Brain, Mind, Behavior General Info, Case Studies, Class
Ch 3:
3.1 Neurons Are the Basic Units of the Nervous System
Central nervous system (CNS) - the brain and spinal cord
Peripheral nervous system (PNS) - all nerve cells in the body that are not part of the CNS; includes the somatic and autonomic nervous systems
Somatic - involved in voluntary behavior
Autonomic - responsible for the less voluntary actions (ex: heart rate)
Neurons - basic units of the nervous system; cells that receive, integrate, and transmit info; operate through electrical impulses, communicate with other neurons through chemical signals, and form neural networks
Communicate with tens of thousands of other neurons
Communicate selectively to form circuits/neural networks
Function of Neurons
Reception phase - neurons take in chemical signals from neighboring neurons
Integration - incoming signals are assessed
Transmission - neurons pass their own signals to other receiving neurons
Types of neurons
Sensory - detect info from physical world and pass the info to brain
Somatosensory nerves - the sensory nerves that provide info for the skin and muscles
Motor - direct muscles to contract/relax, thereby producing movement
Interneurons - act as relay stations facilitating communication between sensory and motor neurons
Sensory and motor work together to control movement
Reflexes - automatic motor responses
Neuron structure (4 regions)
Dendrites - branchlike extensions of the neuron that detect info from other neurons
Cell body (“soma”) - where info from dendrites from thousands of other neurons is collected and integrated
Axon - long, narrow outgrowth of a neuron by which info is conducted from the cell body to the terminal buttons
Vary in length
Terminal buttons - at the ends of axons, small nodules that release chemical signals from the neuron into the synapse
Synapse - the gap between the terminal buttons of a “sending” neuron and the dendrites of a “receiving” neuron, where chemical communication occurs between the neurons
Membrane - outer surface of neuron; fatty barrier that does not dissolve in the watery environment in and out of the neuron, selectively permeable
Controls the movement of ions → plays important role in communication between neurons (regulates concentration of ions)
Ion channels - located on the membrane; specialized pores that allow ions to pass in and out of the cell when the neuron transmits signals down the axon
3.2 Action Potentials Produce Neural Communication
Action potential (neural firing) - the electrical signal that passes along the axon and subsequently causes the release of chemicals from the terminal buttons
Resting membrane potential - electrical charge of a neuron when it is not active; -70 millivolts
Polarized - when a neuron has more negative ions inside than outside
Sodium-potassium pump - increases potassium and decreases sodium in the neuron
Excitatory signals - depolarize the cell membrane (dec polarization by decreasing negative charge in the cell relative to outside the cell)
Inc likelihood that neuron will fire
Inhibitory signals - hyperpolarize the cell (inc polarization by increasing negative charge in the cell relative to outside the cell)
Dec likelihood that neuron will fire
Neuron usually has thousands of excitatory and inhibitory signals
If sum of excitatory and inhibitory signals leads to a positive change in voltage that surpasses neuron’s firing threshold, action potential is generated
Relative refractory period - the brief period of time following action potential when a neuron’s membrane potential is more negative, or hyperpolarized, making it harder to fire again
All-or-none principle - when a neuron fires, it fires with the same potency each time; a neuron either fires or not, although frequency of firing can vary (like turning on/off lights)
Stronger stimulation = more frequently action potentials are generated
Absolute refractory period - brief period of time following an action potential when the ion channel is unable to respond again
Happens before the relative refractory period
Action potential always moves in one direction: down the axon and away from the cell body to the terminal buttons
Myelin sheath - fatty material, made up of glial cells, that insulates some axons to allow for faster movement of electrical impulses along the axon
Because of this, action potential doesn’t have to traverse entire length of axon → skips quickly along gaps of myelin sheath, ion channels of nodes of Ranvier
Nodes of Ranvier - small gaps of exposed axon between the segments of myelin sheath, where action potentials take place
Multiple sclerosis (MS) - when myelin sheath deteriorates, messages from neurons slow down → cause issues with limbs, vision, etc
