Flashcards in Special Senses Deck (45):
- Sense of smell
Describe the olfactory pathway
-Receptors for smell are the dendrites of the olfactory nerves
-(Cr. N I) located in the superior nasal cavity.
-They pass through those olfactory formina of the ethmoid bone
-synapse at the olfactory bulb.
-The pathway continues on as the olfactory tract which is interpreted in the temporal lobe of the cerebral cortex.
Define gustation. Identify the 4 main taste zones
-Sense of taste. The sweet taste zone is at the tip of the tongue, salt is just posterior to it; sour is on sides of tongue and bitter is at the back of the tongue.
Describe the gustatory pathway
-Taste buds are the receptors and are at the base of the taste pores (that is why substances must be liquified for taste).
-The pathway travels along cranial nerves VII (anterior tongue), IX (middle tongue) and X (back of tongue & throat) to be interpreted in the parietal lobe of the cerebral cortex.
Name and describe the structures included in the 3 layers of the eyeball
-Fibrus Tunic: Outter most
-selera- white of eye- blood vessels, pain nerve endings
-Cornea- clear- no BV, nerve endings (can repair with surrounding BV)
Vascular Tunic: Layer below (uvea)
-Choroid- inside selera, BV nurish the next layer, Pigment colorful
- Ciliary Body- Smooth muscle, focus lens, innovated by the ocularmotor nerve ( NERVE III)
-Iris- Color part of eye, smooth muscle around pupil
-Pupil- hole in iris, light regulation, Regulated by ocularmotor nerve III
Nervous Tunic- Retina and optic nerve
-outer pigmented layer: (deflects light reflection)
-Nervous layer: receptors (cones and rods) are here
-macula and fovea centralis
-optic nerve, optic discs, blindspot
-Lens: attached to ciliary bodies, rounded clear, focuses light of fovea centralis
Describe the function and the tissue make-up of the iris
-he iris is pigmented smooth muscle and regulates the light coming through the pupil. A large pupil lets in a lot of light.
Describe the location and function of the retina
- Located in the nervus tunic, inner layer of the wall of the eyeball
-the location of the receptors for vision, the rods and cones.
What and where is the blind spot
- In the retina, the optic disc, where the optic nerve exits
-there are no rod or cones located here. No receptors
Describe the location and function of the lense, aqueous humor and vitreous humor.
-Lense- In the retina
-Attached to the ciliary bodies
-focus light waves to land on the fovea centralis
-no bv, gets nurisment from anterior and posterior cavities
-cataracts are opic spots on lense
-anterior cavity, maintain shape
-posterior cavity, thicker fluid (where glucoma occurs)
Describe the location of the palpebral fissure, medial and lateral commisures, caruncle, tarsal plate, conjunctiva, meibomian glands, palpebrae, and sebaceous ciliary glands
-Palpebral fissure-slip between eyes
-Medial lateral commissures- edge of eyes
-caruncle- gland that makes sticky substance to clean eye at night
-tarsal plate- upper and lower, gives eyelid substance (flip eyelids inside out)
-conjunctiva-attaches to eyeball, palpebral to the bulba of the eyeball (what gets infected with pink eye)
-Meibomian glands- releases oil on rims of eyelids so they don't stick
sebaceous ciliary glands- eyelash oil glands to prevent eyelashes from breaking
Describe the structures that comprise the lacrimal apperatus
- releases antimicrobial substance to protect eye from infection
-tears to lubricate moisten eye and clean from foreign material
-lacrimal gland- superior lateral margin
-lacrimal puncta- hole
-lacrimal cannal into the nasolacrimal duct
Name the photoreceptors and describe their locations
-Rods & cones on the retina.
-Rods tend to be more peripheral and cones more centrally located.
-Black and white and gray- Rods
define refraction as it pertains to vision
-The bending of light rays so that they all converge on one spot called the focal point. If they all converge on one point and that point is on your fovea centralis, you have clear vision.
- the cornia and lense
Describe how images are focused
-The light rays are refracted by the cornea and again by the lens.
-Hanging from the ciliary body are suspensory ligaments attached to the retina so that the lens can be changed in shape.
-A straighter lens does not bend the light rays very much, a more curved lens bends the light rays a lot.
-normal vision, all light rays come to focus on the single point behind the lens called the focal point
-accommodation is the ability to change the shape of your lens to change from far vision where the lens is relatively straight to close vision where the lens is very curved.
-You lose this ability with age.
define near point of vision
-The near point of vision is the closest point that you can still focus. It is very close to the eyes in the young and farther away in older people.
Describe the controls over eyeball movements
-voluntary fixation movement- premotor/ frontal lobe
-involuntary fixation movement- as the image becomes out of the field of view, the occipital lobe, eyes flicker back and forth, cannot hold eye still.
Describe binocular vision
-Each eye sees a slightly different field of view. This difference allows for judging distance/3D/depth
-If your eyes are not fixating in a coordinated fashion, such as after being drunk, the corresponding image does not land on the eyes' fovea centralis. You have double vision, or diplopia.
-Strabismus is when your eyes point different directions & with time you fix images with one eye and the other becomes functionally blind.
-Rhodopsin is the photopigment in rods requiring vitamin A for its synthesis.
Describe how the photoreceptors function
-As with any receptor, it turns light into depolarization response.
-Rods respond more to grays/blacks/whites and cones to bright colors.
Contrast rods and cones
-many more rods than cones.
-Rhodopsin is the photopigment (eating carrots) needed vit a to produce
-very sensitive to light, peripheral, night vision, poor detail, converge.
-are less numerous and are very dense in fovea centralis.
-centrally, There are red, green and blue responding cones but we see more colors due to the blending of these three cones.
