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Week 19 Flashcards

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1
Q

What is the ora serrata

A

The ora serrata is the serrated junction between the choroid and ciliary body.

marks the transition from the simple, non-photosensitive area of the ciliary body to the complex, multi-layered, photosensitive region of the retina.

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2
Q

Differences between Rods and Cones?

A

Rods:
- Around the retina, not in the fovea

  • Monochromatic
  • Contain rhodopsin
  • Low acuity
  • High sensitivity

Cones:

  • Highest concentration in the fovea
  • Trichromatic (red, green, and blue detecting cones)
  • High acuity
  • Low sensitivity
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3
Q

How do rods function in darkness?

A
  • Rhodopsin consists of cis-retinal and opsin
  • Na⁺ enters channels on the outer segment of the rod
  • Gets pumped out of the inner segment
  • More Na⁺ in than out → rod depolarises
  • Releases glutamate (inhibitory neurotransmitter)
  • Inhibits bipolar neuron
  • No impulse in optic nerve
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4
Q

How do Rods function in low light intensity?

A
  • Rhodopsin is bleached

-Na⁺ enters channels on the outer segment of rod

  • Is pumped out of inner segment
  • More Na⁺ out than in → rod hyperpolarises
  • No neurotransmitter (glutamate) released
  • Bipolar neuron depolarises → depolarises ganglion cell
  • Impulse in axon of optic nerve
  • Light hits rhodopsin and converts cis-retinal to trans-retinal
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5
Q

What does Glutamate do?

A

It is inhibitory and stops the bipolar neuron from depolarising

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6
Q

What is Critical Flicker Fusion Frequency (CFF)?

A

The ability of an eye to fuse signals to give a constant image

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7
Q

What happens during accommodation for close objects?

A
  • Increased convexity of the lens
  • Suspensory ligament inserts peripherally into lens
  • At rest: ligament keeps lens flat
  • During accommodation:
  • Parasympathetic neurons contract ciliary muscles
  • This relaxes ligament tension
  • Lens becomes thick
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8
Q

What happens during disaccommodation for distant objects

A

Ciliary muscles relax

Suspensory ligaments become tense

Pulls lens thin

Focus is on distant object

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9
Q

How does frequency detection change along the cochlear?

A

Basilar membrane inside cochlea, membrane changes in stiffness and width from base to apex

Base is narrow and stiff(High frequency) , apex is wide and flexible (Low frequency)

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10
Q

What are the features of the basilar membrane and hair cells?

A

Basilar membrane has hair cells in rows:

  • Inner hair cells: 1 row
  • Outer hair cells: 3 rows
  • Outer hair cells have stereocilia embedded in the tectorial membrane – control amplitude of sound
  • Inner hair cells have stereocilia with tip links
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11
Q

How does the Organ of Corti transduce sound?

A

Stereocilia bend toward the tall edge of bundle

Tip links (fibres) are connected to gated channels

Sound vibrations cause endolymph movement

Tension in tip links opens trap doors

K⁺ moves in and depolarises cell

Voltage-gated Ca²⁺ channels open

Ca²⁺ influx triggers glutamate release via exocytosis

Action potential is generated in cochlear branch of vestibulocochlear nerve

Impulse sent to brain – we can hear

Has hair cells with stereocilia

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12
Q

What is olfaction and where does odour detection occur?

A

Olfaction is the sensation of smell from detection of aerosols in the environment

Occurs at top of the nasal cavity
Odour molecules reach olafactory epithelium from nose and via the mouth

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13
Q

How does the body detect smell?

A
  • Odour molecules dissolve in a mucus layer over the olfactory epithelium (necessary for detection)
  • Olfactory epithelium contains millions of receptor cells
  • Each receptor cell has a single dendrite and cilia
  • Odorant binds to cilia → causes depolarisation
  • Action potential travels along axon to olfactory bulb
  • Axons synapse with mitral and tufted relay neurons in olfactory bulb
  • Depolarisation travels along olfactory tract to olfactory cortex
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14
Q

How is smell processed in the brain?

A

Olfactory bulb signals are transmitted to the olfactory cortex for processing

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15
Q

Where are taste receptors located and how do they vary?

