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Brain Mind and Behavior - midterm 2
Terms in this set (278)
Explain the study using different ads and its effect on cognitive effect
researchers had the same study advertised in 2 ways: either do it for credit or "participate in this study studying cognitive training - cognitive training has been SHOWN to improve cognition" and people who responded to the second add did better in their IQ tests.
explain the cardiac angioplasty surgery and the placebo effect
people have stent inserted in their arteries to open up the vessel
when they did a sham surgey in a trial, people had the same decrease in pain when getting the sham surgeries than people who had the stem inserted
explain the placebo control clinical trial on the BIMAL surgery
They gave "fake" surgeries (opening the chest but not doing anything) to half of the patients in the trial (this was before informed consent lol)
half of the patients got the real surgery.
Both gave the same results!!!
how do we treat angina pectoris?
medication that open up the blood vessels OR by doing a bilateral internal mammary artery ligation (BIMAL) where we attach the mammary arteries to the heart to force blood flow into the heart
What is angina pectoris?
chest pain (believed to be) caused by inadequate flow of blood and oxygen to the heart
Why cant we just take placebo instead of antidepressants to treat depression?
because it would require a whole worldview shift, a deep paradigm shift - we trust the neurochemical understanding of depression too much.
what is the most used psychoactive drug in the world
what is the second most common psychoactive drug in the world? 3rd and 4th and 5th?
4rd: arecoline in the betel nut
5th: cannabis (probably)
what was one of the first molecule to be identified in plants
caffeine (in 1820)
What does the caffeine molecule look like?
it looks like adenosine (a neurotransmitter in the brain)
how does caffeine work in the brain
adenosine receptor antagonist (blocks the receptor so no adenosine can bind to the receptor)
what kind of neurotransmitter is adenosine
inhibitory - slows things down
where is tobacco from?
latin name of tobacco
how does nicotine work in the brain
agonist at nicotinic AChRs
CNS effects: stimulation of the mind AND relaxation of the body
why doesnt nicotine stimulate muscles
because the nicotinic Ach receptor at the neuromuscular junction is slightly different than the one in the brain so it doesnt active it as much
where is acetylcholine circuitry in the brain
basal forebrain nuclei and midbrain pontine nuclei
What is the structure of ethanol
describe the properties of alcohol
it is both hydrophilic AND hydrophobic so it can dissolve almost anything
how is alcohol made?
with anything that has sugar in it can be turned into alcohol using stuff like yeast to ferment the sugar.
what is the effect of alcohol in the brain
sedative hyponitic drugs
what other sedative hypnotic drugs exist
barbiturates (pharmacological compounds, dont exist in nature) dont memorize their name please
what are sedative hypnotics dangerous
because their therapeutic index is pretty low
TI = lethal dose / therapeutic dose
used in execution
what were problems with execution
people giving the drugs weren't trained medical professionals so there were a lot of cases of botched executions where people suffered a lot
what are benzodiazepines used for
What do all sedative hypnotic drugs have in common
they facilitate/enhance inhibitory action of GABA
GABA are ionotropic GABA receptors that let chloride- ions go through
where is the areca nut palm from
east and south asia
latin name of areca nut
how is the areca nut consumed
you wrap the areca nut around piper betel which is black papper
what molecules are found in the areca nut responsible for the psychoactive activity
arecoline and arecaidine
arecoline is a muscarinic acetylcholine receptor agonist which activates the parasympathetic nervous system and causes relaxation
also is a CNS stimulant
what is the poison aspect of areca nuts
stained and damaged teeth
where does coca come from
found in south america
how does cocaine work in the brain
blocks reuptake transporters for dopamine and norepinephrine so you have more stimulation from those 2 neurotransmitters
effects of cocaine
CNS: stimulant: wakefulness, stamina, appetite suppressant
toxicities: sympathetic overstimulation
also a local anesthetic
why does the coca plant make cocaine
it's an insecticide
what tax was passed in berkeley in 2014 regarding sugar
soda tax: sugary drinks need to be taxed 0.01$ per ounce of sugary beverage.
