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MCAT Behavioral Sciences > Ch 2 - Sensation and Perception > Flashcards

Ch 2 - Sensation and Perception Flashcards

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MCAT flashcards
1
Q

What is sensation?

A
  • the conversion, or transduction, of physical, electromagnetic, auditory, and other information from our internal and external environment to electric signals in the nervous system
  • performed by receptors in the PNS, which forward the stimuli to the CNS in the form of action potentials and neurotransmitters
  • raw signal that is unfiltered/unprocessed until it enters the CNS
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2
Q

What is Perception?

A
  • the processing of this information to make sense of its significance
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3
Q

What are sensory receptors?

A
  • neurons that respond to stimuli and trigger electrical signals
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4
Q

What is the difference between distal and proximal stimuli?

A
  • distal: originate outside the body
  • proximal: directly interact with and affect the sensory receptors, and inform the observer about the presence of distal stimuli
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5
Q

What is the study of psychophysics?

A

the relationship between the physical nature of stimuli and the sensations and perceptions they evoke

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6
Q

What are ganglia?

A
  • collections of neuron cell bodies found outside the CNS
  • once transduction occurs, the electrochemical energy is sent along neural pathways to various projections areas in the brain, which further analyze the sensory input
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7
Q

What are the 7 most common sensory receptors?

A
  • photoreceptors: respond to electromagnetic waves int the visible spectrum (sight)
  • hair cells: respond to movement of fluid in the inner war structures (hearing, rotational/linear acceleration)
  • nociceptors: respond to painful or noxious stimuli (somatosensation)
  • thermoreceptors: respond to changes in temperature (theromsensation)
  • osmoreceptors: respond to the osmolarity of the blood (water homeostasis)
  • olfactory receptors: respond to the volatile compounds (smell)
  • taste receptors: respond to dissolved compounds (taste)
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8
Q

What is a threshold?

A
  • the minimum amount of a stimulus that renders a difference in perception
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9
Q

What is the absolute threshold?

A
  • the minimum stimulus energy that is needed to activate a sensory system
  • threshold in sensation, not in perception
  • how bright, loud, or intense a stimulus must be before it is sensed
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10
Q

What is the threshold of conscious perception?

A
  • when sensory systems send signals to the CNS without a person perceiving them; may be because the stimulus is too subtle to demand our attention or may last for too brief of a duration for the brain to fully process the information
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11
Q

What is the difference threshold?

A
  • the minimum difference in magnitude between 2 stimuli before one can perceive this difference
  • just noticeable
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12
Q

What is Weber’s law?

A
  • there is a constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus
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13
Q

Signal detection theory?

A
  • focuses on the changes in our perception of the same stimuli depending on bother internal (psychological) and external (environmental) context
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14
Q

Response bias?

A

the tendency of subjects to systematically respond to a stimulus in a particular way due to nonsensory factors

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15
Q

What is the difference between catch and noise trials?

A
  • catch: signal is presented

- noise: signal is not presented

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16
Q

What are the 4 possible outcomes of using catch/noise trials in response bias?

A
  • hits: the subject correctly perceives the signal
  • misses: subject fails to perceive a given signal
  • false alarms: subject seems to perceive a signal when none was given
  • correct negatives: subject correctly identifies that no signal was given
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17
Q

How does sensory adaptation affect a different threshold?

A
  • usually raises the difference threshold for a sensory response
  • as one becomes used to small fluctuations in the stimulus, the difference in stimulus required to evoke a response must be larger
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18
Q

What is the pathway for a stimulus to reach conscious perception?

A

sensory receptor –> afferent neurons –> sensory ganglia –> spinal cord –> brain

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19
Q

Sclera?

A
  • provides structural support

- white part of the eye

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20
Q

What vessels supply the eye with nutrients?

A
  • choroidal: a complex intermingling of blood vessels between the sclera and retina
  • retinal:
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21
Q

Retina?

A
  • innermost layer of eye
  • convert incoming photons of light to electrical signals
  • detects images
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22
Q

Cornea?

A
  • clear, dome-like window in the front of the eye

- gathers and focuses the incoming light

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23
Q

What is the pupil and how is it divided?

A
  • allows passage of light from anterior to posterior chamber
  • anterior chamber: lies in front of the iris
  • posterior chamber: between the iris and the lens
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24
Q

Iris?

A
  • the colored part of the eye

- controls size of pupil

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25
Q

What 2 muscles compose the iris?

A
  • dilator pupillae: opens the pupil under sympathetic stimulation
  • constrictor pupillae: constricts the pupil under the parasympathetic stimulation
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26
Q

Ciliary body?

A
  • produces the aqueous humor that bathes the front part of the eye before draining into the canal of Schlemm
  • accommodation of the lens
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27
Q

Lens?

