Special Senses Flashcards
1
Q
Special senses
A
- smell, taste, vision, hearing, equilibrium
- housed in complex sensory organs
- olfaction and gustation: chemical receptors
2
Q
Olfactory epithelium
A
-covers superior nasal cavity and cribriform plate of the ethmoid bone
3
Q
Olfaction: sense of smell cells
A
- olfactory receptor cells
- bipolar neurons with non motile cilia
- contain olfactory receptors
- supporting cells
- columnar epithelium
- basal cells: stem cells
- replace receptors monthly
- olfactory (bowmans glands)
4
Q
Olfactory pathway
A
- axons from olfactory receptors from the olfactory nerves (cranial nerve I) that synapse in the olfactory bulb
- pass through foramina in cribriform plate
- second order neurons within the olfactory bulb for the olfactory tract that reaches the olfactory cortex
- olfactory sensation are the only sensation that reach the cerebral cortex without first synapsing in the thalamus
- some fibres form the olfactory tract project to the limbic system
- emotional response to odors
5
Q
Gustatory Sensation: taste
A
- taste requires dissolving of substances
- five classes of stimuli: sour, bitter, sweet, salty, and unami
- taste buds found on tongue, soft palate and epiglotis
- found on sides of gallate, foliage and fungiform papillae
6
Q
Anatomy of taste buds
A
- an oval body consisting of 3 cell types: supporting, receptor and basal
- supporting cells: contain microvilli and surround a group of about 50 gustatory receptor cells
- gustatory receptor cells: have gustatory microvilli that pass to the external surface through the taste pores
- basal cells: stem cells that produce supporting cells. The supporting cells then develop into gustatory receptor cells, which have a life span of about 10 days
7
Q
Why do you lose your sense of smell/taste when sick
A
- flavour of food involves both smell and taste
- odors from food pass upward from the mouth into the nasal cavity, where they stimulate olfactory receptors
- olfaction is much more sensitive than taste
- when you are sick your olfaction is blocked
8
Q
Gustatory pathway
A
- dissolved substance contacts gustatory hairs
- nerve impulse formed in 1st order neuron
- first order gustatory fibres found in cranial nerves
- CN VII (facial) serves posterior 1/3 of tongue
- CN IX (glossopharyngeal) serves posterior 1/3 of tongue
- CN X (vagus) serves palate and epiglottis
- signals travel to brain steam and thalamus or limbic system and hypothalamus
- taste fibres extend from the thalamus to the primary gustatory area on parietal lobe of the cerebral cortex
- providing conscious perception of taste
9
Q
Visual sensations
A
- accessory structures of the eye
- eyelids protect and lubricate eye
- eyelashes and eyebrows protect from foreign materials, perspiration and sunlight
- lacrimal glands
- palpebral fissure is gap between the eyelids
- sebaceous glands found at base of eyelashes
10
Q
Lacrimal apparatus
A
- about 1 ml of tears produced per day.
- spread over eye by blinking
- contains bactericidal enzyme called lysozyme
11
Q
Extraocular muscles
A
- muscles that move the eyeball
- innervated by CN III IV & VI
- superior rectus muscle
- interior oblique muscle
- inferior rectus muscle
12
Q
Tunics (layers) of eyeball
A
- fibrous tunic (outer layer)
- vascular tunic (middle layer)
- nervous tunic (inner layer)
13
Q
Fibrous tunic - cornea
A
- nonvascular
- transparent
- helps focus light
- parallel collagen fibres
- transplants are common, no blood vessels so no antibodies to cause rejection
- nourished by tears and aqueous humour
14
Q
Fibrous tunic - Sclera
A
- white of eye
- dense irregular connective tissue layer: collagen and fibroblasts
- provides shape and support
- at the junction of the sclera and cornea is an opening (sclera venous sinus)
- posteriorly pierced by optic nerve (CN II)
15
Q
Vascular Tunic - choroid
A
- pigmented epithelial cells (melanocytes) and blood vessels
- provides nutrients to retina
- black pigment in melanocytes absorb scattered light
16
Q
Vascular tunic: ciliary body
A
- ciliary processes
- folds on ciliary body
- secrete aqueous humour
- ciliary muscle
- smooth muscles that alters shape of lens
- suspensions ligaments attach lens to ciliary process
- ciliary muscle contrails tension on ligaments and lens
17
Q
Vascular tunic: iris
A
-coloured portion of eye
-shape of flat donut suspended between cornea and lens
-hole in centre is pupil
Function is to regular amounts of light entering eye
18
Q
Vascular tunic: muscles of iris
A
- constrictor pupillae (circular) are innervated by parasympathetic fibres while dilator pupillae are innervated by sympathetic fibres
- response varies with different levels of light
19
Q
Iris recognition
A
- method of biometric authentication
- use intricate structures of the iris (crypts, folds, ridges) which constitute and distinctive fingerprint
20
Q
Description of lens
A
- avascular
- crystallin proteins arranged like layers in an onion
- clear capsule and perfectly transparent
- lens held in place by suspension ligaments
- focuses light on retina
21
Q
Cataract
A
-lens is normally transparent and avascular but with ageing, congenital abnormality, trauma or inflammation, damage of lens fibres –> opacity of lens
22
Q
Nervous tunic
A
- posterior 3/4 of eyeball
- macula lutes with central fovea
- optic disc
- optic nerve exiting back of eyeball
23
Q
Layers of retina
A
- pigmented layer
- no visual portion
- absorbs stray light and helps keep image clear
- neural layer
