Vision and Eyes=



[|serendip.brynmawr.edu/.../ 50?page=1&destination=]

The human eye is very complex and is made up of many parts. The human eye is like a camera. Light comes in through the cornea, a clear cover that is like the glass of a camera's aperture. The amount of light coming in is controlled by the pupil, an opening that opens and closes a little like a camera shutter. The light focuses on the retina, a series of light-sensitive cells lining the back of the eye. The retina acts like camera film, reacting to the incoming light and sending a record of it via the optic nerve to the brain.

How do we see color?

When light passes through a prism, it separates light passing through it into the colors of the rainbow. Every color has a different wavelength. The human eye and brain together translate light into color. The light receptors within the eye send messages to the brain, producing the sensation of color. This process begins in the retina of the eye. The retina contains millions of cells called photoreceptors that are sensitive to light. We have two types of photoreceptors, some shaped like rods and some like cones. These photoreceptors process light into nerve impulses and pass them along to the cortex of the brain via the optic nerve. Rods, which transmit mostly black and white information to the brain, help your eyes adjust when you enter a darkened room. Cones in each eye transmit the higher level of light intensity that creates the sensation of color.

Neural Control of Eye movement
http://images.google.com/imgres?imgurl=http://www.susqneuro.com/publications/vision/Vision2_files/image004.gif&imgrefurl=http://www.susqneuro.com/publications/vision/Vision2.htm&usg=__MghA4gJB83-pGXrSqHJckmYtQlc=&h=447&w=505&sz=20&hl=en&start=13&sig2=FNfPbEuiNV351Zu_98lGmw&um=1&itbs=1&tbnid=4iSHmNCvHPuo6M:&tbnh=115&tbnw=130&prev=/images%3Fq%3Dretina%2Beye%2Bmovement%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26hs%3DCSV%26sa%3DN%26rls%3Dorg.mozilla:en-US:official%26tbs%3Disch:1&ei=MBW6S_LWKoGglAfUr_ygDw

This chapter was very complex and really makes you think how amazing the human body is. Just the simple act of moving your eye or smelling baking bread is truely remarkable how the body can allow us to do these things.

Personal application: I will be working with the elderly and with people who have brain damage who will have decreased sensation or loss of sensation due to injury and I will need to be able to help them to function on a daily basis. It also gave me an understanding of how complex these sensations are and how valuable they are to us and how easily they can be disrupted or taken away.

Questions?

1. The sound transduction process involves complex mechanical transduction of sound waves through the external ear and the external acoustic meatus and across the tympanic membrane;Next it inters the middle ear via the oval window to produce a fluid wave in the cochlear duct. This fluid wave causes differential movement of the basilar membrane, stimulating hairs on the apical portion of hair cells to release neurotransmitters that stimulate primary sensory axons of neurons of the cochlear ganglion.

2. Light from the object is observed by the cornea and lens onto the photoreceptive retina at the back of the eye. The eyes transduce energy in the electromagnetic spectrum into nerve impulses. The iris is like the diaphragm of a camera; it can increase of decrease the diameter of its aperture, pupil, to admit more or less light. Posterior to the iris is the lens, posterior to the lens is the vitreus body. Light that passes though the vitreous body enters the neural layer, which contains photoreceptors a the back of the eye. This is called the retina. Some of the light stimulates the photoreceptors- they exit the retina as the optic nerve as the optic nerve. Light that passes from a medium of one density into a medium of a different density is refracted or bent. This causes the image to be upside down and right to left. The visual field which is part of the external world projected onto the retina is then reversed in each eye.

References: All information was obtained for sites provided and our text Human Physiology, by Stuart Ira Fox.