;Chapter 18-General and Special Senses Flashcards
sensory receptor
- specialized receptor that sends sensations to CNS
- tonic receptor
- phasic receptor
tonic receptor
always sending signals to CNS
phasic receptor
becomes active only with changes in the conditions they monitor
types of receptors
chemoreceptors -taste -smell nociceptors -cell damage (mechanical, electrical, thermal) thermoreceptors -thermal mechanoreceptors -hearing -stretching -body position photoreceptors -light
receptor characteristics
receptive field: area monitored by a single receptor cell
receptor specificity:
-each receptor responds to a specific stimulus
-example: photoreceptor will no respond to a chemical stimulus
more receptor fields=more precise responses
sensation vs perception
sensation: -sensory information arriving at the CNS Perception: -conscious awareness of sensation --all nerve impulses are identical (just action potentials) --brain interprets impulses --"feeling" that occurs when sensory impulses are interpreted sensation=perception?
sensory adaptation
- occurs when sensory receptors are subjected to continuous stimulation
- results in a reduction of sensitivity
- at some point along the pathway, impulses are conducted at a decreased rate
- several types
types of sensory adaptation
- peripheral adaptation
- central adaptation
peripheral adaptation
when sensory receptors decrease their level of activity
central adaptation
- sensory neurons are still active
- CNS causes reduced perception
sensory limitations
sensory information from receptors is incomplete
- do not have receptors for every stimulus
- other animals can detect things we cannot: infrared, ultraviolet, ultrasound, etc.
- receptors have limited ranges
- stimulation requires a neural event that is interpreted
general vs special senses
general senses
-do not have specialized receptor cells or sensory organs
special senses
-can have specialized receptor cells separate from the sensory neuron
-structurally more complex
-receptors localized in sense organs
general senses
3 major groups
- exteroceptors
- propriocepts
- interoceptors
exteroceptors
relay info about external environment
proprioceptors
-depict body position in space
interoceptors
monitor the internal environment
nociceptors
-sense tissue damage
-perceived as pain
-free nerve endings with large receptive field
–found everywhere except brain
–provide a protective function
–do not adapt well (do not want to prolong injury)
deters behavior that is damaging
types of pain
fast pain: quick, inducing a reflex usually; end when stimulus unds
slow pain (burning): begins later; persists longer; ache
referred pain
-visceral pain that feels like it is coming from a more superficial region
-due to superficial structures being innervated by the same spinal nerves as damaged viscera
-“brain freeze”
thermoreceptors
- invovle heat and cold
- -no difference in structure between the two
- free nerve endings in skin
- quick to adapt
- felt as pain
- -if temp goes above 45C
- -if temp goes below 10C
mechanoreceptors
- sensitive to mechanical forces that cause tissues to be deformed
- types:
- tactile
- baroreceptors
- proprioceptors
tactile receptor
touch, pressure and vibration
baroreceptors
pressure changes in walls of vessels, etc
proprioceptors
position of joints and muscles
tactile receptors: two categories
unencapsulated (3 types)
encapsulated (3 types)
tactile receptors: unencapsulated
free nerve endings -in papuillary of dermis -general touch root hair -monitor distortions and movement across body surface tactile sic -expand nerve terminal that synapses with merkel cell -sensitive to fine touch
tactile receptors: encapsulated
tactile corpuscles -found where tactile sensitivities are very well developed -hands lamellated corpuscle -respond to deep pressure -squeeze arm ruffini corpuscle -in dermis -detect pressure with little adaptation
baroreceptors
-stretch receptors
-monitor changes in pressure
–detect stretching of tissue walls
-regulates autonomic activities
–digestive tract
–bladder
-carotid sinus
–lung
-colon
–major arteries
similar to ruffini corpuscles but difference is location
proprioceptors