does this law seem to work?
yes because there was a decrease in consumption of sugary beverages in berkeley compared to oakland.
what was the opposition to the soda tax
in SF - 7.7 million $ were put into campaining against it and it worked, no law was passed.
how do amphetamines work in the brain
causes neurons to become leaky so that norepinephrine and dopamine are always released from he axon terminal. They also block reuptake of norepinephrine and dopamine which increases their presence in the synaptic cleft
effects of amphetamine
CNS stimulant: wakefulness, stamina, appetite suppressant
toxicities: sympathetic overstimulation, CNS overstimulation
Describe the opium poppy
white liquid that comes out of the poppy is the opium
acute effects of opium
analgesia (reduces pain), anxiolytic, sedation, cough suppression, decreased intestinal motility, pupil constriction
what did friedrich wilhelm serturner discover
discovered that morphine was responsible for the effects of opium. called it morphine. interesting because first time someone single out one purified chemical component in a plant and attributed all its properties to this one chemical.
how was heroine first made
synthetic modification of morphine - adding an acetate group to morphine instead of and OH group and it becomes more hydrophobic so it goes through the brain even better than morphine! 2-3x more potent than morphine. marketted by bayer for pain and cough
is strength of opioids related to their legality/illegality?
no pretty arbitrary
describe the synthetic opioids
not directly related to morphine in chemical structure but they have the same effect. ex: fentanyl
how much stronger in fentanyl compared to morphine
100x more potent
what is 10 000x more potent than morphine
carfentanyl - used in elephants
toxicity of opioids
depression of respiratory control centers in brainstem
potential overdose and death from respiratory depression
describe the trend in drug overdose deaths in the US
it is increasing every year. the main cause is fentanyl and other synthetics.
84% of deaths due to drug overdose were due to opioids
the rest was due to stimulants, benzos and antidepressants.
Where do opioids act in the brain
agonists at opioid receptors (GPCRs of different types: mu, delta, kappa)
how does naloxone work
antagonist of opioid receptors
blocks and reverses the effects of opioid agonist.
almost the same shape of morphine.
used as an antidote in overdoses with opioids.
what naturally binds to the opioid receptors in the body?
endorphins = endogenous morphines
opioid peptides (short chain of amino acids)
different names for cannabis
marijuana, pot, hash, weed, etc.
do people die of cannabis overdose
cannabis is a schedule one controlled substance, what does this mean
no currently accepted medical use, lack of accepted safety for use under medical supervision, high potential for abuse
tensions between federal and state laws
effects of cannabis
reduces intraoculr pressure
psychedelic like state
uniqur botanical chemistry known nowhere else
what is the active molecule in cannabis
cannabinoids: CBD, THC, CBN and THCA-A
what are terpenes
molecules that are responsible for the smell of plants
found in cannabis too
possible therapeutic effects
probable synergistic interactions with cannabinoids.
what naturally binds to cannabinoid receptors in the brain?
the endocannabinoids (endogenous cannabinoids)
anandamine and 2-AG
found throughout the brain and body
how do endocannabinoids work in the brain
the cannabinoid receptors are largely presynaptic meaning found on the axon terminal (before the cleft).
When glutamate is released by the axon, this causes the post synaptic neuron to form endocannabinoids. Once synthesized, the endocannabinoids travel towards the pre synaptic axon where they bind the cannabinoid receptors. this is called retrograde signal because it goes "backwards"
who is raphael mechoulam
in 1963 discovere that THC was the primary psychoactive component of cannabis
What do psychedelics do
amplify the mind
example of psychedelics
LSD, psilocibyn, psilocin,
Who discovered LSD
Albert Hoffman - pharmaceutical chemist at Sandoz in Switzerland.
wrote a book called LSD my problem child.
what are psilocybe mushrooms?
mushrooms with psychoactive properties. used in southern mexico. in the 1950s, maria sabina told the story of psilocybe use in their community and the LIFE magazine wrote a story about it and then psychedelics became known to the world.
