Special senses Flashcards
1
Q
What are the General senses receptors?
A
- Chemoreceptors
- Mechanoreceptors
- Thermoreceptors
- Nociceptors
- PHOTORECEPTORS→melanocytes found to contain rhodopsin, which responds to light
2
Q
What are the Special senses receptor types?
A
- Chemoreceptors
- Mechanoreceptors
- Photoreceptors
3
Q
What is the purpose/what are Receptors?
A
- In order to detect a stimulus, there must be a receptor –
something to receive the information - Receptors are:
- Sensory nerve endings or
- Specialized cells adjacent to sensory nerves
4
Q
What are sensory pathways?
A
- A stimulus (light, sound, taste, etc) generates a receptor
potential - Receptor potentials can be weak or strong, unlike action
potentials which are all-or-none - The receptor potential triggers an action potential in the sensory nerve
- Action potential travels to the brain where it is ”sensed”
5
Q
What are Mechanoreceptors?
A
Mechanoreceptors: detect changes in pressure or movement;
-Ex. pressure receptors in skin, proprioceptors in muscles and joints
6
Q
What are Thermoreceptors?
A
Thermoreceptors: detect temperature change
7
Q
What are Nociceptors?
A
Nociceptors: detect pain
8
Q
What are Chemoreceptors?
A
Chemoreceptors: detect changes in chemical concentrations;
- Ex. taste buds and olfactory receptors
9
Q
What are Photoreceptors?
A
Photoreceptors: detect light energy;
-Ex. the eye
10
Q
Where are special senses located?
A
*Special senses are localized and confined to the head region
- The receptors are specialized receptor cells
11
Q
How is Taste (Gustation) recepted?
A
- Taste receptors are found taste buds in the mucosa of the mouth and pharynx
- Taste buds are found on tongue, posterior palate, pharynx, inside of cheeks, posterior wall of pharynx, and the epiglottis
- Most taste buds are found in papillae on tongue
12
Q
What are the types of the papillae that contain taste buds?
A
Papillae that contain taste buds:
* Vallate (circumvallate) papillae
- Inverted “V” on back of tongue
* Fungiform papillae
- Scattered throughout surface of tongue
* Foliate papillae
- Posterolateral surface of tongue
13
Q
What are the components of taste buds?
A
*Each papilla has many taste buds (except filiform papillae)
*Each taste bud is made of 50-100 epithelial cells:
- Gustatory epithelial cells (taste)
– Have long microvilli called gustatory hairs that extend through taste pore
- Basal epithelial cells (replace old and damaged cells every 7-10 days)
14
Q
What are the components of taste?
A
*Dissolved molecules in saliva enter taste pore
*Molecules bind to receptors on gustatory hair cells
*Action potentials are generated, sensory neurons stimulated, signals sent to CNS
*Types of tastes:
- Sweet
- Sour
- Salty
- Bitter
- Umami
*These different tastes occur all over the tongue (taste map is incorrect)
15
Q
How do smell and taste work together?
A
*Flavor = combination of taste, smell, and texture
*Smell and taste work hand-in hand
- Food has less taste when you have a cold
- Good smells stimulate appetite; bad smells do not
16
Q
What is the Gustatory Pathway in brain?
A
*Taste receptors→sensory nerve fibers in cranial nerves →brainstem →thalamus →gustatory cortex (insula)
17
Q
What is Olfaction (Smell)?
A
*Olfactory receptors are in the olfactory epithelium (pseudostratified columnar) that covers superior nasal concha and the superior part of nasal septum
*Millions of bipolar neurons = olfactory sensory cells
*Olfactory stem cells
- Continually form new olfactory sensory neurons
18
Q
What are the components of Olfactory Receptors?
A
- Each bipolar olfactory neuron
- Has an apical dendrite that is near surface of epithelium
– Has olfactory cilia (hairs)—location of chemoreceptors - Mucus traps and dissolves molecules from inhaled air
- Chemical binds to chemoreceptor and activates olfactory sensory neuron
- Extensions of sensory neurons = filaments of olfactory nerve
- Enter CNS through cribriform plate of ethmoid bone
- Synapse with mitral cells in olfactory bulb at glomeruli
19
Q
What is olfaction?