-They are not very sensitive to light and work well in very bright light. They do not work well in the dark.
-no converge, so that each cone has its own "line" to the brain. very precise and clear images. That is why your fovea centralis is your spot with the most accurate vision because it is filled with numerous cones.
describe the neural components of the retina and explain lateral inhibition,
-Rods and cones synapse with bipolar neurons which synapse with ganglion cells. The ganglion cells actually comprise the optic nerve (cranial nerve II)
- Horizontal and amacrine cells reach between pathways and can inhibit weakly stimulated pathways (lateral inhibition).
Describe the visual pathway
-From the optic nerve, passing through the optic foramen, half of the pathway crosses at the optic chiasma.
-The pathway continues on as the optic tract, sends messages to the lateral geniculate body in the thalamus, (as well as the superior colliculi for visual reflex responses)
- then continues to the occipital lobe of the cerebral cortex for interpretation of the image.
Describe visual acuity
- accurate, to distinguish detail, measured by the 20/20 Snellen eye chart
Describe snellen eye chart
-the first number is you. If your vision is 20/60, you must stand 20 feet from the chart to see clearly what the "normal" person can stand 60 feet from the chart.
Describe visual resolving power.
-Visual resolving power is similar to acuity in that it is the ability to tell that 2 closely spaced points are indeed 2. It would be best if the image lands on fovea centralis where your receptors are the densest.
Describe mechanisms of light and dark adaptation
-The quickest response is pupillary constriction in bright light and then pupillary dilation in dark areas. -photopigment concentration, the smallest change in rhodopsin concentration in rods can influence light sensitivity. make/break down rhodopsin, but this does take a few minutes.
-If you make more rhodopsin you are more sensitive to the light and can see better in the dark. In bright light, you break down rhodposin.
Describe direct and indirect pupillary light reflexes
-Direct is ipsilateral. If you shine a light in your right eye, the right pupil constricts. However, the left also constricts and this contralateral response is the indirect reflex.
List the three parts of the external ear
-Outer ear contains the pinna (elastic cartilage)
-the ear canal = external auditory meatus
-the eardrum = tympanic membrane.
Where would one find ceruminous glands
-Ear canal, as these are earwax glands
Describe the location and functions of the auditory (eustachian) tube
-The auditory tube connects the middle ear with the throat. This allows pressure release in the middle ear, so that you don't explode your eardrum with too much pressure. (kids dont go straight down because they have a more rounded face)
List the parts of the middle ear, describe their functions
-(inside the tympanic membrane)
-Auditory= Eustachian tube
-equalizes air pressure in middle air
-3 ossicles (lateral to medial)- vibrate and amplify sound, Malleus, Incus, and Stapes bones (6 in total)
-he malleus touches the tympanic membrane and the stapes touches the oval window
-Oval Window- seperates middle and inner ear
-round window- at the end, bulges back into middle ear to keep inner ear pressure stable
List the parts of the inner ear, describe their functions
-Osseous Labyrinth (perilymph fluid)
-Membraneous labyrinth (endolymph fluid)
-saccule- (endolymph)- balance
-semicircular canals (3) (perilymph)- are placed at 90 degrees from each other. They are lined with the semi circular ducts
- have a widened portion called the ampulla.
-cochlear duct which houses the receptors for hearing.
-vestibular membrane- endolymph-upper
-Basilar membrane- endolymph- lower
-housed within the temporal bone.
Describe the location of perilymph and endolymph
-Perilymph is in bone
-endolymph is in membrane
Describe the mechanism of hearing.
-Sound waves are collected from the pinna, travel down the ear canal and vibrate the tympanic membrane.
-This in turn, vibrates the ossicles which magnify the sound wave.
- The stapes pushes against the oval window making the perilymph in the scala vestibuli move, which in turn makes the perilymph in the lower channel, the scala tympani, move.
-This causes the endolymph in the cochlear duct to move at the same frequency, thus stimulating the Organ of Corti that sits on the floor of the cochlear duct.
-This is the location of tiny hairs that will be stimulated according to the frequency of the sound wave.
-The hairs nearest the apex of the Organ are long and stimulated by low frequency (low tone) sound waves.
Those nearest the base of the Organ are short tiny hairs that respond to higher frequence pulses (high tones
Describe the tympanic reflex (sound attenuation)
- muscles dampen ossicle vibration in response to loud sound to protect against hearing loss
-mediated by the trigyminal (5) nerve
Explain how one determines the location, loudness and pitch of sound
-Location is based on the disparity between the two ears. If the sound were on the right, the sound waves reach the right ear first and is louder in the right ear.
-The loudness is the amplitude of the sound wave the strength of the sound wave.
-The pitch is based on the frequency of the sound wave with high frequency being high pitches.
Describe the mechanism for detecting linear acceleration and deceleration
-think of the marbles in water in a car example
-otoliths in the utricle and saccule move as you accelerate/decelerate thus bending the hair cells leading to a nerve impulse.
Describe the mechanism for detecting head position
- The otoliths in the urticle and saccule move as you move your head
Describe the mechanism for detecting rotational acceleration and deceleration
-otoliths in the urticle and saccule move as you move you move, the decelration causes dizzyness, because they are still moving. -initally enersha is the resistance to the movement, the hairs bend the opposite way
-the hair cells (=crista) in the ampulla of the semicircular ducts are stimulated leading to a nerve impulse.
-cupula- the gelatienous mass (endolympy
Explain vestibular nystagmus
- eyes stay fixed on objects while moving- its our brain trying to avoid dizzyness, to make sense of the spinning world
-If you are spinning to the right, your eyeballs move slowly to the left and then quickly catch up to you by flicking to the right.