I.    Ch 34 - Senses Receptors
     A.    Ex 34-1: Cutaneous Receptors - Touch

• Mainly pain receptors
• Skin and visceroreceptors (on the organs)

• touch receptors in the skin
• used in 2 point discrimination

• dermis or hypodermis
• deep cutaneous pressure and vibration

• dermis of the skin, in fingers
• Temperature

• temperature

• page 387
• we will collect class results on board and discuss in class

• page 388-389
• we will collect results on board and discuss in class

• Gustation - sense of taste
• Taste buds
• located on tongue, pharynx, lips
• mainly chemoreceptors.
• Function
• sweet, sour, salty, bitter
• carbo = sweet, acid = sour, metal ions = salt, alkaloid = bitter
• much of taste is strongly influenced by olfaction.(think of a cold)
• body craves sweet and salty = needs
• Experiment
• Pages 390-391
• Solutions located at side bench
• map the four basic tastes onto the regions of the tongue

• Olfaction - sense of smell
• nasal recess
• located at the extreme superior region of the nasal cavity
• made of specialized epithelium that surrounds fibers of the CN I. These absorb the molecules and stimulate CN I.
• camphoraceous, musky, floral, pepperminty, ethereal, pungent, putrid.(total of 4000 smells made primarily from these)
• Experiment
• Page 391
• Solutions located at side bench
• How does the sense of smell influence taste?

• palpebra = eyelid
• muscles involved = levator palpebra, orbicularis oculi
• conjunctiva - a mucous membrane on the eyelid and the surface of the eye. (i.e. conjunctivitis = pink-eye)
• The lacrimal apparatus
• superior and inferior lacrimal glands
• superior and inferior lacrimal ducts

• superior levator palpebra
• superior and inferior rectus
• medial and lateral rectus
• superior and inferior oblique
• orbicularis oculi

• Sclera - dense collagenous connective tissue that helps protect the eye and helps give it shape (white of the eye)
• The eyeball is divided up into 3 layers
• the outer scleroid coat
• the middle choroid coat
• the innermost retinal coat
• the retina is disrupted by two structures the optic nerve and the fovea centralis
• Iris and pupil
• Iris - is composed of pigmented radiating and circular muscle tissue which can change size and regulate the amount of light the that hits the lens.
• Pupil - is simply the hole leading to the lens.
• Cornea
•  is a clear, protective extension of the scleroid coat that covers and protects the rest of the eye
• Anterior and Posterior compartments
• anterior = in front of the lens, contains aqueous humor
• posterior = behind the lens, contains vitreous humor
• Lens
• suspensory ligament, with the attached ciliary body of smooth muscle
• elastic in life, ciliary muscles causes it to change shape in order to focus.

• follow instructions on pp. 400-401
• try and identify all of the structures we discussed in class
• also try and identify the tapetum lucidum

• Make sure you do these tests and understand what they are used for

• The standard Snellen eye chart, be able to tell me what it means to have 20/20 vision or 20/200 vision

• tests for uneven curvature of the lens of the eye
• test using chart on page 402.

• eye has red, green and blue cones
• tests to see which cones are defective
• Use the Ishihara colorblindness test book at the side bench

• illustrates the fact that the optic disk has no receptors
• use figure on page 403 to test this phenomenon

• deals with elasticity of the lens
• Index cards and tape measures will be provided
• Report results on board and discuss

• Distance reflex
• Light accommodation reflex - use penlight
• (note: never shine the penlight into someone's eye for more that a few seconds)

• auricle or pinna - the fleshy outer ear made out of elastic cartilage, directs sound into the middle ear.
• external auditory meatus - lined with hairs and modified oil glands, prevents foreign objects from reaching the eardrum.
• tympanic membrane - semitransparent, oval trilayered membrane that separates the external ear form the middle.

• an air filled cavity with a round and oval window opening into the inner ear.
• eustachian tube - opening leading into the pharynx which equalizes pressure between the middle ear and the outside environment (oral cavity)
• also contains the three middle ears bones the, malleus incus and stapes. These bones are connected in series from the eardrum to the oval window and transmit vibrations

• the cochlea, vestibule and semicircular canals
• cochlea divide into three chambers, scala tympani, scala vestibuli, and the cochlear duct
• inside the cochlear duct are special sensory hairs that make up the organ of Corti (a.k.a. spiral organ)
• cochlea is for hearing, other two are mainly for balance

             2.    Middle ear

• vibrations from tympanic membrane cause the ossicles to vibrate, which is transmitted to the oval window
• since the membrane of the oval window is much thinner the sound is magnified about 20 X before it enters the perilymph
• The sound attenuation reflex is regulated by the Stapedius and tensor Tympani muscles which contract and prevent excessively loud sounds from damaging the ear.

• as the vibrations pass through the oval window they simultaneously travel through the perilymph and endolymph where they stimulate the basal membrane
• the hair cells imbedded this membrane are stimulated and induce AP’s through direct electrical connections to CN VIII.
• the round window is important in hearing, because it allows the sound waves to continue back into the middle ear, rather than reverberating back through the inner ear and restimulating it.

• always clean the ear pieces before and after using the otoscope
• wait for TA's to assist you, DO NOT force the scope into you partner's ear

• pages 412-413

• tests for air and bone conduction essential in hearing

• tests for differences between air conduction and neural hearing damages

• these structures evaluate head movements relative to gravity, acceleration and deceleration
• maculae lie parallel to the cranial base and function to help the head restore balance

• semicircular canals located at right angles so they register movement in 3D
• Since the endolymph does not move as fast as the head, the cupolas are stimulated by the fluid moving past them and send signals about head position. When movement ceases, the fluid rushes back past them and balance is restored
• Clinical - motion sickness results from over stimulation of the semicircular canals, which results in disorientation, dizziness and nausea treatments include drugs which decrease the excitability of vestibular neurons (scopolamine) and those which affect the neural pathways of the vestibular system(Dramamine)

• NOTE: Do not let your partner fall over when their eyes are closed

• Remember, proprioceptors give continual feedback on body position in space.
• Many proprioceptors are located in skeletal muscles and around joints

• NOTE: do not spin your lab partner too fast or make them sick.
• Tests the semicircular canals
• Remember what I said about the movements of endolymph across the cupolas