A
*Extensions from mitral cells relay olfactory information via olfactory tract to
1. Limbic system
- Smells elicit emotions and memories
2. Primary olfactory cortex in temporal lobe
20
Q
What is Chemical Sense Disorders?
A
Olfactory disorders are most common (compared to taste disorders)
* Anosmia = absence of smell
- Blow to head/whiplash
- Colds/allergies
- Zinc deficiency
* Uncinate fits = olfactory hallucinations
- Brain disorders
21
Q
Components of vision?
A
Vision
*Humans use vision as our dominant sense
*70% all sensory receptors in our body are located in our eyes
22
Q
What are the Accessory Structures of the Eye?
A
- Eyebrows
- Shade eyes from sunlight
- Prevent sweat from running into eyes
- Palpebrae = eyelids
- Have eyelashes at free margin
– Keep foreign objects out of eye
– Very sensitive→blinking reflex - Sebaceous glands in palpebrae
–Lubricate surface of eye
– Those associated with eyelashes can get infected = sty
- Have eyelashes at free margin
- Palpebral fissure
- Space between eyelids
- Lacrimal caruncles
- Pink raised portion; medial angle
23
Q
Surface Anatomy of the Eye?
A
Conjunctiva
* Transparent mucous membrane
* Covers inner surface of eyelids and anterior surface of eyeball (except cornea)
* Conjunctivitis (very contagious)
24
Q
Tear Production
A
Lacrimal apparatus is made of the lacrimal gland and ducts that drain lacrimal fluid
* Lacrimal gland
- Superolateral region of the orbit
- Serous cells produce lacrimal fluid = tears
– Contains mucus, antibodies, and lysozyme (destroys bacteria)
- Fluid washes irritants away from eye surface
25
Tear Drainage
Tears move across eye, enter puncta
* Drain into lacrimal canaliculi, then
* Lacrimal sac →
* Nasolacrimal duct →
* Nasal cavity
26
What is the Extrinsic Eye Muscles?
*Movement of each eye is controlled by 6 extrinsic eye muscles
*Skeletal muscles
*Attach to outer surface of the eyeball (sclera)
27
What is Strabismus?
*Strabismus = misaligned eyes (cross-eyed)
*Caused by a problem with one or more of extrinsic eye muscles
*Eyes do not align properly
*Some results:
- Double vision
- Lack of stereoscopic (3-D) vision
- Amblyopia (reduced vision in the weaker eye “lazy eye”)
28
What are the layers of the eye?
3 tunics (= layers)
*Fibrous tunic (outermost)
*Vascular tunic
*Sensory tunic (innermost)
29
What is the Fibrous Tunic?
*Outermost layer
*Extension of dura mater
*Provides protection and mechanical support
*Avascular
*Parts
- Sclera (dense irregular CT→opaque)
- Cornea (dense regular CT→transparent)
*Sclera is covered by conjunctiva
- Mucous membrane (stratified columnar with goblet cells)
30
What is Vascular Tunic?
*Middle tunic
Parts
* Choroid: vascular, dark surface absorbs excess light
* Iris is made of smooth muscle
- Contracts and enlarges to regulate light entry to eye ball →pupil changes size
- Melanocytes (brown pigment, eye color)
31
What makes eyes darker in color?
Darker colored eyes have more pigment in anterior region of iris. Light eyes have little to no pigment in the anterior region.
32
What is the ciliary body of the Vascular Tunic?
Ciliary body
* Ciliary muscle
- Smooth muscle
*Suspensory ligaments
*Controls the shape of the lens (which focuses light onto the back surface of the eye)
*Capillaries within produce aqueous humor
33
What is Accommodation?
* The lens changes shape when looking at things up close = accommodation
* Close objects (parasympathetic control)
- Ciliary muscle contracts
- Suspensory ligaments slacken
- Lens becomes round
* Distant objects (sympathetic control)
- Ciliary muscle relaxes
- Suspensory ligaments become taut
- Lens is flattened
* With age, the lens becomes less elastic →presbyopia
- Bifocals or reading glasses are needed
34
What is Sensory Tunic?