dimethyltryptamine - looks a lot like psilocybin. made from tryptophan (amino acid).
lots of DMT in nature
where is DMT famously found
who is richard evans schultes
ethnobotanist - founder of ethnobotany in the US - professor at harvard - spent year living in the jungle of south america and learning about their plants.
what psychoactive molecule is found in peyote
how do psychedelics work in the brain
all interact with the 5HT-2A receptor (type of serotonin receptor)
what is the history of the legal status of psychedelics
psychedelics are all schedule one drugs under the US controlled substance Act which means they have "no currently accepted medical use, lack of accepted safety for use under medical supervision, high potential for abuse"
not legally available
describe the research done on psychedelics
in the 1940s to 1970s clinical and neurobiology research was done on anxiety, depression, addiction, PTSD, impact on brain functionality and neuroplasticity, but it for socio cultural legal reasons. in the 1990s, it resumed. Now possible to obtain some for research legally
describe the quest for simple explanation
we always try to breakdown observation to a single explanation, for example, with the plants that act on the brain, we broke it down to one single molecule in the plant that acts on one single NT.
Same for the "double helix effect"
% of adults that take prescribed psychiatric medications
% of adults that take psychiatric medications for long term use
impairment in "reality testing"
characteristic symptoms: delusions, hallucinations
describe schizophrenia and prevalence
chronic psychotic condition (1%)
How do antipsychotics work?
block dopamine receptors (dopamine receptor antagonists)
describe the dopamine hypothesis of psychosis
psychosis is related to excess activity in particular dopamine pathways in the brain
antipsychotic drugs are dopamine receptor antagonists
cocaine and amphetamine activate dopamine pathways and produce psychosis
a simple story (likely not the whole story)
symptoms of depression
feelings: mood, interest, pleasure
thoughts: guilt, suicidal ideation
somatic: sleep, appetite, fatigue, agitation
actions: eating, suicide attempt
lifetime prevalence of depression in the US
current prevalence of depression in the US
current drugs to treat depression
Monoamine oxidase inhibitors (MAOIs)
tricyclic antidepressants (TCAs)
serotonin selective reuptake inhibitor (SSRIs)
Describe the monoamine hypothesis of depression
depressed mood is related to underactivity in certain monoamine neurotransmitter systems in the brain, especially serotonin
So the logic is if you take drugs that increase serotonin then you cure your depression
what law passed in 1997
FDA allows direct to consumer advertising of prescription medicines
massive advertising to consumers
even more popular enthusiasm
how was prozac made
started from benadryl and this company turns it into a new molecule.
they run it through a clinical trial
what are the steps of clinical trials
1. preclinical investigations: cells and animals, toxicity, LD50
2. once it passes the animal tests, it moves to phase 1: safety
3. phase2: efficacy in a small sample
4. phase 3: efficacy, safety in a larger sample, placebo control, double blind
to be considered for approval, new drug must demosntrate statistical significance over placebo effect
what is the standard test for depression in mice
tail suspension test: hang a mouse by its tail and looks at it wiggle
forced swim test: when you put a mouse in water it starts swimming and at some point it stops and just floats
antidepressants promote prolonged mobility
what is a placebo
an inactive substance or condition that has no effect on the body
what do meta analyses show us about the effect of antidepressants
the drug effect and psychotherapy have about the same effect, the placebo also has an effect!
but then the group used the access to information clause to look at all the clinical trials even the ones that werent published because they were not statistically significant - they found that antidepressant drugs found not superior to placebo for mild and moderate depression, for severe depression, small statistically significant effect.
what is the hypothesis around antidepressants
antidepressants work but placebo too
hypothesis: effectiveness of antidepressant medications results from non-specific factors: enhanced placebo effect via side effects - other non-specific brain perturbation.
what are the withdrawal symptoms of antidepressants
nausea, headache, dizziness
why cant we replace our medication with placebo
because we have a deeply wired in worldview that depression is explained by molecules thus it would require a worldview shift to work
Define synaptic plasticity
the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity
give an example of what plasticity might look like
for example, if calcium channels stay open for a longer time, this leads to more vesicle being released. The length of time that calcium channels stay open is mediated by various things and changing that is an example of synaptic plasticity.
other example: trigger the synthesis and release of neurotransmitter - basically creating more NT and thus ultimately increasing the strength of the synapse.
where can synaptic plasticity be increased or decreased
1. Ca2+ channels
3. reuptake transporters
4. post synaptic NT receptors.
