Midterm 2 Flashcards
Lectures 9-17
Photoreceptors
- sensory cells of vision
- contain light-sensitive opsin proteins
- release neurotransmitter in graded fashion
- at rest (in the dark), depolarized to -40mV constantly releasing glutamate due to Na leak channels
- when light hits them, hyperpolarize to -70mV and stop releasing glutamate due to opsin proteins
Sensation vs perception
Sensation: how cells of nervous system receive information and transduce into action potential
Perception: the conscious interpretation of sensory info
Opsin proteins
- are metabotropic receptors
- bind molecule of retinal which when hit by light, activates opsin protein
- launches g-protein cascade that hyperpolarize neuron
Blue cone opsins are most sensitive to ____ wavelenghts
Short
Green cone opsins are most sensitive to _____ wavelengths
medium
Red cone opsin most sensitive to ______ wavelengths
long
Brightness, saturation and hue
In order, relates to:
- intensity
- purity in terms of wavelength mixture
- dominant wavelength (what color is actually seen)
Protanopia
- absence of red cone opsin
- visual acuity doesn’t change -> red photoreceptors switch to using green cone opsin
Deuteranopia
- absence of green cone opsin
- visual acuity doesn’t change -> green photoreceptors switch to using red cone opsin
Tritanopia
- absence of blue cone opsin
- visual acuity not noticeably changed -> not that sensitive to light in first place
Achromatopsia
- true color blindness
- usually caused by mutations in g-protein cascade used by all cone ospin
Saccadic eye movement
- rapid, jerky shifts in gaze
Pursuit eye movement
- only time eyes calm down and move smoothly
- maintaining focus on moving object
Visual info pathway within eye
Photoreceptors -> bipolar cells -> retinal ganglion cells -> to brain
- ganglion cells are only cells that send APs to brain
What areas do ganglion cells’ axons project to and what are they responsible for?
- thalamus: which sends info to V1 where it enters consciousness and then association cortex where it is analysed and made sense of
- midbrain (superior colliculi): used to control fast-visually guided reflexive movements, no conscious awareness of it here, midbrain has no clue what you’re looking at but it draws attention to unexpected visual events
- hypothalamus: where sleep-wake cycles and circadian rhythms are monitored/controlled.
Predictive coding theory
- suggests that each node in visual cortex is trying to predict ascending input (incoming input) based on previous input
- any top-down (descending) activity represents sensory predictions that neutralize any correctly predicted bottom-up (ascending) signals
- any signal that propagates up would therefore be prediction error signals, whatever has not been cancelled out by interplay b/w the two signals
Bipolar cells
- no APs, release glutamate in graded manner
- in fovea, receptive fields directly from only one photoreceptor
- outside of fovea, receptive fields from horizontal and mutliple photoreceptor cells
- OFF bipolar cells: express excitatory ionotropic glutamate receptor, follow whatever activity pattern of previous photoreceptor (OFF because they don’t affect the activity pattern)
- ON bipolar cells: express inhibitory metabotropic glutamate receptors, reverse activity pattern of previous photoreceptor (ON because they do affect activity pattern)
Horizontal cells
- compare activity of neighbouring photoreceptor cells and adjust their glutamate release to accentuate contours
- e.g. if center photoreceptor signals bright light (no glutamate released) and the surrounding photoreceptors signal dim light (a little glutamate release), horizontal cell will depolarize “axon terminals” of surrounding photoreceptors
Dorsal stream
- “where” pathway: how objects are moving, how to interact with them
- parietal lobe
Ventral stream
- “what” pathway: identifies shape, color of object
- in temporal lobe
Akinetopsia
- inability to perceive movement
- damage to dorsal stream in parietal lobe
Cerebral achromatopsia
- inability to perceive color that is not due to deficiency of opsin protein
- damage to ventral “what” pathway in temporal lobe
Prosopagnosia
- inability to recognize faces, even of familiar people
- damage to fusiform gyrus (fusiform face area) in ventral stream
Anterior auditory pathway
- “what” pathway
- temporal and frontal lobes
Identifying vertical direction of sounds at high-frequency
- in adults, using precise mixture of overtones, timbre
Outer hair cells
- act like muscles to adjust sensitivity of tectorial membrane to vibrations
- are attached to tectorial membrane
Inner hair cells
- sway back and forth with movement of solution
- sound waves cause basilar membrane to move relative to tectorial membrane pulling open ion channels on hair cilia
Anatomy of cochlea
- divided into three divisions
- receptive organ in scala media is organ of corti, consists of basilar membrane on bottom, tectorial membrane on top and hair cells in middle
Place coding
- principle of auditory coding in which dif frequencies produce maximal stimulation of hair cells at dif points on basilar membrane
- moderate to high frequencies entirely encoded by place coding. e.g. human speech
Rate coding
- for low frequency
- pattern of nrtrm release from hair cell deepest in cochlea determines perception
Pathway from ear to A1
organ of Corti through cochlear nerve -> cochlear nuclei in medulla
—-> superior olivary nuclei in medulla for sound localization, where ITD and ILD are measured
—-> inferior colliculi in midbrain, also for sound localization -> medial geniculate nucleus of thalamus -> A1
Posterior auditory pathway
- aka dorsal
- where pathway in parietal lobe
Amusia
- inability to perceive or produce melodic music
- can still converse and understand speech
- can typically still recognise the emotions conveyed by music but not tell whether it is dissonant or consonant
If you play a very sad song and a very happy song to an amusia patient, they will not be able to _________ (3 things), but will likely ________________ .