*Innermost tunic
*Two layered structure:
1. Pigmented layer (next to choroid)
* Single epithelial layer, contains melanin granules
* Absorbs light
* Nourishes neural layer
2. Neural layer (in contact with lumen of eye)
* Three types of neural cells
- Photoreceptor cells
- Bipolar cells
- Ganglion cells
35
What are Rods of the Neural Layer of Retina?
Photoreceptors (activated by light)
*Rod cells
- Most numerous (~120 million per eye)
- Most sensitive to light (good for night vision)
- Most numerous in periphery of retina (sides)
36
What are cones of Neural Layer of Retina?
Photoreceptors (activated by light) = Cone cells
* Color vision
* 3 subtypes that respond to different
types of light:
- Blue light
- Red light
- Green light
* Work best in bright light (do not function well in low light)
* Concentrated in central part of retina (straight back)
37
What are Bipolar cells of Neural Layer of Retina?
Bipolar cells
* Activated by rods and cones
38
What are Ganglion cells of the Neural Layer of Retina?
Ganglion cells
* Activated by bipolar cells
* Axons of ganglion cells transmit impulse to brain through optic nerve
39
Path way of light through retina
*Photoreceptors activate bipolar cells →bipolar cells activate ganglion cells →axons of ganglion cells form optic nerve →brain
40
What is the purpose of Photoreceptors?
*Different types of cells contain different pigments
*Pigments are broken down by different wavelengths of light
41
What is Circadian Photoreception?
Some cells in the retina are not involved with vision
* They contain a protein called melanopsin
* Signals from these cells don’t go to the visual cortex but to the circadian clock
region of the brain (suprachiasmatic nucleus)
* The suprachiasmatic nucleus influences the pineal gland to release melatonin
- Input from the melanopsin cells signals daylight →no release of melatonin
*BTW, melanopsin is most sensitive to blue light
- Why it is not a good idea to look at your phone or computer screen late at night
42
What is the Visual Pathway?
*Optic nerve →optic chiasma →optic tract→thalamus →optic radiations→occipital lobe (primary visual cortex)
43
What is the optic disc?
Optic disc
* Location at back of eye where axons of ganglion cells leave eye
* Called blind spot
* No photoreceptors
44
what is the internal structure of the eye?
*Fovea centralis is located in the center of the macula lutea
- Only cones
- Greatest visual acuity here
- Why central vision is sharpest
*Age-related macular degeneration (AMD)
- Progressive deterioration of macula lutea portion of the retina
45
What are the fovea centralis and macula lutea?
*The fovea centralis is in the middle of the macula lutea
*The goal is for light that enters the eye to land on the fovea centralis
- There are only cones here
- Greatest visual acuity
*If the focal point does not land on the
fovea centralis, then the image is
blurry
46
What is the lens of the eye?
*Simple cuboidal epithelium along anterior surface
*Concentric layers of fibers produced by epithelial cells
*Ciliary body changes shape to focus light on fovea centralis
*Separates anterior segment from posterior segment of eye
- Anterior segment contains aqueous humor
- Posterior segment contains vitreous humor
47
What is the anterior segment?
Anterior segment
*Anterior 1/3 of eye (cornea to lens)
*Has two chambers:
- Anterior chamber
-- Anterior to iris
- Posterior chamber
-- Between iris and lens
48
What is the Aqueous Humor?
Anterior segment is filled with aqueous humor
*A blood filtrate from ciliary bodies
*Supplies nutrients and oxygen to lens and cornea
*Removed by scleral venous sinus
49
Process of the aqueous humor?
Ciliary processes of ciliary body
1. Produces aqueous humor
2. Aqueous humor circulates through anterior segment of eye
3. Scleral venous sinus Removes aqueous humor
50
What is Glaucoma?
*Condition where aqueous humor is drained slower than it is produced
*Increases intraocular pressure
* Damages optic nerve
* Leading cause of irreversible blindness in the world
51
What is the Posterior Segment?