3.3 Neurotransmitters Influence Mental Activity & Behavior
Neurons do not touch each other → synapse separates them
Presynaptic neuron - the neuron that sends the signal
Postsynaptic neuron - the neuron that receives the signal
Neurotransmitters - chemical substances that transmit signals from one neuron to another
Different neurotransmitters influence emotion, thought, or behavior, depending on type of receptor and location in brain
EXAMPLES:
Acetylcholine - motor control over muscles; learning, memory, sleeping, and dreaming
Norepinephrine - arousal, vigilance, and attention
Serotonin - emotional states and impulsiveness; dreaming
Dopamine - reward and motivation; motor control over voluntary mvmt
GABA (gamma-aminobutyric acid) - inhibition of action potentials; anxiety reduction
Glutamate - enhancement of action potentials; learning and memory
Endorphins - pain reduction; reward
Receptors - in neurons, specialized protein molecules on the postsynaptic membrane; neurotransmitters bind to them after passing across the synapse
3 major events that terminate the neurotransmitter’s influence on the synapse (since neurotransmitters exert an effect until its influence is terminated):
Reuptake - the process whereby a neurotransmitter is taken back into the presynaptic terminal buttons, thereby stopping its activity
Enzyme deactivation - when an enzyme destroys the neurotransmitter in the synapse
Different enzymes break down different neurotransmitters
Autoreception - when neurotransmitters bind with receptors on the presynaptic neuron
Autoreceptors - monitor how much neurotransmitter has been released into the synapse
When an excess is detected, autoreceptors signal the presynaptic neuron to stop releasing the neurotransmitter
Agonists - drugs and toxins that enhance the actions of neurotransmitters
Ex: introducing a substance that helps produce the neurotransmitter → inc amount of neurotransmitter made and released by presynaptic neuron
Ex: blocking receptors on presynaptic cell that trigger the reuptake of the neurotransmitter → keeping it in the synapse longer
Ex: mimicking the action of the neurotransmitter on the postsynaptic cell → activating receptor or increasing neurotransmitter impact
Antagonists - those that inhibit the actions of neurotransmitters
Ex: introducing a substance that reduces the amount of neurotransmitter made and released into the synapse
Ex: introducing a substance that facilitates the destruction or breaking down of neurotransmitter → dec time it is in synapse
Ex: blocking the postsynaptic receptors → preventing neurotransmitter from activating them
Addictive drugs (ex: heroin) are chemically similar to endorphins (naturally occurring neurotransmitters)
Selective serotonin reuptake inhibitors (SSRIs) - antidepressant drugs that bind with receptors on the presynaptic cell to trigger the reuptake of serotonin, inhibiting its reuptake and increasing its availability in the synapse
Levodopa (L-DOPA) - increases production of dopamine, used to treat Parkinson’s disease (since the people need more dopamine- they are losing it)
Drugs used to treat schizophrenia, block dopamine from binding do receptors (antagonist)
3.4 The Ability to Study Brain Function Has Improved Dramatically
Brain is a collection of interacting neural circuits
Phrenology - carefully feeling someone’s skull to learn about their personality
Came from Gall and Spurzheim hypothesis that the areas of the brain that people use more grow larger and create bumps on the skull
Pierre Paul Broca - first person to have strong evidence that brain regions have specialized functions (study: man could only say “tan”, when he died, realized front left side of brain was damaged → must be area for speech)
Broca’s area - a small portion of the left frontal region of the brain, crucial for the production of language
Brain lesion methodology - studying people’s brains and behavioral deficits after brain injuries to learn the function of the brain
Limitation: can only be done on those who have brain lesions, injuries, or surgical interventions to treat a disease
So now they are studying the function of the brains of healthy people
Electroencephalography (EEG) - technique used for measuring electrical activity in the brain (when a response occurs)
Different behavioral states produce different and predictable EEG patterns
Limitation: reflect all brain activity, so too much to be able to focus on one thing
Event-related potential (ERP) - conducting many trials with a single indiv and averaging across trials (to find patterns)
Provide info about speed that brain processes events and their timing
Limitation: measure all electrical activity at scalp → difficult to pinpoint where in the brain the processes take place
