Exam 2 Flashcards
(neurochemical)
- released at directed synapses
- act on neurons in immediate vicinity
neurotransmitters
(neurochemical) (two)
- non-directed synapses (volume-transmission)
- act on more distant neurons
neuromodulators and neurohormones
(neurochemical)
diffuse away from point of release
neuromodulators
(neurochemical) travel in blood supply
neurohormones
Acetylcholine synthesis
Choline + Acetate via enzyme ChAT
Acetylcholine receptors
nicotinic (ionotropic)
muscarinic (metabotropic)
Acetylcholine degradation
reuptake or broken down by enzyme AChE
Acetylcholine role in peripheral nervous system (autonomic)
both pre-ganglionic, parasympathetic post-ganglionic
Acetylcholine role in peripheral nervous system (somatic)
neuromuscular junction (think botox)
Acetylcholine role in central nervous system
projections from basal forebrain to hippocampus and amygdala; septal area (part of limbic system); brainstem
Acetylcholine behaviors
autonomic functions, movement, learning and memory
Acetylcholine clinical conditions
Alzheimer’s, myasthenia gravis (effects neuromuscular junction), schizophrenia (lots of chemicals involved in schizo)?
lose cells in these area
cholinergic areas
cholinergic projections of the human brain
basal forebrain
pons and midbrain
- binds nicotine
- blocked by curare
- ionotropic
- response is fast and brief
- located at NMJ, ANS, CNS
- excites target cells
- postsynaptic
Nicotinic ACh Receptors
plant based poison
curare
- binds muscarine
- blocked by atropine
- metabotropic./GPCR
- response is slow and prolonged, amplified
- found on Myocardial and smooth muscle, CNS
- mediates inhibition and excitation in target cells
- both pre- and postsynaptic
Muscarinic ACh Receptiors
Small molecule neurotransmitters: monoamine neurotransmitters
- catecholamines
- indoleamines
- histamine
- include: dopamine, norepinephrine, epinephrine
- synthesized from tyrosine
catecholamines
- include: serotonin, melatonin
- serotonin is synthesized from tryptophan
indoleamines
catecholamine synthesis rate limiting step
Tyrosine Hydroxylase
Dopamine (DA) role in PNS
neuromodulator for other neurotransmitters
Dopamine role in CNS
- substantia nigra (SN) -> basal ganglia
- ventral tegmental area (VTA) -> hippocampus, amygdala, nucleus accumbens, and frontal lobe
Dopamine behavior(s)
movement control, reinforcement, planning
Dopamine clinical conditions
Parkinson’s disease, schizophrenia, drug abuse
Dopamine synthesis
- tyrosine hydroxylase is rate-limiting step
- dopa decarboxylase converts L-Dopa into dopamine
Dopamine receptors
- D1 D5 = stimulatory G-protein coupled receptors
- D2 D3 D4 = inhibitory G-protein coupled receptors
Dopamine degradation
enzymes Monomine oxidase (MAO), catechol-O-methyl transferase (COMT), and aldehyde dehydrogenase, acting in sequence to break down dopamine
finite resource. determines how much of these diff compounds you can produce
rate limiting step
area involved in decision making/reward
Ventral Tegmental Area (VTA)
precursor to Dopamine
L-Dopa
D1 family (D1 and D5)
beginning and end
D2 family (D2 D3 and D4)
all metabotropic
D2 is important in ______
Schizophrenia
what breaks down catecholamines?
