lecture 11: senses Flashcards
how many steps are there for sensations
2
describe step 1 of sensations
sensory receptors detect and transduce different forms of energy into nerve impulses
nerve impulses travel to different regions of the brain along sensory neurons
describe step 2 of sensations
perception = awareness and interpretation of sensation
name all types of sensory receptors (5)
mechanoreceptors
nocioreceptors
thermoreceptors
chemoreceptors
photoreceptors
what do mechanoreceptors do
respond to mechanical energy
how are sensory receptors characterized
by the type of energy they transduce
describe mechanoreceptors (specifics)
muscle spindles that respond to stretching
hair cells in inner ear detect motion
what do nocioreceptors do
respond to different types of pain
what do thermoreceptors do
respond to heat and cold
what do chemoreceptors do
respond to chemical stimuli
what do photoreceptors do
respond to radiation (visible light)
describe nocioreceptors (specifics)
prostaglandins increase pain by decreasing a pain’s receptor threshold
making an action potential more likely
how to anti inflammatories like advil work to reduce pain
block prostaglandins
name types of chemoreceptors
specific
general
describe general chemoreceptors
respond to total solute concentration
ex = osmoreceptors in hypothalamus
describe specific chemoreceptors
respond to specific types of molecules
name the types of specific chemoreceptors and describe
internal chemoreceptors = glucose, oxygen, carbon dioxide, amino acids, etc
external chemoreceptors = gustatory and olfactory receptors
where do sensory receptors send the information
central nervous system
sensory receptors can be
part of sensory neuron
ORRRR
a sensory receptor cell that transmits message to a sensory neuron
describe seeing (3 statements)
humans have single lens eye
70% of body’s sensory receptors in eye
almost half of cerebral cortex involved in visual processing
name all parts of the eye
sclera
conjunctiva
cornea
choroid
iris
ciliary body
pupil
aqueous humour
vitreous humour
what is glaucoma
any increase in pressure on optic nerve
ex = increased amount of aqueous humour
what do lens, aqueous humour and vitreous humour do
work together to focus light into retina
what do ciliary muscles do
change the shape of the lens to focus on objects at different distances
what happens to lens when looking at a distant object
lens flattens
what happens to lens when looking at a near object
lens is rounded
describe sclera
tough white layer of connective tissue that covers all of eyeball (except cornea)
describe function of sclera
protects/shapes eyeball
anchors extrinsic eye muscles
continuous with dura mater of brain
describe conjunctiva
transparent mucous membrane that covers anterior sclera and under eyelid
what is function of conjunctiva
lubrication
describe cornea
transparent covering in front of eye
what is function of cornea
allows passage of light
describe choroid
thin
pigmented layer
lines the interior surface of sclera
describe function of choroid
prevents light rays from scattering and distorting image
forms the iris (continuation of choroid)
describe iris
coloured part of eye
“formed” by choroid
what is function of iris
controls size of pupil
describe ciliary body
smooth muscle bundles
continuous with choroid
attaches to lens
what is function of ciliary body
controls shape of lens
describe pupil
central opening
what is function of pupil
regulates amount of light entering eye
what do lens and ciliary body do
separate eye into 2 cavities
name the 2 cavities eye is separated into
anterior cavity
posterior cavity
describe anterior cavity of eye
filled with aqueous humour
(produced by ciliary body)
describe posterior cavity of eye
filled with vitreous humour
why does hot food smell more
a hot thing has more volatile molecules to bind to receptors in nose
describe the retina
contains photoreceptors - rods and cones
what is the blindspot
on retina
optic disc where optic nerve attaches
describe rods
light sensitive cells
do not distinguish colour
allow us to see at night but only in black and white
describe cones
not as light sensitive as rods
sensitive to colour
highly concentrated on fovea
TRUE OR FALSE: there are more rod cells than cone cells
TRUE
what types of photoreceptors are on the fovea
only cone cells
area of retina without rod cells
describe visual pathway
retina –> optic nerves –> optic chiasm (crossing of nerves) –> optic tracts –> thalamus –> primary visual cortex (occipital lobe)
name the general parts of the ear
outer ear
middle ear
inner ear
describe outer ear
external pinna and auditory canal
describe function of outer ear
collects sound waves and channels them to tympanic membrane
describe middle ear
3 bones
malleus, incus, stapes
describe pathway of middle ear
tympanic membrane –> malleus –> incus –> stapes –> oval window –> inner ear
describe inner ear
contains cochlea - houses within the temporal bone of skull
what does the cochlea do
converts sound waves into action potentials that travel along the auditory nerve
describe cochlear duct
organ of corti rests on basilar membrane
tectorial membrane rests on the hair cells of the organ of corti
describe pathway of cochlear duct
vibrations are transmitted to the cochlear fuid from the middle ear via the oval window –> basilar membrane vibrates –> hair cells brush against tectorial membrane –> action potential in sensory neuron
describe pathway of hearing
cochlea –> auditory nerve –> medulla oblongata –> thalamus –> primary auditory cortex (temporal lobe)
name the 2 parts of equilibrium in inner ear
vestibule
2 semicircular canals
describe vestibule
contains utricle and saccule
tells you which way is up and if you are accelerating
describe the 3 semicircular canals
detect head rotation
how many steps to the mechanism of inner ear equilibrium
3
describe step 1 of mechanism for equilibrium
hair cells project into a gelatinous material
describe step 2 of mechanism for equilibrium
change in head position causes hairs to bend
describe step 3 of mechanism for equilibrium
bending hairs causes an action potential to be generated in a sensory neuron
what do utricle/saccule also contain (mechanism for equilibrium step 1)
otoliths (tiny CaCO3 stones) that respond to gravitational force
TRUE OR FALSE: perceptions of taste and smell are not interrelated
FALSE
they are interrelated - affect each other
where are taste receptors located
taste buds on the surface of the tongue
describe characteristics of taste receptors
each one responds to a wide array of chemicals
pattern of taste receptor response determines what flavour is perceived
taste buds in all regions of the tongue contain
sensory receptors for the five taste types
name the 5 types of taste
sweet
salty
bitter
umami
sour
is there a sixth taste
long chain fatty acids from lipids ?
explain the sweet taste
sugars
saccharin
alcohol
some amino acids
some lead salts
miraculin
explain the salty taste
metal ions like NaCl
explain the sour taste
hydrogen ions in solution
explain the bitter taste
alkaloids like quinine, nicotine, caffeine
explain the umami taste
amino acid glutamate and aspartate
(msg = monosodium glutamate)
how does taste work
binding of tastant depolarizes cell membrane of gustatory receptor cells casing the release of a neurotransmitter
neurotransmitter binds to dendrites of sensory neuron, initiating a nerve impulse (travels along sensory neuron to CNS)
what do different gustatory receptor cells have
different thresholds for activation
ex = bitter receptors are more sensitive but adapt quickly ~3-5 seconds (evolutionary process - bitter things usually are poison or toxic, sweet = safe)
describe taste pathway
taste bud –> cranial nerves –> medulla –> thalamus –> gustatory cortex (insular lobe and frontal lobe)
what is a tastant
food chemical
what is olfaction
smell
what do olfactory receptor neurons do
line upper potion of nasal cavity and act as chemoreceptor
what to odorant molecules bind to
olfactory receptors in membrane of olfactory neurone
initiates action potential
what do olfactory receptor neurons synapse with
neurons in olfactory bulbs
what does each olfactory neuron have
one type of receptor that binds to one type of molecule
describe smell pathway
olfactory receptor –> olfactory bulb –> olfactory tract –> olfactory cortex (temporal lobe)