Brain’s electrical activity = associated with changes in the flow of blood carrying oxygen and nutrients to active brain regions
Positron emission tomography (PET) - method of brain imaging that assesses metabolic activity by using a radioactive substance injected into the bloodstream (where a response occurs)
Find most active brain areas by tagging brain chemicals w/ radioactive tracer - inc radioactive material → regions emit more radiation, detected outside the body
Magnetic resonance imaging (MRI) - method of brain imaging that uses a powerful magnetic field to produce high-quality images of the brain
Can adjust it to measure certain tissues or substances in the body
Can be used to determine location of brain damage or brain structure
Functional magnetic resonance imaging (fMRI) - an imaging technique used to examine changes in the activity of the working human brain by measuring changes in the blood’s oxygen level (where a response occurs)
Participant performs experimental task that differs in 1 way from control task - then researchers can explore diffs in images and blood flow (brain activity)
Transcranial magnetic stimulation (TMS) - use of strong magnets to briefly interrupt normal brain activity as a way to study brain regions
Limitation: only be used for short durations to examine brain areas close to scalp
3.5 Cerebral Cortex Underlies Complex Mental Activity
Forebrain - largest part of brain; made up of cerebral cortex and underlying subcortical areas; consists of 2 hemispheres
Cerebral cortex - outer layer of brain tissue, which forms the wrinkled surface of the brain; the site of all thoughts, perceptions, and complex behaviors
Cortex is Latin for “bark” (trees), cortex has consistency of soft-boiled egg
Lateral fissure and central fissure - folds on the surface of the cerebral cortex; divide the brain into lobes
Each cerebral hemisphere has 4 lobes: occipital parietal, temporal, and frontal
Gray matter - outer layer of the cerebral cortex (the bark); dominated by neurons’ cell bodies, dendrites, and unmyelinated axons that only communicate w nearby neurons
White matter - under the gray matter; consists mostly of axons and the fatty myelin sheaths that surround them
Corpus callosum - massive bridge of millions of (myelinated) axons (white matter) that connects the hemispheres of the brain and allows info to flow between them
4 lobes of cerebral cortex are site of all thoughts, detailed perceptions, and complex behaviors
Enable us to comprehend ourselves, others, and the world
Occipital lobes - regions of cerebral cortex–at the back of the brain–important for vision
Primary visual cortex - the major destination for visual info
Visual info is organized for cerebral cortex in way that preserves spatial relationships
Second visual areas surround primary visual cortex and attribute to the visual image (colors, forms, motions, etc)
Parietal lobes - regions of the cerebral cortex–in front of the occipital lobes and behind the frontal lobes–important for the sense of touch and for attention to the environment
Left hemisphere receives touch info from the right side of the body; right hemisphere receives touch info from the left side of the body
Primary somatosensory cortex - a strip in the front part of the lobe that runs along the central fissure from the top of the brain down the sides (where the info is directed); group nearby sensations
Somatosensory homunculus - distorted representation of the entire body; distorted because more cortical area is devoted to body’s more sensitive areas (face and fingers)
Based on brain maps by Wilder Penfield
Stroke or damage to right parietal region can result in hemineglect - syndrome where patients fail to pay attention to anything on their left side (eyes still work)
Temporal lobes - regions of the cerebral cortex–below the parietal lobes and in front of the occipital lobes–important for processing auditory info, for memory, and for object and face perception
Primary auditory cortex - in temporal lobe; brain region responsible for hearing
Fusiform face area - intersection of temporal and occipital lobes; name comes from fact that this area is more active when people look at faces than other things
Damage to the area can cause difficulty recognizing people, not objects
Frontal lobes - regions of the cerebral cortex–at the front of the brain–important for mvmt and higher-level psychological processes (planning) associated with the prefrontal cortex
Primary motor cortex - includes neurons that project directly to the spinal cord to move the body’s muscles; responsibilities divided down middle of body
Prefrontal cortex - frontmost portion of the frontal lobes, especially prominent in humans; important for attention, working memory, decision making, appropriate social behavior, and personality