COMT
Norepinephrine: role in PNS
autonomic: sympathetic post-ganglionic synapses
Norepinephrine: role in CNS
widespread projections from locus coeruleus (Pons) {blue spot. widespread projections to rest of brain}; medulla, hypothalamus
Norepinephrine: behavior(s)
arousal and vigilance, mood
Norepinephrine: clinical conditions
Depression, mania, PTSD
Norepinephrine: synthesis
dopamine beta hydroxolase converts DA into NE
DA
Dopamine
NE
Norepinephrine
Norepinephrine: receptors
Alpha and Beta
Norepinephrine: degradation
enzymes MAO, COMT, and aldehyde dehydrogenase, acting in sequence to break down norepinephrine
- slow heart down
- off label use
- alter physical effects of sympathetic nervous system
Betablockers
Locus Coeruleus
arousal, stress, anxiety, mania
- relatively minor role in brain, strong neurohumoral effect
- adrenergic neurons
- regulation of blood pressure, eating
Epinephrine/Adrenaline
Serotonin(5HT): role in PNS
enteric: digestive motility
Serotonin(5HT): role in CNS
widespread projection from Raphe nucleus (pons) to brain and spinal cord
Serotonin(5HT): behaviors
sleep-wake cycles, appetite, mood, aggression, social rank
Serotonin(5HT): clinical conditions
depression, OCD, alcoholism
Serotonin(5HT): synthesis
made from tryptophan
Serotonin(5HT): receptors
at least 15 types and sub-types
most are metabotropic, can be excitatory or inhibitory
Serotonin(5HT): degradation
- reuptake (why SSRIs are so effective)
- monamine oxidase
Raphe Nuclei
sleep/wake cycles, depression
in the brain neurotransmitter: regulates sleep, hormonal secretion, memory formation, and brain arousal
Histamine
Benadryl
anti-histamine helps w/ allergic reactions. makes you feel tired and drowsy most of the time
Amino Acid Neurotransmitters
GABA and Glutamate
principle inhibitory NT
mood. seizure threshold
GABA
principle excitatory NT
long term mem. may be associated w/ neurotrauma
Glutamate
- off switch
- main inhibitory NT
- always votes no
- tied to anxiety
GABA
- on switch
- yes vote
- main excitatory NT
Glutamate
- product of Kreb’s Cycle
- terminated by high affinity uptake systems in neurons and astrocytes
Glutamate synthesis and removal
Glia: Glutamine synthesis –>
glutamine –> neuron: Glutamate
Glutamate receptors: ionotropic
AMPA
Kainate
NMDA
Glutamate receptors: metabotropic
mGluRs
Glutamate receptors(ionotropic) most common. opens sodium channel.
AMPA
Glutamate receptors(ionotropic) opens sodium channel. rare.
Kainate
Glutamate receptors(ionotropic) opens channel for sodium and calcium. special.
NMDA
GABA is synthesized from ________ in reaction catalyzed by ___
- glutamate
- GAD
____ converts glutamate into GABA. inhibitory.
GAD
GABA is terminated by
high affinity uptake systems in neurons and glia
GABA receptors: synthesized from __________
glutamate
- GABA receptor
- ionotopic
- made up of 5 subunits
- Cl ion channel
- has multiple binding sites including benzodiazepines, barbiturates, and ethanol
- more common
GABA A
- GABA receptor
- metrabotropic
- gates K+ channel
GABA B
Glycine: role in CNS
- major inhibitory NT in spinal cord interneurons
- lesser role in brain
- excitatory co-activator at NMDA Glutamate receptor
Glycine: behavior(s)
sleep/wake cycles
Glycine: toxins
strychnine
act in the CNS and in connections between autonomic neurons and the vas deferens, bladder, heart, and gut
ATP and Adenosine
is associated w/ pain perception and sleep-waking cycles
ATP
inhibits the release of namy neurochemicals, correlated with drowsiness
blocked by caffeine
adenosine
more __________ that builds up the more sleepy you feel
adenosine
small molecule NTs are synthesized here
axon terminal
do small molecule NTs recycle vesicles?
yes
small molecule NTs activation`
moderate action potential frequency
small molecule NTs deactivation
reuptake or enzymatic degradation
Neuropeptide synthesis takes place
in cell body; require transport
Neuropeptides recycle vesicles?