A
  • lie right behind the iris

- help control the refraction of incoming light to focus it on the retina

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28
Q

What happens with the ciliary muscle contracts?

A
  • under parasympathetic control

- it pulls on the suspensory ligaments and changes the shape of the lens (accomodation)

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29
Q

Vitresous?

A
  • behind the lens

- a transparent gel that supports the retina

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30
Q

What is the duplicity theory of vision (duplexity)?

A

states that the retina contains 2 kinds of photoreceptors: those specialized for light and dark detection and those specialized for color detection

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31
Q

Cones?

A
  • used for color vision and to sense fine detail

- most effective in bright light and come in 3 forms, named for the wavelength of light they best absorb

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32
Q

Rods?

A
  • more functional in reduced illumination and only allow sensation of light and dark because they all contain rhodopsin
  • low sensitivity to detains and are not involved in color vision, but permit night vision
  • more rods than cones in eye
33
Q

Macula?

A
  • central section of the retina
  • high concentration of cones
  • center most point (fovea) contains only cones
34
Q

How do rods and cones connect with the optic nerve?

A
  • with bipolar cells that highlight gradients between adjacent rods and cones
  • bipolar cells synapse with ganglion cells, which group together to form the optic nerve
35
Q

How do amacrine and horizontal cells work together in the eye?

A
  • receive input from multiple retinal cells in the same area before the information is passed on to ganglion cells
  • can accentuate slight differences between the visual information in each bipolar cell
36
Q

Visual pathways?

A
  • refer to both the physical anatomical connections between the eyes and the brain and the flow of visual information along these connections
37
Q

Optic chiasm?

A
  • where the first significant event occurs once the signal travels through the optic nerve to the brain
  • here, fibers from the nasal half of each retina cross paths and carry the temporal visual field from each eye
38
Q

Where does the information go once through the optic chaism?

A
  • lateral geniculate nucleus of the thalamus, through radiation in the temporal/parietal lobes to the visual cortex in the occipital lobe
39
Q

Parallel processing?

A
  • the ability to simultaneously analyze and combine information regarding color, shape, and motion and to integrate this information to create a cohesive image of the world
  • calls on memory systems to compare visual stimulus to past experiences to help determine the object’s identity
40
Q

Feature detection?

A
  • our visual pathways contain cells specialized in detection of color, shape, or motion
41
Q

How is shape detected by the eyes?

A
  • by parvocellular cells, which have very high color spatial resolution (they permit us to see very fine detail when thoroughly examining an object)
  • can only work with stationary or slow-moving objects because they have very low temporal resolution
42
Q

How is motion detected by eyes?

A
  • by magnocellular cells because they have high temporal resolution, but low spatial resolution
43
Q

List the sructures in the visual pathway, from where the light enters the cornea to the visual projection areas in the brain.

A

cornea –> pupil –> lens –> vitreous –> retina (rods/cones –> bipolar cells –> ganglion cells) –> optic nerve –> optic chiasm –> optic tract –> LGN –> radiation through parieta/temporal lobes –> visual cortex (occipital lobe)

44
Q

What are the 3 parts of the ear?

A
  • a sound wave first reaches the cartilaginous outside part of the ear, pinnae (auricle)
  • pinnae channel sound waves into the external auditory canal (middle), which directs the sound waves to the tympanic membrane (inner - eardrum)
45
Q

Intensity?

A

corresponds to an increased amplitude of vibration

46
Q

What are the 3 smallest bones in the body?

A

all in the middle ear

  • ossicles: help transmit and amplify the vibrations from the TM to the inner ear
  • malleus: affixed to the TM, acts on the incus which acts on the stapes
47
Q

Eustachian tueb?

A
  • connects the middle ear to the nasal cavity

- helps equalize pressure between the middle ear and the environment

48
Q

Where does the inner ear sit and what does it contain?

A
  • sits within the bony labyrinth

- contains the cochlea, vestibule, and semicircular canals

49
Q

Cochlea?

A
  • a spiral shaped organ divided into 3 parts called scalae
  • middle scala houses the actual hearing apparatus (organ of Corti) which rests on a thin flexible membrane (basilar membrane)
  • other 2 scalae, filled with perilymph, surround the hearing apparatus and are continuous with the oval and round windows of cochlea
50
Q

What converts the physical stimulus into electrical signals in the organ of Corti?

A

hair cells

51
Q

Vestibule?

A
  • the portio of the bony labyrinth that contains the utricle and saccule (sensitive to linear acceleration)
52
Q

Semicircular canals?

A
  • sensitive to rotational acceleration

- arranged perpendicularly to each other and each ends in a swelling ampulla where hair cells are located

53
Q

Medial geniculate nucleus (MGN)?

