EXAM REVIEW Flashcards
Development is
the study of how individuals change and remain the same between conception and birth
Learning is
- relatively permanent changes in our thoughts, behaviours and feelings as a result of our experiences
- new information
Maturation is
- the biologically-timed unfolding of changes within an individual according to that individuals genetic plan
The interactionist perspective
the view that holds that maturation and learning interact during development
Maturation & Learning
- biological maturation restricts the timeline of learning from the environment
- learning from the environment
- you can’t learn to walk before you grow legs
Studying Development
- most human development occurs during the early stages of life
- changes early in life are more dramatic than those late in life
Habituation Procedure
- can test for an infant’s ability to detect novel stimuli
- habituation: a decrease in the responsiveness to a stimulus following its repeated representation
- dishabituation: an increase in the responsiveness to a stimulus that is somehow different from the habituated stimulus
Event Related Potentials
- changes in brain activity in specific areas indicate responses to certain stimuli
- wear a head cap
High Amplitude Sucking Method
- The rate of sucking on a pacifier indicates the level of preference
- infants hear a sound stimulus every time they suck hard on a pacifier
Preference Method
- The level of attention towards one stimulus relative to another stimulus indicates a preference
- Shown at the same time
Competence-performance Distinction
- An individual may fail a task not because they lack cognitive abilities, but because they are unable to demonstrate those abilities
- a baby can’t say like like something, because they can’t talk yet
Developmental Research Method
- Developmental studies look at how certain abilities change over a lifetime
- Longitudinal or Cross-sectional
The Longitudinal Design
- the same person is tested repeatedly over their life at different ages
- Allows for accurate and direct comparisons over time
- NOT optimal for long studies
- Expensive and time consuming
- Some participants die and the study ends up not being reflective of the whole population
Cross-sectional Design
- individuals from different age groups are studied at the same point in time
- Faster comparisons between age groups
- Assesses developmental change
- Less time-consuming and cheaper
- IGNORES individuals and generational effects
zyogte
single cell that contains 46 chromosomes
Monozygotic twins
- same sperm and ovum, genetically identical
Dizygotic twins
- different sperm and ovum, share 50% of genes
Sex chromosome
- males determine sex of child
- first 22 pairs autosomes
- gender is determined on 23 chromosome
genotype
- inherited genes
phenotype
- expression of individuals genotype (observable characteristics)
Simple-dominant-recessive inheritance
- regular inheritance
- homozygous or heterozygous
Polygenetic Inheritance
- expression of a trait is determined by multiple genes
- no single gene can account of most complex behaviours
Codominance
- expression of a trait is equally determined by two alleles
Sex-linked Inheritance
- expression of a trait is determined by genes on the X chromosome
- sex-linked recessive disorders are less common in females because they have 2 X chromosomes
Interactionalist Perspective
- Nuturists = external factors alone influence development
- Naturists = genes predetermine the path of development
- Our genes and environment interact to influence development
Canalization Principle
- All individuals are restricted to a similar phenotype despite variations in the environment
- Genotype restricts the phenotype to a small number of possible development outcomes
- ex. height will fall in range regardless of environment
Range of Reaction Principle
- genotype establishes a range of possible responses to different kinds of life experiences
- dictates that our genotype restricts us to a range of possible phenotypes whose expression is dependent on environmental conditions
- depending on how you grow up, you could be taller or shorter
Passive Correlations
- the environment that parents choose to raise their children in was influenced by their parents own genes
Evocative Correlations
- the traits we inherit affect how others react or behave towards us
Active Correlatins
- our genotype influences the kinds of environments we seek
- gene-environment interactions change their influence across a life span
Critical Periods
- a window of opportunity within an individuals development in which particular environmental stimulation is necessary to see a permanent change in specific abilities
- Ex. visual deprivation outside of the critical period doesn’t affect development
