PSL300 > 20 > Flashcards

20 Flashcards

(53 cards)

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1
Q

what is the fundamental language of the brain?

A

electricity; it is the medium through which our brain processes and communicates all sensory and motor information

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2
Q

5 special senses

A

vision, hearing, equilibrium, taste, and smell

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3
Q

4 somatic senses

A

touch, temperature, proprioception, nociception

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4
Q

proprioception

A

the body’s sense of its own position

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5
Q

nociception

A

the body’s sense of potentially damaging stimuli

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6
Q

describe the two types of human consciousness relating to the senses

A
  • we are usually at least partly conscious of data from the 9 senses (5 special, 4 somatic)
  • we are largely unconscious of other sense data such as blood pressure, lung inflation, blood-glucose concentration, etc
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7
Q

how does every sensory system begin?

A

with receptors

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8
Q

function of receptors

A

transduction: convert stimuli (eg light, sound) into electrical signals

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9
Q

two types of receptors

A
  • in some sensory systems (such as vision) the receptor cells are neurons
  • in others (such as hearing) they are non-neuronal epithelial cells
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10
Q

how does a receptor work?

A
  • converts stimulus energy into a receptor potential (graded change in membrane potential)
  • receptor may then release neurotransmitter to affect a neuron. if the receptor is itself a neuron, it may fire action potential.
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11
Q

adequate stimulus

A

a receptor cell’s adequate stimulus is the form of energy to which a receptor is most responsive

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12
Q

do receptors only respond to their adequate stimuli?

A

no, many receptors also respond to other forms of energy as well, if those other forms are powerful enough (eg some thermoreceptors also respond to certain chemicals)

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13
Q

how are receptors classified?

A

according to their adequate stimuli

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14
Q

sensory receptors are divided into five major groups

A
  • chemoreceptors
  • mechanoreceptors
  • photoreceptors
  • thermoreceptors
  • nocireceptors
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15
Q

chemoreceptors

A

pH, O2, organic molecules

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16
Q

mechanoreceptors

A

vibration, acceleration, sound

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17
Q

thermoreceptors

A

temperature

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18
Q

photoreceptors

A

light

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19
Q

nociceptors

A

tissue damage (pain)

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20
Q

Muller’s Law (law of specific nerve energies)

A

the specificity of a receptor for a particular type of stimulus

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21
Q

receptor threshold

A

weakest stimulus that will cause a response in the receptor

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22
Q

give two examples of receptor threshold

Study These Flashcards
A
  • some photoreceptors can detect a single photon of light
  • chemoreceptors for smell may respond to a single molecule of an odorant
23
Q

perceptual threshold

Study These Flashcards
A

weakest stimulus that will cause a conscious perception in the organism

24
Q

give an example of perceptual threshold

Study These Flashcards
A

it takes 40 odourant molecules for you to perceive a smell

25
what four stimulus properties much the brain distinguish to create an accurate neural representation of sensory stimuli?
- stimulus modality - stimulus intensity - stimulus duration - stimulus location
26
stimulus modality
- ie whether it is a light, a sound, a touch, etc - sensory systems indicate modality by labeled lines, ie which axons carry the signals (eg activity on neurons in visual pathway means light)
27
groups of neurons can represent intensity in 2 ways
- population coding of intensity - frequency coding
28
population coding of intensity
- stimulus intensity represented by number of active neurons - stronger stimuli may activate more neurons
29
frequency coding
stronger stimuli may make the individual neurons fire at a faster rate
30
are population coding of intensity and frequency coding mutually exclusive?
no; both mechanisms may operate together. a stronger stimulus may increase the firing rates of neurons and also cause more neurons to be active
31
what does it mean for receptors and neurons to have dynamics?
their activities may depend not only on the stimulus right now, but on how it changes through time
32
how do cells signal changes in stimuli rather than steady levels?
when a stimulus suddenly increases or decreases, many receptors and neurons respond briefly then fall silent again
33
do all cells have the same dynamics?
no; different cells have different dynamics
34
phasic cells
respond briefly to any change and then cease firing
35
tonic cells
maintain their activity when the stimulus is not changing, signalling its present level
36
phasic-tonic cells
react to change but don't return all the way to zero firing when the stimulus is constant, so they also carry information about it steady level
37
give an example of phasic cells
- many retinal cells are phasic - they report changes in your visual world, as when something moves
38
give an example of the phasic nature of retinal cells
- you wave your arms to catch a friend's attention - your arm motion activates phasic cells in your friend's retinas
39
what is the purpose of having phasic signals?
because our world is fairly stable, it is more efficient to report changes than to repeat similar messages over and over
40
temporal changes
changes that occur through time, between one moment and the next
41
stimulus location receptive field
each sensory receptor is most sensitive to stimulation of a specific area
42
describe the hierarchy of neurons in sensory processing
1. primary sensory neurons: first neurons in the system (either the receptors or the cells immediately downstream) 2. primary sensory neurons synapse onto secondary sensory neurons, and these synapse onto tertiaries
43
what is convergence and why is it important?
- at each stage, many presynaptic cells may contact any one post-synaptic cell - this allows secondary and higher neurons to combine data from many receptors
44
state a pro and a con of convergence
convergence of inputs onto a single sensory neuron enhances that neuron's sensitivity, but reduces its spatial resolution
45
spatial changes
- differences between neighbouring regions in space (eg neighbouring patches of retina or skin) - also called contrasts
46
locations where there is strong contrast are called
edges
47
how do sensory systems accentuate edges?
by lateral inhibition
48
describe and explain lateral inhibition
cells inhibit their neighbours, or they inhibit the cells their neighbours excite
49
give an example of an edge detected by sensory neurons and how lateral inhibition can improve contrast
- if an object presses against the skin, primary and therefore secondary neurons in the area of contact are activated whereas cells outside the contact area are at baseline (ie resting) activity - cell A powerfully excites E and powerfully inhibits D and F. cell B is less active than A, so its effects are weaker: it moderately excites F and moderately inhibits E and G - thus, E is more active than D, and F is less active than G - for cells away from the edge (C, D, G, H), excitation and inhibition cancel out, so these cells are near baseline activity - so the territory cells act as an edge (contrast) detector); only near the edge are there cells (E and F) whose activity is not at baseline
50
how do most sensory pathways run?
most pathways run through the thalamus, which is near the centre of the brain, out to the sensory cortices on the surface of the cerebrum
51
what pathway is an exception to running via the thalamus to the cortex?
olfactory (smell) pathways; they don't project via the thalamus, they bypass it
52
equilibrium pathways project mainly to
the cerebellum
53
importance of inference in sensory processing
- our senses evolved to guide our behaviour; a big part of this guidance is deducing what is going on around us - this is a hard job, because sense data are incomplete and ambiguous, so the brain has to infer - the inference is unconscious and fast
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