A

Tongue has papillae that contain taste buds

Taste buds are arranged in different areas but all respond to all tastes

Some areas are more sensitive to specific tastes

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16
Q

How do taste buds work?

A
  • Found in walls of papillae
  • Each taste bud has 50–150 taste receptor cells
  • Gustatory hairs protrude from the top
  • Hairs contact taste molecules in a fluid-filled funnel
  • Ion channels open → cell depolarises → releases neurotransmitter
  • Sensory neurons depolarise → impulse travels to gustatory cortex
  • Taste is determined by interaction between gustatory and olfactory input
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17
Q

What are two ways animals use senses similarly to humans but differently?

A

Vision: tetrachromatic vision and compound eyes; Hearing: detection of different frequency ranges; Other senses: Echolocation, Electric field detection.

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18
Q

What is the difference between trichromacy and tetrachromacy?

A

Trichromacy: 3 types of cone cell; Tetrachromacy: 4 types of cone cell.

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19
Q

Which animals are tetrachromatic?

A

Birds, fish, and reptiles.

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20
Q

What is convergent evolution of eyes?

A

Different species evolving similar eye structures independently

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21
Q

What are the three types of eyes discussed in the slides?

A

Camera eye, Compound eye, and Ocelli.

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22
Q

How does a camera eye function?

A

A single lens focuses light onto the retina to produce an image.

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23
Q

How does a compound eye function?

A

Each lens captures a small part of the animal’s field of vision, and the brain pieces them together to form one image.

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24
Q

What trade-off is made in animals with compound eyes?

A

They sacrifice acuity for a panoramic view.

