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Flashcards in Chapter 2 Deck (72):
1

What does it mean to say that the brain has a modular organization?

Specific information is processed by different cortical areas

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3 Primary sensory areas in the cortex

Occipital - visual

Temporal - auditory

Parietal - skin senses like touch, temperature, and pain

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Neuron

A cell that specializes in sending and receiving information

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Dendrites main role

receive information

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Axon's main purpose

Send information

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Myelin sheath

layer of protective cells

provides nutrients

speeds electrical signals

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Nodes of ranvier

gaps in myelin sheath

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Receptors

neurons that change physical energy into an electrical signal

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What is the resting potential charge of a neuron?

-70mv

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Describe action potentials

A stimulus from the environment causes the neuron to transmit a signal and the cell membrane then becomes permeable

Na+ rushes in, the neuron has a rapid increase in positive charge

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Refractory period

Neuron now permeable to K+

Brief period after Na+ leaves inside of neuron

cannot fire again

hyperpolarization

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5 properties of action potentials

  1. All or none response
  2. Propogated response (goes to end without stopping, no decrease in amplitude)
  3. Magnitude never changes
  4. The rate/speed of firing indicates the intensity of the stimulus
  5. There are limits on firing rate (the refractory period)

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Synapse

small gap between neurons

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Neurotransmitter

Chemical released into synapse

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Vesicle

stores neurotransmitters

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Receptor sites

the spot on the postsynaptic neuron that receives the neurotransmitter

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Types of responses to a neurotransmitter

Exitatory (postsynaptic fires more)

Inhibitory (postsynaptic fires less)

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Excitatory response

electrical potential increases

next neuron is more likely to fire

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Inhibitory response

Electrical potential decreases

Next neuron less likely to fire

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Neural circuits

groups of interconnected neurons

-simple linear

-converging circuits

-complex circuits

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Simple linear circuit

simple passing on of input

firing rate remains stagnant

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Converging circuits

Many receptors to one neuron

Firing rate gradually increases in number

More stimulated receptors means a greater response from the neuron

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Complex circuits

some receptors excite and some inhibit

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Receptive fields

Determine which receptors contribute to a neural circuit

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On response

increased firing with stimulation

return to base rate after stimulation

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Off response

decreased firing with stimulation

burst of firing after stimulation

return to base rate

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3 ways nerve impulses represent things in the environment

  1. Local representation
  2. Fully distributed representation
  3. Sparse distributed representation

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Local representation

Specificity coding

All information about a stimulus or event is in a single neuron called the "grandmother cell"

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Fully distributed representation

Distributed coding

All information is in all neurons of a given population

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Sparse distributed representation

Sparse coding

Small proportion of neurons carry information about a stimulus or event

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Just noticeable differences (JNDs)

the smallest detectable difference between two stimuli

also called differenze limen (DL)

 

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In what way are JNDs dependent on the intensity of stimuli?

More of a difference is needed for more intense stimuli

ex: 2 inches of long hair isn't as noticeable as 2 inches of short hair

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Equidistant physical stimuli.......

are NOT perceived as perceptually equidistant

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reflective light

the light that bounces off objects and hits your retina

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Continuum of energy

electromagnetic spectrum

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wavelength (frequency)

distance between peaks

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wavelength of visible light

between 400-700 nanometers

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retina

layer of light receptors and nerve cells lining back of eye

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photoreceptors

rods and cones

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rods

outnumber cones

most prevalent in peripheral retina

best at detecting faint light

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cones

fewer

most abundant in the fovea

better at detecting fine detail

give us color vision

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fovea

middle of retina

only cone receptors here (reduce as you go out to peripheral)

very small and pit like

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optic nerve

collection of axons that leave the eye

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blind spot

where the optic nerve leaves the eye

45

what are the visual pigment molecules that transform light into energy

opsin (moves)

retinal (attached to opsin)

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photon

smallest packet of light energy

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isomerization

retinal absorbs light, changes shape and goes from bent to straight

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Differences between rods and cones (4)

dark adaptation

pigment regeneration

spectral sensitivity

convergence

49

stages of dark adaptation

fast stage - done by cones, takes 3-4 minutes

slower stage - done by rods, takes 25-30 minutes

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rod-cone break

when you go from relying on cones to rods

51

why did pirates where eye patches

pre electricity (on boats)

wore to always keep one eye dark adjusted

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pigment bleaching

after the retinal changes shape - it detaches 

retinal starts becoming lighter

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pigment regeneration

opsin and retinal rejoin

retina becomes darker

cones take about 6 minutes

rods take about 30 minutes

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When are we most sensitive to light?

In the dark

55

How does light enter the eye?

What focuses it?

Pupil and iris

Lens and cornea

56

what is a visual pigment

light-sensitive chemicals that react to light and trigger electrical signals

57

Ratio of eye focusing power

80% cornea (fixed)

20% lens

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How do ciliary muscles help lens focus?

Increase the curvature which increases ability to bend light

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isomerization

when retinal straightens up

starts a chemical chain reaction among the molecules that activate the receptor

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spectral sensitivity

the sensitivity to light as a function of its wavelength

61

What level of light are rods most sensitive to?

500 nm greens

62

What colors look brighter in dim light and why?

Greens and blues

What rods are most sensitive to

Rods predominant in dim lighting

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3 types of cones and their spectral sensitivities

short - dark blues

medium - light green

long - yellows

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convergence

many neurons synapse to one

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Ratio of receptors to ganglion (macro and micro)

126 million to 1 million

120 rods and 6 cones per 1 ganglion cell

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Difference in convergence between rods and cones

rods - converge more; more sensitive because it takes less light to create a response

cones - more direct lines; better acuity because more specific details are transmitted

67

Neurons in the retina

bipolar cells

ganglion

horizontal 

amacrine

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bipolar cells

connect to receptors and send messages to ganglion

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horizontal cells

between receptors

to bipolar cells

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amacrine

between bipolar and ganglion cells

71

center-surround antagonism

if the entire receptive field is stimulated, the end result is no change from baseline firing (middle - on, outside - off)

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