- recognize any of the two songs, process/perceive musical content (e.g. beat, melody, harmony), or sing them back
- be emotionally affected just like any other person.
What happens if the tip links of your inner hair cells break during a loud concert?
- will grow back
- temporarily damage hearing
Otolith organs
- vestibular sacs
- monitor angle of head and linear acceleration
Semicircular canals
- detect head rotation
Exteroceptive system
- monitors external stimuli applied on surface of skin
Triglycerides
- long-term source of energy stored in adipose tissue
- converted from fatty acids by insulin
Interoceptive system
- monitors what is happening inside of body organs
- e.g. bowel movement, thirst, hunger, heart rate
Main estrogen of many mammals?
estradiol
Proprioceptive system
- monitors position of limbs, position of body, posture and movement
Poorly vs highly localized sensory info
- poorly localized (e.g. crude touch, temp, pain) crosses over in spinal cord, just after first synaptic connection
- highly localized (e.g. fine touch) ascends ipsilaterally through dorsal column of spinal cord, first synapse in medulla where info crosses over to go to thalamus
- both get bundled up together in midbrain before going to somatosensory cortex
Role of oxytocin and vasopressin in sexual behavior
- released as neuropeptides in brain and hormones in blood
- in prairie vole species, affects pair-bonding behavior: artificially increasing expression of oxytocin and vasopressin receptors in non-monagamous prairie vole brains made them form life-long monogamous pair bonds.
The layers of skin
Epidermis: top layer, dead cells on top and constantly regenerating cells at bottom, cells get oxygen from air
Dermis: middle layer, tones of sensory neurons and blood vessels
Hypordermis: bottom layer, subcutaneous layer of fat
Hairless skin
Glabrous skin: a lot more sensitive than hairy skin
Feeling a light piece of paper on your hand involves which kind of sensory neuron?
Meissner’s corpuscles:
- only found on glabrous skin
- sense very light touch and localized edge contours
Feeling the small grooves and texture in a knifed table involves which kind of sensory neuron?
Merkel’s disks:
- respond to local skin indentation
If an animal has no ability to associate its own behavior to a positive response in particular context so that it eventually becomes automatic behavior in such context, it most likely has damage to the _______ ________ .
The Basal Ganglia
- supports reinforcement learning leaving more processing capacity for transcortical regions for other task
- every neuron of cerebral cortex projects to basal ganglia and synapse in striatum
- through dopamine signaling that regulate strength of synaptic connections in striatum
Feeling the vibrations of a game controller involves the ________ ____________
Pacinian corpuscles: respond to skin vibration
Feeling the stretch of your skin involves ___ __________
ruffini corpuscles: sensitive to stretch and kinesthetic sense of finger position and movement
Free nerve endings are:
- sensitive to temp
- embedded with temp gated ion channels which can be activated by some other molecule (red peppers, tiger balm)
- poorly localized
- not myelinated so quite slow
Nociceptors are:
- free nerve endings that transduce pain
- embedded with ATP receptors all over that will get out of cell to activate nearby cells if cut open
A newborn will turn toward ______ and _______ types of foods.
sweet: detected with single metabotropic receptor
umami: single metabotropic receptor
- both of these are inherently good from birth, other tastes are “learned” to be liked
the six categories of taste receptors
sweetness
umami
bitterness: detected with 50 dif metabotropic receptors
saltiness: detected with ion channel highly permeable to Na
sourness: detected with ion channel highly permeable to free protons, detects pH level
some evidence for fat: metabotropic receptors and fatty acid transporters
Anatomy of taste buds
- contain 20 to 150 taste receptor cells, some for each type of taste
- taste receptor cells do not have APs, release nrtrm in graded fashion
- taste receptor cells replaced every ten days bc hostile environment
replacing mice’s sugar receptor gene with bitter receptor gene provokes what type of behavior? what does suggest about our perception of taste?
