exam 2 Flashcards
first stage of neuron development
proliferation
second stage of neuron development
migration
third stage of neuron development
differentiation
fourth stage of neuron development
myelination
fifth stage of neuron development
synaptogenesis
proliferation
what is it?
when does it occur?
(1)
production of new cells in brain
occurs mostly in early life
when do stem cells begin to develop
after 20 weeks
migration
what is it?
what happens if harm occurs?
(2)
movement of the newly formed neurons/glia to their eventual locations
harm = permanent deformations
what chemicals guide neuron migration?
immunoglobulins and chemokines
radial glia aid
homeobox genes
what do they do?
what do mutations here do?
influence migration patterns
regulate expression and control start of anatomical development
mutation = brain disorders, physical deformities
differentiation
what is it?
order?
(3)
forming of the axon and dendrites that give the neuron its distinct shape
1. axon (during migration or after reaching target)
2. dendrites
myelination
what is it?
when does it occur?
where does it occur?
(4)
process by which glia produce the fatty sheath that covers the axons of some neurons
occurs: gradually for decades
occurs: spinal cord to hindbrain to midbrain to forebrain
glia important for myelination
oligodendrocytes (CNS)
Schwann cells (PNS)
synaptogenesis
what is it?
when does it occur?
when does it slow?
(5)
formation of synapses between neurons
occurs: throughout life
slows: in later life (significantly)
stem cells
undifferentiated cells found in the interior of the brain that generate daughter cells that can transform into glia or neurons
where are new neurons formed most primarily throughout life? why?
basal ganglia and hippocampus
because these areas are linked with memory and facilitate learning
diaschisis
decreased activity of surviving neurons after damage to other neurons – thus disrupts patterns of normal stimulation because of connection losses
recovery mechanisms for brain damage
axon regrowth and axon sprouting
axon regrowth
facilitated by glia cells
axons can only grow from cell-body side
axon sprouting
uses neurotrophins to lead axons to form collateral sprouts
what steers axons towards their targets?
chemical gradients
neural darwinism
we start with many neurons & synapses, but over time we keep & reject specific combos
the brain wires itself
neurotrophins
chemicals that promote the survival and activity of neurons
(essential for for axon/dendrite growth)
nerve growth factors (NGFs)
proteins sent from target regions back to the neuron attached to it to promote survival and growth
sensation
(sensory systems model)
input for receptors
sent to thalamus
sent to primary sensory cortex
perception
(sensory systems model)
input from primary sensory cortex sent to secondary sensory cortex
sent to association cortex
descending pathways
(in our current sensory model!)
higher levels of sensory systems can influence sensory input
rods
where?
used in what light?
detects what?
where: periphery
light: faint/dim light (bright bleaches them)
detects: patterns
cones
where?
used in what light?
essential for?
where: in/near fovea
light: bright
essential for: color vision
photopigments
what are they?
where are they?
present in both rods and cones
chemicals that release energy when exposed to light
bipolar cells
important for?
connects to?
where?
important for perceiving detail
receptors connects to bipolar which in turn connects to ganglion (the mid-layer)
located near center of eye
the visual path within the eye
net effect?
receptors send their messages to bipolar and horizontal cells, which in turn send messages to amacrine and ganglion cells. The axons of the ganglion cells form the optic nerve
net effect: excitation of the bipolar cell and inhibition of the surrounding bipolar cells
ganglion cells
important for?
connects to?
where?
important for perceiving detail
connects to bipolar cells (the deepest layer)
located near the fovea
horizontal cells
excited by?
inhibits?
why are they considered local?
where are they?
excited by light
inhibits the surrounding bipolar cells
they are local: no axon, no action potentials, therefore the depolarization decays with distance
located between receptors and bipolar cells, perpendicular
lateral inhibition
explained concisely?
used for?
the reduction of activity in one neuron by activity in neighboring neurons
used for heightening contrast
circular receptive fields
occur where?
describe?
in ganglion cells (retina), LGN cells (thalamus)
bullseye of excitation, surrounding circle is inhibitory
bar receptive fields
occur where?
what kinds of zones?