*Poster 2/3 of eyeball
*Behind lens
*Contains vitreous humor
- 98% water
- Collagen (much more viscous than aqueous humor)
- Supports lens and retina
- Helps maintain shape of eyeball
52
Emmetropic eye
Emmetropic eye
* Normal vision
* Light focuses on retina (fovea centralis)
53
Myopic eye
Myopic eye
* Nearsighted (can see things up close, not far)
* Eye may be too long, image focuses in front of retina
* Correction: concave lens
54
Hyperopic Eye
Hyperopic Eye
* Farsighted (can see things far away, not close)
* Eye may be too short, image focuses behind retina
* Correction: convex lens
55
Presbyopia
Presbyopia
* Lens becomes less elastic with age—need bifocals
56
What is lasik surgery?
*Surface of cornea is reshaped using a laser
*This functions to re-direct light properly onto retinal surface
57
What is Astigmatism?
*Abnormal shape of corneal surface causes light rays to diffract differently
*Result: two or more focal points
58
What is a Detached Retina?
*A hole or small tear in the retina allows vitreous humor to leak between the pigmented and neural layers of retina
*Photoreceptor cells will eventually die if neural layer is not reattached to the nourishing underlying layer
59
What is a Cataract?
Lens becomes cloudy
* Most commonly due to age-related damage to the internal part of lens
* Excessive sunlight, smoking, oral steroids can contribute
* Treatment: lens replacement
60
What is the Snellen Eye Chart?
*For accurate results chart must be of correct size and individual must stand 20 feet away and read smallest line they can
*20/20 vision: individual can read from 20 feet what the “normal” eye can
*20/50 vision: individual can read from 20 feet what the normal eye could read from 50 feet
61
What is the ear?
*Sensory functions:
- Hearing
- Balance and equilibrium
*Divided into 3 regions:
- External ear
+ Collects and directs sound waves
- Middle ear
+ Amplifies and transmits sound waves
* Internal (inner) ear
+ Location for sensory organs for hearing and equilibrium
62
What are the External Ear Structures?
*From auricle up to tympanic membrane
(= eardrum)
*Auricle (pinna)
*External acoustic meatus
63
What is the Auricle?
*Auricle (pinna)
- Outer fleshy portion; provides protection
- Made of elastic cartilage
-- Ridges and cavities help the brain to locate where sounds are coming from
- Earlobe = lobule (no cartilage)
64
What is the External acoustic meatus?
External acoustic meatus
* Air-filled canal
* Stratified squamous epithelium lines canal
* Hairs keep insects and foreign material out
* Ceruminous glands and sebaceous glands
- Secrete cerumen (wax) which inhibits microorganism growth, traps dust, repels insects
65
What is the Middle Ear?
*The middle ear extends from the tympanic membrane to oval window
*Contains the auditory ossicles
- Malleus
-- Attached to tympanic membrane
- Incus
- Stapes
-- Attached to oval window
66
What is the Pharyngotympanic tube?
*Pharyngotympanic tube (eustachian tube) connects middle ear with pharynx
- This allows for throat infections to move to the middle ear (= otitis media)
- A myringotomy may be needed to drain excess pus
67
What are the ossicles?
*The ossicles amplify the pressure from the sound vibrations 20-fold at the oval window
*Two skeletal muscles help dampen sound
- Tensor tympani attaches to malleus
- Stapedius attaches to stapes
68
What is the internal ear made of?
1. The bony labyrinth
2. The membranous labyrinth
69
What is the bony labyrinth?
The bony labyrinth
* Cavity in the petrous portion of temporal bone
* Parts are:
- Semicircular canals
- Vestibule
- Cochlea
70
What is the membranous labyrinth?
The membranous labyrinth
* Continuous series of membrane-walled sacs and ducts that fit loosely within bony labyrinth
* The membrane is thin layer CT lined with simple squamous epithelium
- Some thickened regions contain receptors for equilibrium and hearing
Components of membranous labyrinth
* Semicircular ducts (in semicircular canals)
* Utricle and saccule (in vestibule)
* Cochlear duct (scala media) (in cochlea)
71
What is the Endolymph and Perilymph?