5. also retrograde transmission (where NT are released form post synaptic neurons and interacts with pre synaptic receptors that will end up affecting the release of NT from the presynaptic neurons)
When do changes in synaptic strength occur?
ALL THE TIME!
steps in organismal and nervous system development
1. cell differentiation (STEM cells) governed by transcription factor proteins and rna regulation
2. axon and dendrite branching
3. cell migration
what are stem cells?
unspecialized cells from which differentiated cells develop
Describe how gene transcription decides what cell is made
All cells at birth have the capacity to become any type of cell. What decides if a cell becomes an eye cell or an arm cell is what genes are transcribed in this cell. Transcription proteins activate specific gene transcription specialized for certain cell types and once those genes are transcribed, the cell becomes specialized.
steps of gene transcription
transcription factor proteins binds DNA
DNA is transcribed into RNA
RNA is translated to proteins.
% of human genome that codes for functional protein in humans
less than 3%
what is the remaining 97% used for?
most is transcribed into RNA - probably an important reason for that! probably regulatory of turning on and off other genes.
differentiation of brain cells
stem cell - nervous system progenitor cells - various types of neurons and glial cells
how do axon grow?
axon growing tip (growth cone) moves by pushing out filopodia. Inside those growth cones there is a cytoskeleton made of microtubules and microfilaments. This is like a tiny spine that pushes the axon out into space.
what are microtubules made of?
tubulin monomers - they are pretty rigid and are regulatable.
What guides migration and synaptogenesis?
who studied axon migration?
ramon y cajal
what was Roger Sperry's experiment
He cut out the muscle around a frog eye and sowed it back upside down. the frog started seeing the world upside down and never adapted.
then he did it again but he cut the optic nerve too (it has the capacity to regrow in frogs!) and the frog saw the frog upside down and backwards (lol why frog?) they rewired in the same way as before!
what was sperry'S chemoaffinity hypothesis to explain how the optic nerve knew how to regrow
neurons use specific chemical signals to guide their wiring (migration and synaptogenesis) during development
what were the chemical signals that guide neuron growht?
for example: nerve growth factors
proteins produced by the body
important for cell growth and survival
example of one of the chemical signal
NGF: nerve growth factor: dimer of 2 118 aa proteins.
how does chemical guidance work?
1. growth initiated by neurotophin
2. then it encounters contact factors and soluble factors. Contact factors: neuron sticks to them, soluble attraction: attracks neurons with charges. (either repulsion or attraction)
if you zoom in on the axon growing tip, what do you see
what is one receptor that can sense repulsion or attraction
the ephrin receptor (ephrin is the chemoattractant)
what is synaptogenesis dependant on?
stabilized through use
elimination through disuse
at birth, do we have all our neurons?
at birth, how heavy is our brain compared to an adult brain
about 28% of the adult brain
why does the adult brain weigh much more than a baby's brain?
because of the new synapses and because of the myelination happening!
Who studied the physical changes associated with synaptic plasticity at Berkeley?
what are some things that stimulate growth of new synaptic connections
love (social connection)
what is one common characteristics of all living organisms
they all have sensations
the capacity to detect and respond to physical signals in the environment
describe the sensation of bacteria
can detect and respond to physical stimuli through chemotaxis for example (follows a chemical gradient)
how do bacteria move?
