Special Senses Flashcards
Sensory Receptors
- peripheral (distal) endings of sensory neurons
- specific for certain types of stimuli (ex: photoreceptors for light)
- depolarize neurons to produce action potential
Modality-based Receptor Classification
- Chemo-
- Thermo-
- Mechano-
- Photo-
- Noci-
- Baroreceptors
Stimulus Origin-based Receptor Classification
- interoreceptors - detect internal stimuli
- proprioceptors - body position/movement
- exteroceptors - detect external stimuli
Distribution-based Receptor Classification
General Senses - widely distributed
Special Senses - limited to head
General Senses
- temperature
- pain
- touch pressure
- vibration
- proprioception
Special Senses
- smell
- taste
- vision
- equilibrium
- hearing
What makes a sense “special”?
- localized (confined to head)
- special receptor cells
- housed in complex sensory organs or epithelial structures
- cranial nerves carry special sensory info to brain
Chemical Senses
- Chemoreceptors that respond to chemicals binding to them
- Taste - gustation
- Smell - olfaction
Taste Bud
- 50-100 epithelial cells in a bundle containing long microvilli that receive chemicals from food that create flavors
surface elevations of tongue
Tongue Papillae
- contain taste buds
light blue lateral cells
supporting cell of taste bud
central purple cells
gustatory cell
- taste receptor cells
- have long microvilli known as gustatory hairs that extend through taste pores
Gustatory Pathway
- taste info travels primarily via Facial (VII) and Glossopharyngeal (IX) nerves (some via Vagus (X))
- primary sensory neurons synapse in solitary nucleus of medulla
- secondary neurons synapse in thalamus
- tertiary neurons synapse in gustatory cortex of cerebrum
olfactory epithelium
- specialized nasal cavity epithelium containing olfactory receptor cells
purple structure
olfactory neuron
- specialized chemoreceptive cell in olfactory epithelium
- bipolar, basal side has axon, apical side has cilia
- axons gather into bundles that make up olfactory nerve, pass through ethmoid (olfactory foramina of cribriform plate), attach to olfactory bulbs of forebrain
pink structure
supporting cells
- columnar cells that support olfactory neurons
small green inferior structure
Basal Cell
- form new olfactory neurons
orange structure towards bottom
basal cell
- replace gustatory cells
large yellow structure
olfactory bulb
- structure on inferor side of frontal lobes that sits above cribriform plate of ethmoid bone and connects with olfactory nerve filaments
Olfaction Pathway
- Olfactory Bulb
- Olfactory Tract
- then to 3 areas of brain:
- Limbic Region (associate smell w/ emotion)
- Piriform Lobe of Cortex (conscious perception)
- Thalamus and Orbitofrontal Cortex (analysis and comparison of smell)
olfactory tract
not the muscle, but the structure it moves
Palpebrae
- AKA eyelids
- one upper, one lower per eye
Medial and Lateral Canthi (singular: canthus)
- AKA medial/lateral angles
levator palpebrae superioris
- muscle that opens eyelid
thin layer on anterior whites of eyes and inside eyelids
conjunctiva
- straitified squamous epithelium that produces lubricating mucus
- in eyelids, called Palpebral conjunctiva
number 1
Lacrimal gland
- produces tears
- contains lysozyme, a bactericidal enzyme
lacrimal puncta
- tiny openings for lacrimal fluid to drain into
number 5
lacrimal caruncle
- small, pink, globular nodule at the inner corner of eye
- contains sebaceous and sudoriferous glands
- source of “eye boogers”
6
superior oblique muscle
- depresses eye, turns it laterally
8
inferior oblique muscles
- elevates eye, turns it laterally
2
superior rectus muscle
- elevates eye, turns it medially
3
inferior rectus muscle
- depresses eye, turns it medially
4
medial rectus muscle
- moves eye medially
5
lateral rectus muscle
- moves eye laterally
Lacrimal Apparatus
system for keeping eye’s surface moist
- three parts:
- lacrimal gland
- lacrimal sac
- lacrimal fluid
lacrimal sac
area just medial to eye where lacrimal fluid gathers and empties into nasal cavity
lacrimal fluid
- made up of mucus, antibodies and lysozyme
7
Trochlea
- point where superior oblique muscle is anchored above eye
Three Tunics of the Eye
Fibrous - sclera and cornea
Vascular - choroid, ciliary body, iris
Sensory - retina
Fibrous Tunic
- most external layer
- two regions:
- Sclera
- Cornea
Vascular Tunic
3 parts:
- Choroid
- Ciliary Body
- Iris
Sensory Tunic
- AKA Retina
two layers:
- pigmented layer
- neural layer
1
Sclera
- poster 5/6s of fibrous tunic
- white, opaque
- gives eye shape, anchors eye muscles
8
Cornea
- anterior 1/6 of fibrous tunic
- transparent, coveres iris and pupil
- avascular, innervated
5
scleral venous sinus
AKA Schlemm’s Canal
- large blood vessel near junction of sclera and cornea
- drains aqueous humor
28
Choroid
- vascular, darkly pigmented membrane of vascular tunic
- prevents light from scattering within eye
- middle layer between sclera and retina
structure composed of #3 and #12
ciliary body
- thickened ring of smooth muscle tissue encircling lens
- made of ciliary muscles and processes
3
ciliary muscle
muscles of ciliary body that alter lens shape
12 (folds covering ciliary muscle)
Ciliary Processes
- folds of epithelium
- secrete aqueous humor
4
suspensory ligaments
AKA ciliary zonule
- extend from ciliary body to lens, allowing ciliary muscle to move lens
7
Iris
- contractile smooth muscle structure:
- Circular sphincter muscle
- Radial dilator muscle
- colored part of eye
- attached to ciliary body
- regulates amount of light entering eye
8
pupil
- opening in iris through which light enters
- controlled by iris
30
retina
