Chapter 10Senses

SENSESSensory Receptors - detect environmental changes and trigger nerve impulses - somatic senses (touch, pressure, temp, pain)- special senses (smell, taste, vision, equilibrium)

Receptors

1. Chemoreceptors = _____________________

2. Pain receptors = ____________________ 3. Thermoreceptors = _____________________

4. Mechanoreceptors =_____________________

5. Photoreceptors = _____________________

SensationsSensation = feeling that occurs when a brain interprets a sensory impulse

Projection = process where the cerebral cortex causes a feeling to stem from a source (eyes, ears)

Sensory adaptation = sensory receptors stop sending signals when they are repeatedly stimulated

What do you think is going on in this picture?

 

Sensory Deprivation is a technique initially used by neuro-psychiatrists designed to deliberately reduce or completely remove stimuli from one or all of the senses.

Somatic Senses1. Sensory Nerve Fibers - epithelial tissue, pain and pressure2. Meissner's corpuscles - hairless areas of skin (lips, fingertips)3. Pacinian corpuscles - deep pressure (tendons, joints)

Temperature Senses (warm and cold receptors)

Sense of Pain•Visceral Pain - occurs in visceral tissues such

as heart, lungs, intestine•Referred pain - feels as though it is coming

from a different part (heart pain may be felt as pain in arm or shoulder)

•Acute Pain - originates from skin, usually stops when stimulus stops (needle prick)

•Chronic Pain - dull aching sensation

Regulation of Pain

Inhibitors of Pain (natural brain chemicals can be mimiced by drugs such as morphine)

EnkephalinsSerotoninEndorphins

The Rising Tide of Prescription AbuseCourtney Love calls them the new LSD, or "lead singer's drug." Rapper Eminem has a tattoo of one on his bicep. David Spade even joked that they were in the goody bags given away at the Golden Globes. Hollywood is gripped by a new addiction: prescription painkillers. Vicodin and OxyContin have become the latest trendy drugs, and they can be just as powerful as heroin or cocaine.

2.6 million people nationwide now regularly use prescription pain pills for recreational purposes. Taken in small doses, painkillers produce feelings of euphoria with no hangover.  Number of Reported  Deaths

10.4  Special Senses

Olfactory (smell)

Gustatory (taste)

Hearing & Equilibrium

Sight

Sense of Smell (Olfactory)Odor --> Receptor Cell  -->  Olfactory bulb --> Olfactory Tract 

--> LIMBIC SYSTEM

Aromatherapy....

Real or Bunk?

Olfactory Bulb on Sheep Brain

Sense of Taste (Gustatory)SweetSourBitterSalty

Sense of Hearing

External Ear

Auricle (pinna) - outer earExternal Auditory Meatus

Middle Ear (tympanic cavity)•Eardrum (tympanum)

•Auditory Ossicles - malleus, incus, stapes - transmit vibrations and amplify the signal

•Auditory Tube (eustachian tube) - connects the middle ear to the throat - helps maintain air pressure

Inner Ear

•Labyrinth - communicating chambers and tubesOsseous Labyrinth and Membranous LabyrinthPerilymph and Endolymph (fluids within the labyrinth)

•Semicircular Canals - sense of equilibrium 

•Cochlea - sense or hearing

•Organ of Corti - contains hearing receptors, hair cells detect vibrations

Why do children get tubes put in their ears?

Inner Ear: Cochlea•Inside the cochlea are special neurons

called HAIR CELLS•The stapes is attached to the OVAL

WINDOW, and vibrations cause the perilymph to vibrate; the hair cells here transmit this vibration.

•Therefore the HAIR CELLS in this region are receptors for HEARING.

As you age, hair cells become damaged (loud music can speed this process along). Older people usually can’t hear frequencies that younger people can hear. Try the hearing test!

Steps in Hearing

1. Sound waves enter external auditory meatus2. Eardrum vibrates3. Auditory ossicles (malleus, incus, stapes) amplify vibrations4. Stapes hits oval window and transmits vibrations to cochlea5. Organs of corti contain receptor cells (hair cells) that deform from vibrations6. Impulses sent to the vestibulocochlear nerve7. Auditory cortex of the temporal lobe interprets sensory impulses8. (Round window dissipates vibrations within the cochlea)

Cochlear Implants A cochlear implant receives sound from the outside environment, processes it, and sends small electric currents near the auditory nerve.  These electric currents activate the nerve, which then sends a signal to the brain. The brain learns to recognize this signal and the person experiences this as "hearing". The cochlear implant somewhat simulates natural hearing, where sound creates an electric current that stimulates the auditory nerve. However, the result is not the same as normal hearing. 