using flagella, they alternate between running and tumbling
what happens to bacteria when they get close to sugar
tumble less in vicinity of sugar and congregate around it. this is due to chemoreceptor proteins that detect goodies (attractants) this ias random swimming toward attractants by tumbling less
movement toward or away from light
example of phycomyces
it's a fungus that is light-sensitive fungus, it bends towards light with high sensitivity
different from sensation
what does our experience of the world depend on
what is "out there" (objectively)
physics of sensory receptors
processing by brain
what is naive realism
common sense theory of the perception.
belief that we see the world precisely as it is
example that shows naive realism might not be true
describe the neuroscience perception (2 adjectives)
highly transformed and constructed
what is the range of light that humans see
400nm to 700nm
classify the electromagnetic spectrum from long to short wavelength
what was karl von frisch theory
he thought that bees were likely to see colors because they polinate a lot of flowers. honeybee vision and other aspects of animal behavior
what was karl von frisch's experiment
he put sugar water in a blue well surrounded with a bunch of grey wells. Then he removed the color blue and the bees couldnt find the well with sugar anymore.
Also showed that flowers had a different pattern in the UV spectrum.
what range of waves can pit vipers see
two ways that night vision devices work
1. image intensifier
2. infrared/thermal (sees heat)
what is light
an electromagnetic wave
what is light polarization
the plane into which the light is vibrating
What do polarized sunglasses do?
They remove most of the light that is reflected off of surfaces by only allowing one orientation of vibration to go through
range of human ear sensitivity
20-20 000hertz (vibrations per second)
example of animals who can hear high pitch sound
cetaceans: dolphins, killer whales, bats, moth. they use this sounds to ecolocate by listening to the reflection of this sound.
How do sharks use electromagnetic fields
use passive electro-reception to locate food. (bodies generate electromagnetic fields that sharks detect)
how do platypus use electromagnetic fields?
it has a bill bull of electroreceptors. detection of bioelectric fields in invertebrate preys
how does electrolocation work
electric fields are bent by resistors (rocks for example) or conductors (bodies) in the environment and changes in the field is detected by the animal
animals that use the geomagnetic field of the earth for navigation
birds, fish, sea turtles, honeybees, many others
what happens if you take a pigeon many miles away from their house
they will fly directly back to their home if it's a sunny day! on an overcast day they struggle more.
If you put a magnet on the pigeon, then the pigeon cant orient itself.
how are magnetotactic bacteria magnetic?
they have chains of microscopic magnets made of magnetite which is magnetic!
also detected in pigeons.
what is the most ancient sense?
describe the olfactory system in humans
nasal epithelium (where the neurons detect molecules and send signal to the bulb)
olfactory nerve fibers
Describe the different parts of the olfactory epithelium
nerve cells embedded in epithelia
olfactory receptor cells
nasal epithelium structural cells
olfactory stem cells
olfactory nerve fibers to brain
do olfactory receptor cell last forever?
no, they are replaced every few weeks by olfactory stem cells
describe the olfactory receptor proteins
they are GPCRs.
the number of GPCRs differ between different animals.
for ex: fish have 100s, mouse have 1300, humans have 350
what are the pseudogenes in the olfactory system
they are genes that are not transcribed now (don't function anymore) but probably were used for olfactory.
how many different odors can we smell
where is cinnamon from
what causes the aroma of cinnamon
all the different aromatic molecules found in them
how was distillation invented
when people wanted to make plant distillates for perfumes!
spice that was mentioned in the bible as highly prized
properties of myrrh
what is ambergris
waxy substance produced in digestive system of sperm whale
highly valuable in perfume because it has a nice smell and it conserves the molecule of perfume. it's very rare!
how large is the sperm whale
latin name of rose
what main molecule do we recognize as the smell of jasmine
what molecule ressembles benzyl acetate but smells completely different?
geraniol (has an OH group instead of a =O) and this smells like roses!
what are stereoisomers
mirror-image molecules having the same atomic ocmposition and geometric arrangement
s carvone and r carvone smell super different even though they are almost identical!
what is the stinky smell in skunk?
what causes the asparagus smell in urine
asparagusic acid in asparagus is converted in the body to dimethylsulfide and methanethiol which causes this smell
what are anosmias?