- mice will not be able to differentiate sugar water from regular water
- mice will love bitter molecule that now activates cells in their sweet taste receptor cells
- suggests that taste perception is hard-wire, innate from birth to be either pleasurable or aversive
Odorants and what they bind to
- volatile substance with mol weight b/w 15-300
- receptor proteins transducing odorantas into change in membrane potential are meta g-protein couple receptors: around 400 in humans
When female mice housed together without presence of male urine,
their estrous cycles slow down and eventually stop
- lee-boot pheromonal effect
Pheromone in urine of male mice can trigger
synchronous estrous cycles in groups of female mice
- whitten effect
Presence of male mice in female house triggers
earlier onset of puberty
- vandenbergh effect
scent of unfamiliar male can trigger
termination of pregnancies in female rodents
- bruce effect
How do we consciously regulate osmometric thirst?
- with osmoreceptors: neurons whose membrane potential is sensitive to size of cell
- hypotonic (salty) extracellular fluid will cause osmoreceptors to lose water and shrink in size
Volumetric thirst regulation
- when not enough blood in body
- kidney releases renin, initiates cascade of chemical rxns in blood
Ghrelin
- peptide that signals empty stomach
- communicated to brain by stomach
- does not regulate long-term storage
Role of pancreas in energy storage monitoring
- measures blood-glucose levels
- releases insulin when high blood-glucose which takes up glucose and turns it into glycogen for short-term storage in liver and muscles
- releases glucagon when low blood-glucose which breaks down glycogen to be converted into energy
role of duodenum in short term satiety signals
- releases CCK, PYY, GLP-1 in response to ingestion
- monitors amount of food ingested, not amount of nutrients
Role of leptin in hunger regulation
- hormone released by adipocytes (fat cells) as function of their size
- adjust sensitivity of brain to short-term satiety signals, e.g. CCK
- thought to regulate long-term satiety
- leptin receptors all over brain and especially in arcuate nucleus of hypothalamus
ARGP neurons
- promote hunger
- inhibited by leptin and activated by ghrelin
- in arcuate nucleus of hypo
POMC Neurons
- inhibit hunger
- activated by leptin and inhibited by ghrelin
- in arcuate nucleus of hypo
Paraventricular nucleus (PVN) of hypo
- get signals from ARGP and POMC neurons
Prader-willi syndrome
- chromosomal abnormality which deletes gene important to survival of PVN neuron pop
- develop intense hunger, feeling of starving to death
- can accidentally consume enough food in one sitting to fatally rupture stomach
Sexual dimorphic behaviors
- behavior that differ in their forms across males and females
- e.g. parenting behavior, courting, mating
Mullerian system
- embryonic precursors of female internal sex organs
Wolffian system
- embryonic precursors of male internal sex organs
Undifferentiated gonads
- turn into ovaries or testes in 2nd month of gestation
SRY gene
- located on Y chromosome
- encodes protein that start development of undifferentiated gonads into testes by overpowering XX-ovary instructions
- testes that will then release anti-mullerian hormones and androgens
Effect of embryonic testicular hormones
Once testes developed form SRY gene, release
- anti-mullerian hormone: stops mullerian system development (internal female sex organs)
- androgens (testosterone): starts development of internal and external male sex organs
What hypothalamus-produced hormone would be expected to appear a little before puberty and thereafter?
Kisspeptin
- triggers puberty
- maintain reproductive ability by triggering release of gonadotropin-releasing hormone
Gonadotropin hormones
hormones of pituitary gland that have stimulating effects on cells of gonads
- stop release of these hormones and men will no show testicular release of androgens and have decreased sexual interest
How would electric stimulations to mPOA (Medial preoptic area) affect male rodents’ behavior?