- Enriched environments early in life promote proper brain development
Implications of critical periods
- likely to affect parental decisions
- affect decisions to adopt
- affects public policy on child intervention
Excess synapses
- pruned away throughout development
Experience Dependent Brain Growth
- Our brains develop according to our own personal experiences
Experience-Expectant Brain Growth
- brains have evolved to expect a certain amount of environmental input, with this input our brains develop normally
Adaptations
- biological traits that help an individual survive and reproduce in its habitat
- make an organism better suited for its environment
“Higher” Mental Processes
- selective attention
- memory encoding
- memory retrieval
Adaptive Mental Process
- evolves through natural selection
Evolution by Natural Selection
- adaptations emerge in development as a result of the activation of relevant genes in interaction with relevant aspects of the enviroment
Natural selection
- differential survival and reproduction of organisms as a result of the heritable differences between them
1. Individual differences - variation among individuals for any characteristic
2. Differential reproduction - individuals chances of surviving and reproducing
3. Heritable - traits that give rise to differential reproduction have a genetic basis
Stabilizing selection
- selection against any sort of departure for the species-typical adaptive design
Darwins Finches
- drought caused small beak finches to die and birds with bigger beaks to survive
- when drought ended, beak size returned to normal
- reproductive success = fitness
Darwinian Fitness
- average reproductive success of a genotype relative to alternative genotypes
Evolution
- change in gene frequencies over generations
- imagine a predator disappeared and a new predator is introduced that finds it easier to detect the blue fishes instead of red fishes, the gene pool would shift towards the red phenotype
Sexual Selection
- Competition for mates, natural selection acts on mate-findings and reproductive behaviours
- acts on a trait that influence an organisms ability to obtain a mate
Two Subtypes of Sexual Selection
Inter-sexual: female choice of males, (males and females interaction)
Intra-sexual: interaction between members of the same sex (males and males)
- you can either beat up your rivals or get chosen by the opposite sex to get more access to reproducing
Sexually selected traits
- traits that differ between sexes, especially if it only exists during breeding season
Species-Typical Behaviour
- Sanderlings, semipalmated and dunlin sandpipers all look similar
- However, sanderlings forage for food by racing out to the shore and eating insects between waves
- This is a species specific behaviour because only sanderlings act like this
Species-Typical-Behaviour
- Physical form
- Habitat preference
- Group size
- Social system
Behavioural Genetics
- changing the animals typical behaviour over generations
- using animals with short generation times, like fruit fly
Natural Selection favours the
selfish gene… because evolution acts at the gene level and genes that contribute to an individuals fitness will get replicated more often
Group selection
- Adaptations are not for the good of the group or species, they are good for the gene
- Exception: Foraging for food in groups is better because predators lose the “surprise attack”
- Foragers need to keep their head raised to watch for predators, but they can’t eat and watch at the same time
- Therefore, this selection favours the good of the group because it favours the good of the individual
Altruism
- actor incurs a cost to provide a benefit to the recipient
- foraging in group is not altruism because individual benefits
Problem of Altruism
- a group of altruists will thrive because individuals in that group regularly help each other
- the good of the group cannot explain the evolution of altruism because it dies in the bodies of their bearers (lemmings example)
Spite
- and -
Selfish
Actor +, recipient -
Cooperation
+ and +
Altruism
- Actor, + Recipient
Eusocial Hymenoptera
- most individuals spend their lives serving the colony without reproducing (ants, bees)
Direct Fitness
- fitness from personal reproduction
Indirect fitness
- fitness from the reproduction of close relatives
Direct fitness + Indirect fitness =
Inclusive fitness
Hamilton’s Rule: rB > C
predicts when altruistic behaviours are favoured, when rB is greater than C
r = coefficient of relatedness
B = reproductive benefit to the recipients
C = reproductive cost to the actor
Relatedness
- parents = 50% or 0.5
- siblings = 50% or 0.5
- aunt, uncle, grandparent, nephew, niece = 0.25
- first cousins = 0.125
Why don’t eusocial Hymenoptera produce?