no
Neuropeptide activation
high action potential frequency
Neuropeptide deactivation
diffusion away from the synapse or enzymatic degradation
Neuropeptides
- Endorphins
- Substance P
- Insulin and Cholecystokinin
- Oxytocin and Vasopression
- Neuropeptide
- neuromodulators that reduce pain and enhance reinforcement
- “opium within”
- feelings of well-being
endorphins
- Neuropeptide
- transmitter in spinal cord neurons sensitive to pain
Substance P
- Neuropeptides
- digestive functions
Insulin and cholecystokinin
- Neuropeptides
- neuromodulators and neurohormones
- relationships; levels influence whether species is monogamous or not
Oxytocin and vasopression
the cuddle hormone
oxytocin
learning and memory; Alzheimer’s disease; muscle movement in the peripheral nervous system
ACh (Acetylcholine)
reward circuits; motor circuits involved in Parkinson’s disease; schizophrenia
DA (Dopamine)
arousal; depression
NE (Norepinephrine)
depression; aggression; schizophrenia
5HT (serotonin)
learning; major excitatory neurotransmitter in the brain
GLU (glutamate)
anxiety disorders; epilepsy; major inhibitory neurotransmitter in the brain
GABA
pain; analgesia; reward
endorphins
diffuse through membranes and interact with intracellular receptors. can transmit info from the postsynaptic to the presynaptic neurons (retroactive)
gaseous neurotransmitters
Two gaseous NTs
- nitric oxide
- carbon monoxide
- found in CNS and PNS, smooth muscle
- relaxes smooth muscle cells in blood vessels
- erection
nitric oxide
colorless, odorless. undetectable by humans
- low doses: hallucinations and paranoia
- high doses: can kill you
carbon monoxide
any substance that alters the body or its functions
drug
relationship between concentrations of drug and biologic effects. (what drugs do to the body)
pharmacodynamics
what the body does to drugs
- absorption
- distribution
- metabolism
- excretion
pharmacokinetics
ED
effective dose @ 50% of the population
plateau. more drug is not going to have more difference at _________
saturation
characteristics of drugs
- affinity
- potency
- efficacy
tenacity w/ which (how well) a drug binds to its receptor
affinity
fits perfectly to receptor
high affinity
fits but not as perfect of a match
medium affinity
doesn’t bind very well
low affinity
affinity is a property/characteristic of the ______ not the _________
drug; receptor
amount of drug required to produce a certain response
potency
want higher ______ so can have a lower dose to get desired effect (lower dose leads to less likelihood for side effects)
potency
property of a drug that determines its ability to produce its biological effect
efficacy
more _______ leads to more response
efficacy
types of drugs
- agonist
- antagonist
- mimics or enhances the effect of a neurotransmitter
- activate receptor
- partial, full, or inverse
- block reuptake or degradation
agonist
- blocks or decreases the effect of a neurotransmitter
- block receptors without activating
- competitive vs non-competitive
- decrease availability of neurotransmitter by reducing production or release
antagonist
presynaptic drug actions
- neurotransmitter production
- neurotransmitter storage
- neurotransmitter release
manipulating the synthesis of a neurotransmitter will affect the amount available for release
neurotransmitter production
interfering with the storage of a neurotransmitters in vesicles within a neuron
neurotransmitter storage
drugs can modify the release of a neurotransmitter in response to the arrival of an action potential
neurotransmitter release
post synaptic drug actions
postsynaptic receptor effects
- can mimic the action of a neurotransmitter at the site (agonist)
- can block the synaptic activity by occupying a binding site (antagonist)
- can influence the activity of the receptor
postsynaptic receptor effects
drug actions: removal effects
- reuptake effects
- enzymatic degradation -deactivation of neurotransmitters
cocaine, amphetamine, and Ritalin inhibit ________ _______
dopamine reuptake
SSRIs (Prozac) inhibit _________ _______
serotonin reuptake
organophosphates interfere with _______
AChE
enzymatic degradation
drug effects are influenced by
- body weight
- sex
- genetics
- user expectations influence drug effects
- can result in real biochemical and physiological effects in the brain
- needs double-blind experiments
placebo effects
decreased response to drug with repeated use
tolerance
reduction in amount of drug that reaches site of action
metabolic tolerance
reduction in reactivity of sites of drug action
- receptor down regulation (less)
- receptor up regulation (more)
functional tolerance
learned tolerance
context specific
occurs when substance use is discontinued; opposite of the effects caused by the discontinued drug
withdrawal
- characterized by a compulsive need to re-administer a drug despite harm to user
- the dopamine reward system, including nucleus accumbens
- result of complex physical and environmental variables = extremely hard to treat
addiction
increase alertness and mobility
stimulants
list of stimulants
- caffeine
- nicotine
- cocaine
- amphetamine
adenosine antagonist
caffeine (stim)
acetylcholine nicotinic receptor antagonist
nicotine (stim)
dopamine floods synapse, dopamine reuptake inhibitor so dopamine in synapse longer
cocaine (stim)
stimulates release and inhibits reuptake of dopamine and norepinephrine
amphetamine (stim)
decrease activity of CNS
depressants
list of depressants
- opioids
- alcohol
reduced release of GABA, less inhibition on DA neurons so more DA into synapse
opioids
GABA A agonist, increases chloride influx.