* The membranous labyrinth structures are filled with clear liquid = endolymph
- Outside membranous labyrinth is perilymph that is continuous with CSF in subarachnoid space
-- Perilymph and endolymph do not meet
72
What is Cochlea and Cochlear Duct?
*The cochlea is a very small (size of a split pea), spiraling chamber
- The coiling is around a central pillar of bone = modiolus
- The cochlear nerve is located in the modiolus
*The cochlear duct (scala media) is within the cochlea
*Cochlear duct has sensory receptors for hearing
73
What are the components of Cochlear Duct?
*Cochlear duct (also called scala media) is filled with endolymph
- This duct is between two perilymph-filled chambers: scala vestibule and scala tympani
*The base of the cochlear duct sits on the basilar membrane
74
What is the Spiral Organ?
*The spiral organ (= organ of Corti), inside the cochlear duct, has
- One row of inner hair cells and
- Three rows of outer hair cells
*Stereocilia at the tips of hair cells are embedded in tectorial membrane
*At base of hair cells are the fibers of the cochlear nerve
-These bipolar neuron cell bodies are in the spiral ganglion in the modiolus
75
What is the Role of Cochlea in Hearing?
*Sound waves vibrate tympanic membrane
*Ossicles vibrate, pressure is amplified
*Stapes pushes on oval window
* Perilymph in scalavestibuli moves/vibrates
* Sound waves in hearing range go through cochlear duct
- Basilar membrane vibrates
- Tectorial membrane does not move
- Stereocilia on inner hair cells are bent
* Action potentials stimulate cochlear nerve
76
High Pitch versus Low Pitch Sounds
*The frequency (pitch) of the sound waves will cause deflection of the basilar membrane at different places
- Low pitch (low frequency) sounds deflect deep into cochlea
- High pitch (high frequency) sounds deflect near entrance of cochlea
77
What is the Inner versus Outer Hair Cells?
*Both are located in spiral organ
*Inner hair cells
- True receptors, transmit vibrations of basilar membrane to cochlear nerve
*Outer hair cells
- Tune and amplify signal (100X)
-- Helps us hear faint signals
- Can produce otoacoustic emissions
-- Sounds from ear
-- Used to test hearing in newborns
78
What is Utricle and Saccule?
* Are membranous structures found within a bony vestibule
* Both contain a macula
- Region of sensory epithelium
* Utricle
- Responds to acceleration in a horizontal direction
-- Forward acceleration and deceleration
-- And head tilt (“yes”)
* Saccule
- Responds to verticalmovements
-- Up and down in an elevator
79
What is Maculae?
Structures of maculae:
* Hair cells
* Supporting cells
* Otolith membrane
* Otoliths
80
components of hair cells of maculae?
Hair cells
* Mechanoreceptor cells that respond to movement
* Stereocilia
– Extensions of hair cells that areembedded in otolithic membrane; initiate an impulse when bent
81
Components of supporting cells of the maculae?
Supporting cells
* Simple columnar epithelium that
provides protection & support
82
Components of Otolith membrane of the maculae?
Otolith membrane
* Jelly like disc that sits atop sensory epithelium & shifts in response to movement (bend stereocilia)
83
Components of Otoliths membrane of the maculae?
Otoliths
* Calcium carbonate crystals that add weight to membrane and cause more dramatic shift
84
What are the Semicircular Canals and Ducts?
*The membranous semicircular ducts are within the bony semicircular canals
*Are involved with rotational acceleration of the
head
*Each duct has a swelling = membranous ampulla
85
What are crista ampullaris?
*Inside each membranous ampulla is a crista ampullaris
- Contain receptor cells that measure rotational acceleration
86
What are the structures of the crista ampullaris?
Structures of crista ampullaris:
* Supporting cells: simple columnar epithelium; support & protect hair cells
* Hair cells: mechanoreceptors; respond to rotational forces
* Stereocilia: extensions of hair cells that are embedded in ampullary cupula; initiate an impulse when bent
* Ampullary cupula: gelatinous mass that “tips” under rotational forces , bending the stereocilia