A

for music

54
Q

What is the auditory pathway?

A

pinna –> external auditory canal –> TM –> malleus –> incus –> stapes –> oval window –> perilymph in cochlea –> basilar membrane –> hair cells –> vestibularcochlear nerve –> brainstem –> MGN –> auditory cortex (temporal)

55
Q

Hair cells function?

A
  • they sway back and forth as vibrations reach the basilar membrane underlying the organ of Corti
  • swaying opens ion channels which cause receptor potential
56
Q

What is the place theory?

A
  • states that the location of a hair cell on the basilar membrane determines the perception of pitch when that hair cell is vibrated
57
Q

How is the cochlea tonotopically organized?

A
  • which hair cells are vibrating gives the brain an indication of the pitch of the sound
  • high pitch = base of cochlea vibration
  • low pitch = apex of cochlea vibration
58
Q

Olfactory chemoreceptors?

A
  • olfactory nerves
  • located in the epithelium in the upper part of the nasal cavity
  • chemical stimuli must bind to their respective chemoreceptors to causes a signal
59
Q

Pheromones?

A
  • debatable effects on humans, but play an enormous role in many animal social, foraging, and sexual behavior
60
Q

What is the olfactory pathway?

A

nostril –> nasal cavity –> olfactory nerves –> olfactory bulb –> olfactory tract –> brain (limbic system)

61
Q

How is taste detected?

A
  • by chemoreceptors, which are sensitive to dissolved compounds
62
Q

Taste buds?

A
  • receptors for taste

- found in little bumps on the tongue (papillae)

63
Q

What is the taste pathway?

A
  • taste information travels from taste buds to the brainstem, and then ascends to the taste center in the thalamus before traveling to higher-order brain regions
64
Q

What are the 5 receptors of Somatosensation?

A
  • pacinian corpuscles: respond to deep pressure and vibration
  • meissner corpuscles: respond to light touch
  • merkel cells (discs): respond to deep pressure and texture
  • ruffini endings: respond to stretch
  • free nerve endings: respond to pain and temperature
65
Q

Two-point threshold?

A
  • the minimum distance necessary between 2 points of stimulation on the skin such that the points will be felt as 2 distinct stimuli
66
Q

Nocireceptors?

A
  • pain perception
  • can result from signals sent from a variety of sensory receptors
  • relies on thresholds, which may vary from person to person
67
Q

Get theory of pain?

A
  • there is a special “gating” mechanism that can turn pain signals on or off, affecting whether or not we perceive pain
68
Q

Kinesthetic sense?

A
  • proprioception

- the ability to tell where one’s body is in space

69
Q

What is the difference between the types of chemicals smell and taste can sense?

A
  • smell is sensitive to volatile and aerosolized compounds

- taste sensitive to dissolved compounds

70
Q

What are the 4 main modalities of somatosensation?

A

pressure, vibration, pain, temperature

71
Q

Bottom-up processing?

A
  • data-driven
  • refers to object recognition by parallel processing and feature detection
  • the brain takes the individual sensory stimuli and combines them together to create a cohesive image before determining what the object is
72
Q

Top-down processing?

A
  • conceptually driven
  • driven by memories and expectations that allow the brain to recognize the whole object and then recognize the components based on these expectations
  • allows us to quickly recognize objects without needed to analyse their specific parts
73
Q

Perceptual organization?

A
  • refers to the ability to use top down and bottom up processing in tandem with all of the other sensory clues about an object to create a complete picture or idea
74
Q

Depth perception?

A
  • can rely on both monocular (relative size of object, partial obscuring of one object by another, convergence of parallel lines at a distance, position of an object in visual field, lighting/shadowing) and binocular cues (slight differences in images projected on the 2 retinas and the angle required between the 2 eyes to bring an object into focus
75
Q

How is the form of an object usually determined?

A
  • through parallel processing and feature detection and the motion of an object is perceived through magnocellular cells
76
Q

Constancy?

A
  • the idea that we perceive certain characteristics of objects to remain the same, despite differences in the environment
77
Q

Gestalt principles?

A

these are ways for the brain to infer missing parts of the picture when a picture is incomplete

78
Q

What are the 6 elements of Gestalt principles?

A
  • proximity: elements close to one another tend to be perceived as a unit
  • similarity: objects that are similar tend to be grouped together
  • good continuation: elements that appear to follow in the same pathway tend to be grouped together
  • subjective contours: perceiving contours, shapes that are not actually present in the stimulus
  • closure: when a space is enclosed by a contour it tends to be perceived as a complete figure
  • Pragnanz: perceptual organization will always be as regular, simple, and symmetric as possible

MCAT Behavioral Sciences (12 decks)

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