- colonies are made up of very closely related individuals, so it’s good to help your colony
- relatedness explains aggression between colonies, aggression is low between nests of closely related colonies
Relatedness explains agression in humans
- 25% of homicides committed by ‘relatives’
- 6% committed by genetic relatives
- rates of child abuse are higher amount stepchildren than biological children
Kin recognition
- Kin are people who live close to you
Alarm calls
- altruistic warning of approaching predators
- females give more alarm calls than males when they live near kin
- males leave kin early and almost never give alarm calls
Phenotype matching
- evaluation of relatedness between individuals based on an assessment of phenotypic similarity
- individuals trust people who look like kin
Reciprocity
- explains why we help those who don’t look like us
Direct Reciprocity
- refers to situations in which individuals help each other and both benefit
Indirect reciprocity
- occurs when individuals help others who have helped others
- by helping others, you give yourself a good reputation and you’ll get more help from neighbours
- people are less likely to break rules when observed by others
Rene Descartes (Dualist Framework)
- the mind was seen as a separate entity, outside of our body, but still controlled our actions and thoughts
- physical brain was thought to serve as a connection between mind and body
(modern framework considers the brain to be hardware that is driven by the software of the mind)
neuron
- the fundamental building block of the nervous system
receptive zone
- receives signals
- dendrites -> cell body
- the dendrites reach out and connect to other neuron’s
Transmission zone
- passes signals to other cells
- axon -> terminal end
- axons convey signals coming from the dendrites
- terminal ends reach out and make connections with the receptive zone of other neurons
Glial cells
- important in supporting cast that provide structural support, nourishment, and insulation needed by the neuron
- glial cells and neurons work together
Cell membrane
- selectively permeable
- resting potential (inside) = -70mV
- IN = K+ and A- (proteins)
- OUT = Cl- and Na+
Potassium channel
- like a tap that’s always open, allowing K+ to leave the cell
Voltage-gated sodium channel
- closed in the resting state of neuron
- Na+ flows into the cell
Action potential
when -50mV threshold is reached, action potential goes foward
Action potential flow
Start with sodium channels now open, then the force of diffusion causes the positively charged sodium ions to begin rushing into the neurons -> inside to become more positive
○ Electrostatic force begins to push the positively charged potassium out of the cell through its channel
○ Inside of the cell begins to lose positive charge and continues to fall and actually overshoot the baseline -70mv resting potential
■ Voltage gated potassium channel have completely closed
■ The slow closure of the voltage gated potassium channels results in an
excess of potassium leaving the cell and thus hyperpolarizing it to
-100mV.
○ Cell slowly returns to -70mv and short reflection period occurs
Oligodendrocytes
- in the CNS
- myelinate axons in the CNS which allows faster APs
Schwann cells
- in the PNS
- myelinate axons to allow for faster APs
Saltatory Conduction
- when an AP reaches the myelin sheath, it jumps across it through a process called Saltatory conduction
Nodes of Ranvier
- between segments of myelin
- strengthens AP as it continues along myelin sheath
Action Potential messages are encoded by
frequency NOT strength
Synapse
the communication point (not connected) between the terminal end of Neuron A and the receptive zone of Neuron B
Neurotransmitters
- a variety of chemicals found within VESCILES
Vesicles
○ Spills neurotransmitters into the extracellular fluid
○ Variety of neurotransmitters may be released with each having a specific
function
● Once the neurotransmitter molecules are released, they enter the space between two
neurons= synaptic cleft
● Neurotransmitter molecules float freely in the cleft, growth a number of other
molecules which can have direct effect on the neurotransmitter
Excitatory Postsynaptic Potential
- sodium channels open, allowing Na+ into the postsynaptic cell
Temporal summation
- high frequency stimulation by one presynaptic neuron
Spatial summation
- simultaneous stimulation by several presynaptic neurons
Spatiotemporal summation
- simultaneous, high frequency stimulation by several presynaptic neurons
Inhibitory Post Synaptic Potential
- Cl- channels on the cell membrane open and chloride enters the cell, making the cell more negative and unable to meet threshold
Neurogenesis
- nervous system development begins 18 days after conception
- plate -> groove -> tube
- becomes CNS
Ventricular zone
- lined with founder cells that begin divided on day 28
- day 28-42 cell division is symmetrical as one founder cell produces 2 identical daughter cells