(gene change in one olfactory GPCR)
describe the connectivity of the olfactory systems
the olfactory bulb (Relatively small in humans) connects to the thalamus orbitofrontal cortex (associated with our capacity to identify smell) and to the amygdala temporal cortex (limbic system: emotional reponse to certain cells)
what are pheromones
chemical used for intraspecies social communication
examples of roles of pheromones
insects and vertebrates: terriotial marking, sex, social status, etc.
pheromones in ants
some molecules are also plant smells!
describe the use of pheromones in rodents
in rodents they have a different organ for detecting pheromones: the vomeronasal organ (seperate)
do humans have pheromones?
we have a vomeronasal organ but people think it's not used anymore also it is debated.
example of evidence for human pheromones
menstrual synchrony in women
why is loss of smell an early indicator of infection?
infection causes acute viral anosmia
some infections cause persissting post viral anosmia
describe the taste system
structural cells of tongue, pore, microvilli, taste receptor cells, gustatory stem cells, cranial nerve fibers to brain
what is the nerve pathway linking the tongue to the brain
tongue to brainstem to thalamus to insula and somatosensory cortex (logical response to taste, like "this is sweet")
tongue to brainstem to brainstem to hypothalamus and amygdala (emotional response to taste)
5 categories of taste
sweet, sour, salty, bitter, umami
each associated with different receptor cells.
how we taste salty
Na+ ion channels sensitive to sodium on the tongue.
how do we taste sour
ion channels sensitive to hydrogen ions.
how to we taste bitter
bitter receptor proteins consist of about 30 GPCRs
example of bitter plant alkaloids
(molecules associated with a poison, natural warning?)
how do we taste sweet?
binds to sugary molecules like sucrose
almost always dimers - non covalently bound
why do we only have 2 GPCRs for sweet but 30 for bitter?
because there is not much variability in what tastes sweet (all molecules look the same (glucose, sucrose, fructose))
Where did sugar originate
southeast asia and south pacific - then moved everywhere
where is sugar found
in the stem of sugar cane
the stems are dissolved in hot water, then it is purified to obtain the white powder.
example of sweet molecules
saccharin 500x sweeter
fructore and sucrose
why do artificial sweeteners dont have calories
because they are SO sweet (activates our sweet receptors very potently) that we only eat a tiny tiny amount to get the same sweetness, which is essentially 0 calories
who came up with the principle of limited slopiness and what does it mean
max delbruck - sometimes we discover things because we are a little bit sloppy in science - thats how sacarine was discovered
what is the difference between sucrose and sucralose
sucralose has 3 chlorine - makes it a lot sweeter
600x sweeter than sucrose
doesnt have an aftertaste
what is sucralose branded as
why did the equal company sue splenda
(oh boy the US and their infinite random lawsuits?)
Equal sued for false advertising saying "there is no sugar in splenda and splenda's sweet taste does not come from sugar"
what is neotame
10 000x sweeter than sucrose!
what is stevia
powdered plant extract from stevia rebaudiana
active molecule is stevioside (has a part that ressembles glucose)
what is the miracle frit
plant in west africa
contains a molecule called miraculin protein (199 aas)
binds to sweet receptor GPCR dimer but doesnt activate it unless you have it with some sort of acid. So people chew on the berry and then eat a lemon.
What is the umami taste?
presence of the amino acid glutamate activates glutamate receptors
history of the umami taste
published in 1909
discovered in miso
americans and europeans continued to speak of 4 tastes until 1990s
how do we taste spicy
the molecule capsaicin in the fruit (like chili) binds to the capsaicin receptor (TRPV1)
This receptor is also activated by heat! this causes the brain to analyze it as heat.
also activated by piperine in black pepper.
Where are capsaicin receptors located?
somatosensory periphery (skin)
What does TRPM8 respond to?
menthol! also responds to cold
What does TRPA1 respond to?
what receptors does crushed garlin (allicin molecule) activate?
