2 - External Environment Mammalian Flashcards
What do plants use light energy for
Absorb light energy and convert it into biochemical energy (photosynthesis)
What aspects of light do plants monitor
Quality, intensity, duration, and angle
How do animals use light in their environment
To sense their surroundings and make behavioral decisions
List 3 uses of light in animals
Communication, thermoregulation (heat), and producing vitamin D precursors
What is an apposition eye
Composed of thousands of ommatidia over a convex surface
Detects light/shade, color, and polarization; low resolution and inverted image
What is a superposition eye
Similar to apposition but includes reflective surfaces; more sensitive in low light and gives a corrected image
What is a parabolic superposition eye
Like a superposition eye but has a parabolic reflector for better image formation
What is a pit or stemma eye
A concentrated pit with 100+ cells behind a small aperture
What are the features of a spherical lens eye
Pit eye with complex retina, highly refractive lens, and refractive humor — leads to sharper images
What is a multiple lens eye
Eyes with lenses either spread over the body or stacked like a telescope
What is a refractive cornea
A fluid-filled eye where the cornea itself refracts light
What is a reflector eye
Uses a reflective surface to focus light to a single point instead of a lens
Where is the pineal gland located
Between cerebral hemispheres
Pineal gland function
Light-sensitive and secretes melatonin
What does melatonin influence
Reproductive, social, and behavioral activities in vertebrates
In mammals, how is the pineal gland linked to circadian rhythms
Via the brain’s “clock” — the suprachiasmatic nucleus of the hypothalamus
What activates transducin in photoreceptor
Activated opsin
What enzyme does transducin activate
Phosphodiesterase (PDE)
What happens when cyclic-GMP levels decline
Gated Na+ channels close
What is the effect of Na+ channel closure in photoreceptors
Decreased neurotransmitter release
Sound definition
A travelling pressure wave characterized by frequency (pitch) and amplitude (loudness)
How do plants interact with sound
Through vibrational energy (e.g. buzz pollination)
What is the function of the middle ear
Transfers sound from the tympanic membrane to the oval window; aids in impedance matching
What structures help maintain air pressure in the middle ear
Mastoid air cells and Eustachian tube
What are the mechanisms of impedance matching
Larger tympanic membrane area, lever action of ossicles, and buckling of the membrane
What are the main structures of the bony labyrinth
Cochlea (hearing), vestibule and semicircular canals (balance)
Where are cochlear hair cells located
Basilar regions, embedded in the tectorial membrane
What happens when stereocilia bend
Receptor potential changes, leading to net depolarisation
What is the cochlear microphonic
The electrical potential of the perilymph that oscillates with sound
What is unique about the cochlear microphonic signal
No latency and no threshold
How are hair cells tuned
Each responds to a specific frequency band and has a low threshold at that frequency
What does it mean that the cochlea is tonotopically organized
Different regions respond to different frequencies