- 3 layers of neurons (outgrowth of brain)
- photoreceptors layer
- bipolar neuron layer
- ganglion neuron layer
- other cell types (modify the signal)
24
Q
Rods and cones
A
- rods
- 120 million rod cells
- discriminates shape and movement
- shades of gray in dim light
- distributed along periphery
- cones
- 6 million
- sharp vision, colour
- fovea of macula lutes
- densely packed region
- at exact visual axis of eye
- sharpest resolution of acuity
25
Cavities of interior eyeball
- anterior cavity (anterior to lens)
- filled with aqueous humour
- produced by ciliary body
- 2 chambers: anterior chamber between cornea and iris, posterior chamber between iris and lens
- posterior cavity
- filled with vitreous body
- formed once during embryonic life
- floaters are debris in vitreous of older individuals
26
Aqueous humor
- continuously produced by ciliary body
- flows from posterior chamber into anterior through the pupil
- sclera venous sinus
- canal of schlemm
- opening in white of eye at junction of cornea and sclera
- drainage of aqueous humor from eye to bloodstream
- glaucoma
- increased intraocular pressure that could produce blindness
- problem with drainage of aqueous humor
27
Brain pathways of vision
Optic nerve > optic chiasm > optic tract > lateral geniculate > optic radiation > primary visual cortex in occipital lobe
28
External ear
- collects sound
- auricle pinna: elastic ear cartilage covered with skin
- external auditory canal
- curved tube of cartilage and bone leading into temporal bone
- ceruminous glands produce cerumen (ear wax)
- tympanic membrane (eardrum)
- epidermis, collagen and elastic fibres
29
Middle ear cavity
- air filled cavity in the temporal bone
- separated from external ear by eardrum (tympanic membrane) and from internal ear by oval and round window
- 3 ear ossicles connected by synovial joints
- auditory tube leads to nasopharynx
- helps to equalize pressure on both sides of eardrum
- malleus attached to eardrum, incus & stapes attached by footplate to membrane of oval window
30
Muscles of the ear
- stapedius m. Inserts to stapes
- prevents very large vibrations of stapes from loud noises
- tensor tympani attaches to malleus
- limits movements of malleus and stiffens eardrum to prevent damage
31
Inner ear - bony labyrinth
- set of tube-like cavities in temporal bone
- semicircular canals, vestibule and cochlea lines with periosteum and filled with perilymph
- surrounds and protects membranous labyrinth
32
Inner ear - membranous labyrinth
- set of membranous tubes containing sensory receptors for hearing and balance
- filled with endolymph
33
Cochlear anatomy
- 3 fluid filled channels found within cochlea
1. Scalia vestibule
2. Scala tympani
3. Cochlear duct
- partitions that separate the channels are Y shaped
- vestibular membrane above & basilar membrane below form the central fluid filled chamber (cochlear duct)
- receptor cells located in spiral organ of corti
- hair endings on cells insert into tectorial membrane
34
Anatomy of the organ of corti
- hair cells have stereocilia (microvilli)
| - microvilli make contact with tectorial membrane (gelatinous membrane that overlaps the spiral organ of corti)
35
Mechanisms of hearing
- stapes pushes on fluid of scala vestibuli at oval window
- at helicotrema, vibration moves into scala tympani
- fluid vibration dissipated at round window which bulges
- central structure is vibrated (cochlear duct)
36
Distinguishing different sounds
- sounds at different frequencies vibrate different portions of the basilar membrane
- high pitched sounds vibrate the stiffer more basal portion of the cochlea
- low pitched sounds vibrate the more flexible upper cochlea
- loud sounds cause a greater vibration of the basilar membrane and stimulate more hair cells which our brain interprets as louder
37
Auditory pathway
-cochlear part of cranial nerve VIII (vestibularcochlear) carries sensory in parts for hearing into the brain stem and then projects to inferior colliculus, thalamus (medial geniculate nucleus) and primary auditory cortex
38
Vestibular apparatus
- semicircular ducts with ampulla
- utricle
- saccule
39
Physiology of equilibrium (balance)
- static equilibrium
- maintain position of body/head relative to the force of gravity
- macula receptors within saccule and utricle
40
Otolithic organs: saccule and utricle
- thickened regions of macula within the saccule and utricle of the vestibular apparatus
- gelatinous otolithic membrane contains calcium carbonate crystals called otoliths that move when you tip your head
41
Detection of position of head
-movement of stereocilia or kinocilium results in the release of neurotransmitter onto the vestibular branches of the vestibulocochlear nerve
42
Physiology of equilibrium - dynamic equilibrium
- maintain body position during sudden movement or any type of rotation, deceleration or acceleration
- crista receptors within ampulla of semicircular ducts
43
Detection of rotational movement
- when head moves, the attached semicircular ducts and hair cells move with it
- endolymph fluid does not and bends the cupula (gelatinous material) and enclosed hair cells
- receptor region: ampulla, membrane called crista
44
Cranial nerves of ear region
- vestibulocochlear nerve CN VIII
- ampullary, utricular and saccular branches form vestibular branch
- cochlear branch forms other part of CN VIII
-vestibular parry of CN VIII carries sensory inputs for equilibrium into brain stem and then projects to cerebellum, cerebral cortex and spinal cord