TRPA1 and TRPV1
what is flavor
combination of taste smell pungency and texture
How do pit vipers detect prey in the dark?
the pit organ contains TRPA1s that detect heat!
The range of wavelengths of light
400nm to 700nm
this energy causes us to experience color
what is the macula fovea
area of retina with high cone density (pigment)
why do we have a blind spot on our retina?
because thats where the optic nerve exit (no photoreceptors there)
describe rods and cones
rod: contains photo receptor protein - sensitive to low level of light, allows us to see in lightly dim room.
the cones contain cone-opsins - sensitive to bright light day, braigh-light vision. the rod turn off in this situation
how do specific types of cones and rod differ in spectrum
3 types of cone (short, medium, length) and 1 type of rod that each have their own spectrum of detectable light. Rod: peaks at 498nm for example
s-cone is associated with which color
blue! (shorter wavelength)
describe the distribution of cones and rods in the retina
cones concentration peak at the fovea
rods are where cones arent. even at the edges there are a few rods.
how many rods and cones do humans have
100 million rods
5 million cones
what is retinal achromatopsia
complete lost of all cone cells - no color vision. some people are born this way! they see black and white
3 parts of the photoreceptors
outer segment: detects light stimulus
inner segment: metabolic machinery of cell
synaptic terminal: transmits signal generated to next cells in visual pathway
how many photoreceptors proteins do have per cell
what molecule absorbs light
how is retinal made
made from retinol (which is vitamin A) or from a precurosr (beta-carotene found in carrots.
what happens when light hits retinal
retinal changes shape - goes from bent to straigth (cis to trans)
what kind of receptors are rhodopsin and cone-opsins
what happens to GPCRs when light hits
when retinal changes shape and leads to a decrease in cGMP in the cell. the decrease in cGMP causes sodium channels found elsewhere in the cell to close. Those channels are normally always open
one photon of light acivates one rhodopsin can activate 100 g proteins and those activates 100 phosphodiesterases which in turn hydrolyzes cGMPs (degrades them). HUGE amplification.
describe the layers of the retina
rods and cone - horizontal cells - then bipolar cells - then bipolar cells -then ganglion cells
in ganglion cells, information has been summed so there are fewer ganglion cells than rods.
thickness of retina
100 micrometer (0.1mm)
how is the octopus eye different form humans?
the photo receptors are in the top layer of the retina
what does contralateral connectivity mean?
left organ sends input to right side of brain.
is vision transmitted to the brain contralaterally?
what is the receptive field of a cell
the region of space from which a stimulus elicits a neural response
where in the brain is vision interpreted
in the visual cortex which can be divided into 5 different regions. They all responds to different visual cues. they are all interconnected.
what happens when you cause a lesion in the V1 region of the visual cortex
causes a scotoma - a blind spot/region
what is hemianopia
blindness over half the field of vision
what happens if you cause a lesion in V4
problem in color perception
what does lesion in V5 cause
problem with vision of movement
lesion in human posterior temporal lobe (in the fusiform gyrus)
prosopagnosia - face-recognition problems! this also happens on a spectrum, some people have more trouble recognizing faces
What is blindsight?
a condition in which a person can respond to a visual stimulus without consciously experiencing it
what causes blindsight?
about 90% of our visual neurons go to the V1 region and 10% goes to superior colliculus which apparently tells you that you are aware that something is happening in front of your eyes
why do we use electron microscopy for viruses
the smaller matter is, the more potent are its wave qualities
the wavelength emitted from the virus is way tinier than what the human eye can see.
what is sound?
waves of changes in density (pressure) of air molecules
also: the human experience/perception of sound
how can sound be quantified
air pressure = air molecule density
sound wave= air pressure variation over time
frequency (hz)= pitch
amplitude = loudness
how does capacity to detect sound change between animals
have different range of frequency that they can hear (dogs have a very large range)
what is timbre
complex waveforms composed of a combination of frequencies
what is the principle of the fournier analysis
you can decompose any waveform into a sum of sinusoidal frequency components (analysis of timbre)
describe the auditory system in the ear
sound hits the pinna, this captures the sound which enter the external ear canal and hits the eardrum which is attached to the ossicle which hits the choclea. the choclea has fluid inside which vibrates once hit!