- monitor position of joints, tension in tendons, state of muscle contraction
- everywhere, skeletal muscle
- no adaptation to stimulus
types of proprioceptors
muscle spindle: monitor length of muscle
golgi tendon organ
-monitor tension in a tendon during contraction
chemoreceptors
- respond to substances dissolved in surrounding fluids
- monitor chemical composition of body fluids
- -example: sensitive to pH, CO2 changes
- found:
- -inside CNS, medulla
- -aortic bodies
- -carotid bodies
special senses
next ones
olofaction
- sense of smell
- olfactory organ
- -located within the nasal cavity on either side of nasal septum
- -covers the cribiform plate of ethmoid
- -made up of olfactory epithelium
olfactory cells
olfactory epithelium consists of
-olfactory receptors: chemoreceptors
-supporting cells: surround the receptors
-basal cells: stem cells that grow new cells
covered in secretions from olfactory glans
olfactory receptors
- highly modified bipolar neurons
- have cilia that extend into mucus secreted by olfactory glands
- odorous particles dissolve into mucus and cause depolarization
olfactory nerve pathway
- impulses travel along axons of receptor cells
- pass through openings in cribiform plate
- go to olfactory bulb and cranial nerve I
- unique in that the impulse does NOT go through the thalamus
- travel along tracts to limbic system
- -smells can trigger strong emotions
- interpreted as smell in temporal lobe and base of fronts
olfactory discrimination
- no structural difference in receptor cells
- olfactory can turn over (reproduce)
- -but numbers decrease with age
- 50 primary smells
- -combinations allow us to distinguish thousands of smells
- adapt quickly
gustation
- taste
- chemoreceptors in structures called taste buds
- taste buds on superior surface of tongue in papillae
- gustatory receptors found in taste buds found in papillae found on your tongue
papillae
- epithelial projections
- taste buds lie along papillae
- three types of papillae
- filiform
- fungiform
- cicumvallate
taste buds and receptors
- gustatory cells: receptor clusters
- -about 40 per bud
- also have basal cells
- -replace receptors every 10-12 days
- gustatory cells extend microvilli called a taste hair into taste pore
gustatory pathway
- uses cranial nerves VII, IX, and X
- afferent fibers synapse with nucleus solitarius in medulla
- goes to thalamus and cerebral cortex
gustatory discrimination
primary tastes
- sour
- sweet
- salt
- bitter
- water
- umami-meat
- individual differences in taste
- number and sensitivity decrease with age
external ear
- auricle: external structure supported elastic cartilage
- external acoustic meatus: canal to middle ear
- -ceruminous glands: make wax
- -hairs
- ends at tympanic membrane
middle ear
consists of tympanic cavity
-air filled space between external and inner ear
tympanic membrane
-thin, transparent connective tissue sheet
auditory tube
-when open
–middle ear equalized to atmospheric pressure
–can be induced by chewing or yawning
–allows for microbes to get in and cause an ‘ear infection’
middle ear ossicles and muscles
-tiny bones in middle ear
-transfer vibrations from the tympanic membrane to inner ear
-includes: malleus, incus, stapes
muscles:
-tensor tympani muscle
–inserts on malleus
-stapedius muscle
–inserts on stapes
inner ear
- a series of tubes and cavities
- split into two sections:
- -vestibule (balance)
- -cochlea (hearing)
layers of inner ear
- memranous labyrinth
- -contains endolymph fluid
- bony labyrinth
- -dense bone layer of the temporal
- -contains perilymph fluid
cochlea
- converts vibrations to sound
- contacts the stapes at the oval window
- coiled tube with cochlear duct
- divided into three ducts
- -vestibular duct: divided by vestibular membrane
- -cochlear duct: divided by basilar membrane
- -tympanic duct
organ of corti
found on the basilar membrane
-mass of epithelial cells
contains:
-hair cells: mechanoreceptors with stereocilia (stick out in order to be deformed, send signals to dendrites)
-cranial nerve VIII: cochlear branch contacts hair cells
-tectorial membrane: positioned right above hair cell stereocilia, deforms sterocilia
the path of vibrations