Glutamate antagonist, reduces excitation
alcohol
cause perceptional distortions
hallucinogens
list of hallucinogens
- marijuana
- LSD
- ecstasy
- ketamine
- PCP
active ingredient THC is an endogenous cannabinoid receptor agonist
marijuana
serotonin agonist
LSD
stimulates massive release of serotonin (and some oxytocin). taken up by serotonin transporters, reverse flow of serotonin, toxic to serotonin neurons
ecstasy (molly)
NMDA glutamate antagonist
ketamine
NMDA glutamate antagonist, nicotinic Ach antagonist
PCP (angel dust)
DNA –> RNA –>
proteins
candidate gene
look for specific gene associated with specific trait. spotlight search
genome-wide
large scale. zoomed out.
approx. ____________ genes in the human genome
20,000
__ autosomes pus X and Y
22 (46 diploid)
genes have ____ and _____
exons and introns
exons
coding sequence
introns
noncoding sequence found between exons
recessive genes on one X chromosome that are not duplicated on the Y chromosome will be expressed in male offspring
sex-linked characteristics
X-chromosome inactivation
one X is randomly silenced in females to equalize protein production in males and females
Genetic modification approaches
- knock in
- knock out
- CRISPR
- retroviral gene therapy
take a gene from another species and insert it
knock in
delete a gene and see how it effects receptors and how that effects behavior
knock out
use viruses. put DNA in target cells
retroviral gene therapy
errors in DNA replication
mutations
single nucleotide polymorphisms (SNPs)
- DNA sequence change at one nucleotide
- SNPs in the APOE gene can predict risk for Alzheimer’s disease
copy-number variations (CNVs)
- variable numbers of genes in gene series
- associated w autism and schizophrenia
A goes w
T
C goes w
G
can occur spontaneously or in response to radiation, chemicals, or other mutagens
genetic mutations
average human baby born w __________ mutations
~130 (most have little to no effect)
a dominant mutant allele or two copies of a recessive mutant allele will affect organism’s ___________
phenotype
neg effects: poor oxygen capacity
pos effects: some protection against malaria
sickle cell anemia
genetic variant near olfactory receptor genes influences cilantro preference
Genetics of cilantro
_____ markedly exacerbates tau-mediated neurodegeneration in a mouse model of tauopathy
ApoE4
three copies of 21st chromosome. developmental delays. physical disabilities
down syndrome
the contribution of genetics to the variation of a trait observed in a population
heritability
heritability always refers to a __________, not to individuals
population
o = genes play no role in __________
phenotypical differences
X = X% of the __________ ____________ we see in a trait can be accounted for by genetic differences
population variation
100 = genetics are ___________ responsible for phenotypical differences
completely
changes in gene expression or phenotype that don’t involve changes to the DNA sequence
epigenetics
DNA may unwrap or be stopped from unwrapping from the histone
a methyl group or other molecule bind to the tails of histones, either blocking them from opening or allowing them to open for transcription
histone modification
transcription of DNA into mRNA may be enabled or blocked methyl groups (m) bind to CG base pairs to block transcription
DNA modification
mRNA translation may be enabled or blocked
ncRNA binds to mRNA preventing translation
mRNA modification
first week: human zygote has divided into three germ layers
ectoderm
mesoderm
endoderm
second week: zygote is referred to as an ________
embryo
third week: inducing factors differentiate the ectoderm layer into skin and ________ _________
neural plate
the developing neural plate forms the _________ _________
neural tube
outer layer; becomes skin and neural tissue
ectoderm
middle layer; becomes connective tissue such as ligaments, muscles, blood vessels, and urogenital system
mesoderm
inner layer; becomes many internal organs
endoderm
thickened region of the ectodermal layer that gives rise to the neural tube
- neural plate
formed when the plate invaginates
- neural groove
structure in the early stage of brain development from which the brain and spinal cord develop
- neural tube
______ ______ forms ventricles and central canal of spinal cord
surrounding tissue becomes brain and spinal cord
neural tube
stages of neural development