Occupies about 30% of the brain in humans
Gage’s case: provided basis for first modern theories of prefrontal cortex’s role in personality and self-control
Got iron rod through head and frontal lobes → unconscious for 2 weeks → big personality changes → evidence that some areas of brain have specific functions
3.8 The Insula and Subcortical Structures Contribute to Taste, Emotions, Memory, and Reward
Insula (insular cortex) - part of the cerebral cortex lying inside the lateral fissure; important for taste, pain, perception of bodily states (related to emotion), and empathy
Gustatory cortex - inside the insula; necessary for the sense of taste and important for perceiving disgust
Thalamus - gateway to the brain; receives almost all incoming sensory info before the info reaches the cortex, organizes it, and relays it to the cortex
Only exception is sense of smell (direct route to cortex)
During sleep, thalamus partially shuts gate on incoming sensations while brain rests
Hypothalamus - brain structure that is involved in the regulation of bodily functions, including body temp, body rhythms, blood pressure, and blood glucose levels; also influences our basic motivated behaviors (ex: thirst, hunger, aggression, etc)
Brain’s main regulatory structure, indispensable for survival
Located just below the thalamus
Hippocampus - brain structure associated with the formation of memories (by creating new interconnections within the cerebral cortex with each new experience)
Takes its name from the Greek word for “sea horse” because of its shape
Involved in how we remember the arrangements of places and objects in space (ex: how streets are laid out or furniture is positioned)
Study: one hippocampal region much larger in taxi drivers’ brains, and volume of gray matter correlated with number of years of experience
Amygdala - brain structure that serves a vital role in learning to associate things with emotional responses and in processing emotional info
Got its name from Latin word for “almond” because of its shape
Located immediately in front of the hippocampus
Plays special role in responding to stimuli that elicit fear
Developed over evolution to protect animals from danger
Intensifies the function of memory during times of emotional arousal
Basal Ganglia - system of subcortical structures that are important for the planning and production of mvmt
Receive input from the entire cerebral cortex → send input to the motor centers of the brain stem and (via the thalamus) send the input back to the motor planning area of the cerebral cortex
Damage to this area can produce wide range of symptoms (tremors and rigidity of Parkinson’s to involuntary writhing mvmts of Hungtington’s disease)
Can also impair learning of mvmts and habits (ex: looking for cars before crossing the street)
Nucleus accumbens - in the basal ganglia; important for experiencing reward and motivating behavior
3.9 The Brain Stem and Cerebellum House Basic Programs for Survival and Movement
Spinal cord - rope of neural tissue
Runs inside the hollows of the vertebrae from the base of the skull to just above the pelvis
Functions: coordination of reflexes, carry sensory info up to the brain and carry motor signals from the brain to the body parts below to initiate action
Brain stem - extension of the spinal cord; houses structures that control functions associated with survival (HR, breathing, swallowing, vomiting, urination, and orgasm)
Consists of medulla oblongata, the pons, and the midbrain
Reticular formation - network of neurons in brain stem that projects up into the cerebral cortex and affects general alertness; also involved in inducing and terminating the diff stages of sleep
Cerebellum - large, convoluted protuberance at the back of the brain stem; essential for coordinated mvmt and balance
Latin for “little brain”
Extremely important for proper motor function
Damage to diff parts affect diff movements
Little nodes → head tilt, balance problems, loss of smooth eye mvmts
Ridge that runs up the back of it → affect walking
Bulging lobes on either side → loss of limb coordination
Most obvious role is in motor learning and motor memory; operates unconsciously
Helps w making plans, remembering events, using language, experiencing emotion
3.11 The Peripheral Nervous System Includes the Somatic and Autonomic Systems
Somatic nervous system (SNS) - component of the peripheral nervous system; transmits sensory signals and motor signals between the CNS and the skin, muscles, and joints
Sends info to spinal cord and eventually to brain
Autonomic nervous system (ANS) - component of the peripheral nervous system; transmits sensory signals and motor signals between the CNS and the body’s glands and internal organs