- day 42-125 cell division is asymmetrical, dividing cell produces one founder cell that stays put and a neuron or glial cell that migrates out of the ventricular zone
Neurons are always produced before glial cells, except…
- radial glial cells which are like scaffolding that extend out of the ventricular zone, neurons use this to migrate out of the ventricular zone
- brain is formed from the inside to the outside
Differentiation
- neuron differentiation is partly determined by where a founder cell originated
- environment input can also play a factor, its influenced by (surrounding cells, external environment) *a blind child’s vision neurons wouldn’t develop and would be recruited somewhere else
Making connections
- after differentiation, neurons must make connections
- only neurons that make connections will survive
- # of synapses increase until around 1 year of age, and then decline for the rest of our life
- the brain is increasing its efficiency and retain only useful connections
Neuroaxis
- dorsal = head (top), spinal cord (back)
- ventral = front
- caudal = bottom
- rostral = top looking up
Medial
- towards midline
Lateral
- away from midline
Phineas gage
- construction worker had 3 foot pole lodged through his brain
- used be athletic, intelligent, full of life
- now selfish, unreliable, profane and erratic
Dr. Wilder Penfield
- montreal procedure, electrically an area of the brain and observe the result
- visual cortex = flash of light
- motor cortex = muscle twitch
Single cell recording
- electrodes can be used to record ongoing electrical activity in the brain through this
- neural activity is recorded while the animal performs a task
- pattern of firing reveals a neurons functional role
Computed Tomography (CT)
- structural
- x-ray slices are taken and put together to give a quick picture of the brain
- helpful to diagnose brain injury
- low resolution, not used in research
Magnetic Resonance Imaging (MRI)
- structural
- magnetic fields align hydrogen atoms in the brain
- higher resolution than CT
PET scan
- functional
- tracer of glucose or oxygen is injected into the blood
- makes it way to the brain and get used by metabolic processes which can be seen
- more active areas of brain use more glucose/oxygen
fMRI
- functional
- preferred because it gives clear image with tracer
- measure the use of oxygen in the brain
Limitations
1. oxygen use by the brain spikes a few seconds after the spikes of functional activity in the brain , a lot can happen in this time
2. not the best to capture precise timing
EEG
- functional
- cap of electrodes measure brain activity
- ERP (stimuli is presented to the participants while the EEG is recording)
Hindbrain
RCMP
- reticular formation (arousal, circadian, posture, balance)
- cerebellum (coordinated movement)
- medulla (breathing, digestion, HR)
- pons ( movement, auditory perception, emotional processing)
Midbrain
Perception, arousal, motor control
Tectum = (superior colliculi - visual) and inferior colliculi (auditory)
Tegmentum = (red nucleus - motor control) and (substantia nigra - dopamine and rewards)
Forebrain
- PHAT-H
- largest region
- limbic system
- emotion, memory, perception and thought
- Hypothalamus (stress response, energy metabolism, hormonal control)
- Pituitary = anterior (hormones regulate endocrine glands) and posterior (releases oxytocin and vasopressin)
- Thalamus (relay station and sense of smell)
- Hippocampus is horseshoe shaped in temporal lobe (short term to long term memory, spatial mapping, neurogenesis through adulthood)
- Amygdala = FEAR! and almond shaped
The 4 lobes
FPOT
Frontal = motor and decision making (higher order thought)
Parietal = spatial and touch
Occipital = visual processing and cortex
Temporal = auditory processing and higher visual processing, memory and language
Gyrus
a ridge on the cortex (buldges)
Sulci
indents and gaps between
deep sulci = fissures
Aphasia
speech deficit
receptive aphasia
- fluent words but meaningless sentences
Wernickes Area
- important area for language comprehension
Right hemisphere
- special regions involved in processing spatial world
Corpus Callosum
- carries info between two hemispheres of the brain
- sensory and motor information cross over from one side of the body to the other through the thalamus
- a severed corpus callosum leads to split brain syndrome
Split brain syndrome
- once information arrives on the on the opposite side of the brain, it’s trapped
- these people are relatively unaffected because stimuli in the world are perceived bilaterally
Gestalt Principles
- human experience should not be reduced to it’s elements, but observed as a whole
- laws that describe how we organize visual input, innate or we acquire them rapidly after birth
kafta
the whole is other than the sum of its parts
Structuralist approach
- focus was to reduce perception to its basic elements
- a movie is made from thousands of flashing parts, but the movie is viewed differently than thousands of still photos
6 gestalt principles
Figure ground - ability to distinguish an object from its background in a visual scene