- cell proliferation
- migration
- differentiation
- circuit formation
- neuron death (apoptosis)
- refinement of connections
cell proliferation
make cells
generation of new neurons
neurogenesis
generation of new glia
gliogenesis
migration
put them where need to be
differentiation
specialized roles
circuit growth
(connections)
axon growth
synaptogenesis
neuron death
apoptosis
refinement of connections
synaptic pruning
synaptic rearrangement
embryonic stem cell
totipotent
unlimited capacity for self-renewal
ability to develop into any type of cell in the body
totipotent
neural stem cell
pluripotent
on neural or glial track
ability to develop into many types of mature nervous system cells
pluripotent
neural progenitor cell (blast cells)
unipotent or oligopotent
limited capacity for self-renewal
ability to develop into one or a few types of mature nervous system cells
unipotent or oligopotent
new neural cells are produced from the mitosis of neural or glial progenitor cells in the _______ _______ lining the neural tube
ventricular zone
up to 250,000 new neural cells
per minute
migration via _____ ____ ____
radial glial cells
provide structural support
rope to climb up
radial glial cells
neurons move from _____ ______ outward to final location
ventricular zone
“inside out” _____
subcortical (towards skull)
migration
differentiation of neural tube (dorsal-ventral axis)
dorsal half –>
sensory neurons (BMP Protein) dorsal root in spinal cord
differentiation of neural tube (dorsal-ventral axis)
ventral half –>
motor neurons (Sonic Hedgehog; linked w very fast motor output) ventral root in spinal cord
differentiation of neural tube (rostral-caudal axis)
rostral-caudal (anterior-posterior) Hox genes
rostral-caudal (anterior-posterior) Hox genes
- spinal cord
- myelencephalon
- mesencephalon
- diencephalon
- telencephalon
neuronal maturation and circuit formation
chemical and molecular signposts attract or repel advancing neurites
________ grow to provide surface area for synapses w other cells
dendrites
______ grow toward target cells and form functional connections
axons
dendrites
listen
axons
have something to say
reading the environment with growth cones: flopodia
long, fingerlike extensions from growth cones of neurites
reading the environment with growth cones: lamellipodia
flat, sheet like extensions from core of growth cones
axons growing in same direction stick together
fasciculation
once axons reach their destination they must establish new synapses
synaptogenesis
significant numbers of new neurons die during a process called
apoptosis
destroyer. begins apoptosis. inhibiting the destroyer keeps you cell alive
caspase
brain produces extra neurons.
excess neurons and synapses must be eliminated
synaptic pruning
use it or lose it =
activity dependence
occipital peak
4 mos
prefrontal cortex peak
1-4 years
occurs in rostral direction starting w the spinal cord, then hindbrain, midbrain, and forebrain
burst in myelination around the time of birth
myelinogenesis
___________ _________ not completely myelinated until early adulthood (age 21-25)
prefrontal cortex
the nervous system’s ability to change
plasticity
time when particular experience is influential and after which experience has little or no effect
critical period
adult neurogenesis fist discovered in _________ and _________ _______
hippocampus and olfactory bulbs
the brain in adolescence : puberty
- surge of gray matter development and pruning
- thickening of cortex; frontal lobe
- amygdala matures first (explains teen risky behavior?)
brain is fully mature at age
25
weight of brain starts to decrease at age
45
stimulus for vision is
light
light =
moving waves of photons
wavelength =
color or shades of gray
amplitude =
brightness
light can be
- reflected
- absorbed
- refracted
our eyes _________ light
refract
protecting the eyes
- located in orbit of the skull
- cushioned by fat
- eyelids/eyelashes/blinking
- tears produced from lacrimal gland
optical functions:
capture light and form detailed spatial images
neural functions:
of the eye
transduce light into neural signals, then relay and process those signals
outer surface of the eye. curved, transparent dome that initially bends incoming light (lot of pain receptors here)
cornea
neural tube defects associated with folic acid
spinal bifida
anencephaly
strong immune response to phenylaniline, found in food.