Regulates body’s internal environment by stimulating glands (ex: sweat glands) and maintaining internal organs
Ex: provide info about the fullness of stomach or how anxious you feel
Sympathetic division - division of the autonomic nervous system; it prepares the body for action (ex: fire alarm goes off, sexual arousal, anxiety/unhappiness)
Parasympathetic division - division of the autonomic nervous system; returns the body to its resting state
3.14 The Brain Can Recover from Injury
Following injury in cortex, surrounding gray matter may assume the fxn of damaged area
Radical hemispherectomy - can only be done on children; surgical procedure to remove an entire cerebral hemisphere (when young children have severe, uncontrollable epilepsy)
Remaining hemisphere usually takes on most of the lost hemisphere’s fxns
Children regain almost complete use of their limbs
In adults, cortical reorganization can lead to recovery from more limited brain injuries
Gene expression - whether a particular gene is turned on or off
Environmental factors can affect gene expression and how a gene, once turned on, influences our thoughts, feelings, and behavior
Genetic predispositions also influence the environments people select
So biology and environment mutually influence each other
They both influence the development of the brain (one’s genes and every experience one ever has)
3.15 All of Human Development Has a Genetic Basis
Genome - blueprint that provides detailed instructions for everything from how to grow a gallbladder to where the nose gets placed on the face
Genome provides the options, environment determined which options are taken
Chromosomes - structures within the cell body that are made up of DNA, segments of which comprise individual genes
Every human cell contains 23 pairs of chromosomes (one in each pair from mom, one from dad)
DNA - substance that consists of two intertwined strands of molecules in a double helix shape; segments of them are genes
Genes - the units of heredity that help to determine an organism’s characteristics
Each specifies in an exact instruction to manufacture a distinct polypeptide
Polypeptides - building blocks of proteins, the basic chemicals that make up the structure of cells and direct their activities
Thousands of types of proteins, each type carries out specific task
Environment determines which proteins are produced and when
Human Genome Project
People have fewer than 30,000 genes
3.16 Heredity Involves Passing Along Genes Through Reproduction
Gregor Mendel - gave first clues to mechanisms responsible for heredity
Selective breeding - controlled which plants bred with which plants (pea plants)
Purple vs white flowers → realized that some genes are dominant
White are recessive, purple are dominant
Dominant gene - gene that is expressed in the offspring whenever it is present
Recessive gene - gene that is expressed only when it is matched with a similar gene from the other parent
Genotype - genetic constitution of an organism, determined at the moment of conception
Phenotype - observable physical characteristics, which result from both genetic and environmental influences
Polygenic - when a trait is influenced by many genes (as well as by environment) (ex: skin color)
Sexual reproduction
Females have two X chromosomes, males have one X and one Y
After sperm and egg combine during fertilization, fertilized cell results, called zygote (w 23 pairs of chromosomes)
Zygote grows through cell division (2 stages)
First: chromosomes duplicate
Then: cell divides into two new cells w identical chromosome structure
Cell division= basis of life cycle and responsible for growth and development
Genetic mutations
Mutations - alterations in the DNA
Most are benign and have little influence on the organism
Occasionally gives some an advantage/disadvantage in survival or reproduction
Industrial melanism - moths and butterflies tend to be darker in color in places with heavy soot or smog
Darker insects → harder to see now with darker backgrounds (global warming)
Typically the genes that improve survival are the ones that survive and spread
Genes that lead to diseases AFTER reproductive age do not confer a reproductive disadvantage and are not removed from the population
Sickle-cell disease - genetic disorder that alters the bloodstream’s processing of oxygen; can lead to pain, organ and bone damage, and anemia; certain races
Recessive, so must receive from both parents
Sickle-cell trait - if only received from one parent
3.17 Genes Affect Behavior
Behavioral genetics - the study of how genes and environment interact to influence psychological activity
Twin studies - compare similarities between different types of twins to determine the genetic basis of specific traits