- auricle funnels vibrations into meatus
- tympanic membrane vibrates
- transmits to ossicles
- malleus to incus to stapes - stapes connected to oval window
- transmits vibrations to inner ear - oval window vibrates; perilymph moves
- membranous labyrinth vibrates
- cochlear duct vibrates within - basilar membran bounces
- hair cell stereocilia contact tectorial membrane
- become deformed and creates depolarization
- transmits an action potential down of CN VIII
pathway for auditory sensations
-carried by cochlear branch of cranial nerve VIII
-goes to cochlear nucleus of medulla
-travels through thalamus
-processed in auditory cortex of temporal lobe
mechanoreceptors detect different pitches of sound in different portions of the cochlea
vestibule
consists of:
semicircular canals
utricle and saccule
semicircular canals
- three total: anterior, posterior, lateral
- surrounding semicircular ducts
- ampulla (swellings) at base: each possess cristae that attaches to a cupula (inside critae, creates action potential)
utricle and saccule
- paired membranous sacs
- connected by endolymphatic duct
- saccule possess maculae (creates action potential
semicircular canals
- contains fluid thats pulled on by gravity
- cupula has hair cells
- head rotation:
- -causes fluid to move through canals
- -fluid moves cupula
- hair cell stereocilia bends
- depolarization occurs
utricle and saccule
deal with head orientation Maculae consists of -hair cells -otolith: --small calcium carbonat ecrystals --gel like substance Head orientation changes -gravity pulls on crystals -moves otolith -deforms hair cell stereocilia -depolarization occurs
pathway for balance sensation
hair cells
- activate neurons of vestibular branch of cranial nerve VIII
- synapses with vestibular nuclei
eye accessory structures
- eyelids or palpebrae
- tarsal glands
- conjunctiva
- lacrimal apparatus
eyelids or palpebrae
- protect and lubricate
- epidermis, dermis, CT
tarsal glands
-oily secretions keep lids from sticking together
conjuctiva
- thin protective mucus membrane-what you see when you look at eye
- palpebral (eyelid) and bulbar (on eye)
- stopes at coneal edge
- dilated BV–bloodshot
lacrimal apparatus
-produce tears
consists of:
-lacrimal gland: produces tears
-lacrimal punctum: drains tears into lacrimal canaliculi
-lacrimal canaliculi: passageway that leads to the lacrimal sacc
-lacrimal sac: fills groove on lacrimal bone, connects to the nasolacrimal duct
-nasolacrimal duct: delivers tears to nasal cavity
eye layers
3 layers
- fibrous tunic
- vascular tunic
- neural tunic
fibrous tunic
outer
- sclera
- -white of eye
- -dense irregular CT
- Cornea
- -transparent layer
vascular tunic
iris -smooth muscles and pigments choroid -vascularized, pigmented layer lens -layered proteins -refracts light
vascular tunic: ciliary body
- below the iris
- has ciliary processes
- -attach to suspensory ligaments
- -attach to lens
- ciliary muscles change the lens shape
- -focus
vascular tunic: functions
- route for BV’s
- regulate amount of light
- secrete and absorb aqueous humor
- control shape of lens
neural tunic
- inner most layer
- retina
- 5 groups of retinal neurons
retinal neurons
- receptor cells
- -rods and cones
- -detect light
- bipolar neurons
- -synapse with above
- ganglion cells
- -synapse with above
- amacrine cells
- -modulate communication between bipolar and ganglion cells
rods and cones
rods -very light sensitive -do not discriminate color -require less light cones -color vision -three types: red, blue, green -give sharper image
neural tunic: regions of the retina
- macula lutea: area of no rods
- fovea centralis: area of most cones, within macula
- optic disc: beginning of optic nerve, “blind spot”
visual pathway
- photoreceptors to
- bipolar cells to
- ganglion axons converge on optic disc into optic nerve (cranial nerve II)
- optic tract to optic chiasm
- relayed to lateral geniculate nucleus
- on the visual cortex of occipital lobe-finally see, associate it with previous sights
cavities
posterior cavity (behind lens)
-contains gelatinous vitreous body-gel like
anterior cavity( between leans and cornea)
-contains clear aqueous humor-watery
