Lecture 20 - senses II Flashcards
can most invertebrates hear?
no
What do some insects use to detect sound?
Tympanic organs
how does a Moth’s detection of bat ultrasound work?
A1 & A2 receptors: different sensitivity
A2 signals ‘too loud’
(bat too close -> moth drops)
What are the key structures in Vertebrate hearing?
Pinna Tympanic membrane Middle ear bones - Malleus - Incus - Stapes Inner ear Oval window Cochlea - Tectorial membrane - Hair cells
how does the inner ear detect sounds?
Fluid moves hair cells of Organ of Corti (in cochlea), causing the Basilar membrane & hair cells to
oscillate.
The location of Resonance of basilar membrane allows the ear to determine?
frequency
what are the different Hair cells of Organ of Corti?
Outer hair cells: attached to tectorial, mainly amplify
Inner hair cells: free in fluid, mainly detect
What frequency range can most mammals hear in?
<20 kHz
How do owls detect vertical angles?
Asymmetrical “ear flaps” and placement of ear canals
How do males and females differ in hearing loss?
females lose lower freq,
males lose higher freq
What are Bats hearing adaptations for echolocation?
high pitch for high temporal
resolution
modified larynx
What is Photoreception
sight/light detection
What makes soft-furred tree mice unique?
convergent evolution: tree mice use Ultrasonic sounds to navigate environment
How does Photoreception work?
There are Light-sensitive pigments (rhodopsins = retinal + opsin). Light causes photochemical reaction with retinal (carotenoid derivative of vitamin A)
What is the signal pathway of Photoreception?
Isomerisation of retinal -> opsin protein ->
excitatory cascade -> nerve signal
What are lights key traits?
Direction
Colour (wavelengths)
Polarity
What is the structure of compound eyes?
Many sensilla with lens and receptor cells
ommatidia
Apposition eyes
each ommatidium (with lens and photoreceptor) acts
independently.
Good for bright conditions
Superposition eyes
transparent zone below lens where light from several
ommatidia reach same photoreceptor.
Good for dark conditions
Prevent damage in bright conditions using pigment to block side of ommatidium
Neural superposition
Apposition eye with lenses and nerves that results in
seven times stronger signal
What causes the blindspot in vertebrate eyes?
Optic nerve passes through retina
How do Vertebrate eyes work?
light is refracted by the cornea and lens. Light then passes through neurons and photoreceptors.
What are the two types of photoreceptor cells?
Rods and cones
what is the Fovea?
The area with the highest density of cones