- increased sexual behavior
Menstrual cycle vs estrous cycle
- menstrual cycles: in most primates, concealed ovulation and no mating season, no affect on sexual activity
- estrous cycle: in most mammals excluding primates, mating season and clearly shown ovulation, no sexual activity outside of these cycles
REM sleep
- Rapid Eye Movement
Associated with
- desynchronized EEG activity, dreaming, muscle paralysis, increase in cerebral blood flow and oxygen consumption
Slow-wave sleep
- stage 3/4 non-REM sleep
- deep sleep
- large amplitude, low frequency oscillations of brain activity: large collection of neurons coordinate to fire together but rather slowly
Main theories explaining why animals sleep?
- memory consolidation
- waste removal, some evidence but not the strongest
- recovering from physical or mental exertion, almost no correlation
Lesions to the suprachiasmatic nucleus would lead to…
- broken circadian rhythms, individual would sleep same amount but at random intervals
- in hippothalamus, receives direct input from retina
Electrical stimulations of the ventral lateral preoptic area (vlPOA) cause…
- drowsiness and sometimes immediate sleep
- lesions supress sleep and cause insomnia
- in negative feedback loop with wake-promoting area, when one is active, it inhibits the other
Narcolepsy is associated with absence of ______
Orexin
- peptide produced by neurons in lateral hypo
- promotes wakefulness
A patient who does not feel temperature changes in the right side of their body most likely has damage to
left spinothalamic tract
A patient with lesions in the right dorsal column will not feel
- fine touch in their right hand
A patient with lesions to the left medial lemniscus (above crossing point) part of the dorsal column-medial lemniscus pathway will not feel
- fine touch in their right hand
Turner syndrome
- only one chromosome: X-, no gonadal development
- female sex organs will develop because no anti-Mullerian hormone
- no gonads -> sterile
Swyer syndrome
- XY but bad SRY gene needed for development of testes
- female sex organs because no anti-mullerian hormone
- no gonads -> sterile
A bad SRY gene can lead to no hormone release at all (Swyer syndrome) but can also lead to two dif scenarios. What are they and what are their effects?
Insufficient anti-Mullerian hormone signaling:
- development of female internal sex organs
- androgen release still intact so internal and external male sex organs
- tangled up internal male and female sex organs but external male organs
Insuficient androgens signaling (androgen insensitivity syndrome):
- anti-Mullerian hormones still intact so defeminization okay
- no or poor development of male sex organs (in extreme cases, will look like external female organ; in mild cases, external genitalia is fully masculinized)
Organizational vs activational effects of sex hormones
Organaziational:
- largely over by birth but continue to continue a few weeks after birth, at least in rodents
- life-long effects that generally speaking are hard to overturn
Activational:
- puberty causes sex hormone release which changes mind and body (kisspeptin -> gonadotropin releasing hrm -> gonadotropin -> acts on gonad activity)
In female rodents: no hormone treatment immediately after birth + testosterone treatment when fully grown results in:
- no sexual behavior at all
In female rodents: testosterone immediately after birth + testosterone treatment when fully grown results in:
- male typical sexual behavior
- evidence for masculinization as testosterone promotes male sexual behavior
In female rodents: testosterone treatment immediately after birth + estradiol and progesterone treatment when fully grown results in:
- no sexual behavior at all
- evidence of defeminization as estradiol and progesterone fail to facilitate female sexual behavior
Congenital adrenal hyperplasia (CAH)
- abnormally high levels of androgens at birth in females
- results in masculinization of brain, body, or both
- if high levels during development, can lead to masculinized sex organs
- females with CAH higher likelyhood of identifying as male and being attracted to women
Electrical stimulations of/direct injections of estradiol and progesterone into the VMH (ventromedial hypothalamus) of a female rodent’s brain facilitates
- sexual behavior
Beta activity
- typical of aroused state
- desynchronous activity
Alpha activity
- typical of wake person in relaxation state
theta activity
- appears intermittently when ppl drowsy
- prominent during early stages of sleep
Delta activity
- <4 Hz
- reflects large population of neurons firing together at low frequency, large amplitude
- characteristic of deep non-REM sleep
Lymphatic vs glymphatic system
Glymphatic system clears waste from brain as CSF moves through interstitial space
Lymphatic clears waste from everywhere else in body
How does serotonin and norepinephrine neuron activity correlate with sleep?
- those neurons decrease their activity during sleep
Retrograde signaling molecules for long-term depression
endocannabinoids
Retrograde signaling molecules for long-term potentiation
Nitric oxide