Proximity - helps with grouping, objects close together tend to belong together
Closure - the tendency to fill in gaps to perceive a whole objects (a truck behind a pole)
Similarity - the tendency to group elements that are physically similar
Continuity - the ability to perceive a simple, continuous form rather than a combination of forms
Common fate - the tendency to group together elements that change in the same way
Law of pragnanz
we have bias to organize things into the simplest organization. A pyramid of triangles is simpler than “triangle, triangle, triangle”.
Bottom-up processing
we allow the stimulus itself to shape our perception, without any preconceived ideas.
Top-down processing
your own beliefs/expectations are the primary influence for determining what you see
Priming: recognition can be primed in top-down. Providing an expectation prior to presenting a stimulus will lead to the participant reacting quicker
Bi-directional activation
- the features of the object with our expectations guide recognition
Geon theory
- we have 36 different geons (geometric shapes in our memory), which allow us to perceive 150 million different objects
- criticism: for complex stimuli, what geons would be used? but we can still recognize these objects
Template theory
Suggests we compare objects to templates in memory. Unfamiliar template = new memory
Criticism: too many stimuli exist to feasibly store in memory
Prototype theory
- suggests we store the most typical or ideal examples of an object and compare objects to our ideal prototype
- explains how we recognize common objects that weve never seen before
Perceptual constancy
our ability to perceive an object an unchanging even though the visual image produced by the object is constantly changing. They exist from prior knowledge and cues in our scene
Shape constancy
- an object is perceived to have a constant shape despite changes in object position
Location constancy
- an object is perceived to be stationary despite changing location on our retina
Size constancy
- an object is perceived to be the same size despite the size of the retinal image varying with distance
Brightness constancy
- an object is perceived to be the same brightness despite reflecting more or less light onto our retina
colour constancy
- ab object is perceived to have a constant colour despite different illumination conditions
Muller-Lyer Illusion
- misapplies size constancy and misinterprets depth
- things without right angles are less susceptible to this
Ames room illusion
- manipulates distance of corners to trick size constancy
Ponzo illusion
manipulates depth cues to trick size constancy
Magno and Parvo cells
transduce light stimuli into neural impulse
Magno cells
found mainly in periphery of retina, used to detect changes in brightness, motion, depth
Parvo cells
found throughout the retina, detect colour, pattern and form
Simple cell
responds maximally to a bar of certain orientation in a particular region of the retina (certain orientation and location)
Complex cell
- responds maximally to a bar of a certain orientation and direction of movement, regardless of where the bar is located in the receptive field
(certain orientation and direction, location doesn’t matter)
Hypercomplex cells
responds maximally to a bar of a particular orientation and direction of movement, ending at specific points in the receptive field
(inhibited by a bar of light that is not within the ON region )
Extrastriate cortex surrounds the PVC
has multiple subregions that each receive a different type of info from the PVC about the visual scene
Two streams of info in the extrastriate cortex
- dorsal stream: the “where stream, it processes where objects are located in the visual scene. PVC -> parietal cortex
- ventral stream: the “what” stream, processes information about what the object is (form and colour), PVC -> temporal cortex
Cells in the temporal cortex respond to very specific and complex stimuli (hands, faces, chairs)
- arranged in vertical and columns and oriented perpendicularly to the surface
- within each column, there are 6 layers of neurons. Each layer responds to complex stimuli that come from the same category however each layer responds to slightly
different features within that category - For example, one column of neurons might respond best to apples and each layer of
that column would prefer and fire for specific colours of apples - Objects are represented by unique activity patterns across many cells, rather than specific neurons
Infants do not perceive patterns
- infant’s poor visual acuity may limit their ability to perceive whole forms
- infants only begin focusing on whole forms after 2 months
- develop perceptual constancy at 4 months (brightness, colour, shape) but size constancy needs more development
- 5 months use cues like colour and texture to distinguish objects
Preferential looking method
- used to determine what kinds of patterns infants can perceive by measuring which of the two patterns the infants look at the most.