in simple cells (visual cortex)
zones: fixed excitatory and inhibitory – specific orientation
what are amacrine cells for
fine-tuning
retina
where?
how many receptors?
located at the back of the eye
has most of the cells (lined with receptors)
fovea
purpose?
kind of axons?
cones or rods?
for acute/detailed vision
axons are thin/unmyelinated, and go directly to the brain (receptors use just one axon)
high concentration of cones
blindspot
where?
why?
receptors?
located at the optic nerve
created by axons leaving & blood vessels blocking
no receptors here
magnocellular pathway
dorsal or ventral?
through which lobe?
where or what?
for (elaborate)?
large or small ganglion?
dorsal
parietal lobe
the “where” path
for visually guided movements
large ganglion cells go to LGN
parvocellular pathway
dorsal or ventral?
through which lobe?
where or what?
for (elaborate)?
large or small ganglion?
ventral
temporal lobe
the “what” path
for fine detail (color), recognizing objects
small ganglion cells go to LGN
primary visual cortex
where?
role in visual pathways?
in occipital lobe
pathways from retina go here
information may get sent back to thalamus for refining, then sent back to PVC
LGN
what is it?
where?
role in visual pathway?
lateral geniculate nucleus
in thalamus
most ganglion cell axons go here
superior colliculus
role in vision?
where?
some ganglion cell axons go here
in the midbrain
physics : amplitude
perception : ?
loudness
physics : frequency
perception : ?
pitch
physics : complexity
perception : ?
timbre
steps of auditory perception
- sound enters
- sound strikes tympanic membrane
- auditory ossicles
- displace hair cells on cochlea
- action potentials on auditory nerve
pitch perception
low frequencies: basilar membrane vibrations in synchrony with waves
high frequencies: neurons fire at some of the waves, but are phase-locked at the peak of cells
volley principle
the auditory nerve as a whole can have volleys of impulses up to about 4,000 Hz per second
primary auditory cortex
organized how?
damage?
tonotopically organized
damage = issues with speech/music
secondary auditory cortex
what does it do?
neurons respond to complex combinations of sound
posterior speech cortex
what does it do?
which Area is here?
finalizes speech processing
Wernicke’s Area (speech comprehension)
middle-ear deafness
another way to describe?
can’t hear others well but…?
role of auditory ossicles?
temporary or permanent?
what can help?
conductive deafness - can hear themselves clearly
auditory ossicles fail to transmit sound waves
sometimes temporary
sometimes hearing-aids help, or even surgery
inner-ear deafness
results from damage to what?
what happens to perception?
how is this obtained?
what can help?
damage to cochlea, hair cells, or auditory nerve
impairs hearing of certain frequencies
can be inherited, from disease, or exposure to loud noises
hearing aids can help
flavor
taste and smell
taste receptors
modified __?
excitable or inhibitory?
modified skin cells
excitable
release neurotransmitters
transmit information
taste buds
what are they?
where are they found?
how many papillae?
name the papillae
bundles of 50+ taste receptors
found mostly along sides of tongue – none in center
3 papillae
1. circumvallate
2. foliate
3. fungiform
medial superior olives
what are they for?
what do they do?
for sound localization
they respond to the difference in time of arrival between ears
lateral superior olives
what are they for?
what do they do?
for sound localization
they respond to the difference in amplitude of sound between ears
superior colliculus
role in audition?
where?
map of auditory space, directs head and eye movement
located in midbrain
pathway of taste that uses cranial nerve 7
and is it first or second?
damage here?
another name for cranial nerve 7’s branch?
from the anterior part of tongue to the brain
the first path
damage = inability to taste saltiness
branch: chords tympani
pathway of taste that uses cranial nerves 4 & 5
and is it first or second?
from cranial nerves 4&5 to tractus soliatirus (the NTS in medulla), then to many other places (such as pons, hypothalamus, thalamus, insult, etc.)
the second path
olfactory cells
responsible for?
where?
where are dendrites?
responsible for smell
line the olfactory epithelium, at the rear of the nasal passage
dendrites are in the mucous surface of the nasal cavity (like cilia)