PKU
transparent, gelatinous mass that fills space from cornea to pupil (first point where light can be refracted)
aqueous humor of anterior chamber
colored area; contains muscles that control the pupil
iris
black opening that lets light in
pupil
transparent disk that uses accommodation to focus light rays for near or far distances (bends the light)
lens
transparent, gelatinous mass that fills space from pupil to retina (large fluid filled area. jello like texture)
vitreous humor
innermost layer in back of the eye where light is converted to neural impulses. contains visual interneurons and photoreceptors.
retina
part of the retina where light rays are most sharply focused (focal point. where we have most clear vision)
fovea
transmits impulses from retina to brain
optic nerve
6 muscles rotates eye in all directions
eye muscles
the eye is like a camera
accommodation:
changing the shape of the lens to focus on objects of varying distances
convex
( ) near object
concave
) ( far object
features of retina
-visual interneurons and photoreceptors
-optic disk
-macula
(fovea)
-tapetum lucidum
very center of macula is where we have our …
fovea
cows and most mammals have this in their eyes. shiny. reflective. helps w night vision.
tapetum lucidum
filled w light-sensitive chemicals called photopigments
photoreceptor cells
- scotopic vision (dim light)
- useful at night
- no color, low acuity
- high density in the peripheral retina
rods
- photopic vision (bright light)
- color, high acuity
- high density near fovea
cones
contains rhodopsin photopigment
sensitive to dim light in the blue to green range of electromagnetic spectrum
rods
contain lodopsin
requires more light than rds in order to respond
3 diff types
cones
3 diff types of cones
- blue/short
- green/middle
- red/long wavelength
the resting potential of rod outer segment in complete darkness is about
-30 mV
_____ have more activity in the dark than they do in the light
rods
dark =
depolarized
light =
hyperpolarized (more negative)
light releases enzyme that breaks cGMP. less cGMP means fewer _______ channels remain open, and receptor hyperpolarizes
sodium
In the dark photoreceptors are
depolarized
in the light photoreceptors are
hyperpolarized
photoreceptors produce __________ __________ not action potentials
graded potentials
graded potentials: the more photons, the less ___________
neurotransmitter
optic disk
blind spot
where blood vessels and optic nerve leaves the retina there are no photoreceptors = no vision
the blind spot
located between photoreceptors and bipolar cells. perform lateral inhibition. responsible for center-surround receptive fields.
horizontal cells
bridge between photoreceptors and ganglion cells
bipolar cells
connection between eye and brain. receives info from bipolar cells and sends info via the optic nerve. uses action potentials.