Monozygotic twins - aka identical twins; twin siblings that result from one zygote splitting in two and that therefore share the same genes
Dizygotic twins - aka fraternal twins; twin siblings that result from two separately fertilized eggs and therefore are no more similar genetically than nontwin siblings
Adoption studies - compare similarities between biological relatives and adoptive relatives
Nonbiological adopted siblings may share similar home environments, but diff genes
So similarities among non biological adopted siblings have more to do w environment than genes
Thomas Bouchard and colleagues found that identical twins, whether raised together or not, were likely to be similar
May be some evidence that twins raised apart are more similar than those raised together
Heredity - transmission of characteristics from parents to offspring through genes
Heritability - a statistical estimate of the extent to which variation in a trait within a population is due to genetics
Relevant to understanding the population as a whole, not an individual
Knowing the heritability of a trait does not indicate whether an indiv’s expression of that trait is due to genes or environment
Variation - the measure of the overall difference among a group of people for that particular trait
Brain stem
Located at top of spinal cord, connecting to brain
Controls functions for survival - HR, breathing, swallowing, etc
Oldest part and central core of brain
Cerebellum
Located at back and bottom of brain, behind and on top of brain stem
Means “little brain”
Important for balance and coordinated movement
Where purkinje cells are located
Has more than 50% of brain’s neurons, but only takes up 10% of brain
Broca’s area
Small area on left hemisphere in frontal lobe
Important for producing speech and controlling language expression
Connected to Wernicke’s area with a bundle of nerves → helps connect language comprehension and speech production
Wernicke’s area
Located in left hemisphere in temporal lobe (where it meets parietal lobe)
Important for language comprehension - understanding spoken and written language
Helps you process sign language too, not just spoken language
Parietal lobe
Located at top of brain - in front of occipital lobe and behind frontal lobe
Important for sense of touch and sensory information
Develops around age 5
Temporal lobe
Located below parietal lobe and infront of occipital lobe
Important for hearing, memory, and object and face recognition
Each side receives auditory information from the opposite ear
Occipital lobe
Located at the back and bottom of the brain
Important for vision and perceiving distance/size/etc
Smallest lobe of the brain OR flips the retina image so it is right side up
Hypothalamus
Located below the thalamus and above brain stem
Important for bodily functions (hunger, thirst, body temp, blood pressure, etc)
It acts like your body’s internal thermostat
Thalamus
Located on the top of the brainstem, in the center of the brain
Receives all incoming sensory info before sending it to the brain (cerebral cortex)
Shaped like and egg and can block out sensory info when you are sleeping
Hippocampus
Located in the middle of the temporal lobe
Important for the formation of memories, and object locations
Age-related memory decline is associated with hippocampus OR comes from greek word for seahorse because of its shape
Pons
Part of the brainstem, between midbrain and medulla
Handles unconscious processes and jobs (breathing, alertness level, etc)
Means bridge in latin - it is the bridge from the cerebrum to the cerebellum
Vagus nerve
Runs from brain to chest to large intestine
Regulates HR, controls breathing, facilitates digestion, etc
Longest nerve in the body
corpus callosum
Located between right and left hemispheres of cerebral cortex
Allows info to be sent from one hemisphere to the other, integrates sensory and motor info from both
Split brain: condition that results from surgery that isolates the brain’s hemispheres
prefrontal cortex
Located at very front of frontal lobe - where the forehead is
Important for attention, learning, decision making, problem solving, personality
Fully develops around age 25
Motor cortex
Located at the back of the frontal lobe
Important for voluntary movements
It is activated when you even imagine movement and a few seconds before you actually move
Somatosensory cortex
Strip located in the parietal lobe behind the motor cortex, towards front of lobe
Important for processing movement and touch sensations
Phantom limb pain - when limb has been amputated and no longer receive info from limb
Amygdala
Located infront of the hippocampus, in the temporal lobe
Important in emotional processing, especially fear, facial expression understanding
Named after “almond” in latin because of its shape