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25
What protein is found in light-sensitive cells of compound eyes?
Rhodopsin proteins.
26
What determines the wavelength detected by a photoreceptor cell?
The type of rhodopsin protein present.
27
What are the two types of compound eyes?
Apposition eyes and superposition eyes.
28
What are the features of apposition eyes?
Ommatidia are isolated; creates multiple inverted images; good for fast motion detection.
29
What are the features of superposition eyes?
Ommatidia are connected by gaps in the protective sheath; creates one image; highly sensitive; found in nocturnal insects.
30
What are middle ear adaptations in elephants?
Large tympanic membrane collects more sound energy and reduces background noise; protected by a long (~20 cm) outer ear canal; large ossicles to withstand forces from tympanic membrane vibration; cochlea structure similar to reptiles to increase vibration sensitivity.
31
What is the typical call frequency range for most insectivorous bats?
20–60 kHz.
32
Why do bats use call frequencies between 20–60 kHz?
Lower frequencies would result in wavelengths longer than an insect wing, making detection harder.
33
What advantage does low frequency give bats when hunting moths?
Low-frequency calls cannot be heard by moths.
34
What is Doppler shift compensation in bats?
Some bats adjust their call frequency as they change speed toward a target to maintain echo detection.
35
What is convergent evolution in echolocation?
Echolocation types evolved independently in different bat groups.
36
What is an example of an evolutionary arms race between bats and moths?
Tiger moths produce clicks to jam bat echolocation; Barbastelle bats whisper to avoid moth detection.
37
What adaptations support echolocation in bats?
Modified skull bone (stylohyal) to support throat muscles and voice box Acoustic fovea (thickened area of cochlea basilar membrane) Cochlear hairs resistant to noise degradation Sensory neurons that respond strongest to specific frequencies Specialized outer ear shape and nose leaves
38
What is passive electrolocation?
Sensing bioelectric fields generated by nerve/muscle activity in other animals without producing an electric field.
39
What is active electrolocation?
Producing an electric field and detecting distortions in that field.
40
What organs enable passive electrolocation in sharks?
Ampullae of Lorenzini.
41
What is the lateral-line system?
A system in aquatic animals containing sensory nerves and receptors for electrical, mechanical, and chemical stimuli.
42
What special property does the ampullae of Lorenzini gel have?
It has semiconducting properties.
43
How does electroreception work in sharks?
Ampullae detect voltage differences between skin pores and the base of the ampulla.
44
What happens when voltage is detected by electroreceptive organs?
Opens voltage-gated calcium channels Causes membrane depolarization (action potential) Triggers neurotransmitter release Impulse travels down sensory neuron Flashcard 35
45
What photoreceptors do plants use to detect light?
Phototropins, cryptochromes, and phytochromes.
46
What are the three types of responses plants show to light detection?
Phototropism (movement towards light sources) Photomorphogenesis (alterations to physical structure due to light) Photoperiodism (adaptation to changing day lengths)
47
What is phototropism?
The growth of an organism (like a plant) in direct response to a light stimulus.
48
What are the two types of phototropism?
Positive phototropism: growth towards the light source Negative phototropism: growth away from the light source
49
Which photoreceptors mediate detection of blue light for phototropism?
Phototropins Phot1 and Phot2.
50
What controls the morphological response in phototropism?
Accumulation of auxin.
51
According to the Cholodny-Went Hypothesis, how is blue light detected?
Blue light is asymmetrically detected by Phot1/2 on the coleoptile (shoot tip).
52
What happens after blue light detection in the Cholodny-Went Hypothesis?
Activation and promotion of PIN genes PIN genes produce auxin efflux transporters Auxin is transported from light-side cells into dark-side cells.
53
How does auxin accumulation on the dark side affect cells?
Increases osmotic pressure Decreases cellular pH Activates expansins.
54
What role do expansins play in phototropism?
They weaken hydrogen bonds between cell walls, reducing rigidity, and allow cells to flex more easily.
55
How does increased osmotic pressure affect dark-side cells?
It causes the dark-side cells to swell larger than light-side cells, bending the coleoptile towards the light.
56
What is photoperiodism?
The physiological reaction of an organism to the length of time within a light or dark period.
57
Why is photoperiodism important for plants?
It helps plants evaluate seasonality and undergo physiological changes (such as flowering) based on changes in day length.
58
Which molecule regulates photoperiodism?
Phytochrome, based on the length of the dark period.
59
What are the three categories of plants based on photoperiodic flowering?
Long-day plants (flower after night lengths fall below a critical time) Short-day plants (flower after night lengths exceed a critical time) Day-neutral plants (flower regardless of night length)
60
How does phytochrome detect photoperiod length?
Phytochrome (Pr) reacts with red-light to form active Pfr. Pfr promotes germination and other processes. During darkness, Pfr slowly reverts to Pr. Plants evaluate night length by measuring Pfr/Pr ratios.
61
How do long-day and short-day plants differ in Pfr detection?
Long-day plants require high Pfr concentrations to trigger flowering. Short-day plants require low Pfr concentrations to flower.
62
What is gravitropism?
The ability for organisms to undergo morphological and physiological changes in response to gravity.
63
What are the two types of gravitropism?
Positive gravitropism: growth towards gravity (e.g., roots) Negative gravitropism: growth away from gravity (e.g., shoots)
64
Why is gravitropism important for plants?
It allows for stable root anchorage and ensures shoots grow upward away from the ground.
65
What are statoliths?
Highly dense amyloplast organelles that produce and store starch grains in specialized statocytes.
66
Where are statocytes located?
Near the vascular tissues of shoots and near the caps of roots.
67
How do statoliths help plants detect gravity?
Their increased drag on the actin web activates mechanosensitive channels, which then activate more auxin efflux carrier proteins.
68
In shoots, how does auxin accumulation affect gravitropic response?
Auxin accumulates at the bottom of the shoot. Promotes growth of the bottom edge. Causes the shoot to curve upward, away from gravity.
69
In roots, how does auxin accumulation affect gravitropic response?
Auxin accumulates at the bottom of the root. Suppresses growth of the bottom edge. Causes the root to curve downward, towards gravity.
70
Gravitropic Mutants
Those with Gravitrophic mutations showed no gravitrophic responses
71
What is thigmotropism?
Detection and specific directional growth of a plant in response to a touch stimulus.
72
How does thigmotropism cause directional growth?
Growth rate is reduced on the side of contact, causing the outer edge to bend around the object.
73
What mechanisms are believed to contribute to thigmotropism?
Touch-sensitive calcium channels, auxin accumulation, and reduced ethylene production.
74
How do Venus fly traps detect and respond to touch?
Venus fly traps have touch-sensitive cilia lining their leaves. Stimulation of cilia triggers an action potential. Action potential stimulates motor cells to close the leaves.

Organ systems (9 decks)

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