- they prefer patterns with high contrast and sharp boundaries
- infants will prefer the most complex looking stimuli
we are born to prefer face stimuli over other stimuli
4 days old - infants prefer looking at faces over other stimuli that they are shown, even scrambled faces
- 2 months - infants prefer to look at attractive faces over unattractive faces. They will also look at their mom’s face longer than other peoples faces
- 5 months - they can begin to detect different emotional expressions such as happiness or sadness
- all of these studies suggest that we were born with a readiness to perceive and prefer face stimuli compared to other stimuli
In summary: It is our early experience with faces that develops our preference for them. At birth, we simply have a preference to look at complex, high contrast stimuli, whether these are faces or not.
Innate abilities and environmental stimulation
work together for normal development.
- *if we didn’t have the innate architecture in place, then no amount of environmental stimulation would allow for normal vision. However, the reverse is also true. The innate architecture needs early visual experience for vision to develop normally.
Sensitive periods
- 1 month old kittens kept in the dark for 3-4 days suffer visual degradation
- 1 month old kittens kept in the dark for an entire week or longer suffer severe/permanent visual degradation
Cataracts disrupts light from passing through the lens of the eye
- a thick cloud in the lens of your eye that results in complete loss of ability to perceive objects, patterns or details
Humans require some form of early visual input for proper development
early period in devleopment where we need a certain amount and type of visual input to proceed normally
Damage to the primary visual cortex does not disrupt object recognition
recall that perception of objects depends heavily on the extrastriate cortex
- if you suffer damage to the primary visual cortex, you’ll lose vision in some parts of your visual field, but the parts that you do see will seem normal so you’ll be able to
perceive objects in those intact areas of your visual field
- It would be like you were looking at a scene though a keyhole so essentially you
would be able to see and perceive everything normally within the boundaries of the keyhole, but everything in the scene around the keyhole would be invisible to you
Damage to the extrastriate cortex disrupts object recognition, NOT SIGHT
- if you damage your visual association cortex, your entire visual scene might be intact and you would probably be able to see all the objects in the scene, however you would have difficulty in recognizing some or all of the objects
- this is called visual agnosia, which is when you can see everything but you don’t know what anything is
Object agnosia
- inability to perceive objects
- can see the objects perfectly and can read words and sentences but can’t identify or recognize objects
Prosopagnosia
- inability to perceive faces
- can identify facial features but cant put them together identify a whole face, even their own
- can recognize a dog or car but can’t recognize their own dog or car
Liver breaks down…
glycogen
Pancreas produces…
insulin
body stores glucose as…
glycogen which is released in between meals (mainly in the liver)
Neuropeptide Y
- high activity in the hypothalamus
- potent appetite stimulant that increases food seeking behaviour
Low glucose levels and glycogen stores means
HUNGRY
High glucose levels and glycogen stores means
SATIETY/FULL!