ganglion cells
order of cells (for eye)
photoreceptor cells
bipolar cells
ganglion cells
receives input from photoreceptors and horizontal cells
bipolar cells
input from one cone –> ganglion cells
in bipolar cells
midget
input from several photoreceptors –> ganglion cells
diffuse
bipolar cell depolarized
on-center cell
bipolar cell hyperpolarized
off-center
direct input from singe set of photoreceptors
center
indirect input from horizontal cells connected to photoreceptors
surround
on-center is always
off-surround
- receives input from amacrine and bipolar cells
- generates action potentials
- provides sole output of visual info to brain, axons form optic nerve
- have receptive fields w antagonistic center-surround organization
ganglion cells
- horizontal cells inhibit activity of neighboring bipolar cells
- contrast enhancement helps us see edges, boraders
lateral inhibition
ganglion cells are _______ detectors, not light detectors
contrast
types of ganglion cells
P-type
M-type
K-type
-90% of ganglion cells, small receptive fields
-receive input from midget bipolar cells
-involved in fine visual acuity, color, and shape processing
slow but detailed
P-type
-5% of ganglion cells, larger receptive field
-receive input from diffuse bipolar cells
-involved in motion processing
fast but fuzzy
M-type
similar to P cells, color sensitive but less well understood
K-type
part of environment registered on retina
visual field (VF)
processed in left hemisphere (not just right eye)
Right VF
processed in right hemisphere (not just left eye)
left VF
looks like an X. where cross over of right and left VFs goes to brain
optic chiasm
ganglion cell axons bundle together and exit each eye through the optic disk, forming an _______ ______ leaving each eye
optic nerve
- located in hypothalamus
- regulates sleep/wake cycle
- small number of retinal axons
suprachiasmatic nucleus
- located in midbrain
- guides head and eye movements
- about 10% of retinal axons
superior colliculus
- located in thalamus
- projects to primary visual cortex (V1), visual perception
- about 90% of retinal axons
Lateral geniculate nucleus (LGN)
main destination of fibers
main sensory pathway
lateral geniculate nucleus
optic nerve to optic chiasm to
optic tract
- 6 distinct sacked layers (1 and 2 magnocellular, 3-6 parvocellular)
- keeps input from each eye separate
- antagonistic center-surround receptive fields
Lateral geniculate nucleus (LGN)
about 80% of input to LGN comes from
primary visual cortex
layers 1 and 2 of LGN
where we get input from M ganglion cells
layers 3-6 of LGN
where we get input from P ganglion cells
- large cells. layers 1 and 2.
- receive input from M ganglion cells
- respond best to large, fast moving objects
Magnocellular
- smaller cells. top 4 layers (3-6)
- receive input from P ganglion cells
- respond best to fine spatial details of stationary objects
Parvocellular
a major transformation of visual info takes place in
striate cortex (aka primary visual cortex, or V1)
with V1 we look at
lines of light and how they’re moving
locations of retina and LGN correspond to location in
V1
areas 4, 5, and 6. most of V1 is in very close proximity to fovea. where we have most processing for vision
foveal magnification
- receptive fields maintain antagonistic center surround, produced by combining outputs of LGN cells
- shape of receptive field elongated
- respond to stimuli shaped like bars or edges that have a particular slat or orientation
- reinotropic mapping
simple cortical cells
- longer receptive fields
- no off region
- shows preferred stimulus size and orientation but not location within visual field
- sensitive to unidirectional movement
- retinotopic mapping
complex cortical cells
preferred stimulus = vertical but off to side. moving light. less vertical.
less firing. sensitive to direction of movement
complex cortical cells
responds to lines of a single angle for single eye
made of simple cortical cells
orientation column
responds to input from either the left or right eye, but not both. preferred orientation changes.
ocular dominance column
complex cells
movement
cytochrome oxidase blobs
color
“what” and “where” pathways
“what”
ventral stream
“what” and “where” pathways
“where/how”
dorsal stream
- magnocellular
- specialized for movement, locating objects, and visual control of skilled actions
- “how”; provides info on how to interact w object
the dorsal pathway
- rare disorder of motion blindness caused by damage at the occipito-parietal junction
- vision without movement
- can’t perceive motion
akinetopsia
- parvocellular
- responds to shapes (different forms) and colors
- associated w storage of long-term memory
the ventral pathway
rare disorder of face blindness caused by damage at the fusiform face area within temporal lobe
prosopagnosia
responds preferentially to places, such as pictures of houses
PPA: Parahippocampal place area
responds to faces more than other objects (damage –> prosopangnosia)
FFA: fusiform face area
specifically involved in the perception of body parts
EBA: extrastriate body area
striate cortex responds to patterns of lines
gratings
color visiton based on combo of activity in short (B), medium (G), and long sensitive (R) cones
trichromatic theory of color
color vision based on exciting one color and inhibiting its opposites
supported by complementary colors, afterimage effects
opponent process theory of color vision
3 types of color receptors
red
blue
green
myopia
nearsighted
hyperopia
farsighted
process of converting an external energy or substance into neural activity
transduction
activation is greatest when we first detect a stimulus
sensory adaptation
sound results from
a collision of molecules
intensity (loudness) of sound wave
amplitude
wavelength of a sound wave
frequency
above range of human hearing
used in imaging
ultrasound
below range of human hearing
used by many animals
dizziness, nausea, bowel movements
infrared sound
- collects, focuses, and localizes sound
- signals emotion in some animals
pinna
- tube-shaped opening to middle ear
- the length and shape enhances certain sound frequencies
the auditory canal
boundaries of middle ear are formed by two membranes
- tympanic membrane
- oval window
eardrum
tympanic membrane
leads to cochlea
oval window
bones that amplify and transfer vibrations from air to fluid
ossicles
ossicle bones
- malleus
- incus
- stapes
malleus
hammer
incus
anvil
stapes
stirrup
muscles that decrease ossicle vibrations when tensed
tensor tympani and stapedius
responds to vibrations from middle ear
cochlea
fluid filled. 3 different chambers.
