20-23 Flashcards

1
Q

What is the dynamic range of light detection in the human eye?

A

The eye can detect light over a dynamic range of more than 100 million to 1, from bright sunlight to faint starlight.

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2
Q

How does the human retina’s resolution compare to digital imaging?

A

The human retina has an equivalent resolution of about 576 megapixels.

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3
Q

What is the role of the brain in vision?

A

The brain interprets the inverted and smaller retinal image to form a coherent visual perception.

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4
Q

What are the two types of photoreceptors in the retina, and which one is more abundant?

A

Rods and cones; rods outnumber cones by 20-fold.

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5
Q

What is the photopigment found in rods, and what is its function?

A

Rhodopsin; it helps rods detect light, especially in low-light conditions.

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6
Q

What triggers the phototransduction cascade?

A

The isomerization of 11-cis-retinal to all-trans-retinal, which activates transducin, a specialized G-protein.

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7
Q

What happens to photoreceptor cells in the dark?

A

Photoreceptors are depolarized in the dark with a membrane potential of approximately -40 mV.

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8
Q

What is a receptive field in the retina?

A

It’s the area from which a ganglion cell receives input, with ON-center and OFF-center configurations.

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9
Q

How do ON-center and OFF-center ganglion cells respond to light?

A

ON-center cells signal increases in light intensity, while OFF-center cells signal decreases.

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10
Q

What does the retina primarily detect in a visual scene?

A

The retina acts as a contrast detector, focusing on variations in light rather than absolute intensity.

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11
Q

What visual pathways project information from the retina to the brain?

A

The M (magnocellular) pathway for movement analysis and the P (parvocellular) pathway for fine detail and color.

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12
Q

What is the role of simple cells in the visual cortex?

A

They respond to specific orientations of stimuli and have distinct excitatory and inhibitory regions.

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13
Q

What are intrinsically photosensitive retinal ganglion cells (ipRGCs)?

A

They are light-sensitive cells involved in circadian clock regulation and pupillary response, using the photopigment melanopsin.

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14
Q

What are the primary brain targets of ipRGCs?

A

The olivary pretectal nucleus (pupil reflex), suprachiasmatic nucleus (circadian rhythms), and ventrolateral preoptic nucleus (sleep).

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15
Q

What condition is linked to damage in the retina’s photoreceptors with aging?

A

Age-related macular degeneration.

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16
Q

What are the three main stages of hearing?

A

Capture, transmit, and transduce sound waves.

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17
Q

How is sound magnitude expressed?

A
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18
Q

What is the function of the basilar membrane?

A

It acts as a mechanical analyzer of sound, separating frequencies along its length.

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19
Q

How does the basilar membrane vary along its length?

A

It is wider and more flexible at the apex for low frequencies, and narrower and stiffer at the base for high frequencies.

20
Q

What are the two types of hair cells in the cochlea, and what are their roles?

A

Inner hair cells (IHCs) are responsible for sound transduction, while outer hair cells (OHCs) amplify sound, especially at low intensities.

21
Q

What is the role of prestin in hearing?

A

Prestin is a motor protein in OHCs responsible for electromotility, enhancing cochlear amplification.

22
Q

How is sound transduced into electrical signals?

A

Movements of stereocilia on hair cells open mechanosensitive ion channels, allowing K⁺ ions to flow in and create receptor potentials.

23
Q

Why is potassium (K⁺) used for mechanotransduction in hair cells?

A

K⁺ influx causes minimal changes in cytosolic concentration and requires little energy for both influx and extrusion due to the electrochemical gradient.

24
Q

What genetic factors are associated with hearing loss?

A

Mutations in genes like GJB2 (Cx26), Myo7a, and KCNQ4 affect potassium recycling and hair cell function, leading to deafness.

25
Q

What does the spiral ganglion do?

A

It consists of neurons that transmit signals from inner hair cells to the brain, encoding sound frequency and intensity.

26
Q

What is the function of the medial superior olive (MSO)?

A

It localizes sound by detecting inter-aural time differences, helping distinguish the direction of sound.

27
Q

How do cochlear implants restore hearing?

A

They electrically stimulate the auditory nerve fibers based on a tonotopic map, mimicking natural frequency encoding.

28
Q

What is tonotopy in hearing?

A

It’s the spatial arrangement where different sound frequencies are processed at specific locations, from the cochlea to the auditory cortex.

29
Q

What brain areas are involved in processing language from sound?

A

Wernicke’s area handles language comprehension, while Broca’s area is responsible for language production.

30
Q

What role do outer hair cells (OHCs) play in hearing sensitivity?

A

They actively amplify low-intensity sounds through mechanical movements, enhancing frequency selectivity and sensitivity.

31
Q

What is the concentration of oxygen in the atmosphere up to 100,000 feet?

A

The concentration of oxygen remains constant at 21%.

32
Q

According to Dalton’s Law, what happens to atmospheric pressure with altitude?

A

Atmospheric pressure decreases as altitude increases, even though the oxygen concentration remains constant.

33
Q

What is hypoxia, and what are its symptoms at high altitude?

A

Hypoxia is oxygen deprivation, with symptoms including euphoria, poor judgement, slowed thinking, muscle weakness, and unconsciousness.

34
Q

What is the “Time of Useful Consciousness” (TUC)?

A

The period during which a person can perform tasks efficiently without supplemental oxygen; ranges from 90 seconds to 4 minutes at high altitude.

35
Q

Why does oxygen supplementation at 40,000 feet still result in hypoxia?

A

Even with 100% oxygen, the partial pressure only reaches 188 mbar, which is lower than sea-level oxygen pressure (212 mbar).

36
Q

How does high altitude affect physical performance?

A

Maximal oxygen consumption decreases, falling to 85% at 3000 m, 60% at 5000 m, and 20% at the summit of Everest.

37
Q

What are the effects of high altitude on mental performance?

A

Reduced attention span, increased mental fatigue, more arithmetic errors, and a 50% reduction in night vision at 5000 m.

38
Q

What is periodic breathing, and how does it affect sleep at high altitude?

A

Instability in respiratory control causes alternating periods of hyperventilation and apnea, disrupting sleep.

39
Q

How does the body adapt to high altitude over time?

A

Increased erythrocyte production raises oxygen-carrying capacity, though full adaptation requires several weeks.

40
Q

What is Acute Mountain Sickness (AMS)?

A

A condition with symptoms like headache, fatigue, insomnia, and nausea, typically occurring above 3000 m within 2-3 hours of ascent.

41
Q

What is High Altitude Pulmonary Edema (HAPE)?

A

A condition characterized by fluid in the lungs, causing labored breathing, dry cough, and reduced exercise tolerance; requires descent for treatment.

42
Q

What is High Altitude Cerebral Edema (HACE)?

A

A potentially fatal swelling of the brain at high altitudes, causing confusion, hallucinations, and loss of coordination.

43
Q

How do bar-headed geese survive extreme altitudes during migration?

A

They have specialized lung structures for efficient oxygen exchange and thin blood-gas barriers to optimize oxygen uptake.

44
Q

How do elephants manage pressure changes during underwater breathing?

A

Elephants have no pleural space; instead, they possess dense connective tissue that prevents microvessel rupture under pressure.

45
Q

What evolutionary adaptation allows mole rats to tolerate low oxygen environments?

A

Enhanced CO₂-binding to Cx26 receptors allows them to rebreathe air efficiently in underground burrows.