How cochlear implants work (youtube video)

Sense of EquilibriumStatic Equilibrium - sense the position of the head, maintain stability and posture Dynamic Equilibrium (semicircular canals) - balance the head during sudden movement Cerebellum - interprets impulses from the semicircular canals and maintains overall balance and stability

What You Need to Know1.Label the ear (see handout)

2.Identify structures on the models

3.Watch the tutorials (understand the steps and structures involved in hearing)

Quiz: Label the ear

(no word bank)

• The eye is in the orbit of the skull for protection.• Within the orbit are 6 extrinsic eye muscles, which move

the eye. • There are 4 cranial nerves: Optic (II),

Occulomotor (III), Trochlear (IV), and Abducens (VI).

People of Asian descent have an EPICANTHIC FOLD in the upper eyelid; no functional difference.

THE EYE

Visual Accessory Organs• Eyelid• Conjuctiva• Lacrimal Gland• Extrinsic Muscles

Eyelid

Covers and protects the eye, thin skin Skin will not protect you from intense radiation, that’s why we use special goggles in a tanning bed

CONJUNCTIVA is like a covering around the eye and under the eyelids.  PINK EYE - also known as CONJUNCTIVITIS  (from bacteria, very contagious) Pink Eye Slide Show f

rom Web MD

Extrinsic Eye Muscles

Moves the eyeball

• LACRIMAL GLANDS are the largest set. They are on the superior lateral eyelid and they produce tears, which drain into the nasal cavity via the LACRIMAL DUCT.

• The function is to moisten and lubricate the eye surface, and it has enzymes to kill bacteria (which thrive in warm, moist conditions).

Figure 16.5b

Outer Tunic• Cornea - transparent, focuses light

rays• Sclera – continuation of cornea,

going toward the back of the eye (white of the eye)

• Optic Nerve – exits at the optic disk and transmits visual information from the eye to the brain.

Middle TunicChoroid Coat – contains blood vessels

Ciliary Body – holds the lens in place

Lens – focusing

Iris – colored portion of the eye

Aqueous humor – liquid surrounding the lens

Pupil – opening for light to enter

Figure 16.9a

Inner TunicRetina - visual receptor cells Fovea Centralis - region of the sharpest vision (aka, macula) Optic Disc – where nerve fibers leave the eye, creating the blind spot Vitreous Humor – supports internal parts, fluid

Figure 16.7a

Retina

The retina is made up of PHOTORECEPTORS, which are sensors for light.

Rods = monochromatic (b&w)Cones  = color vision

Light RefractionLight bends around objects Images viewed by the eye are upside down

R.O.Y.G.B.I.V Rainbows are seen after rain because light is passing through water droplets.  This separates the white light into the individual colors of the spectrum

The Eye as an Optical Device

Figure 16.14a–c

We have difficult interpreting images that are upside down

Which one is the real mona lisa?

• Fun Fact: -When you are looking at someone you love, your pupils dilate, and they do the same when you are looking at someone you hate.

What causes red-eye?

The flash on a camera is bright enough to cause a reflection off of the retina -- what you see is the red color from the blood vessels.

Many cameras have a "red eye reduction" feature. In these cameras, the flash goes off twice -- once right before the picture is taken, and then again to actually take the picture. The first flash causes people's pupils to contract, reducing "red eye" 

Problems with the Eyes

CataractsClouding of the lens leads to a clinical condition known as CATARACTS. 

Treatment is to remove the lens and replace it with a plastic one (which is not flexible either).

The function is to constrict or dilate the pupil (opening) to allow light in.  Therefore, it regulates the amount of light passing to the visual receptors of the eye.

Problems with the IRIS and PUPIL

ANIRIDIA = a condition where a person is born without an iris

Why are all babies born with blue eyes? Melanin is a brownish pigment that adds color to your hair, eyes, and skin. At the time babies are born, melanin hasn't yet been "deposited" in the eyes' iris. Hence, they appear blue.   After about six months, eyes change color depending on the amount of melanin. If you have a lot of it, your eyes will turn dark brown.  If you have little, they'll stay blue. And if you have no melanin, your eyes may appear pink (albino). .

ColorblindnessA genetic trait that affects boys more than girls. The location of the gene is on the X chromosome

• The region where the optic nerve and blood vessels goes in and out of the eye has no photoreceptors = BLIND SPOT.

• Hold your hands out at 45° and that’s the location of the blind spot.

• You can still see your hands because the other eye sees it. Close your right eye and look for your right hand and you’ll find the blind spot.

FLOATERS are when a capillary breaks and cells break off.  Floaters don’t actually move, the eye just tries to track them.

HYPEROPIA (far-sighted)

eyes are too short MYOPIA (nearsighted)eyes are too long

ASTIGMATISMASTIGMATISM is when the cornea has an irregular shape. Part of the field of view is out of focus. They eyeball changes shape until age 24.

Lasik Surgery

See a real LASIK surgery (not for the squeamish)