cochlea
cochlea’s 3 chambers are
vestibular canal (perilymph) middle canal (endolymph) tympanic canal (perilymph)
perilymph
like CSF
endolymph
high K+, low Na+
type of fluid in vestibular and tympanic canals
perilymph
type of fluid in middle canal
endolymph
two membranes of inner ear
reissner’s and basilar
extends from oval window at base of cochlea to helicotrema at the apex. contains perilymph
vestibular canal
thin sheath of tissue separating the vestibular and middle canals
reissner’s membrane
sandwiched between the tympanic and vestibular canals and contains the cochlear partition. contains endolymph
middle canal
plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea
basilar membrane
extends from round window at base of cochlea to helicotrema at the apex. contains perilymph
tympanic canal
on the basilar membrane, composed of hair cells and dendrites of auditory nerve fibers. transduces movements of cochlear partition
organ of corti
a gelatinous structure, attached on one end, tat extends into the middle canal of the ear, floating above inner hair cells and touching outer hair cells
tectorial membrane
convey almost all info about sound waves to brain. 3,500 total. (important for sensory processes)
inner hair cells
convey info from brain (use of efferent fibers). they are involved in elaborate feedback system/. 10,500 total.
outer hair cells
“tip links”
stereocilia movement opens and closes mechanically-gated K+ channels
carries signals from cochlea to brain stem. projects to both hemispheres.
the auditory nerve
in medulla. first brain stem nucleus at which afferent auditory nerve fibers synapse
cochlear nucleus
an early brain stem region (mostly pons) in the auditory pathway where inputs from both ears converge. useful for timing
superior olive
a midbrain nucleus in the auditory pathway
inferior colliculus
in thalamus. relays auditory signals to the primary auditory cortex (part of temporal cortex) and receives input from the inferior colliculus
medial geniculate nucleus
in temporal lobe
auditory cortex (A1)
most of hearing is processed
contralaterally
contralaterally
sounds in left ear processed mostly in right side of brain
descussation (crossing over) in
brainstem
- columns respond to frequencies
- some neurons respond maximally to input from one ear, others respond maximally to input from both ears
- some neurons respond to intensity of sounds
primary auditory cortex
- activated by more complex sounds including speech
- responds to vibration
- dorsal where and ventral what pathways
secondary / association auditory cortices
firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency
phase locking
multiple neurons can provide a temporal code for frequency if each neuron fires at a distinct point in the period of a sound wave but does not fire on every period
the volley principle
pitch at proximal end of cochlea (near oval window)
high pitch
pitch at distal end of cochlea (near center of coil)
low pitch
frequency follows individual neuronal firing up to 4 kHz
frequency theory
higher frequencies better represented by the patterns of neuronal firing
place theory
- comparison of arrival times of sounds at each ear and differences in intensities; important in horizontal plane
- pinna important for this in vertical plane
localization of sound
arrival time and intensity of sound at each ear analyzed by
superior olive
smooth muscles :
digestive tract
arteries
reproductive system
striated muscles :
skeletal muscles
cardiac muscles of the heart