describe the choclea
semi circular canals made of bones
what does the basical membrane do
performs a fourier deocmposition of the incoming sound. the thick end will vibrate at high frequency and the thing end will vibrate at low frequency which deocmposes the sound.
what is founs on the basilar membrane
cilia! hair cells
Role of hair cells in the cochlea
molecular cables coupled to K+ channels. when it vibrates, it opens the the K+ channels, K+ flows in and the cell becomes depolarized.
cable diameter of 3nm
steps in depolarization following a sound entering the ear
1. hair cell embedded in basilar membrane with hairs extending into the tectorial membrane will move and cause K+ channels to open, depolarizing the membrane.
2. This causes Ca2+ channels to open and causes further membrane depolarization and release of NT
describe the neural pathway linking the cochlea to the cortex
hair cell activated 8th cranial nerve which goes through the brainstem, midbrain, thalamus and finally cortex in the A1 cortical area. some neurons respond to lower frequencies and other to higher frequency.
how do we locate sound
we are sensitive to the time it takes to reach our ears (left vs right) so we can estimate where the sound comes from
why are owl cools
because they had ear asymmetry which allows them to locate animals without any light using time difference
causes of hearing loss
-genetic impairment of cochlea (connexin genes for ion channels)
noise-induced hearing loss (chronically or locally<) (over 85db chronically)
due to toxicity when theres too much excitement
how do we measure sound
decibels (log scale)
is hear loss damage reversibile
How many hair cells are in the cochlea
3500 only :( easy to lose some forever
how do we treat hearing loss
using acoustic amplifier hearing aid - a microphone that records sounds and plays it using a mini speaker in the ear.
also cochlear implant for complete loss of cholear function - they do fourier decomposition and then stimulate the auditory nerve directly!
role of semicircular canals
contains hair cells and, otoconia/otoliths (little calcium carbonate stones) which produces a vibration that our brain uses to orient ourselves in space
what happens if the little rocks are stimulted without movement
you get vertigo! feel dizzy
largest organ of the body
What receptors are found in skin
somatosensory receptors (touch, heat, etc.)
specifically: free nerve endings, meissner's corpuscle, ruffini endings, pacinian corpuscle, merkel's disks
What is the role of the dorsal root ganglia
receive signals from all the receptors through axon and dendrite with somatory sensory receptors
where do skin signals go in the brain?
the somatosensory cortex
what did wilder penfield discover?
he was stimulating different parts of the brain and the patients would feel a tingling in the part of the body stimulated.
he came up with the somatosensory body map
guys he discovered this at the montreal neurological institute where i used to work :')
explain the distorted size of different body parts on the somatosensory map
some parts of the body are overrepresented like the lips for example compared the the back which have very few sensory neurons going to the brain. body part with more space in the cortex are way more sensitive
what happens when someone has a lesion to S1
there will be a region of the body with no sensation
what happens if you have a lesion in the S2 or S3 region
those are secondary sensation area: lesion causes sensory weirdness and neglect syndromes
what does the S1 represent in the mouse
the location of the whiskers!
what happens when you pull out a whiker in mouse
the corresponding barrel in S1 connects to the surrounding barrels which increases the sensitivity of the other whiskers
what happens if you have a lesion in the primary motor cortex M1?
Why does phantom limb occur?
because the neurons that use to enervate the limb that is lost will reorganize and link up to other region of the somatosensory map in the brain. Thus, if your lost arm rewires with your shoulder region, you will feel your lost arm in your shoulder.
where is the primary motor cortex found
what happens when you cause a lesion to the prefrontal cortex in the motor areas
causes apraxias: movement organization problems
what are the frontal lobe mirror neurons used for
they are active during movement AND during observation of movement so probably used to model the behavior of other people
role of the cerebellum
timing and coordination of movement
% of all neurons found in the cerebellum
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