Sensory Part 2 Flashcards
What are the regions of the inner ear?
- semicircular canals
- vestibule
- cochlea
What is the nerve of the inner ear and what are its branches?
vestibulocochlear nerve (VIII) - vestibule branch & cochlear branch
What 3 layers make up semicircular canals (outside in)
- bony labyrinth
- perilymph
- membranous labyrinth with endolymph
Organ of corti
hair cells that actually let us hear sound via vibrations of stereocilia
Scala synonymous duct names
- scala tympani = tympanic duct
- scala vestibuli = vestibular duct
- scala media = cochlear duct
Spiral ganglia
in spiral of cochlea and get stimulated by hair cells in organ of Corti
How do we detect the pitch of sound?
- kinocilium vs. sterieocilia
- variation in basilar membrane
- which spiral ganglion was stimulated (close to oval window high pitch vs. far away low pitch)
Describe pitch variation at basilar membrane
high freq=high pitch - stiff/thick region near round window
low freq=low pitch - flexible region hear helicotrema
Helicotrema
if sound makes it to the helicotrema it is considered infrasound (a sound you can’t hear because its so low) - sound never crosses basilar membrane
How do we detect the amplitude of sounds?
action potential firing more rapidly if sound is loud
How do we sense directionality?
time delay of sound hitting one ear than the other
Locations and functions of membranous labyrinth (3)
- cochlear duct - hearing
- semicircular canals & ampullae - rotation of the head
- utricle & saccule - up & down and linear accel/decel
Where did the crista ampullaris evolve from?
neuromast organ of lateral line - instead of detecting water movement it detects endolymph movement
What direction do each semicircular canal rotate the head?
- lateral = “no”
- anterior = “yes”
- posterior = “tilt head”
What do hair cells of the ear respond to?
CHANGE in endolymph
What causes dizziness when spinning?
fluid has inertia - spin then stop causes endolymph to continue spinning and endolymph continuing to stimulate hair cells.
Otoliths
crystals that move in response to gravitational forces (CaCO3)
When an elevator starts to drop you sense this via _____.
saccule
When a plane accelerates for take off you sense this with the ______.
utricle
Where does CN 8 take its information?
from vestibular brach into cerebellum - and cochlear branch into thalamus
Auditory system of fish:
- no pinna/tympanum
- no ear bones
- lagena = non-coiled cochlea
What is the order that sound waves pass through a fish?
water -> fish tissue -> sacculus -> utriculus -> lagena
What can you use to age fish?
the amount of concentric rings on otoliths
Anatomy of avian ear:
- elongation of the lagena (cochlea)
- one ossicle - stapes/columella
Why do owl have great hearing?
- because they have L&R ears, but also have one higher than the other - vertical & horizontal directions
- no pinna, but feathers funnel into ear
- very large external ear canals covered by movable flap
Function of auditory bullae
bouncing around increases amplitude of sound - resonance chamber amplification (like acoustic guitar)
What is the pupil?
lack of structure open space
What happens to the pupil in well-lit areas?
- pupillary constriction (via parasympathetic)
- sphincter pupillae - muscle contracts
- dilator papillae - muscle relaxes
What happens to the pupil in dimly-lit areas?
- pupillary dilation (sympathetic)
- sphincter pupillae - muscle relaxes
- dilator pupillae - muscle contracts
Lens
focuses light on fovea centralis
Why would people need corrective lenses?
if light is not focused on fovea centralis
How does visual accommodation work in bony fish and non-amniote vertebrates?
lens moves forwards and backwards (similar to camera lens)
How does visual accommodation work in amniotes?
lens changes shape - thick & think - but it stays in the same place
(far=thin; close=thick) - does this with the ciliary muscle
How does the ciliary muscle (body) contract for near vision?
- sphincter muscle
- suspensory ligaments relax as ciliary body contracts
- lens rounded
- near point of accommodation limited by natural shape of lens
How does the ciliary muscle (body) relaxes for distant vision?
- suspensory ligaments taut
- lens flattens out
What are the 3 limits to visual accommodation?
- no antagonistic muscles
- near vision limited by natural shape of lens
- distant vision limited by shape of relaxed sphincter
Presbyopia
- lens loses flexibility; doesn’t get as thick
- common in middle age
- near point of accommodation increases
- focal point behind retina
Why is there a blind spot?
There is a spot where there is no rods or cones so light detection doesn’t exist - there’s nothing there because its where the optic nerve is (also no retina)
What animal does not have a blind spot?
mollusks
Rods & cones definition
- absorptive range of visual pigments
- 400-750nm wavelength (visible range)
What are the three types of cones in humans?
- blue cones
- green cones
- red cones
- named after the color they are sensitive to
Define cones.
- color vision
- need lots of light
- high visual acuity
- more towards center of eye
Define rods.
- presence/absence of light
- function in low light
- low visual acuity (high convergence)
- more towards periphery
Why do humans have good depth perception?
because of the overlap between each eye
What is the trend by trophic level for depth perception and vision?
- herbivore has broader vision, but less overlap
- carnivore has narrower vision, but more overlap
What kind of photoreceptors did ancestral vertebrates have?
tetrachromatic (red, blue, green, violet)
What kind of photoreceptors do cats and dogs have?
dichromatic vision (blue, green) - have way better night vision and more rods
What is the benefit of evolving to be a trichromate?
- sexual communication (red bottoms)
- finding fruit
What are the 2 types of colorblindness?
- trichromatic - green shifts to red - 5% of males
- dichromatic - no green cones/only red and blue - 1% of males
Why is colorblindness in males?
because blue is autosomal and green & red is on x-chromosome
What animals are tetrachromatic and what is the new color?
fish, reptiles, birds - violet (UV range)
What cones do insects have?
trichromatic - UV,B,G
What features do nocturnal animals have?
- tapetum lucidum
- rods (increase)
- vertical pupils (slit shape cats-larger range of open close)
- large eyes (owls)
Tapetum lucidum
reflects light - gives good night vision by giving rods a “second chance” at light
How do owls see well at night?
They have large eyes, but because of this they have little extra-ocular musculature, so they can’t move their eyes. To compensate for this they can turn their heads 270* in each direction
Sclerotic ring
ring of eye bone in birds - protects and keeps sclera in place under high pressure during flying
Nictitating membrane
3rd eyelid - protects eyes while still giving visibility
What animals have a nictitating membrane?
sharks, birds, reptiles and some mammals
How does the nictitating membrane close?
medial-lateral
What is the vestigial nictitating membrane in humans?
plica semilunaris
Pit organs
thermoreception - heat coming off of prey in IR spectrum
What are two examples of pit organ thermoreception?
- IR sensitive free nerve endings - vampire bats - have them on mouth and go to where heat is given off
- IR detection in snakes - labial pits
What’s the function of the tensor tympani?
tighten tympanic membrane
What’s the function of the stapedius muscle?
pull stapes away from oval window
a- scala vestibuli (vestibular duct)
b- scala media (cochlear duct)
c- scala tympani (tympanic duct)
d- cochlear nerve division of the vestibulocohlear nerve