- layer lining back of interior of eye
- contains photoreceptors
- contains two layers:
- pigmented layer - melanocytes
- neural layer - rods, cones, bipolar cells, ganglion cells
jagged portion here where choroid meets ciliary body
ora serrata
- posterior margin of ciliary body, where neural layer meets front of eye
25
macula lutea
- yellowish region of retina
- small pit at center of posterior pole
- area of maximum visual acuity
26
fovea centralis
- the center of the macula
- contains only cone cells
- region of highest visual acuity
18
optic disc
AKA blind spot
- lacks neurons
- where optic nerve exits eye
10 and #11
Lens
- transparent body behind iris and pupil, in front of vitreous humor
- focuses light onto retina
- made up of lens fibers produced by lens epithelium
22
optic nerve
- cranial nerve II
- carries signals from eye to optic chiasm
1
pigmented layer of retina
- layer of melanocytes between retinal neurons and choroid
2-9
Neural Layer of Retina
- contains 3 types of cells:
- photoreceptors
- bipolar cells
- ganglion cells
entire structure
rod cell
- more sensitive to light
- allows vision in dim light
entire structure
cone cell
- operate best in bright light
- allows high-acuity color vision
structure shown in red
bipolar cells
- bipolar neurons which transmit signals from photoreceptor cells to ganglion cells
leftmost, darker structures
Ganglion Cells
- outermost neurons of retina whose axons exit at optic nerve to carry visual stimuli to brain
visible outer ear
Pinna
- AKA auricle
- collects sound, directs it to outer ear canal
indicated by black line
external auditory canal (or acoustic meatus)
- tube through which sound travels to eardrum
tympanic membrane
AKA eardrum
- vibrates when soundwave hits it
- separates outer and middle ear
malleus
- AKA hammer
- passes vibrations from eardrum to anvil
Incus
- passes vibrations from malleus to stapes
stapes
- AKA stirrups
- tiny U-shaped bone that passes vibrations from anvil to cochlea
- smallest bone in body
reddened area
auditory tube
AKA Eustachian tube or pharyngotympanic tube
- connects middle ear to back of nose
- equalizes pressure between midle ear and outside air
round window
- located below where stapes meets oval window
- moves outward as sound moves oval window inward to allow for movement of fluid within cochlea
middle hole in structure
oval window
- membrane between middle ear and vestibule of cochlea
- stapes fits into and vibrates it, transmitting sound into cochlea
14
Vestibule
- detects acceleration and deceleration of head via macula
- central part of bony labyrinth
- contains utricle and saccule, egg-shaped parts of membranous labyrinth
1, #7, and #8
semicircular canals
- contain three loops of fluid-filled tubes attached to cochlea via vestibule
- detect rotational head movement via crista ampullaris
Portion of structure at right containing 5, 6, 12 and 13
cochlea
- contains spiral-shaped, fluid-filled inner ear structure
- detects vibration of sound waves and creates nerve impules
membranous labyrinth structures
semicircular ducts
- detect rotational movement of head
9, 3 and 2
Ampulla
- expanded region of each semicircular duct which contains the sensory structure that detects rotational movement of the head
whole structure
crista ampullaris
- strcture within ampulla that contains receptor hair cells to detect rotational movement of head
top part marked A
cupula
- jelly-like, pointed structure on top of crista ampullaris into which hairs of receptor cells project
part of vestibule just at base of semicircular ducts
utricle
- part of membranous labyrinth within bony vestibule
- contains sensory epithelium to detect gravity and linear acceleration
4
saccule
- part of membranous labyrinth within bony vestibule
- contains sensory epithelium to detect gravity and acceleration
whole structure
Macula
- within utricle and saccule
- contains receptor cells (hair cells) with cilia (many stereo-, one kino-)
- monitor the position of the head when still (static equilibrium) and moving linearly
- cilia of cells stick into otolithic membrane
this is a cross section of which portion of the membranous labyrinth?
cochlear duct
- AKA scala media
- contains receptors for hearing
Which nerve innervates the inner ear and what are its two branches?
Vestibulocochlear Nerve (VIII)
- vestibular branch
- cochlear branch
- seen below in yellow
blue area
scala vestibuli
- superior chamber of bony labyrinth of cochlea
black arrow
vestibular membrane
- roof of cochlear duct between it and scala vestibuli
3
scala tympani
- inferior chamber of bony labyrinth of cochlea
complex structure within central chamber
Spiral Organ or Organ of Corti
- at floor of scala media
- contains hearing receptors in thick sensory epithelium
the light blue part underlying the complex structure
basilar membrane
- sheet fibers which support the organ of Corti
- pressure waves in the fluid of the inner ear cause this membrane to bounce, disrupting the sensory cells above it
whole brown structure
hair cell
- cells of organ of corti with many apical stereocilia which detect sound via vibrations
6
tectorial membrane
- gelatinous structure over hair cells in the organ of corti
- keeps hair cells in place via their embedded cilia which bend when vibrated, causing them to release neurotransmitters
- fluid within chambers 2 and 3
Perilymph
- fluid in the bony labyrinth which surrounds and protects the membranous labyrinth
- continuous with CSF in subarachnoid space
fluid within cavity 1
endolymph
- clear fluid in membranous labyrinth
- pictured here in cochlear duct, but is also in utricle, saccule and semicircular ducts