CCK
small intestine releases CCK which is a hormone indicating satiety (regulates short term satiety)
adipose tissues was classified as an…
endocrine organ
Adipose tissue secretes
- LEPTIN, which is involved in long term energy balance
- act on receptors in the hypothalamus to reduce appetite which reduces food consumption
Leptin production is regulated by the OB gene
Unregulated OB gene = increased fat storage
Regulated OB gene = decreased fat storage
Leptin indicates low energy stores rather than inhibiting appetite
- studies on mice suggest that a contributing factor for obesity in humans may involve defective OB genes or receptors. However, it has been found that very few obese individuals have known defects in the leptin signalling system
- giving additional leptin to an obese animal who has normal leptin levels actually does not result in weight loss to return to normal levels
- humans and animals are capable of becoming leptin resistant. At a certain point, leptin’s ability to inhibit appetite is reduced.
Leptin and NPY interact
Leptin acts to inhibit the actions of NPY. The NPY mediated increase in appetite is prevented by leptin, leading to decreased appetite and energy consumption. NPY activity in the hypothalamus stimulates appetite. High levels of leptin inhibit NPY. Leptin and NPY interact together to regulate your weight to optimal levels.
NPY acts to increase
carb consumption.
Rats with preexisting preferences for carbs had an even greater preference after NPY injection
Endogenous opioids
Nolaxone reduces intake of saccharin, sucrose and saline. Blocking opioid receptors in the brain with naloxone would result in reduced intake of rewarding foods like saccharin and sucrose
Evolutionary significance of leptin
low levels of leptin serve as signal to increase foraging effort and/or decrease activity levels in order to conserve energy. Note that our physiology guards against weight loss more so than weight gain
Taste is indicative of nutritional quality
bitter and sour - not enjoyed (toxic)
sweet, salty, umami -highly craved (safe)
Taste and smell influence your perception of
flavour
Taste sensation begins with taste receptor cells
- taste buds containing taste receptor cells detect and respond to the dissolved food molecules
- each taste bud has anywhere between 50 to 150 taste receptor cells
- about two thirds of our taste buds are located on our tongue. The remaining are on the soft
palate and the opening of the throat
Types of taste
Sweet - energy rich
Salty - essential electrolytes
Bitter - harmful, spoiled, poisonous
Sour - harmful, spoiled, poisonous
Umami - detects amino acids like glutamate and aspartate
All areas of the tongue detects all type of taste
- each taste bud contains some proportion of all 5 taste receptors
Taste pathways diverge in the brainstem
- one pathway travels through the medulla to the thalamus, from which info is sent to the primary somatosensory cortex and the gustatory cortex
- second pathway goes from brainstem to the pons –> then hypothalamus and amygdala (involved in satiety)
The somatosensory cortex processes the
feel and texture of food
The gustatory cortex processes
taste
(smell and taste info is combined to result in favour)
sensation of flavour begins at the
- nasal pharynx
- this is our sophisticated ability to sense flavour (red vs blue jellybean)
Taste and smell info is combined in the
orbital cortex
Humans can distinguish
10,000 smells but can we really label them all?
Smell sensation links directly to the cortex
- bypasses the thalamus
smell sensation begins with the olfactory cillia
- your sense of taste is concerned with processing chemical molecules of stimuli found in the air
- as you breathe, chemical molecules enter the nasal cavity and dissolve in the mucus of your nose. This allows the chemical molecules to interact with the olfactory cilia which are tiny hair like structures that cover the receptor surface of the nasal cavity (aka the olfactory epithelium)
- each olfactory receptor cell receives input from between 10 to 20 cilia
Smell is distinguished by patterns of firing, rather than single receptor firing
- olfactory receptor cells respond to a range of stimuli
- a specific smell does not activate a unique receptor cell but rather activates a unique pattern
of firing across receptors - once an action potential is triggered in an olfactory receptor cell, it travels down the axon and
synapses with cells in the olfactory bulb of the brain. Here the cells form synapses with dendrites of other cells called glomeruli, each of which receives input from thousands of olfactory receptor cells
Output from glomeruli are processed in higher brain areas
- output from glomeruli is sent to hypothalamus and areas of the limbic system
- also goes to primary olfactory cortex in the temporal lobe and secondary olfactory cortex in the frontal lobe
